Table Of Contents

Welcome

Welcome to DragonRuby Game Toolkit!

The information contained here is all available in your the zip file at ./docs/docs.html. You can browse the docs in a local website by starting up DragonRuby and going to http://localhost:9001.

Community

Our Discord server is extremely supportive and helpful. It's the best place to get answers to your questions. The developers of DragonRuby are also on this server if you have any feedback or bug reports.

The Link to Our Discord Server is: http://discord.dragonruby.org.

The News Letter will keep you in the loop with regards to current DragonRuby Events: http://dragonrubydispatch.com.

Book

Brett Chalupa (one of our community members) has written a book to help you get started: https://book.dragonriders.community/

Tutorial Video

Here are some videos to help you get the lay of the land.

  1. Building Tetris - Part 1: https://youtu.be/xZMwRSbC4rY
  2. Building Tetris - Part 2: https://youtu.be/C3LLzDUDgz4

Getting Started Tutorial

This is a tutorial written by Ryan C Gordon (a Juggernaut in the industry who has contracted to Valve, Epic, Activision, and EA... check out his Wikipedia page: https://en.wikipedia.org/wiki/Ryan_C._Gordon).

Introduction

Welcome!

Here's just a little push to get you started if you're new to programming or game development.

If you want to write a game, it's no different than writing any other program for any other framework: there are a few simple rules that might be new to you, but more or less programming is programming no matter what you are building.

Did you not know that? Did you think you couldn't write a game because you're a "web guy" or you're writing Java at a desk job? Stop letting people tell you that you can't, because you already have everything you need.

Here, we're going to be programming in a language called "Ruby." In the interest of full disclosure, I (Ryan Gordon) wrote the C parts of this toolkit and Ruby looks a little strange to me (Amir Rajan wrote the Ruby parts, discounting the parts I mangled), but I'm going to walk you through the basics because we're all learning together, and if you mostly think of yourself as someone that writes C (or C++, C#, Objective-C), PHP, or Java, then you're only a step behind me right now.

Prerequisites

Here's the most important thing you should know: Ruby lets you do some complicated things really easily, and you can learn that stuff later. I'm going to show you one or two cool tricks, but that's all.

Do you know what an if statement is? A for-loop? An array? That's all you'll need to start.

The Game Loop

Ok, here are few rules with regards to game development with GTK:

That's an entire video game in one run-on sentence.

Here's that function. You're going to want to put this in mygame/app/main.rb, because that's where we'll look for it by default. Load it up in your favorite text editor. 

def tick args
  args.outputs.labels << [580, 400, 'Hello World!']
end

Now run dragonruby ...did you get a window with "Hello World!" written in it? Good, you're officially a game developer!

Breakdown Of The tick Method

mygame/app/main.rb, is where the Ruby source code is located. This looks a little strange, so I'll break it down line by line. In Ruby, a '#' character starts a single-line comment, so I'll talk about this inline. 

# This "def"ines a function, named "tick," which takes a single argument
# named "args". DragonRuby looks for this function and calls it every
# frame, 60 times a second. "args" is a magic structure with lots of
# information in it. You can set variables in there for your own game state,
# and every frame it will updated if keys are pressed, joysticks moved,
# mice clicked, etc.
def tick args

  # One of the things in "args" is the "outputs" object that your game uses
  # to draw things. Afraid of rendering APIs? No problem. In DragonRuby,
  # you use arrays to draw things and we figure out the details.
  # If you want to draw text on the screen, you give it an array (the thing
  # in the [ brackets ]), with an X and Y coordinate and the text to draw.
  # The "<<" thing says "append this array onto the list of them at
  # args.outputs.labels)
  args.outputs.labels << [580, 400, 'Hello World!']
end

Once your tick function finishes, we look at all the arrays you made and figure out how to draw it. You don't need to know about graphics APIs. You're just setting up some arrays! DragonRuby clears out these arrays every frame, so you just need to add what you need _right now_ each time.

Rendering A Sprite

Now let's spice this up a little.

We're going to add some graphics. Each 2D image in DragonRuby is called a "sprite," and to use them, you just make sure they exist in a reasonable file format (png, jpg, gif, bmp, etc) and specify them by filename. The first time you use one, DragonRuby will load it and keep it in video memory for fast access in the future. If you use a filename that doesn't exist, you get a fun checkerboard pattern!

There's a "dragonruby.png" file included, just to get you started. Let's have it draw every frame with our text: 

def tick args
  args.outputs.labels  << [580, 400, 'Hello World!']
  args.outputs.sprites << [576, 100, 128, 101, 'dragonruby.png']
end

(Pro Tip: you don't have to restart DragonRuby to test your changes; when you save main.rb, DragonRuby will notice and reload your program.)

That .sprites line says "add a sprite to the list of sprites we're drawing, and draw it at position (576, 100) at a size of 128x101 pixels". You can find the image to draw at dragonruby.png.

Coordinate System and Virtual Canvas

Quick note about coordinates: (0, 0) is the bottom left corner of the screen, and positive numbers go up and to the right. This is more "geometrically correct," even if it's not how you remember doing 2D graphics, but we chose this for a simpler reason: when you're making Super Mario Brothers and you want Mario to jump, you should be able to add to Mario's y position as he goes up and subtract as he falls. It makes things easier to understand.

Also: your game screen is _always_ 1280x720 pixels. If you resize the window, we will scale and letterbox everything appropriately, so you never have to worry about different resolutions.

Ok, now we have an image on the screen, let's animate it: 

def tick args
  args.state.rotation  ||= 0
  args.outputs.labels  << [580, 400, 'Hello World!' ]
  args.outputs.sprites << [576, 100, 128, 101, 'dragonruby.png', args.state.rotation]
  args.state.rotation  -= 1
end

Now you can see that this function is getting called a lot!

Game State

Here's a fun Ruby thing: args.state.rotation ||= 0 is shorthand for "if args.state.rotation isn't initialized, set it to zero." It's a nice way to embed your initialization code right next to where you need the variable.

args.state is a place you can hang your own data. It's an open data structure that allows you to define properties that are arbitrarily nested. You don't need to define any kind of class.

In this case, the current rotation of our sprite, which is happily spinning at 60 frames per second. If you don't specify rotation (or alpha, or color modulation, or a source rectangle, etc), DragonRuby picks a reasonable default, and the array is ordered by the most likely things you need to tell us: position, size, name.

There Is No Delta Time

One thing we decided to do in DragonRuby is not make you worry about delta time: your function runs at 60 frames per second (about 16 milliseconds) and that's that. Having to worry about framerate is something massive triple-AAA games do, but for fun little 2D games? You'd have to work really hard to not hit 60fps. All your drawing is happening on a GPU designed to run Fortnite quickly; it can definitely handle this.

Since we didn't make you worry about delta time, you can just move the rotation by 1 every time and it works without you having to keep track of time and math. Want it to move faster? Subtract 2.

Handling User Input

Now, let's move that image around. 

def tick args
  args.state.rotation ||= 0
  args.state.x ||= 576
  args.state.y ||= 100

  if args.inputs.mouse.click
    args.state.x = args.inputs.mouse.click.point.x - 64
    args.state.y = args.inputs.mouse.click.point.y - 50
  end

  args.outputs.labels  << [580, 400, 'Hello World!']
  args.outputs.sprites << [args.state.x,
                           args.state.y,
                           128,
                           101,
                           'dragonruby.png',
                           args.state.rotation]

  args.state.rotation -= 1
end

Everywhere you click your mouse, the image moves there. We set a default location for it with args.state.x ||= 576, and then we change those variables when we see the mouse button in action. You can get at the keyboard and game controllers in similar ways.

Coding On A Raspberry Pi

We have only tested DragonRuby on a Raspberry Pi 3, Models B and B+, but we believe it _should_ work on any model with comparable specs.

If you're running DragonRuby Game Toolkit on a Raspberry Pi, or trying to run a game made with the Toolkit on a Raspberry Pi, and it's really really slow-- like one frame every few seconds--then there's likely a simple fix.

You're probably running a desktop environment: menus, apps, web browsers, etc. This is okay! Launch the terminal app and type: 

do raspi-config

It'll ask you for your password (if you don't know, try "raspberry"), and then give you a menu of options. Find your way to "Advanced Options", then "GL Driver", and change this to "GL (Full KMS)" ... not "fake KMS," which is also listed there. Save and reboot. In theory, this should fix the problem.

If you're _still_ having problems and have a Raspberry Pi 2 or better, go back to raspi-config and head over to "Advanced Options", "Memory split," and give the GPU 256 megabytes. You might be able to avoid this for simple games, as this takes RAM away from the system and reserves it for graphics. You can also try 128 megabytes as a gentler option.

Note that you can also run DragonRuby without X11 at all: if you run it from a virtual terminal it will render fullscreen and won't need the "Full KMS" option. This might be attractive if you want to use it as a game console sort of thing, or develop over ssh, or launch it from RetroPie, etc.

Conclusion

There is a lot more you can do with DragonRuby, but now you've already got just about everything you need to make a simple game. After all, even the most fancy games are just creating objects and moving them around. Experiment a little. Add a few more things and have them interact in small ways. Want something to go away? Just don't add it to args.output anymore.

Starting a New DragonRuby Project

The DRGTK zip that contains the engine is a complete, self contained project structure. To create a new project, unzip the zip file again in its entirety and use that as a starting point for another game. This is the recommended approach to starting a new project.

Rationale

The DRGTK binary/package in its entirety is designed to be committed with your source code (it’s why we keep it small). It’s to protect “shelf life”. 3 years from now we might be on a vastly different version of the engine. But you know that the code you’ve written will definitely work with the version that was committed to source control. It's strongly recommended that you do **not** keep DragonRuby Game Toolkit in a shared location and instead unzip a clean copy for ever game. That being said, You can optionally pass a directory when starting up DragonRuby from the terminal: ./dragonruby ./non-defualt-game-directory.

Deploying To Itch.io

Once you've built your game, you're all set to deploy! Good luck in your game dev journey and if you get stuck, come to the Discord channel!

Creating Your Game Landing Page

Log into Itch.io and go to https://itch.io/game/new.

You can fill out all the other options later.

Update Your Game's Metadata

Point your text editor at mygame/metadata/game_metadata.txt and make it look like this:

NOTE: Remove the # at the beginning of each line. 

devid=bob
devtitle=Bob The Game Developer
gameid=mygame
gametitle=My Game
version=0.1

The devid property is the username you use to log into Itch.io. The devtitle is your name or company name (it can contain spaces). The gameid is the Project URL value. The gametitle is the name of your game (it can contain spaces). The version can be any major.minor number format.

Building Your Game For Distribution

Open up the terminal and run this from the command line: 

./dragonruby-publish --only-package mygame

(if you're on Windows, don't put the "./" on the front. That's a Mac and Linux thing.)

A directory called ./build will be created that contains your binaries. You can upload this to Itch.io manually.

Browser Game Settings

For the HTML version of your game, after you upload the zip file, check the checkbox labeled This file will be played in the browser.

IMPORTANT: Be sure to set the Viewport dimensions to 1280x720 or your game will not be positioned correctly on your Itch.io page.

For subsequent updates you can use an automated deployment to Itch.io: 

./dragonruby-publish mygame

DragonRuby will package _and publish_ your game to itch.io! Tell your friends to go to your game's very own webpage and buy it!

If you make changes to your game, just re-run dragonruby-publish and it'll update the downloads for you.

Deploying To Mobile Devices

If you have a Pro subscription, you also have the capability to deploy to mobile devices.

To deploy to iOS, you need to have a Mac running MacOS Catalina, an iOS device, and an active/paid Developer Account with Apple. From the Console type: $wizards.ios.start and you will be guided through the deployment process.

To deploy to Android, you need to have an Android emulator/device, and an environment that is able to run Android SDK. dragonruby-publish will create an APK for you. From there, you can sign the APK and install it to your device. The signing and installation procedure varies from OS to OS. Here's an example of what the command might look like: 

> adb logcat -e mygame # you'll want to run this in a separate terminal
> keytool -genkey -v -keystore mygame.keystore -alias mygame -keyalg RSA -keysize 2048 -validity 10000
> apksigner sign --ks mygame.keystore mygame-android.apk
> adb install mygame-android.apk

DragonRuby's Philosophy

The following tenants of DragonRuby are what set us apart from other game engines. Given that Game Toolkit is a relatively new engine, there are definitely features that are missing. So having a big check list of "all the cool things" is not this engine's forte. This is compensated with a strong commitment to the following principles.

Challenge The Status Quo

Game engines of today are in a local maximum and don't take into consideration the challenges of this day and age. Unity and GameMaker specifically rot your brain. It's not sufficient to say:

But that's how we've always done it.

It's a hard pill to swallow, but forget blindly accepted best practices and try to figure out the underlying motivation for a specific approach to game development. Collaborate with us.

Continuity of Design

There is a programming idiom in software called "The Pit of Success". The term normalizes upfront pain as a necessity/requirement in the hopes that the investment will yield dividends "when you become successful" or "when the code becomes more complicated". This approach to development is strongly discouraged by us. It leads to over-architected and unnecessary code; creates barriers to rapid prototyping and shipping a game; and overwhelms beginners who are new to the engine or programming in general.

DragonRuby's philosophy is to provide multiple options across the "make it fast" vs "make it right" spectrum, with incremental/intuitive transitions between the options provided. A concrete example of this philosophy would be render primitives: the spectrum of options allows renderable constructs that take the form of tuples/arrays (easy to pickup, simple, and fast to code/prototype with), hashes (a little more work, but gives you the ability to add additional properties), open and strict entities (more work than hashes, but yields cleaner apis), and finally - if you really need full power/flexibility in rendering - classes (which take the most amount of code and programming knowledge to create).

Release Early and Often

The biggest mistake game devs make is spending too much time in isolation building their game. Release something, however small, and release it soon.

Stop worrying about everything being pixel perfect. Don't wait until your game is 100% complete. Build your game publicly and iterate. Post in the #show-and-tell channel in the community Discord. You'll find a lot of support and encouragement there.

Real artists ship. Remember that.

Sustainable And Ethical Monetization

We all aspire to put food on the table doing what we love. Whether it is building games, writing tools to support game development, or anything in between.

Charge a fair amount of money for the things you create. It's expected and encouraged within the community. Give what you create away for free to those that can't afford it.

If you are gainfully employed, pay full price for the things you use. If you do end up getting something at a discount, pay the difference "forward" to someone else.

Sustainable And Ethical Open Source

This goes hand in hand with sustainable and ethical monetization. The current state of open source is not sustainable. There is an immense amount of contributor burnout. Users of open source expect everything to be free, and few give back. This is a problem we want to fix (we're still trying to figure out the best solution).

So, don't be "that guy" in the Discord that says "DragonRuby should be free and open source!" You will be personally flogged by Amir.

People Over Entities

We prioritize the endorsement of real people over faceless entities. This game engine, and other products we create, are not insignificant line items of a large company. And you aren't a generic "commodity" or "corporate resource". So be active in the community Discord and you'll reap the benefits as more devs use DragonRuby.

Building A Game Should Be Fun And Bring Happiness

We will prioritize the removal of pain. The aesthetics of Ruby make it such a joy to work with, and we want to capture that within the engine.

Real World Application Drives Features

We are bombarded by marketing speak day in and day out. We don't do that here. There are things that are really great in the engine, and things that need a lot of work. Collaborate with us so we can help you reach your goals. Ask for features you actually need as opposed to anything speculative.

We want DragonRuby to *actually* help you build the game you want to build (as opposed to sell you something piece of demoware that doesn't work).

Frequently Asked Questions, Comments, and Concerns

Here are questions, comments, and concerns that frequently come up.

Frequently Asked Questions

What is DragonRuby LLP?

DragonRuby LLP is a partnership of four devs who came together with the goal of bringing the aesthetics and joy of Ruby, everywhere possible.

Under DragonRuby LLP, we offer a number of products (with more on the way):

All of the products above leverage a shared core called DragonRuby.

NOTE: From an official branding standpoint each one of the products is suffixed with "A DragonRuby LLP Product" tagline. Also, DragonRuby is _one word, title cased_.

NOTE: We leave the "A DragonRuby LLP Product" off of this one because that just sounds really weird.

NOTE: Devs who use DragonRuby are "Dragon Riders/Riders of Dragons". That's a bad ass identifier huh?

What is DragonRuby?

The response to this question requires a few subparts. First we need to clarify some terms. Specifically _language specification_ vs _runtime_.

Okay... so what is the difference between a language specification and a runtime?

A runtime is an _implementation_ of a language specification. When people say "Ruby," they are usually referring to "the Ruby 3.0+ language specification implemented via the CRuby/MRI Runtime."

But, there are many Ruby Runtimes: CRuby/MRI, JRuby, Truffle, Rubinius, Artichoke, and (last but certainly not least) DragonRuby.

Okay... what language specification does DragonRuby use then?

DragonRuby's goal is to be compliant with the ISO/IEC 30170:2012 standard. It's syntax is Ruby 2.x compatible, but also contains semantic changes that help it natively interface with platform specific libraries.

So... why another runtime?

The elevator pitch is:

DragonRuby is a Multilevel Cross-platform Runtime. The "multiple levels" within the runtime allows us to target platforms no other Ruby can target: PC, Mac, Linux, Raspberry Pi, WASM, iOS, Android, Nintendo Switch, PS4, Xbox, and Stadia.

What does Multilevel Cross-platform mean?

There are complexities associated with targeting all the platforms we support. Because of this, the runtime had to be architected in such a way that new platforms could be easily added (which lead to us partitioning the runtime internally):

Levels 1 through 3 are fairly commonplace in many runtime implementations (with level 1 being the most portable, and level 3 being the fastest). But the DragonRuby Runtime has taken things a bit further:

These levels allow us to stay up to date with open source implementations of Ruby; provide fast, native code execution on proprietary platforms; ensure good separation between these two worlds; and provides a means to add new platforms without going insane.

Cool cool. So given that I understand everything to this point, can we answer the original question? What is DragonRuby?

DragonRuby is a Ruby runtime implementation that takes all the lessons we've learned from MRI/CRuby, and merges it with the latest and greatest compiler and OSS technologies.

How is DragonRuby different than MRI?

DragonRuby supports a subset of MRI apis. Our target is to support all of mRuby's standard lib. There are challenges to this given the number of platforms we are trying to support (specifically console).

Does DragonRuby support Gems?

DragonRuby does not support gems because that requires the installation of MRI Ruby on the developer's machine (which is a non-starter given that we want DragonRuby to be a zero dependency runtime). While this seems easy for Mac and Linux, it is much harder on Windows and Raspberry Pi. mRuby has taken the approach of having a git repository for compatible gems and we will most likely follow suite: https://github.com/mruby/mgem-list.

Does DragonRuby have a REPL/IRB?

You can use DragonRuby's Console within the game to inspect object and execute small pieces of code. For more complex pieces of code create a file called repl.rb and put it in mygame/app/repl.rb: 

repl do
  puts "hello world"
  puts 1 + 1
end

4. To ignore code in repl.rb, instead of commenting it out, prefix repl with the letter x and it'll be ignored. 

xrepl do # <------- line is prefixed with an "x"
  puts "hello world"
  puts 1 + 1
end

# This code will be executed when you save the file.
repl do
  puts "Hello"
end

repl do
  puts "This code will also be executed."
end

# use xrepl to "comment out" code
xrepl do
  puts "This code will not be executed because of the x in front of repl".
end

Does DragonRuby support pry or have any other debugging facilities?

pry is a gem that assumes you are using the MRI Runtime (which is incompatible with DragonRuby). Eventually DragonRuby will have a pry based experience that is compatible with a debugging infrastructure called LLDB. Take the time to read about LLDB as it shows the challenges in creating something that is compatible.

You can use DragonRuby's replay capabilities to troubleshoot:

  1. DragonRuby is hot loaded which gives you a very fast feedback loop (if the game throws an exception, it's because of the code you just added).
  2. Use ./dragonruby mygame --record to create a game play recording that you can use to find the exception (you can replay a recording by executing ./dragonruby mygame --replay last_replay.txt or through the DragonRuby Console using $gtk.recording.start_replay "last_replay.txt".
  3. DragonRuby also ships with a unit testing facility. You can invoke the following command to run a test: ./dragonruby . --eval some_ruby_file.rb --no-tick.
  4. Get into the habit of adding debugging facilities within the game itself. You can add drawing primitives to args.outputs.debug that will render on top of your game but will be ignored in a production release.
  5. Debugging something that runs at 60fps is (imo) not that helpful. The exception you are seeing could have been because of a change that occurred many frames ago.

Frequent Comments About Ruby as a Language Choice

But Ruby is dead.

Let's check the official source for the answer to this question: isrubydead.com: https://isrubydead.com/.

On a more serious note, Ruby's _quantity_ levels aren't what they used to be. And that's totally fine. Everyone chases the new and shiny.

What really matters is _quality/maturity_. Here's a StackOverflow Survey sorted by highest paid developers: https://insights.stackoverflow.com/survey/2021#section-top-paying-technologies-top-paying-technologies.

Let's stop making this comment shall we?

But Ruby is slow.

That doesn't make any sense. A language specification can't be slow... it's a language spec. Sure, an _implementation/runtime_ can be slow though, but then we'd have to talk about which runtime.

Here's a some quick demonstrations of how well DragonRuby Game Toolkit Performs:

Dynamic languages are slow.

They are certainly slower than statically compiled languages. With the processing power and compiler optimizations we have today, dynamic languages like Ruby are _fast enough_.

Unless you are writing in some form of intermediate representation by hand, your language of choice also suffers this same fallacy of slow. Like, nothing is faster than a low level assembly-like language. So unless you're writing in that, let's stop making this comment.

NOTE: If you _are_ hand writing LLVM IR, we are always open to bringing on new partners with such a skill set. Email us ^_^.

Frequent Concerns

DragonRuby is not open source. That's not right.

The current state of open source is unsustainable. Contributors work for free, most all open source repositories are severely under-staffed, and burnout from core members is rampant.

We believe in open source very strongly. Parts of DragonRuby are in fact, open source. Just not all of it (for legal reasons, and because the IP we've created has value). And we promise that we are looking for (or creating) ways to _sustainably_ open source everything we do.

If you have ideas on how we can do this, email us!

If the reason above isn't sufficient, then definitely use something else.

All this being said, we do have parts of the engine open sourced on GitHub: https://github.com/dragonruby/dragonruby-game-toolkit-contrib/

DragonRuby is for pay. You should offer a free version.

If you can afford to pay for DragonRuby, you should (and will). We don't go around telling writers that they should give us their books for free, and only require payment if we read the entire thing. It's time we stop asking that of software products.

That being said, we will _never_ put someone out financially. We have income assistance for anyone that can't afford a license to any one of our products.

You qualify for a free, unrestricted license to DragonRuby products if any of the following items pertain to you:

Just contact Amir at amir.rajan@dragonruby.org with a short explanation of your current situation and he'll set you up. No questions asked.

But still, you should offer a free version. So I can try it out and see if I like it.

You can try our web-based sandbox environment at http://fiddle.dragonruby.org. But it won't do the runtime justice. Or just come to our Discord Channel at http://discord.dragonruby.org and ask questions. We'd be happy to have a one on one video chat with you and show off all the cool stuff we're doing.

Seriously just buy it. Get a refund if you don't like it. We make it stupid easy to do so.

I still think you should do a free version. Think of all people who would give it a shot.

Free isn't a sustainable financial model. We don't want to spam your email. We don't want to collect usage data off of you either. We just want to provide quality toolchains to quality developers (as opposed to a large quantity of developers).

The people that pay for DragonRuby and make an effort to understand it are the ones we want to build a community around, partner with, and collaborate with. So having that small monetary wall deters entitled individuals that don't value the same things we do.

What if I build something with DragonRuby, but DragonRuby LLP becomes insolvent.

That won't happen if the development world stop asking for free stuff and non-trivially compensate open source developers. Look, we want to be able to work on the stuff we love, every day of our lives. And we'll go to great lengths to make that happen.

But, in the event that sad day comes, our partnership bylaws state that _all_ DragonRuby IP that can be legally open sourced, will be released under a permissive license.

RECIPIES:

How To Determine What Frame You Are On

There is a property on state called tick_count that is incremented by DragonRuby every time the tick method is called. The following code renders a label that displays the current tick_count. 

def tick args
  args.outputs.labels << [10, 670, "#{args.state.tick_count}"]
end

How To Get Current Framerate

Current framerate is a top level property on the Game Toolkit Runtime and is accessible via args.gtk.current_framerate. 

def tick args
  args.outputs.labels << [10, 710, "framerate: #{args.gtk.current_framerate.round}"]
end

How To Render A Sprite Using An Array

All file paths should use the forward slash / *not* backslash . Game Toolkit includes a number of sprites in the sprites folder (everything about your game is located in the mygame directory).

The following code renders a sprite with a width and height of 100 in the center of the screen.

args.outputs.sprites is used to render a sprite. 

def tick args
  args.outputs.sprites << [
    640 - 50,                 # X
    360 - 50,                 # Y
    100,                      # W
    100,                      # H
    'sprites/square-blue.png' # PATH
 ]
end

More Sprite Properties As An Array

Here are all the properties you can set on a sprite. 

def tick args
  args.outputs.sprites << [
    100,                       # X
    100,                       # Y
    32,                        # W
    64,                        # H
    'sprites/square-blue.png', # PATH
    0,                         # ANGLE
    255,                       # ALPHA
    0,                         # RED_SATURATION
    255,                       # GREEN_SATURATION
    0                          # BLUE_SATURATION
  ]
end

Different Sprite Representations

Using ordinal positioning can get a little unruly given so many properties you have control over.

You can represent a sprite as a Hash: 

def tick args
  args.outputs.sprites << {
    x: 640 - 50,
    y: 360 - 50,
    w: 100,
    h: 100,

    path: 'sprites/square-blue.png',
    angle: 0,

    a: 255,
    r: 255,
    g: 255,
    b: 255,

    # source_ properties have origin of bottom left
    source_x:  0,
    source_y:  0,
    source_w: -1,
    source_h: -1,

    # tile_ properties have origin of top left
    tile_x:  0,
    tile_y:  0,
    tile_w: -1,
    tile_h: -1,

    flip_vertically: false,
    flip_horizontally: false,

    angle_anchor_x: 0.5,
    angle_anchor_y: 1.0,

    blendmode_enum: 1
  }
end

The blendmode_enum value can be set to 0 (no blending), 1 (alpha blending), 2 (additive blending), 3 (modulo blending), 4 (multiply blending).

You can represent a sprite as an object: 

# Create type with ALL sprite properties AND primitive_marker
class Sprite
  attr_accessor :x, :y, :w, :h, :path, :angle, :a, :r, :g, :b,
                :source_x, :source_y, :source_w, :source_h,
                :tile_x, :tile_y, :tile_w, :tile_h,
                :flip_horizontally, :flip_vertically,
                :angle_anchor_x, :angle_anchor_y, :blendmode_enum

  def primitive_marker
    :sprite
  end
end

class BlueSquare < Sprite
  def initialize opts
    @x = opts[:x]
    @y = opts[:y]
    @w = opts[:w]
    @h = opts[:h]
    @path = 'sprites/square-blue.png'
  end
end

def tick args
  args.outputs.sprites << (BlueSquare.new x: 640 - 50,
                                          y: 360 - 50,
                                          w: 50,
                                          h: 50)
end

How To Render A Label

args.outputs.labels is used to render labels.

Labels are how you display text. This code will go directly inside of the def tick args method.

Here is the minimum code: 

def tick args
  #                       X    Y    TEXT
  args.outputs.labels << [640, 360, "I am a black label."]
end

A Colored Label

def tick args
  # A colored label
  #                       X    Y    TEXT,                   RED    GREEN  BLUE  ALPHA
  args.outputs.labels << [640, 360, "I am a redish label.", 255,     128,  128,   255]
end

Extended Label Properties

def tick args
  # A colored label
  #                       X    Y     TEXT           SIZE  ALIGNMENT  RED  GREEN  BLUE  ALPHA  FONT FILE
  args.outputs.labels << [
    640,                   # X
    360,                   # Y
    "Hello world",         # TEXT
    0,                     # SIZE_ENUM
    1,                     # ALIGNMENT_ENUM
    0,                     # RED
    0,                     # GREEN
    0,                     # BLUE
    255,                   # ALPHA
    "fonts/coolfont.ttf"   # FONT
  ]
end

A SIZE_ENUM of 0 represents "default size". A negative value will decrease the label size. A positive value will increase the label's size.

An ALIGNMENT_ENUM of 0 represents "left aligned". 1 represents "center aligned". 2 represents "right aligned".

Rendering A Label As A Hash

You can add additional metadata about your game within a label, which requires you to use a `Hash` instead. 

def tick args
  args.outputs.labels << {
    x:                       200,
    y:                       550,
    text:                    "dragonruby",
    size_enum:               2,
    alignment_enum:          1,
    r:                       155,
    g:                       50,
    b:                       50,
    a:                       255,
    font:                    "fonts/manaspc.ttf",
    vertical_alignment_enum: 0, # 0 is bottom, 1 is middle, 2 is top
    # You can add any properties you like (this will be ignored/won't cause errors)
    game_data_one:  "Something",
    game_data_two: {
       value_1: "value",
       value_2: "value two",
       a_number: 15
    }
  }
end

Getting The Size Of A Piece Of Text

You can get the render size of any string using args.gtk.calcstringbox. 

def tick args
  #                             TEXT           SIZE_ENUM  FONT
  w, h = args.gtk.calcstringbox("some string",         0, "font.ttf")

  # NOTE: The SIZE_ENUM and FONT are optional arguments.

  # Render a label showing the w and h of the text:
  args.outputs.labels << [
    10,
    710,
    # This string uses Ruby's string interpolation literal: #{}
    "'some string' has width: #{w}, and height: #{h}."
  ]
end

Rendering Labels With New Line Characters And Wrapping

You can use a strategy like the following to create multiple labels from a String. 

def tick args
  long_string = "Lorem ipsum dolor sit amet, consectetur adipiscing elitteger dolor velit, ultricies vitae libero vel, aliquam imperdiet enim."
  max_character_length = 30
  long_strings_split = args.string.wrapped_lines long_string, max_character_length
  args.outputs.labels << long_strings_split.map_with_index do |s, i|
    { x: 10, y: 600 - (i * 20), text: s }
  end
end

How To Play A Sound

Sounds that end .wav will play once: 

def tick args
  # Play a sound every second
  if (args.state.tick_count % 60) == 0
    args.outputs.sounds << 'something.wav'
  end
end

Sounds that end .ogg is considered background music and will loop: 

def tick args
  # Start a sound loop at the beginning of the game
  if args.state.tick_count == 0
    args.outputs.sounds << 'background_music.ogg'
  end
end

If you want to play a .ogg once as if it were a sound effect, you can do: 

def tick args
  # Play a sound every second
  if (args.state.tick_count % 60) == 0
    args.gtk.queue_sound 'some-ogg.ogg'
  end
end

Using args.state To Store Your Game State

args.state is a open data structure that allows you to define properties that are arbitrarily nested. You don't need to define any kind of class.

To initialize your game state, use the ||= operator. Any value on the right side of ||= will only be assigned _once_.

To assign a value every frame, just use the = operator, but _make sure_ you've initialized a default value. 

def tick args
  # initialize your game state ONCE
  args.state.player.x  ||= 0
  args.state.player.y  ||= 0
  args.state.player.hp ||= 100

  # increment the x position of the character by one every frame
  args.state.player.x += 1

  # Render a sprite with a label above the sprite
  args.outputs.sprites << [
    args.state.player.x,
    args.state.player.y,
    32, 32,
    "player.png"
  ]

  args.outputs.labels << [
    args.state.player.x,
    args.state.player.y - 50,
    args.state.player.hp
  ]
end

Accessing files

DragonRuby uses a sandboxed filesystem which will automatically read from and write to a location appropriate for your platform so you don't have to worry about theses details in your code. You can just use gtk.read_file, gtk.write_file, and gtk.append_file with a relative path and the engine will take care of the rest.

The data directories that will be written to in a production build are:

The values in square brackets are the values you set in your app/metadata/game_metadata.txt file.

When reading files, the engine will first look in the game's data directory and then in the game directory itself. This means that if you write a file to the data directory that already exists in your game directory, the file in the data directory will be used instead of the one that is in your game.

When running a development build you will directly write to your game directory (and thus overwrite existing files). This can be useful for built-in development tools like level editors.

For more details on the implementation of the sandboxed filesystem, see Ryan C. Gordon's PhysicsFS documentation: https://icculus.org/physfs/

Troubleshoot Performance

  1. If you're using Arrays for your primitives (args.outputs.sprites << []), use Hash instead (args.outputs.sprites << { x: ... }).
  2. If you're using Entity for your primitives (args.outputs.sprites << args.state.new_entity), use StrictEntity instead (args.outputs.sprites << args.state.new_entity_strict).
  3. Use .each instead of .map if you don't care about the return value.
  4. When concatenating primitives to outputs, do them in bulk. Instead of:
args.state.bullets.each do |bullet|
  args.outputs.sprites << bullet.sprite
end

do 

args.outputs.sprites << args.state.bullets.map do |b|
  b.sprite
end

5. Use args.outputs.static_ variant for things that don't change often (take a look at the Basic Gorillas sample app and Dueling Starships sample app to see how static_ is leveraged.

6. Consider using a render_target if you're doing some form of a camera that moves a lot of primitives (take a look at the Render Target sample apps for more info).

Runtime

The GTK::Runtime class is the core of DragonRuby. It is globally accessible via $gtk or inside of the tick method through args. 

def tick args
  args.gtk # accessible like this
  $gtk # or like this
end

get_pixels

Given a file_path to a sprite, this function returns a one dimensional array of hexadecimal values representing the ARGB of each pixel in a sprite.

See the following sample app for a full demonstration of how to use this function: ./samples/07_advanced_rendering/06_pixel_arrays_from_file

dlopen

Loads a precompiled C Extension into your game.

See the sample apps at ./samples/12_c_extensions for detailed walkthroughs of creating C extensions.

calcstringbox

Returns the render width and render height as a tuple for a piece of text. The parameters this method takes are: 

def tick args
  text = "a piece of text"
  size_enum = 5 # "large font size"

  # path is relative to your game directory (eg mygame/fonts/courier-new.ttf)
  font = "fonts/courier-new.ttf"

  # get the render width and height
  string_w, string_h = args.gtk.calcstringbox text, size_enum, font

  # render the label
  args.outputs.labels << {
    x: 100,
    y: 100,
    text: text,
    size_enum: size_enum,
    font: font
  }

  # render a border around the label based on the results from calcstringbox
  args.outputs.borders << {
    x: 100,
    y: 100,
    w: string_w,
    h: string_h,
    r: 0,
    g: 0,
    b: 0
  }
end

request_quit

Call this function to exit your game. You will be given one additional tick if you need to perform any housekeeping before that game closes. 

def tick args
  # exit the game after 600 frames (10 seconds)
  if args.state.tick_count == 600
    args.gtk.request_quit
  end
end

quit_requested?

This function will return true if the game is about to exit (either from the user closing the game or if request_quit was invoked).

set_window_fullscreen

This function takes in a single boolean parameter. true to make the game fullscreen, false to return the game back to windowed mode. 

def tick args
  # make the game full screen after 600 frames (10 seconds)
  if args.state.tick_count == 600
    args.gtk.set_window_fullscreen true
  end

  # return the game to windowed mode after 20 seconds
  if args.state.tick_count == 1200
    args.gtk.set_window_fullscreen false
  end
end

window_fullscreen?

Returns true if the window is currently in fullscreen mode.

platform?

You can ask DragonRuby which platform your game is currently being run on. This can be useful if you want to perform different pieces of logic based on where the game is running.

The raw platform string value is available via args.gtk.platform which takes in a symbol representing the platform's categorization/mapping.

You can see all available platform categorizations via the args.gtk.platform_mappings function.

Here's an example of how to use args.gtk.platform? category_symbol: 

def tick args
  if    args.gtk.platform? :macos
    args.outputs.labels << { x: 640, y: 360,
                             text: "I am running on MacOS.", alignment_enum: 1 }
  elsif args.gtk.platform? :win
    args.outputs.labels << { x: 640, y: 360,
                             text: "I am running on Windows.", alignment_enum: 1 }
  elsif args.gtk.platform? :linux
    args.outputs.labels << { x: 640, y: 360,
                             text: "I am running on Linux.", alignment_enum: 1 }
  elsif args.gtk.platform? :web
    args.outputs.labels << { x: 640, y: 360,
                             text: "I am running on a web page.", alignment_enum: 1 }
  elsif args.gtk.platform? :android
    args.outputs.labels << { x: 640, y: 360,
                             text: "I am running on Android.", alignment_enum: 1 }
  elsif args.gtk.platform? :ios
    args.outputs.labels << { x: 640, y: 360,
                             text: "I am running on iOS.", alignment_enum: 1 }
  end
end

platform_mappings

These are the current platform categorizations (args.gtk.platform_mappings): 

{
  "Mac OS X"   => [:desktop, :macos, :osx, :mac, :macosx],
  "Windows"    => [:desktop, :windows, :win],
  "Linux"      => [:desktop, :linux, :nix],
  "Emscripten" => [:web,     :wasm, :html, :emscripten],
  "iOS"        => [:mobile,  :ios, ],
  "Android"    => [:mobile,  :android],
}

Given the mappings above, args.gtk.platform? :desktop would return true if the game is running on a player's computer irrespective of OS (MacOS, Linux, and Windows are all categorized as :desktop platforms).

open_url

Given a uri represented as a string. This fuction will open the uri in the user's default browser. 

def tick args
  # open a url after 600 frames (10 seconds)
  if args.state.tick_count == 600
    args.gtk.open_url "http://dragonruby.org"
  end
end

system

Given an OS dependent cli command represented as a string, this function executes the command and puts the results to the DragonRuby Console (returns nil). 

def tick args
  # execute ls on the current directory in 10 seconds
  if args.state.tick_count == 600
    args.gtk.system "ls ."
  end
end

exec

Given an OS dependent cli command represented as a string, this function executes the command and returns a string representing the results. 

def tick args
  # execute ls on the current directory in 10 seconds
  if args.state.tick_count == 600
    results = args.gtk.exec "ls ."
    puts "The results of the command are:"
    puts results
  end
end

show_cursor

Shows the mouse cursor.

hide_cursor

Hides the mouse cursor.

cursor_shown?

Returns true if the mouse cursor is visible.

set_mouse_grab

Takes in a numeric parameter representing the mouse grab mode.

set_system_cursor

Takes in a string value of "arrow", "ibeam", "wait", or "hand" and sets the mouse curosor to the corresponding system cursor (if available on the OS).

set_cursor

Replaces the mouse cursor with a sprite. Takes in a path to the sprite, and optionally an x and y value representing the realtive positioning the sprite will have to the mouse cursor. 

def tick args
  if args.state.tick_count == 0
    # assumes a sprite of size 80x80 and centers the sprite
    # relative to the cursor position.
    args.gtk.set_cursor "sprites/square/blue.png", 40, 40
  end
end

list_files

This function takes in one parameter. The parameter is the directory path and assumes the the game directory is the root. The method returns an Array of String representing all files within the directory. Use stat_file to determine whether a specific path is a file or a directory.

stat_file

This function takes in one parameter. The parameter is the file path and assumes the the game directory is the root. The method returns nil if the file doesn't exist otherwise it returns a Hash with the following information: 

# {
#   path: String,
#   file_size: Int,
#   mod_time: Int,
#   create_time: Int,
#   access_time: Int,
#   readonly: Boolean,
#   file_type: Symbol (:regular, :directory, :symlink, :other),
# }

def tick args
  if args.inputs.mouse.click
    args.gtk.write_file "last-mouse-click.txt", "Mouse was clicked at #{args.state.tick_count}."
  end

  file_info = args.gtk.stat_file "last-mouse-click.txt"

  if file_info
    args.outputs.labels << {
      x: 30,
      y: 30.from_top,
      text: file_info.to_s,
      size_enum: -3
    }
  else
    args.outputs.labels << {
      x: 30,
      y: 30.from_top,
      text: "file does not exist, click to create file",
      size_enum: -3
    }
  end
end

read_file

Given a file path, a string will be returned representing the contents of the file. nil will be returned if the file does not exist. You can use stat_file to get additional information of a file.

write_file

This function takes in two parameters. The first parameter is the file path and assumes the the game directory is the root. The second parameter is the string that will be written. The method **overwrites** whatever is currently in the file. Use append_file to append to the file as opposed to overwriting. 

def tick args
  if args.inputs.mouse.click
    args.gtk.write_file "last-mouse-click.txt", "Mouse was clicked at #{args.state.tick_count}."
  end
end

append_file

This function takes in two parameters. The first parameter is the file path and assumes the the game directory is the root. The second parameter is the string that will be written. The method appends to whatever is currently in the file (a new file is created if one does not alread exist). Use write_file to overwrite the file's contents as opposed to appending. 

def tick args
  if args.inputs.mouse.click
    args.gtk.write_file "last-mouse-click.txt", "Mouse was clicked at #{args.state.tick_count}."
  end
end

delete_file

This function takes in a single parameters. The parameter is the file path that should be deleted. This function will raise an exception if the path requesting to be deleted does not exist.

Notes:

Here is a list of reasons an exception could be raised:

- If the path is not found. - If the path is still open (for reading or writing). - If the path is not a file or directory. - If the path is a circular symlink. - If you do not have permissions to delete the path. - If the directory attempting to be deleted is not empty. 

def tick args
  if args.inputs.mouse.click
    args.gtk.write_file "last-mouse-click.txt", "Mouse was clicked at #{args.state.tick_count}."
  end
end

delete_file_if_exist

Has the same behavior as delete_file except this function does not throw an exception.

parse_json

Given a json string, this function returns a hash representing the json data. 

sh = args.gtk.parse_json '{ "name": "John Doe", "aliases": ["JD"] }'
structure of hash: { "name"=>"John Doe", "aliases"=>["JD"] }

parse_json_file

Same behavior as parse_json_file except a file path is read for the json string.

parse_xml

Given xml data as a string, this function will return a hash that represents the xml data in the following recursive structure: 

type: :element,
name: "Person",
children: [...]

parse_xml_file

Function has the same behavior as parse_xml except that the parameter must be a file path that contains xml contents.

http_get

Returns an object that represents an http response which will eventually have a value. This http_get method is invoked asynchronously. Check for completion before attempting to read results. 

def tick args
  # perform an http get and print the response when available
  args.state.result ||= args.gtk.http_get "https://httpbin.org/html"

  if args.state.result && args.state.result[:complete] && !args.state.printed
    if args.state.result[:http_response_code] == 200
      puts "The response was successful. The body is:"
      puts args.state.result[:response_data]
    else
      puts "The response failed. Status code:"
      puts args.state.result[:http_response_code]
    end
    # set a flag denoting that the response has been printed
    args.state.printed = true

    # show the console
    args.gtk.show_console
  end
end

http_post

Returns an object that represents an http response which will eventually have a value. This http_post method is invoked asynchronously. Check for completion before attempting to read results. 

def tick args
  # perform an http get and print the response when available

  args.state.form_fields ||= { "userId" => "#{Time.now.to_i}" }
  args.state.result ||= args.gtk.http_post "http://httpbin.org/post",
                                           form_fields,
                                           ["Content-Type: application/x-www-form-urlencoded"]


  if args.state.result && args.state.result[:complete] && !args.state.printed
    if args.state.result[:http_response_code] == 200
      puts "The response was successful. The body is:"
      puts args.state.result[:response_data]
    else
      puts "The response failed. Status code:"
      puts args.state.result[:http_response_code]
    end
    # set a flag denoting that the response has been printed
    args.state.printed = true

    # show the console
    args.gtk.show_console
  end
end

http_post_body

Returns an object that represents an http response which will eventually have a value. This http_post_body method is invoked asynchronously. Check for completion before attempting to read results. 

def tick args
  # perform an http get and print the response when available

  args.state.json ||= "{ "userId": "#{Time.now.to_i}"}"
  args.state.result ||= args.gtk.http_post_body "http://httpbin.org/post",
                                                args.state.json,
                                                ["Content-Type: application/json", "Content-Length: #{args.state.json.length}"]


  if args.state.result && args.state.result[:complete] && !args.state.printed
    if args.state.result[:http_response_code] == 200
      puts "The response was successful. The body is:"
      puts args.state.result[:response_data]
    else
      puts "The response failed. Status code:"
      puts args.state.result[:http_response_code]
    end
    # set a flag denoting that the response has been printed
    args.state.printed = true

    # show the console
    args.gtk.show_console
  end
end

start_server!

Starts a in-game http server that can be process http requests. When your game is running in development mode. A dev server is started at http://localhost:9001

You can start an in-game http server in production via: 

def tick args
  # server explicitly enabled in production
  args.gtk.start_server! port: 9001, enable_in_prod: true
end

Here's how you would responde to http requests: 

def tick args
  # server explicitly enabled in production
  args.gtk.start_server! port: 9001, enable_in_prod: true

  # loop through pending requests and respond to them
  args.inputs.http_requests.each do |request|
    puts "#{request}"
    request.respond 200, "ok"
  end
end

production?

Returns true if the game is being run in a released/shipped state.

version

Returns a string representing the version of DragonRuby you are running.

version_pro?

Returns true if the version of DragonRuby is NOT Standard Edition.

reset

Resets DragonRuby's internal state as if it were just started. args.state.tick_count is set to 0 and args.state is cleared of any values. This function is helpful when you are developing your game and want to reset everything as if the game just booted up. 

def tick args
end

# reset the game if this file is hotloaded/required
# (removes the need to press "r" when I file is updated)
$gtk.reset

NOTE: args.gtk.reset does not reset global variables or instance of classes you have have constructed.

reset_next_tick

Has the same behavior as reset except the reset occurs before tick is executed again. reset resets the environment immediately (while the tick method is inflight). It's recommended that reset should be called outside of the tick method (invoked when a file is saved/hotloaded), and reset_next_tick be used inside of the tick method so you don't accidentally blow away state the your game depends on to complete the current tick without exceptions. 

def tick args
  # reset the game if "r" is pressed on the keyboard
  if args.inputs.keyboard.key_down.r
    args.gtk.reset_next_tick # use reset_next_tick instead of reset
  end
end

# reset the game if this file is hotloaded/required
# (removes the need to press "r" when I file is updated)
$gtk.reset

reset_sprite

Sprites when loaded are cached. This method invalidates the cache record of a sprite so that updates on from the disk can be loaded.

calcspritebox

Given a path to a sprite, this method returns the width and height of a sprite as a tuple.

NOTE: This method should be used for development purposes only and is expensive to call every frame. Do not use this method to set the size of sprite when rendering (hard code those values since you know what they are beforehand).

current_framerate

Returns a float value representing the framerate of your game. This is an approximation/moving average of your framerate and should eventually settle to 60fps. 

def tick args
  # render a label to the screen that shows the current framerate
  # formatted as a floating point number with two decimal places
  args.outputs.labels << { x: 30, y: 30.from_top, text: "#{args.gtk.current_framerate.to_sf}" }
end

framerate_diagnostics_primitives

Returns a set of primitives that can be rendered to the screen which provide more detailed information about the speed of your simulation (framerate, draw call count, mouse position, etc). 

def tick args
  args.outputs.primitives << args.gtk.framerate_diagnostics_primitives
end

warn_array_primitives!

This function helps you audit your game of usages of array-based primitives. While array-based primitives are simple to create and use, they are slower to process than Hash or Class based primitives. 

def tick args
  # enable array based primitives warnings
  args.gtk.warn_array_primitives!

  # array-based primitive elsewhere in code
  # an log message will be posted giving the location of the array
  # based primitive usage
  args.outputs.sprites << [100, 100, 200, 200, "sprites/square/blue.png"]

  # instead of using array based primitives, migrate to hashes as needed
  args.outputs.sprites << {
    x: 100,
    y: 100,
    w: 200,
    h: 200, path:
    "sprites/square/blue.png"
  }
end

benchmark

You can use this function to compare the relative performance of methods. 

def tick args
  # press r to run benchmark
  if args.inputs.keyboard.key_down.r
    args.gtk.console.show
    args.gtk.benchmark iterations: 1000, # number of iterations
                       # label for experiment
                       using_numeric_map: -> () {
                         # experiment body
                         v = 100.map_with_index do |i|
                           i * 100
                         end
                       },
                       # label for experiment
                       using_numeric_times: -> () {
                         # experiment body
                         v = []
                         100.times do |i|
                           v << i * 100
                         end
                       }
  end
end

notify!

Given a string, this function will present a message at the bottom of your game. This method is only invoked in dev mode and is useful for debugging.

An optional parameter of duration (number value representing ticks) can also be passed in. The default value if 300 ticks (5 seconds). 

def tick args
  if args.inputs.mouse.click
    args.gtk.notify! "Mouse was clicked!"
  end

  if args.inputs.keyboard.key_down.r
    # optional duration parameter
    args.gtk.notify! "R key was pressed!", 600 # present message for 10 seconds/600 frames
  end
end

notify_extended!

Has similar behavior as notify! except you have additional options to show messages in a production environment. 

def tick args
  if args.inputs.mouse.click
    args.gtk.notify_extended! message: "message",
                              duration: 300,
                              env: :prod
  end
end

slowmo!

Given a numeric value representing the factor of 60fps. This function will bring your simulation loop down to slower rate. This method is intended to be used for debugging purposes. 

def tick args
  # set your simulation speed to (15 fps): args.gtk.slowmo! 4
  # set your simulation speed to (1 fps): args.gtk.slowmo! 60
  # set your simulation speed to (30 fps):
  args.gtk.slowmo! 2
end

Remove this line from your tick method will automatically set your simulation speed back to 60 fps.

show_console

Shows the DragonRuby console. Useful when debugging/customizing an in-game dev workflow.

hide_console

Shows the DragonRuby console. Useful when debugging/customizing an in-game dev workflow.

enable_console

Enables the DragonRuby Console so that it can be presented by pressing the tilde key (the key next to the number 1 key).

disable_console

Disables the DragonRuby Console so that it won't show up even if you press the tilde key or call args.gtk.show_console.

start_recording

Resets the game to tick 0 and starts recording gameplay. Useful for visual regression tests/verification.

stop_recording

Function takes in a destination file for the currently recording gameplay. This file can be used to replay a recording.

cancel_recording

Function cancels a gameplay recording session and discards the replay.

start_replay

Given a file that represents a recording, this method will run the recording against the current codebase.

You can start a replay from the command line also: 

first argument: the game directory
--replay switch is the file path relative to the game directory
--speed switch is optional. a value of 4 will run the replay and game at 4x speed
cli command example is in the context of Linux and Mac, for Windows the binary would be ./dragonruby.exe
dragonruby ./mygame --replay ./replay.txt --speed 4

stop_replay

Function stops a replay that is currently executing.

get_base_dir

Returns the path to the location of the dragonruby binary. In production mode, this value will be the same as the value returned by get_game_dir. Function should only be used for debugging/development workflows.

get_game_dir

Returns the location within sandbox storage that the game is running. When developing your game, this value will be your mygame directory. In production, it'll return a value that is OS specific (eg the Roaming directory on Windows or the Application Support directory on Mac).

Invocations of ~(write|append)_file will write to this sandboxed directory.

get_game_dir_url

Returns a url encoded string representing the sandbox location for game data.

open_game_dir

Opens the game directory in the OS's file explorer. This should be used for debugging purposes only.

write_file_root

Given a file path and contents, the contents will be written to a directory outside of the game directory. This method should be used for development purposes only. In production this method will write to the same sandboxed location as write_file.

append_file_root

Has the same behavior as write_file_root except that it appends the contents as opposed to overwriting them.

argv

Returns a string representing the command line arguments passed to the DragonRuby binary. This should be used for development/debugging purposes only.

cli_arguments

Returns a Hash for command line arguments in the format of --switch value (two hyphens preceding the switch flag with the value seperated by a space). This should be used for development/debugging purposes only.

reload_history

Returns a Hash representing the code files that have be loaded for your game along with timings for the events. This should be used for development/debugging purposes only.

reload_history_pending

Returns a Hash for files that have been queued for reload, but haven't been processed yet. This should be used for development/debugging purposes only.

reload_if_needed

Given a file name, this function will queue the file for reload if it's been modified. An optional second parameter can be passed in to signify if the file should be forced loaded regardless of modified time (true means to force load, false means to load only if the file has been modified). This function should be used for development/debugging purposes only.

args.state

Store your game state inside of this state. Properties with arbitrary nesting is allowed and a backing Entity will be created on your behalf. 

def tick args
  args.state.player.x ||= 0
  args.state.player.y ||= 0
end

args.state.*.entity_id

Entities automatically receive an entity_id of type Fixnum.

args.state.*.entity_type

Entities can have an entity_type which is represented as a Symbol.

args.state.*.created_at

Entities have created_at set to args.state.tick_count when they are created.

args.state.*.created_at_elapsed

Returns the elapsed number of ticks since creation.

args.state.*.global_created_at

Entities have global_created_at set to Kernel.global_tick_count when they are created.

args.state.*.global_created_at_elapsed

Returns the elapsed number of global ticks since creation.

args.state.*.as_hash

Entity cast to a Hash so you can update values as if you were updating a Hash.

args.state.new_entity

Creates a new Entity with a type, and initial properties. An option block can be passed to change the newly created entity: 

def tick args
  args.state.player ||= args.state.new_entity :player, x: 0, y: 0 do |e|
    e.max_hp = 100
    e.hp     = e.max_hp * rand
  end
end

args.state.new_entity_strict

Creates a new Strict Entity. While Entities created via args.state.new_entity can have new properties added later on, Entities created using args.state.new_entity must define all properties that are allowed during its initialization. Attempting to add new properties after initialization will result in an exception.

args.state.tick_count

Returns the current tick of the game. args.state.tick_count is 0 when the game is first started or if the game is reset via $gtk.reset.

args.inputs

Access using input using args.inputs.

args.inputs.up

Returns true if: the up arrow or w key is pressed or held on the keyboard; or if up is pressed or held on controller_one; or if the left_analog on controller_one is tilted upwards.

args.inputs.down

Returns true if: the down arrow or s key is pressed or held on the keyboard; or if down is pressed or held on controller_one; or if the left_analog on controller_one is tilted downwards.

args.inputs.left

Returns true if: the left arrow or a key is pressed or held on the keyboard; or if left is pressed or held on controller_one; or if the left_analog on controller_one is tilted to the left.

args.inputs.right

Returns true if: the right arrow or d key is pressed or held on the keyboard; or if right is pressed or held on controller_one; or if the left_analog on controller_one is tilted to the right.

args.inputs.left_right

Returns -1 (left), 0 (neutral), or +1 (right) depending on results of args.inputs.left and args.inputs.right. 

args.state.player[:x] += args.inputs.left_right * args.state.speed

args.inputs.up_down

Returns -1 (down), 0 (neutral), or +1 (up) depending on results of args.inputs.down and args.inputs.up. 

args.state.player[:y] += args.inputs.up_down * args.state.speed

args.inputs.text OR args.inputs.history

Returns a string that represents the last key that was pressed on the keyboard.

args.inputs.mouse

Represents the user's mouse.

args.inputs.mouse.has_focus

Return's true if the game has mouse focus.

args.inputs.mouse.x

Returns the current x location of the mouse.

args.inputs.mouse.y

Returns the current y location of the mouse.

args.inputs.mouse.inside_rect? rect

Return. args.inputs.mouse.inside_rect? takes in any primitive that responds to x, y, w, h:

args.inputs.mouse.inside_circle? center_point, radius

Returns true if the mouse is inside of a specified circle. args.inputs.mouse.inside_circle? takes in any primitive that responds to x, y (which represents the circle's center), and takes in a radius:

args.inputs.mouse.moved

Returns true if the mouse has moved on the current frame.

args.inputs.mouse.button_left

Returns true if the left mouse button is down.

args.inputs.mouse.button_middle

Returns true if the middle mouse button is down.

args.inputs.mouse.button_right

Returns true if the right mouse button is down.

args.inputs.mouse.button_bits

Returns a bitmask for all buttons on the mouse: 1 for a button in the down state, 0 for a button in the up state.

args.inputs.mouse.wheel

Represents the mouse wheel. Returns nil if no mouse wheel actions occurred.

args.inputs.mouse.wheel.x

Returns the negative or positive number if the mouse wheel has changed in the x axis.

args.inputs.mouse.wheel.y

Returns the negative or positive number if the mouse wheel has changed in the y axis.

args.inputs.mouse.click OR .down, .previous_click, .up

The properties args.inputs.mouse.(click|down|previous_click|up) each return nil if the mouse button event didn't occur. And return an Entity that has an x, y properties along with helper functions to determine collision: inside_rect?, inside_circle.

args.inputs.controller_(one-four)

Represents controllers connected to the usb ports.

args.inputs.controller_(one-four).up

Returns true if up is pressed or held on the directional or left analog.

args.inputs.controller_(one-four).down

Returns true if down is pressed or held on the directional or left analog.

args.inputs.controller_(one-four).left

Returns true if left is pressed or held on the directional or left analog.

args.inputs.controller_(one-four).right

Returns true if right is pressed or held on the directional or left analog.

args.inputs.controller_(one-four).left_right

Returns -1 (left), 0 (neutral), or +1 (right) depending on results of args.inputs.controller_(one-four).left and args.inputs.controller_(one-four).right.

args.inputs.controller_(one-four).up_down

Returns -1 (down), 0 (neutral), or +1 (up) depending on results of args.inputs.controller_(one-four).up and args.inputs.controller_(one-four).down.

args.inputs.controller_(one-four).(left_analog_x_raw|right_analog_x_raw)

Returns the raw integer value for the analog's horizontal movement (-32,000 to +32,000).

args.inputs.controller_(one-four).left_analog_y_raw|right_analog_y_raw)

Returns the raw integer value for the analog's vertical movement (-32,000 to +32,000).

args.inputs.controller_(one-four).left_analog_x_perc|right_analog_x_perc)

Returns a number between -1 and 1 which represents the percentage the analog is moved horizontally as a ratio of the maximum horizontal movement.

args.inputs.controller_(one-four).left_analog_y_perc|right_analog_y_perc)

Returns a number between -1 and 1 which represents the percentage the analog is moved vertically as a ratio of the maximum vertical movement.

args.inputs.controller_(one-four).directional_up

Returns true if up is pressed or held on the directional.

args.inputs.controller_(one-four).directional_down

Returns true if down is pressed or held on the directional.

args.inputs.controller_(one-four).directional_left

Returns true if left is pressed or held on the directional.

args.inputs.controller_(one-four).directional_right

Returns true if right is pressed or held on the directional.

args.inputs.controller_(one-four).(a|b|x|y|l1|r1|l2|r2|l3|r3|start|select)

Returns true if the specific button is pressed or held.

args.inputs.controller_(one-four).truthy_keys

Returns a collection of Symbols that represent all keys that are in the pressed or held state.

args.inputs.controller_(one-four).key_down

Returns true if the specific button was pressed on this frame. args.inputs.controller_(one-four).key_down.BUTTON will only be true on the frame it was pressed.

args.inputs.controller_(one-four).key_held

Returns true if the specific button is being held. args.inputs.controller_(one-four).key_held.BUTTON will be true for all frames after key_down (until released).

args.inputs.controller_(one-four).key_up

Returns true if the specific button was released. args.inputs.controller_(one-four).key_up.BUTTON will be true only on the frame the button was released.

args.inputs.keyboard

Represents the user's keyboard

args.inputs.keyboard.has_focus

Returns true if the game has keyboard focus.

args.inputs.keyboard.up

Returns true if up or w is pressed or held on the keyboard.

args.inputs.keyboard.down

Returns true if down or s is pressed or held on the keyboard.

args.inputs.keyboard.left

Returns true if left or a is pressed or held on the keyboard.

args.inputs.keyboard.right

Returns true if right or d is pressed or held on the keyboard.

args.inputs.keyboard.left_right

Returns -1 (left), 0 (neutral), or +1 (right) depending on results of args.inputs.keyboard.left and args.inputs.keyboard.right.

args.inputs.keyboard.up_down

Returns -1 (left), 0 (neutral), or +1 (right) depending on results of args.inputs.keyboard.up and args.inputs.keyboard.up.

keyboard properties

The following properties represent keys on the keyboard and are available on args.inputs.keyboard.KEY, args.inputs.keyboard.key_down.KEY, args.inputs.keyboard.key_held.KEY, and args.inputs.keyboard.key_up.KEY:

inputs.keyboard.keys

Returns a Hash with all keys on the keyboard in their respective state. The Hash contains the following keys

args.inputs.touch

Returns a Hash representing all touch points on a touch device. This api is only available in Indie, and Pro versions.

args.inputs.finger_left

Returns a Hash with x and y denoting a touch point that is on the left side of the screen. This api is only available in Indie, and Pro versions.

args.inputs.finger_right

Returns a Hash with x and y denoting a touch point that is on the right side of the screen. This api is only available in Indie, and Pro versions.

args.outputs

Outputs is how you render primitives to the screen. The minimal setup for rendering something to the screen is via a tick method defined in mygame/app/main.rb 

def tick args
  args.outputs.solids     << [0, 0, 100, 100]
  args.outputs.sprites    << [100, 100, 100, 100, "sprites/square/blue.png"]
  args.outputs.labels     << [200, 200, "Hello World"]
  args.outputs.lines      << [300, 300, 400, 400]
end

Primitives are rendered first-in, first-out. The rendering order (sorted by bottom-most to top-most):

args.outputs.background_color

Set args.outputs.background_color to an Array with RGB values (eg. [255, 255, 255] for the color white).

args.outputs.sounds

Send a file path to this collection to play a sound. The sound file must be under the mygame directory. 

args.outputs.sounds << "sounds/jump.wav"

args.outputs.solids

Send a Primitive to this collection to render a filled in rectangle to the screen. This collection is cleared at the end of every frame.

args.outputs.static_solids

Send a Primitive to this collection to render a filled in rectangle to the screen. This collection is not cleared at the end of every frame. And objects can be mutated by reference.

args.outputs.sprites, .static_sprites

Send a Primitive to this collection to render a sprite to the screen.

args.outputs.primitives, .static_primitives

Send a Primitive of any type and it'll be rendered. The Primitive must have a primitive_marker that returns :solid, :sprite, :label, :line, :border.

args.outputs.labels, .static_labels

Send a Primitive to this collection to render text to the screen.

args.outputs.lines, .static_lines

Send a Primitive to this collection to render a line to the screen.

args.outputs.borders, .static_borders

Send a Primitive to this collection to render an unfilled rectangle to the screen.

args.outputs.debug, .static_debug

Send any Primitive to this collection which represents things you render to the screen for debugging purposes. Primitives in this collection will not be rendered in a production release of your game.

args.easing

A set of functions that allow you to determine the current progression of an easing function.

args.easing.ease start_tick, current_tick, duration, easing_functions

Given a start, current, duration, and easing function names, ease returns a number between 0 and 1 that represents the progress of an easing function.

The built in easing definitions you have access to are :identity, :flip, :quad, :cube, :quart, and :quint.

This example will move a box at a linear speed from 0 to 1280. 

def tick args
  start_time = 10
  duration = 60
  current_progress = args.easing.ease start_time,
                                      args.state.tick_count,
                                      duration,
                                      :identity
  args.outputs.solids << { x: 1280 * current_progress, y: 360, w: 10, h: 10 }
end

args.easing.ease_spline start_tick, current_tick, duration, spline

Given a start, current, duration, and a multiple bezier values, this function returns a number between 0 and 1 that represents the progress of an easing function.

This example will move a box at a linear speed from 0 to 1280 and then back to 0 using two bezier definitions (represented as an array with four values). 

def tick args
  start_time = 10
  duration = 60
  spline = [
    [  0, 0.25, 0.75, 1.0],
    [1.0, 0.75, 0.25,   0]
  ]
  current_progress = args.easing.ease_spline start_time,
                                             args.state.tick_count,
                                             duration,
                                             spline
  args.outputs.solids << { x: 1280 * current_progress, y: 360, w: 10, h: 10 }
end

args.string

Useful string functions not included in Ruby core libraries.

args.string.wrapped_lines string, max_character_length

This function will return a collection of strings given an input string and max_character_length. The collection of strings returned will split the input string into strings of length <= max_character_length.

The following example takes a string with new lines and creates a label for each one. Labels (args.outputs.labels) ignore newline characters \n. 

def tick args
  long_string = "Lorem ipsum dolor sit amet, consectetur adipiscing elit.
teger dolor velit, ultricies vitae libero vel, aliquam imperdiet enim."
  max_character_length = 30
  long_strings_split = args.string.wrapped_lines long_string, max_character_length
  args.outputs.labels << long_strings_split.map_with_index do |s, i|
    { x: 10, y: 600 - (i * 20), text: s }
  end
end

args.grid

Returns the virtual grid for the game.

args.grid.name

Returns either :origin_bottom_left or :origin_center.

args.grid.bottom

Returns the y value that represents the bottom of the grid.

args.grid.top

Returns the y value that represents the top of the grid.

args.grid.left

Returns the x value that represents the left of the grid.

args.grid.right

Returns the x value that represents the right of the grid.

args.grid.rect

Returns a rectangle Primitive that represents the grid.

args.grid.origin_bottom_left!

Change the grids coordinate system to 0, 0 at the bottom left corner.

args.grid.origin_center!

Change the grids coordinate system to 0, 0 at the center of the screen.

args.grid.w

Returns the grid's width (always 1280).

args.grid.h

Returns the grid's height (always 720).

Audio

Hash that contains audio sources that are playing. If you want to add a new sound add a hash with keys/values as in the following example: 

def tick args
  # The values below (except for input of course) are the default values that apply if you don't
  # specify the value in the hash.
  args.audio[:my_audio] = {
    input: 'sound/boom.wav',  # Filename
    x: 0.0, y: 0.0, z: 0.0,   # Relative position to the listener, x, y, z from -1.0 to 1.0
    gain: 1.0,                # Volume (0.0 to 1.0)
    pitch: 1.0,               # Pitch of the sound (1.0 = original pitch)
    paused: false,            # Set to true to pause the sound at the current playback position
    looping: false,           # Set to true to loop the sound/music until you stop it
  }
end

Sounds that don't specify looping: true will be removed automatically from the hash after the playback ends. Looping sounds or sounds that should stop early must be removed manually.

When you assign a hash to an audio output, a :length key will be added to the hash on the following tick. This will tell you the duration of the audio file in seconds (float).

Audio synthesis (Pro only)

Instead of a path to an audio file you can specify an array [channels, sample_rate, sound_source] for input to procedurally generate sound. You do this by providing an array of float values between -1.0 and 1.0 that describe the waveform you want to play.

Sound source

A sound source can be one of two things:

When you specify 2 for channels, then the generated sample array will be played back in an interleaved manner. The first element is the first sample for the left channel, the second element is the first sample for the right channel, the third element is the second sample for the left channel etc.

Example:

def tick args
  sample_rate = 48000

  generate_sine_wave = lambda do
    frequency = 440.0 # A5
    samples_per_period = (sample_rate / frequency).ceil
    one_period = samples_per_period.map_with_index { |i|
      Math.sin((2 * Math::PI) * (i / samples_per_period))
    }
    one_period * frequency # Generate 1 second worth of sound
  end

  args.audio[:my_audio] ||= {
    input: [1, sample_rate, generate_sine_wave]
  }
end

Easing

This function will give you a float value between 0 and 1 that represents a percentage. You need to give the funcation a start_tick, current_tick, duration, and easing definitions.

This YouTube video is a fantastic introduction to easing functions: https://www.youtube.com/watch?v=mr5xkf6zSzk

Example

This example shows how to fade in a label at frame 60 over two seconds (120 ticks). The :identity definition implies a linear fade: f(x) -> x. 

def tick args
  fade_in_at   = 60
  current_tick = args.state.tick_count
  duration     = 120
  percentage   = args.easing.ease fade_in_at,
                                  current_tick,
                                  duration,
                                  :identity
  alpha = 255 * percentage
  args.outputs.labels << { x: 640,
                           y: 320, text: "#{percentage.to_sf}",
                           alignment_enum: 1,
                           a: alpha }
end

Easing Definitions

There are a number of easing definitions availble to you:

:identity

The easing definition for :identity is f(x) = x. For example, if start_tick is 0, current_tick is 50, and duration is 100, then args.easing.ease 0, 50, 100, :identity will return 0.5 (since tick 50 is half way between 0 and 100).

:flip

The easing definition for :flip is f(x) = 1 - x. For example, if start_tick is 0, current_tick is 10, and duration is 100, then args.easing.ease 0, 10, 100, :flip will return 0.9 (since tick 10 means 100% - 10%).

:quad, :cube, :quart, :qunit

These are the power easing definitions. :quad is f(x) = x * x (x squared), :cube is f(x) = x * x * x (x cubed), etc.

The power easing definitions represent Smooth Start easing (the percentage changes slow at first and speeds up at the end).

Example

Here is an example of Smooth Start (the percentage changes slow at first and speeds up at the end). 

def tick args
  start_tick   = 60
  current_tick = args.state.tick_count
  duration     = 120
  percentage   = args.easing.ease start_tick,
                                  current_tick,
                                  duration,
                                  :quad
  start_x      = 100
  end_x        = 1180
  distance_x   = end_x - start_x
  final_x      = start_x + (distance_x * percentage)

  start_y      = 100
  end_y        = 620
  distance_y   = end_y - start_y
  final_y      = start_y + (distance_y * percentage)

  args.outputs.labels << { x: final_x,
                           y: final_y,
                           text: "#{percentage.to_sf}",
                           alignment_enum: 1 }
end

Combining Easing Definitions

The base easing definitions can be combined to create common easing functions.

Example

Here is an example of Smooth Stop (the percentage changes fast at first and slows down at the end). 

def tick args
  start_tick   = 60
  current_tick = args.state.tick_count
  duration     = 120

  # :flip, :quad, :flip is Smooth Stop
  percentage   = args.easing.ease start_tick,
                                  current_tick,
                                  duration,
                                  :flip, :quad, :flip
  start_x      = 100
  end_x        = 1180
  distance_x   = end_x - start_x
  final_x      = start_x + (distance_x * percentage)

  start_y      = 100
  end_y        = 620
  distance_y   = end_y - start_y
  final_y      = start_y + (distance_y * percentage)

  args.outputs.labels << { x: final_x,
                           y: final_y,
                           text: "#{percentage.to_sf}",
                           alignment_enum: 1 }
end

Custom Easing Functions

You can define your own easing functions by passing in a lambda as a definition or extending the Easing module.

Example - Using Lambdas

This easing function goes from 0 to 1 for the first half of the ease, then 1 to 0 for the second half of the ease. 

def tick args
  fade_in_at    = 60
  current_tick  = args.state.tick_count
  duration      = 600
  easing_lambda = lambda do |percentage, start_tick, duration|
                    fx = percentage
                    if fx < 0.5
                      fx = percentage * 2
                    else
                      fx = 1 - (percentage - 0.5) * 2
                    end
                    fx
                  end

  percentage    = args.easing.ease fade_in_at,
                                   current_tick,
                                   duration,
                                   easing_lambda

  alpha = 255 * percentage
  args.outputs.labels << { x: 640,
                           y: 320,
                           a: alpha,
                           text: "#{percentage.to_sf}",
                           alignment_enum: 1 }
end

Example - Extending Easing Definitions

If you don't want to create a lambda, you can register an easing definition like so: 

# 1. Extend the Easing module
module Easing
  def self.saw_tooth x
    if x < 0.5
      x * 2
    else
      1 - (x - 0.5) * 2
    end
  end
end

def tick args
  fade_in_at    = 60
  current_tick  = args.state.tick_count
  duration      = 600

  # 2. Reference easing definition by name
  percentage    = args.easing.ease fade_in_at,
                                   current_tick,
                                   duration,
                                   :saw_tooth

  alpha = 255 * percentage
  args.outputs.labels << { x: 640,
                           y: 320,
                           a: alpha,
                           text: "#{percentage.to_sf}",
                           alignment_enum: 1 }

end

Outputs

Outputs is how you render primitives to the screen. The minimal setup for rendering something to the screen is via a tick method defined in mygame/app/main.rb 

def tick args
  args.outputs.solids     << [0, 0, 100, 100]
  args.outputs.sprites    << [100, 100, 100, 100, "sprites/square/blue.png"]
  args.outputs.labels     << [200, 200, "Hello World"]
  args.outputs.lines      << [300, 300, 400, 400]
end

Render Order

Primitives are rendered first-in, first-out. The rendering order (sorted by bottom-most to top-most):

Solids

Add primitives to this collection to render a solid to the screen.

Rendering a solid using an Array

Creates a solid black rectangle located at 100, 100. 160 pixels wide and 90 pixels tall. 

def tick args
  #                         X    Y  WIDTH  HEIGHT
  args.outputs.solids << [100, 100,   160,     90]
end

Rendering a solid using an Array with colors and alpha

The value for the color and alpha is a number between 0 and 255. The alpha property is optional and will be set to 255 if not specified.

Creates a green solid rectangle with an opacity of 50%. 

def tick args
  #                         X    Y  WIDTH  HEIGHT  RED  GREEN  BLUE  ALPHA
  args.outputs.solids << [100, 100,   160,     90,   0,   255,    0,   128]
end

Rendering a solid using a Hash

If you want a more readable invocation. You can use the following hash to create a solid. Any parameters that are not specified will be given a default value. The keys of the hash can be provided in any order. 

def tick args
  args.outputs.solids << {
    x:    0,
    y:    0,
    w:  100,
    h:  100,
    r:    0,
    g:  255,
    b:    0,
    a:  255
  }
end

Rendering a sprite using a Class

You can also create a class with solid properties and render it as a primitive. ALL properties must be on the class. *Additionally*, a method called primitive_marker must be defined on the class.

Here is an example: 

# Create type with ALL solid properties AND primitive_marker
class Solid
  attr_accessor :x, :y, :w, :h, :r, :g, :b, :a

  def primitive_marker
    :solid
  end
end

# Inherit from type
class Square < Solid
  # constructor
  def initialize x, y, size
    self.x = x
    self.y = y
    self.w = size
    self.h = size
  end
end

def tick args
  # render solid/border
  args.outputs.solids  << Square.new(10, 10, 32)
end

Borders

Add primitives to this collection to render an unfilled solid to the screen. Take a look at the documentation for Outputs#solids.

The only difference between the two primitives is where they are added.

Instead of using args.outputs.solids: 

def tick args
  #                         X    Y  WIDTH  HEIGHT
  args.outputs.solids << [100, 100,   160,     90]
end

You have to use args.outputs.borders: 

def tick args
  #                           X    Y  WIDTH  HEIGHT
  args.outputs.borders << [100, 100,   160,     90]
end

Sprites

Add primitives to this collection to render a sprite to the screen.

Rendering a sprite using an Array

Creates a sprite of a white circle located at 100, 100. 160 pixels wide and 90 pixels tall. 

def tick args
  #                         X    Y   WIDTH   HEIGHT                      PATH
  args.outputs.sprites << [100, 100,   160,     90, "sprites/circle/white.png]
end

Rendering a sprite using an Array with colors and alpha

The value for the color and alpha is a number between 0 and 255. The alpha property is optional and will be set to 255 if not specified.

Creates a green circle sprite with an opacity of 50%. 

def tick args
  #                         X    Y  WIDTH  HEIGHT           PATH                ANGLE  ALPHA  RED  GREEN  BLUE
  args.outputs.sprites << [100, 100,  160,     90, "sprites/circle/white.png",     0,    128,   0,   255,    0]
end

Rendering a sprite using a Hash

If you want a more readable invocation. You can use the following hash to create a sprite. Any parameters that are not specified will be given a default value. The keys of the hash can be provided in any order. 

def tick args
  args.outputs.sprites << {
    x:                             0,
    y:                             0,
    w:                           100,
    h:                           100,
    path: "sprites/circle/white.png",
    angle:                         0,
    a:                           255,
    r:                             0,
    g:                           255,
    b:                             0
  }
end

Rendering a solid using a Class

You can also create a class with solid/border properties and render it as a primitive. ALL properties must be on the class. *Additionally*, a method called primitive_marker must be defined on the class.

Here is an example: 

# Create type with ALL sprite properties AND primitive_marker
class Sprite
  attr_accessor :x, :y, :w, :h, :path, :angle, :angle_anchor_x, :angle_anchor_y,  :tile_x, :tile_y, :tile_w, :tile_h, :source_x, :source_y, :source_w, :source_h, :flip_horizontally, :flip_vertically, :a, :r, :g, :b

  def primitive_marker
    :sprite
  end
end

# Inherit from type
class Circle < Sprite
# constructor
  def initialize x, y, size, path
    self.x = x
    self.y = y
    self.w = size
    self.h = size
    self.path = path
  end
  def serlialize
    {x:self.x, y:self.y, w:self.w, h:self.h, path:self.path}
  end

  def inspect
    serlialize.to_s
  end

  def to_s
    serlialize.to_s
  end
end
def tick args
  # render circle sprite
  args.outputs.sprites  << Circle.new(10, 10, 32,"sprites/circle/white.png")
end

Labels

Add primitives to this collection to render a label.

Rendering a label using an Array

Labels represented as Arrays/Tuples: 

def tick args
                         #        X         Y              TEXT   SIZE_ENUM
  args.outputs.labels << [175 + 150, 610 - 50, "Smaller label.",         0]
end

Here are all the properties that you can set with a label represented as an Array. It's recommended to move over to using Hashes once you've specified a lot of properties. 

def tick args
  args.outputs.labels << [
    640,                   # X
    360,                   # Y
    "Hello world",         # TEXT
    0,                     # SIZE_ENUM
    1,                     # ALIGNMENT_ENUM
    0,                     # RED
    0,                     # GREEN
    0,                     # BLUE
    255,                   # ALPHA
    "fonts/coolfont.ttf"   # FONT
  ]
end
d

Rendering a label using a Hash

def tick args
  args.outputs.labels << {
      x:                       200,
      y:                       550,
      text:                    "dragonruby",
      size_enum:               2,
      alignment_enum:          1, # 0 = left, 1 = center, 2 = right
      r:                       155,
      g:                       50,
      b:                       50,
      a:                       255,
      font:                    "fonts/manaspc.ttf",
      vertical_alignment_enum: 0  # 0 = bottom, 1 = center, 2 = top
  }
end

Screenshots

Add a hash to this collection to take a screenshot and save as png file. The keys of the hash can be provided in any order. 

def tick args
  args.outputs.screenshots << {
    x: 0, y: 0, w: 100, h: 100,    # Which portion of the screen should be captured
    path: 'screenshot.png',        # Output path of PNG file (inside game directory)
    r: 255, g: 255, b: 255, a: 0   # Optional chroma key
  }
end

Chroma key (Making a color transparent)

By specifying the r, g, b and a keys of the hash you change the transparency of a color in the resulting PNG file. This can be useful if you want to create files with transparent background like spritesheets. The transparency of the color specified by r, g, b will be set to the transparency specified by a.

The example above sets the color white (255, 255, 255) as transparent.

Mouse

The mouse is accessible via args.inputs.mouse: 

def tick args
  # Rendering a label that shows the mouse's x and y position (via args.inputs.mouse).
  args.outputs.labels << [
    10,
    710,
    "The mouse's position is: #{args.inputs.mouse.x} #{args.inputs.mouse.y}."
  ]
end

The mouse has the following properties.

OpenEntity

OpenEntity is accessible within the DragonRuby's top level tick function via the args.state property. 

def tick args
  args.state.x ||= 100
  args.outputs.labels << [10, 710, "value of x is: #{args.state.x}."]
end

The primary benefit of using args.state as opposed to instance variables is that GTK::OpenEntity allows for arbitrary nesting of properties without the need to create intermediate objects.

For example: 

def tick args
  # intermediate player object does not need to be created
  args.state.player.x ||= 100
  args.state.player.y ||= 100
  args.outputs.labels << [
    10,
    710,
    "player x, y is:#{args.state.player.x}, #{args.state.player.y}."
  ]
end

as_hash

Returns a reference to the GTK::OpenEntity as a Hash. This property is useful when you want to treat args.state as a Hash and invoke methods such as Hash#each.

Example: 

def tick args
  args.state.x ||= 100
  args.state.y ||= 100
  values = args.state
               .as_hash
               .map { |k, v| "#{k} #{v}" }

  args.outputs.labels << values.map.with_index do |v, i|
    [
      10,
      710 - (30 * i),
      v
    ]
  end
end

Array

The Array class has been extend to provide methods that will help in common game development tasks. Array is one of the most powerful classes in Ruby and a very fundamental component of Game Toolkit.

map_2d

Assuming the array is an array of arrays, Given a block, each 2D array index invoked against the block. A 2D array is a common way to store data/layout for a stage. 

repl do
  stage = [
    [:enemy, :empty, :player],
    [:empty, :empty,  :empty],
    [:enemy, :empty,  :enemy],
  ]

  occupied_tiles = stage.map_2d do |row, col, tile|
    if tile == :empty
      nil
    else
      [row, col, tile]
    end
  end.reject_nil

  puts "Stage:"
  puts stage

  puts "Occupied Tiles"
  puts occupied_tiles
end

include_any?

Given a collection of items, the function will return true if any of self's items exists in the collection of items passed in:

any_intersect_rect?

Assuming the array contains objects that respond to left, right, top, bottom, this method returns true if any of the elements within the array intersect the object being passed in. You are given an optional parameter called tolerance which informs how close to the other rectangles the elements need to be for it to be considered intersecting.

The default tolerance is set to 0.1, which means that the primitives are not considered intersecting unless they are overlapping by more than 0.1. 

repl do
  # Here is a player class that has position and implement
  # the ~attr_rect~ contract.
  class Player
    attr_rect
    attr_accessor :x, :y, :w, :h

    def initialize x, y, w, h
      @x = x
      @y = y
      @w = w
      @h = h
    end

    def serialize
      { x: @x, y: @y, w: @w, h: @h }
    end

    def inspect
      "#{serialize}"
    end

    def to_s
      "#{serialize}"
    end
  end

  # Here is a definition of two walls.
  walls = [
     [10, 10, 10, 10],
     { x: 20, y: 20, w: 10, h: 10 },
   ]

  # Display the walls.
  puts "Walls."
  puts walls
  puts ""

  # Check any_intersect_rect? on player
  player = Player.new 30, 20, 10, 10
  puts "Is Player #{player} touching wall?"
  puts (walls.any_intersect_rect? player)
  # => false
  # The value is false because of the default tolerance is 0.1.
  # The overlap of the player rect and any of the wall rects is
  # less than 0.1 (for those that intersect).
  puts ""

  player = Player.new 9, 10, 10, 10
  puts "Is Player #{player} touching wall?"
  puts (walls.any_intersect_rect? player)
  # => true
  puts ""
end

map

The function given a block returns a new Enumerable of values.

Example of using Array#map in conjunction with args.state and args.outputs.sprites to render sprites to the screen. 

def tick args
  # define the colors of the rainbow in ~args.state~
  # as an ~Array~ of ~Hash~es with :order and :name.
  # :order will be used to determine render location
  #  and :name will be used to determine sprite path.
  args.state.rainbow_colors ||= [
    { order: 0, name: :red    },
    { order: 1, name: :orange },
    { order: 2, name: :yellow },
    { order: 3, name: :green  },
    { order: 4, name: :blue   },
    { order: 5, name: :indigo },
    { order: 6, name: :violet },
  ]

  # render sprites diagonally to the screen
  # with a width and height of 50.
  args.outputs
      .sprites << args.state
                      .rainbow_colors
                      .map do |color| # <-- ~Array#map~ usage
                        [
                          color[:order] * 50,
                          color[:order] * 50,
                          50,
                          50,
                          "sprites/square-#{color[:name]}.png"
                        ]
                      end
end

each

The function, given a block, invokes the block for each item in the Array. Array#each is synonymous to foreach constructs in other languages.

Example of using Array#each in conjunction with args.state and args.outputs.sprites to render sprites to the screen: 

def tick args
  # define the colors of the rainbow in ~args.state~
  # as an ~Array~ of ~Hash~es with :order and :name.
  # :order will be used to determine render location
  #  and :name will be used to determine sprite path.
  args.state.rainbow_colors ||= [
    { order: 0, name: :red    },
    { order: 1, name: :orange },
    { order: 2, name: :yellow },
    { order: 3, name: :green  },
    { order: 4, name: :blue   },
    { order: 5, name: :indigo },
    { order: 6, name: :violet },
  ]

  # render sprites diagonally to the screen
  # with a width and height of 50.
  args.state
      .rainbow_colors
      .map do |color| # <-- ~Array#each~ usage
        args.outputs.sprites << [
          color[:order] * 50,
          color[:order] * 50,
          50,
          50,
          "sprites/square-#{color[:name]}.png"
        ]
      end
end

reject_nil

Returns an Enumerable rejecting items that are nil, this is an alias for Array#compact: 

repl do
  a = [1, nil, 4, false, :a]
  puts a.reject_nil
  # => [1, 4, false, :a]
  puts a.compact
  # => [1, 4, false, :a]
end

reject_false

Returns an `Enumerable` rejecting items that are `nil` or `false`. 

repl do
  a = [1, nil, 4, false, :a]
  puts a.reject_false
  # => [1, 4, :a]
end

product

Returns all combinations of values between two arrays.

Here are some examples of using product. Paste the following code at the bottom of main.rb and save the file to see the results: 

repl do
  a = [0, 1]
  puts a.product
  # => [[0, 0], [0, 1], [1, 0], [1, 1]]
end

repl do
  a = [ 0,  1]
  b = [:a, :b]
  puts a.product b
  # => [[0, :a], [0, :b], [1, :a], [1, :b]]
end

frame_index

This function is helpful for determining the index of frame-by-frame sprite animation. The numeric value self represents the moment the animation started.

frame_index takes three additional parameters:

frame_index will return nil if the time for the animation is out of bounds of the parameter specification.

Example using variables: 

def tick args
  start_looping_at = 0
  number_of_sprites = 6
  number_of_frames_to_show_each_sprite = 4
  does_sprite_loop = true

  sprite_index =
    start_looping_at.frame_index number_of_sprites,
                                 number_of_frames_to_show_each_sprite,
                                 does_sprite_loop

  sprite_index ||= 0

  args.outputs.sprites << [
    640 - 50,
    360 - 50,
    100,
    100,
    "sprites/dragon-#{sprite_index}.png"
  ]
end

Example using named parameters: 

def tick args
  start_looping_at = 0

  sprite_index =
    start_looping_at.frame_index count: 6,
                                 hold_for: 4,
                                 repeat: true,
                                 tick_count_override: args.state.tick_count

  sprite_index ||= 0

  args.outputs.sprites << [
    640 - 50,
    360 - 50,
    100,
    100,
    "sprites/dragon-#{sprite_index}.png"
  ]
end

elapsed_time

For a given number, the elapsed frames since that number is returned. `Kernel.tick_count` is used to determine how many frames have elapsed. An optional numeric argument can be passed in which will be used instead of `Kernel.tick_count`.

Here is an example of how elapsed_time can be used. 

def tick args
  args.state.last_click_at ||= 0

  # record when a mouse click occurs
  if args.inputs.mouse.click
    args.state.last_click_at = args.state.tick_count
  end

  # Use Numeric#elapsed_time to determine how long it's been
  if args.state.last_click_at.elapsed_time > 120
    args.outputs.labels << [10, 710, "It has been over 2 seconds since the mouse was clicked."]
  end
end

And here is an example where the override parameter is passed in: 

def tick args
  args.state.last_click_at ||= 0

  # create a state variable that tracks time at half the speed of args.state.tick_count
  args.state.simulation_tick = args.state.tick_count.idiv 2

  # record when a mouse click occurs
  if args.inputs.mouse.click
    args.state.last_click_at = args.state.simulation_tick
  end

  # Use Numeric#elapsed_time to determine how long it's been
  if (args.state.last_click_at.elapsed_time args.state.simulation_tick) > 120
    args.outputs.labels << [10, 710, "It has been over 4 seconds since the mouse was clicked."]
  end
end

elapsed?

Returns true if Numeric#elapsed_time is greater than the number. An optional parameter can be passed into elapsed? which is added to the number before evaluating whether elapsed? is true.

Example usage (no optional parameter): 

def tick args
  args.state.box_queue ||= []

  if args.state.box_queue.empty?
    args.state.box_queue << { name: :red,
                              destroy_at: args.state.tick_count + 60 }
    args.state.box_queue << { name: :green,
                              destroy_at: args.state.tick_count + 60 }
    args.state.box_queue << { name: :blue,
                              destroy_at: args.state.tick_count + 120 }
  end

  boxes_to_destroy = args.state
                         .box_queue
                         .find_all { |b| b[:destroy_at].elapsed? }

  if !boxes_to_destroy.empty?
    puts "boxes to destroy count: #{boxes_to_destroy.length}"
  end

  boxes_to_destroy.each { |b| puts "box #{b} was elapsed? on #{args.state.tick_count}." }

  args.state.box_queue -= boxes_to_destroy
end

Example usage (with optional parameter): 

def tick args
  args.state.box_queue ||= []

  if args.state.box_queue.empty?
    args.state.box_queue << { name: :red,
                              create_at: args.state.tick_count + 120,
                              lifespan: 60 }
    args.state.box_queue << { name: :green,
                              create_at: args.state.tick_count + 120,
                              lifespan: 60 }
    args.state.box_queue << { name: :blue,
                              create_at: args.state.tick_count + 120,
                              lifespan: 120 }
  end

  # lifespan is passed in as a parameter to ~elapsed?~
  boxes_to_destroy = args.state
                         .box_queue
                         .find_all { |b| b[:create_at].elapsed? b[:lifespan] }

  if !boxes_to_destroy.empty?
    puts "boxes to destroy count: #{boxes_to_destroy.length}"
  end

  boxes_to_destroy.each { |b| puts "box #{b} was elapsed? on #{args.state.tick_count}." }

  args.state.box_queue -= boxes_to_destroy
end

new?

Returns true if Numeric#elapsed_time == 0. Essentially communicating that number is equal to the current frame.

Example usage: 

def tick args
  args.state.box_queue ||= []

  if args.state.box_queue.empty?
    args.state.box_queue << { name: :red,
                              create_at: args.state.tick_count + 60 }
  end

  boxes_to_spawn_this_frame = args.state
                                  .box_queue
                                  .find_all { |b| b[:create_at].new? }

  boxes_to_spawn_this_frame.each { |b| puts "box #{b} was new? on #{args.state.tick_count}." }

  args.state.box_queue -= boxes_to_spawn_this_frame
end

Kernel

Kernel in the DragonRuby Runtime has patches for how standard out is handled and also contains a unit of time in games called a tick.

tick_count

Returns the current tick of the game. This value is reset if you call $gtk.reset.

global_tick_count

Returns the current tick of the application from the point it was started. This value is never reset.

Geometry

The Geometry module contains methods for calculations that are frequently used in game development. For convenience, this module is mixed into Hash, Array, and DragonRuby's Entity class. It is also available in a functional variant at args.geometry.

Many of the geometric functions assume the objects have a certain shape: 

def tick args
  # Geometry is mixed into Hash, Array, and Entity

  # define to rectangles
  rect_1 = { x: 0, y: 0, w: 100, h: 100 }
  rect_2 = { x: 50, y: 50, w: 100, h: 100 }

  # call geometry method function from instance of a Hash class
  puts rect_1.intersect_rect?(rect_2)

  # OR

  # use the geometry methods functionally
  puts args.geometry.intersect_rect?(rect_1, rect_2)
end

inside_rect?

Invocation variants:

Given two rectangle primitives this function will return true or false depending on if the first rectangle (or self) is inside of the second rectangle.

Here is an example where one rectangle is stationary, and another rectangle is controlled using directional input. The rectangles change color from blue to read if the movable rectangle is entirely inside the stationary rectangle. 

def tick args
  # define a rectangle in state and position it
  # at the center of the screen with a color of blue
  args.state.box_1 ||= {
    x: 640 - 40,
    y: 360 - 40,
    w: 80,
    h: 80,
    r: 0,
    g: 0,
    b: 255
  }

  # create another rectangle in state and position it
  # at the far left center
  args.state.box_2 ||= {
    x: 0,
    y: 360 - 10,
    w: 20,
    h: 20,
    r: 0,
    g: 0,
    b: 255
  }

  # take the directional input and use that to move the second rectangle around
  # increase or decrease the x value based on if left or right is held
  args.state.box_2.x += args.inputs.left_right * 5
  # increase or decrease the y value based on if up or down is held
  args.state.box_2.y += args.inputs.up_down * 5

  # change the colors of the rectangles based on whether they
  # intersect or not
  if args.state.box_2.inside_rect? args.state.box_1
    args.state.box_1.r = 255
    args.state.box_1.g = 0
    args.state.box_1.b = 0

    args.state.box_2.r = 255
    args.state.box_2.g = 0
    args.state.box_2.b = 0
  else
    args.state.box_1.r = 0
    args.state.box_1.g = 0
    args.state.box_1.b = 255

    args.state.box_2.r = 0
    args.state.box_2.g = 0
    args.state.box_2.b = 255
  end

  # render the rectangles as border primitives on the screen
  args.outputs.borders << args.state.box_1
  args.outputs.borders << args.state.box_2
end

scale_rect

Given a Rectangle this function returns a new rectangle with a scaled size. 

def tick args
  # a rect at the center of the screen
  args.state.rect_1 ||= { x: 640 - 20, y: 360 - 20, w: 40, h: 40 }

  # render the rect
  args.outputs.borders << args.state.rect_1

  # the rect half the size with the x and y position unchanged
  args.outputs.borders << args.state.rect_1.scale_rect(0.5)

  # the rect double the size, repositioned in the center given anchor optional arguments
  args.outputs.borders << args.state.rect_1.scale_rect(2, 0.5, 0.5)
end

scale_rect_extended

The behavior is similar to scale_rect except that you can independently control the scale of each axis. The parameters are all named: 

def tick args
  baseline_rect = { x: 640 - 20, y: 360 - 20, w: 40, h: 40 }
  args.state.rect_1 ||= baseline_rect
  args.state.rect_2 ||= baseline_rect.scale_rect_extended(percentage_x: 2,
                                                          percentage_y: 0.5,
                                                          anchor_x: 0.5,
                                                          anchor_y: 1.0)
  args.outputs.borders << args.state.rect_1
  args.outputs.borders << args.state.rect_2
end

anchor_rect

Returns a new rect that is anchored by an anchor_x and anchor_y value. The width and height of the rectangle is taken into consideration when determining the anchor position: 

def tick args
  args.state.rect ||= {
    x: 640,
    y: 360,
    w: 100,
    h: 100
  }

  # rect's center: 640 + 50, 360 + 50
  args.outputs.borders << args.state.rect.anchor_rect(0, 0)

  # rect's center: 640, 360
  args.outputs.borders << args.state.rect.anchor_rect(0.5, 0.5)

  # rect's center: 640, 360
  args.outputs.borders << args.state.rect.anchor_rect(0.5, 0)
end

angle_from

Invocation variants:

Returns an angle in degrees from the end_point to the start_point (if you want the value in radians, you can call .to_radians on the value returned): 

def tick args
  rect_1 ||= {
    x: 0,
    y: 0,
  }

  rect_2 ||= {
    x: 100,
    y: 100,
  }

  angle = rect_1.angle_from rect_2 # returns 225 degrees
  angle_radians = angle.to_radians
  args.outputs.labels << { x: 30, y: 30.from_top, text: "#{angle}, #{angle_radians}" }

  angle = args.geometry.angle_from rect_1, rect_2 # returns 225 degrees
  angle_radians = angle.to_radians
  args.outputs.labels << { x: 30, y: 60.from_top, text: "#{angle}, #{angle_radians}" }
end

angle_to

Invocation variants:

Returns an angle in degrees to the end_point from the start_point (if you want the value in radians, you can call .to_radians on the value returned): 

def tick args
  rect_1 ||= {
    x: 0,
    y: 0,
  }

  rect_2 ||= {
    x: 100,
    y: 100,
  }

  angle = rect_1.angle_to rect_2 # returns 45 degrees
  angle_radians = angle.to_radians
  args.outputs.labels << { x: 30, y: 30.from_top, text: "#{angle}, #{angle_radians}" }

  angle = args.geometry.angle_to rect_1, rect_2 # returns 45 degrees
  angle_radians = angle.to_radians
  args.outputs.labels << { x: 30, y: 60.from_top, text: "#{angle}, #{angle_radians}" }
end

distance

Returns the distance between two points; 

def tick args
  rect_1 ||= {
    x: 0,
    y: 0,
  }

  rect_2 ||= {
    x: 100,
    y: 100,
  }

  distance = args.geometry.distance rect_1, rect_2
  args.outputs.labels << {
    x: 30,
    y: 30.from_top,
    text: "#{distance}"
  }

  args.outputs.lines << {
    x: rect_1.x,
    y: rect_1.y,
    x2: rect_2.x,
    y2: rect_2.y
  }
end

point_inside_circle?

Invocation variants:

Returns true if a point is inside of a circle defined as a center point and radius. 

def tick args
  # define circle center
  args.state.circle_center ||= {
    x: 640,
    y: 360
  }

  # define circle radius
  args.state.circle_radius ||= 100

  # define point
  args.state.point_1 ||= {
    x: 100,
    y: 100
  }

  # allow point to be moved using keyboard
  args.state.point_1.x += args.inputs.left_right * 5
  args.state.point_1.y += args.inputs.up_down * 5

  # determine if point is inside of circle
  intersection = args.geometry.point_inside_circle? args.state.point_1,
                                                    args.state.circle_center,
                                                    args.state.circle_radius

  # render point as a square
  args.outputs.sprites << {
    x: args.state.point_1.x - 20,
    y: args.state.point_1.y - 20,
    w: 40,
    h: 40,
    path: "sprites/square/blue.png"
  }

  # if there is an intersection, render a red circle
  # otherwise render a blue circle
  if intersection
    args.outputs.sprites << {
      x: args.state.circle_center.x - args.state.circle_radius,
      y: args.state.circle_center.y - args.state.circle_radius,
      w: args.state.circle_radius * 2,
      h: args.state.circle_radius * 2,
      path: "sprites/circle/red.png",
      a: 128
    }
  else
    args.outputs.sprites << {
      x: args.state.circle_center.x - args.state.circle_radius,
      y: args.state.circle_center.y - args.state.circle_radius,
      w: args.state.circle_radius * 2,
      h: args.state.circle_radius * 2,
      path: "sprites/circle/blue.png",
      a: 128
    }
  end
end

center_inside_rect

Invocation variants:

Given a target rect and a reference rect, the target rect is centered inside the reference rect (a new rect is returned). 

def tick args
  rect_1 = {
    x: 0,
    y: 0,
    w: 100,
    h: 100
  }

  rect_2 = {
    x: 640 - 100,
    y: 360 - 100,
    w: 200,
    h: 200
  }

  centered_rect = args.geometry.center_inside_rect rect_1, rect_2
  # OR
  # centered_rect = rect_1.center_inside_rect rect_2

  args.outputs.solids << rect_1.merge(r: 255)
  args.outputs.solids << rect_2.merge(b: 255)
  args.outputs.solids << centered_rect.merge(g: 255)
end

ray_test

Given a point and a line, ray_test returns one of the following symbols based on the location of the point relative to the line: :left, :right, :on 

def tick args
  # create a point based off of the mouse location
  point = {
    x: args.inputs.mouse.x,
    y: args.inputs.mouse.y
  }

  # draw a line from the bottom left to the top right
  line = {
    x: 0,
    y: 0,
    x2: 1280,
    y2: 720
  }

  # perform ray_test on point and line
  ray = args.geometry.ray_test point, line

  # output the results of ray test at mouse location
  args.outputs.labels << {
    x: point.x,
    y: point.y + 25,
    text: "#{ray}",
    alignment_enum: 1,
    vertical_alignment_enum: 1,
  }

  # render line
  args.outputs.lines << line

  # render point
  args.outputs.solids << {
    x: point.x - 5,
    y: point.y - 5,
    w: 10,
    h: 10
  }
end

line_rise_run

Given a line, this function returns a Hash with x and y keys representing a normalized representation of the rise and run of the line. 

def tick args
  # draw a line from the bottom left to the top right
  line = {
    x: 0,
    y: 0,
    x2: 1280,
    y2: 720
  }

  # get rise and run of line
  rise_run = args.geometry.line_rise_run line

  # output the rise and run of line
  args.outputs.labels << {
    x: 640,
    y: 360,
    text: "#{rise_run}",
    alignment_enum: 1,
    vertical_alignment_enum: 1,
  }

  # render the line
  args.outputs.lines << line
end

rotate_point

Given a point and an angle in degrees, a new point is returned that is rotated around the origin by the degrees amount. An optional third argument can be provided to rotate the angle around a point other than the origin. 

def tick args
  args.state.rotate_amount ||= 0
  args.state.rotate_amount  += 1

  if args.state.rotate_amount >= 360
    args.state.rotate_amount = 0
  end

  point_1 = {
    x: 100,
    y: 100
  }

  # rotate point around 0, 0
  rotated_point_1 = args.geometry.rotate_point point_1,
                                               args.state.rotate_amount

  args.outputs.solids << {
    x: rotated_point_1.x - 5,
    y: rotated_point_1.y - 5,
    w: 10,
    h: 10
  }

  point_2 = {
    x: 640 + 100,
    y: 360 + 100
  }

  # rotate point around center screen
  rotated_point_2 = args.geometry.rotate_point point_2,
                                               args.state.rotate_amount,
                                               x: 640, y: 360

  args.outputs.solids << {
    x: rotated_point_2.x - 5,
    y: rotated_point_2.y - 5,
    w: 10,
    h: 10
  }
end

find_intersect_rect

Given a rect and a collection of rects, find_intersect_rect returns the first rect that intersects with the the first parameter. If you find yourself doing this: 

collision = args.state.terrain.find { |t| t.intersect_rect? args.state.player }

Consider using find_intersect_rect instead (it's more descriptive and faster): 

collision = args.geometry.find_intersect_rect args.state.player, args.state.terrain

find_all_intersect_rect

Given a rect and a collection of rects, find_all_intersect_rect returns all rects that intersects with the the first parameter. If you find yourself doing this: 

collisions = args.state.terrain.find_all { |t| t.intersect_rect? args.state.player }

Consider using find_all_intersect_rect instead (it's more descriptive and faster): 

collisions = args.geometry.find_all_intersect_rect args.state.player, args.state.terrain

find_intersect_rect_quad_tree

This is a faster collision algorithm for determining if a rectangle intersects any rectangle in an array. In order to use find_intersect_rect_quad_tree, you must first generate a quad tree data structure using create_quad_tree. Use this function if find_intersect_rect isn't fast enough. 

def tick args
  # create a player
  args.state.player ||= {
    x: 640 - 10,
    y: 360 - 10,
    w: 20,
    h: 20
  }

  # allow control of player movement using arrow keys
  args.state.player.x += args.inputs.left_right * 5
  args.state.player.y += args.inputs.up_down * 5

  # generate 40 random rectangles
  args.state.boxes ||= 40.map do
    {
      x: 1180 * rand + 50,
      y: 620 * rand + 50,
      w: 100,
      h: 100
    }
  end

  # generate a quad tree based off of rectangles.
  # the quad tree should only be generated once for
  # a given array of rectangles. if the rectangles
  # change, then the quad tree must be regenerated
  args.state.quad_tree ||= args.geometry.quad_tree_create args.state.boxes

  # use quad tree and find_intersect_rect_quad_tree to determine collision with player
  collision = args.geometry.find_intersect_rect_quad_tree args.state.player,
                                                          args.state.quad_tree

  # if there is a collision render a red box
  if collision
    args.outputs.solids << collision.merge(r: 255)
  end

  # render player as green
  args.outputs.solids << args.state.player.merge(g: 255)

  # render boxes as borders
  args.outputs.borders << args.state.boxes
end

create_quad_tree

Generates a quad tree from an array of rectangles. See find_intersect_rect_quad_tree for usage.

Source Code

Follows is a source code listing for all files that have been open sourced. This code can be found in the ./samples directory.

Samples

Learn Ruby Optional - Beginner Ruby Primer - automation.rb

# ./samples/00_learn_ruby_optional/00_beginner_ruby_primer/app/automation.rb
# ==========================================================================
#  _    _ ________     __  _      _____  _____ _______ ______ _   _ _ _ _ _
# | |  | |  ____\ \   / / | |    |_   _|/ ____|__   __|  ____| \ | | | | | |
# | |__| | |__   \ \_/ /  | |      | | | (___    | |  | |__  |  \| | | | | |
# |  __  |  __|   \   /   | |      | |  \___ \   | |  |  __| | . ` | | | | |
# | |  | | |____   | |    | |____ _| |_ ____) |  | |  | |____| |\  |_|_|_|_|
# |_|  |_|______|  |_|    |______|_____|_____/   |_|  |______|_| \_(_|_|_|_)
#
#
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                \  |  /
#                                 \ | /
#                                   +
#
# If you are new to the programming language Ruby, then you may find the
# following code a bit overwhelming. Come back to this file when you have
# a better grasp of Ruby and Game Toolkit.
#
# What follows is an automations script # that can be run via terminal:
# ./samples/00_beginner_ruby_primer $ ../../dragonruby . --eval app/automation.rb
# ==========================================================================

$gtk.reset
$gtk.scheduled_callbacks.clear
$gtk.schedule_callback 10 do
  $gtk.console.set_command 'puts "Hello DragonRuby!"'
end

$gtk.schedule_callback 20 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 30 do
  $gtk.console.set_command 'outputs.solids << [910, 200, 100, 100, 255, 0, 0]'
end

$gtk.schedule_callback 40 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 50 do
  $gtk.console.set_command 'outputs.solids << [1010, 200, 100, 100, 0, 0, 255]'
end

$gtk.schedule_callback 60 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 70 do
  $gtk.console.set_command 'outputs.sprites << [1110, 200, 100, 100, "sprites/dragon_fly_0.png"]'
end

$gtk.schedule_callback 80 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 90 do
  $gtk.console.set_command "outputs.labels << [1210, 200, state.tick_count, 0, 255, 0]"
end

$gtk.schedule_callback 100 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 110 do
  $gtk.console.set_command "state.sprite_frame = state.tick_count.idiv(4).mod(6)"
end

$gtk.schedule_callback 120 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 130 do
  $gtk.console.set_command "outputs.labels << [1210, 170, state.sprite_frame, 0, 255, 0]"
end

$gtk.schedule_callback 140 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 150 do
  $gtk.console.set_command "state.sprite_path =  \"sprites/dragon_fly_\#{state.sprite_frame}.png\""
end

$gtk.schedule_callback 160 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 170 do
  $gtk.console.set_command "outputs.labels    << [910, 330, \"path: \#{state.sprite_path}\", 0, 255, 0]"
end

$gtk.schedule_callback 180 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 190 do
  $gtk.console.set_command "outputs.sprites   << [910, 330, 370, 370, state.sprite_path]"
end

$gtk.schedule_callback 200 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 300 do
  $gtk.console.set_command ":wq"
end

$gtk.schedule_callback 400 do
  $gtk.console.eval_the_set_command
end

Learn Ruby Optional - Beginner Ruby Primer - main.rb

# ./samples/00_learn_ruby_optional/00_beginner_ruby_primer/app/main.rb
# ==========================================================================
#  _    _ ________     __  _      _____  _____ _______ ______ _   _ _ _ _ _
# | |  | |  ____\ \   / / | |    |_   _|/ ____|__   __|  ____| \ | | | | | |
# | |__| | |__   \ \_/ /  | |      | | | (___    | |  | |__  |  \| | | | | |
# |  __  |  __|   \   /   | |      | |  \___ \   | |  |  __| | . ` | | | | |
# | |  | | |____   | |    | |____ _| |_ ____) |  | |  | |____| |\  |_|_|_|_|
# |_|  |_|______|  |_|    |______|_____|_____/   |_|  |______|_| \_(_|_|_|_)
#
#
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                \  |  /
#                                 \ | /
#                                   +
#
# If you are new to the programming language Ruby, then you may find the
# following code a bit overwhelming. This sample is only designed to be
# run interactively (as opposed to being manipulated via source code).
#
# Start up this sample and follow along by visiting:
# https://s3.amazonaws.com/s3.dragonruby.org/dragonruby-gtk-primer.mp4
#
# It is STRONGLY recommended that you work through all the samples before
# looking at the code in this file.
# ==========================================================================

class TutorialOutputs
  attr_accessor :solids, :sprites, :labels, :lines, :borders

  def initialize
    @solids  = []
    @sprites = []
    @labels  = []
    @lines   = []
    @borders = []
  end

  def tick
    @solids  ||= []
    @sprites ||= []
    @labels  ||= []
    @lines   ||= []
    @borders ||= []
    @solids.each  { |p| $gtk.args.outputs.reserved << p.solid  }
    @sprites.each { |p| $gtk.args.outputs.reserved << p.sprite }
    @labels.each  { |p| $gtk.args.outputs.reserved << p.label  }
    @lines.each   { |p| $gtk.args.outputs.reserved << p.line   }
    @borders.each { |p| $gtk.args.outputs.reserved << p.border }
  end

  def clear
    @solids.clear
    @sprites.clear
    @labels.clear
    @borders.clear
  end
end

def defaults
  state.reset_button ||=
    state.new_entity(
      :button,
      label:  [1190, 68, "RESTART", -2, 0, 0, 0, 0].label,
      background: [1160, 38, 120, 50, 255, 255, 255].solid
    )
  $gtk.log_level = :off
end

def tick_reset_button
  return unless state.hello_dragonruby_confirmed
  $gtk.args.outputs.reserved << state.reset_button.background
  $gtk.args.outputs.reserved << state.reset_button.label
  if inputs.mouse.click && inputs.mouse.click.point.inside_rect?(state.reset_button.background)
    restart_tutorial
  end
end

def seperator
  @seperator = "=" * 80
end

def tick_intro
  queue_message "Welcome to the DragonRuby GTK primer! Try typing the
code below and press ENTER:

    puts \"Hello DragonRuby!\"
"
end

def tick_hello_dragonruby
  return unless console_has? "Hello DragonRuby!", "puts "

  $gtk.args.state.hello_dragonruby_confirmed = true

  queue_message "Well HELLO to you too!

If you ever want to RESTART the tutorial, just click the \"RESTART\"
button in the bottom right-hand corner.

Let's continue shall we? Type the code below and press ENTER:

    outputs.solids << [910, 200, 100, 100, 255, 0, 0]
"

end

def tick_explain_solid
  return unless $tutorial_outputs.solids.any? {|s| s == [910, 200, 100, 100, 255, 0, 0]}

  queue_message "Sweet!

The code: outputs.solids << [910, 200, 100, 100, 255, 0, 0]
Does the following:
1. GET the place where SOLIDS go: outputs.solids
2. Request that a new SOLID be ADDED: <<
3. The DEFINITION of a SOLID is the ARRAY:
   [910, 200, 100, 100, 255, 0, 0]

      GET       ADD     X      Y    WIDTH  HEIGHT RED  GREEN  BLUE
       |         |      |      |      |      |     |     |     |
       |         |      |      |      |      |     |     |     |
outputs.solids  <<    [910,   200,   100,   100,  255,   0,    0]
                      |_________________________________________|
                                           |
                                           |
                                         ARRAY

Now let's create a blue SOLID. Type:

    outputs.solids << [1010, 200, 100, 100, 0, 0, 255]
"

  state.explain_solid_confirmed = true
end

def tick_explain_solid_blue
  return unless state.explain_solid_confirmed
  return unless $tutorial_outputs.solids.any? {|s| s == [1010, 200, 100, 100, 0, 0, 255]}
  state.explain_solid_blue_confirmed = true

  queue_message "And there is our blue SOLID!

The ARRAY is the MOST important thing in DragonRuby GTK.

Let's create a SPRITE using an ARRAY:

  outputs.sprites << [1110, 200, 100, 100, 'sprites/dragon_fly_0.png']
"
end

def tick_explain_tick_count
  return unless $tutorial_outputs.sprites.any? {|s| s == [1110, 200, 100, 100, 'sprites/dragon_fly_0.png']}
  return if $tutorial_outputs.labels.any? {|l| l == [1210, 200, state.tick_count, 255, 255, 255]}
  state.explain_tick_count_confirmed = true

  queue_message "Look at the cute little dragon!

We can create a LABEL with ARRAYS too. Let's create a LABEL showing
THE PASSAGE OF TIME, which is called TICK_COUNT.

  outputs.labels << [1210, 200, state.tick_count, 0, 255, 0]
"
end

def tick_explain_mod
  return unless $tutorial_outputs.labels.any? {|l| l == [1210, 200, state.tick_count, 0, 255, 0]}
  state.explain_mod_confirmed = true
  queue_message "
The code: outputs.labels << [1210, 200, state.tick_count, 0, 255, 0]
Does the following:
1. GET the place where labels go: outputs.labels
2. Request that a new label be ADDED: <<
3. The DEFINITION of a LABEL is the ARRAY:
   [1210, 200, state.tick_count, 0, 255, 0]

      GET       ADD     X      Y          TEXT         RED  GREEN  BLUE
       |         |      |      |            |           |     |     |
       |         |      |      |            |           |     |     |
outputs.labels  <<    [1210,  200,   state.tick_count,  0,   255,   0]
                      |______________________________________________|
                                              |
                                              |
                                            ARRAY

Now let's do some MATH, save the result to STATE, and create a LABEL:

    state.sprite_frame = state.tick_count.idiv(4).mod(6)
    outputs.labels << [1210, 170, state.sprite_frame, 0, 255, 0]

Type the lines above (pressing ENTER after each line).
"
end

def tick_explain_string_interpolation
  return unless state.explain_mod_confirmed
  return unless state.sprite_frame == state.tick_count.idiv(4).mod(6)
  return unless $tutorial_outputs.labels.any? {|l| l == [1210, 170, state.sprite_frame, 0, 255, 0]}

  queue_message "Here is what the mathematical computation you just typed does:

1. Create an item of STATE named SPRITE_FRAME: state.sprite_frame =
2. Set this SPRITE_FRAME to the PASSAGE OF TIME (tick_count),
   DIVIDED EVENLY (idiv) into 4,
   and then compute the REMAINDER (mod) of 6.

   STATE   SPRITE_FRAME    PASSAGE OF      HOW LONG   HOW MANY
     |          |             TIME         TO SHOW    IMAGES
     |          |              |           AN IMAGE   TO FLIP THROUGH
     |          |              |               |      |
state.sprite_frame =     state.tick_count.idiv(4).mod(6)
                                           |       |
                                           |       +- REMAINDER OF DIVIDE
                                    DIVIDE EVENLY
                                    (NO DECIMALS)

With the information above, we can animate a SPRITE
using STRING INTERPOLATION: \#{}
which creates a unique SPRITE_PATH:

  state.sprite_path =  \"sprites/dragon_fly_\#{state.sprite_frame}.png\"
  outputs.labels    << [910, 330, \"path: \#{state.sprite_path}\", 0, 255, 0]
  outputs.sprites   << [910, 330, 370, 370, state.sprite_path]

Type the lines above (pressing ENTER after each line).
"
end

def tick_reprint_on_error
  return unless console.last_command_errored
  puts $gtk.state.messages.last
  puts "\nWhoops! Try again."
  console.last_command_errored = false
end

def tick_evals
  state.evals ||= []
  if console.last_command && (console.last_command.start_with?("outputs.") || console.last_command.start_with?("state."))
    state.evals << console.last_command
    console.last_command = nil
  end

  state.evals.each do |l|
    Kernel.eval l
  end
rescue Exception => e
  state.evals = state.evals[0..-2]
end

$tutorial_outputs ||= TutorialOutputs.new

def tick args
  $gtk.log_level = :off
  defaults
  console.show
  $tutorial_outputs.clear
  $tutorial_outputs.solids  << [900, 37, 480, 700,   0,   0,   0, 255]
  $tutorial_outputs.borders << [900, 37, 380, 683, 255, 255, 255]
  tick_evals
  $tutorial_outputs.tick
  tick_intro
  tick_hello_dragonruby
  tick_reset_button
  tick_explain_solid
  tick_explain_solid_blue
  tick_reprint_on_error
  tick_explain_tick_count
  tick_explain_mod
  tick_explain_string_interpolation
end

def console
  $gtk.console
end

def queue_message message
  $gtk.args.state.messages ||= []
  return if $gtk.args.state.messages.include? message
  $gtk.args.state.messages << message
  last_three = [$gtk.console.log[-3], $gtk.console.log[-2], $gtk.console.log[-1]].reject_nil
  $gtk.console.log.clear
  puts seperator
  $gtk.console.log += last_three
  puts seperator
  puts message
  puts seperator
end

def console_has? message, not_message = nil
  console.log
         .map(&:upcase)
         .reject { |s| not_message && s.include?(not_message.upcase) }
         .any?   { |s| s.include?("#{message.upcase}") }
end

def restart_tutorial
  $tutorial_outputs.clear
  $gtk.console.log.clear
  $gtk.reset
  puts "Starting the tutorial over!"
end

def state
  $gtk.args.state
end

def inputs
  $gtk.args.inputs
end

def outputs
  $tutorial_outputs
end

Learn Ruby Optional - Intermediate Ruby Primer - printing.txt

# ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/01_printing.txt
# ====================================================================================
# Commenting Code
# ====================================================================================
#
# Prefixing text with a pound sign (#) is how you comment code in Ruby. Example:
#
# I am commented code. And so are the lines above.
#
# I you want more than a quick primer on Ruby, check out https://poignant.guide/. It's
# an entertaining read. Otherwise, go to the next txt file.
#
# Follow along by visiting:
# https://s3.amazonaws.com/s3.dragonruby.org/dragonruby-gtk-intermediate.mp4

# ====================================================================================
#  Printing to the Console:
# ====================================================================================
#
# Every time you save repl.rb file, DragonRuby runs the code within it. Copy this text
# to repl.rb and save to see Hello World printed to the console.

repl do
  puts '* RUBY PRIMER: Printing to the console using the ~puts~ function.'
  puts '===='
  puts '======'
  puts '================================'
  puts 'Hello World'
  puts '================================'
  puts '======'
  puts '===='
end

Learn Ruby Optional - Intermediate Ruby Primer - strings.txt

# ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/02_strings.txt
# ====================================================================================
#  Strings
# ====================================================================================
#
# Here is how you work with strings in Ruby. Take the text
# in this file and paste it into repl.rb and save:

repl do
  puts '* RUBY PRIMER: strings'
  message = "Hello World"
  puts "The value of message is: " + message
  puts "Any value can be interpolated within a string using \#{}."
  puts "Interpolated message: #{message}."
  puts 'This #{message} is not interpolated because the string uses single quotes.'
end

Learn Ruby Optional - Intermediate Ruby Primer - numbers.txt

# ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/03_numbers.txt
# ====================================================================================
#  Numerics
# ====================================================================================
#
# Here is how you work with numbers in Ruby. Take the text
# in this file and paste it into repl.rb and save:

repl do
  puts '* RUBY PRIMER: Fixnum and Floats'
  a = 10
  puts "The value of a is: #{a}"
  puts "a + 1 is: #{a + 1}"
  puts "a / 3 is: #{a / 3}"
  puts ''

  b = 10.12
  puts "The value of b is: #{b}"
  puts "b + 1 is: #{b + 1}"
  puts "b as an integer is: #{b.to_i}"
  puts ''
end

Learn Ruby Optional - Intermediate Ruby Primer - booleans.txt

# ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/04_booleans.txt
# ====================================================================================
#  Booleans
# ====================================================================================
#
# Here is how you work with numbers in Ruby. Take the text
# in this file and paste it into repl.rb and save:

repl do
  puts '* RUBY PRIMER: TrueClass, FalseClass, NilClass (truthy / falsey values)'
  puts "Anything that *isn't* false or nil is true."

  c = 30
  puts "The value of c is #{c}."

  if c
    puts "This if statement ran because c is truthy."
  end

  d = false
  puts "The value if d is #{d}. The type for d is #{d.class}."

  if !d
    puts "This if statement ran because d is falsey, using the not operator (!)."
  end

  e = nil
  puts "Nil is also considered falsey. The value of e is: #{e} (a blank string when printed). Which is of type #{e.class}."

  if !e
    puts "This if statement ran because e is nil and the if statement applied the NOT operator. !e yields a type of #{(!e).class}."
  end
end

Learn Ruby Optional - Intermediate Ruby Primer - conditionals.txt

# ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/05_conditionals.txt
# ====================================================================================
#  Conditionals
# ====================================================================================
#
# Here is how you create conditionals in Ruby. Take the text
# in this file and paste it into repl.rb and save:

repl do
  puts "* RUBY PRIMER: Conditionals"
end

# ====================================================================================
#  if
# ====================================================================================

repl do
  puts "** INFO: if statement"
  i_am_one = 1
  if i_am_one
    puts "This was printed because i_am_one is truthy."
  end
end

# ====================================================================================
#  if/else
# ====================================================================================

repl do
  puts "** INFO: if/else statement"
  i_am_false = false
  if i_am_false
    puts "This will NOT get printed because i_am_false is false."
  else
    puts "This was printed because i_am_false is false."
  end
end


# ====================================================================================
#  if/elsif/else
# ====================================================================================

repl do
  puts "** INFO: if/elsif/else statement"
  i_am_false = false
  i_am_true  = true
  if i_am_false
    puts "This will NOT get printed because i_am_false is false."
  elsif i_am_true
    puts "This was printed because i_am_true is true."
  else
    puts "This will NOT get printed i_am_true was true."
  end
end

# ====================================================================================
#  case
# ====================================================================================

repl do
  puts "** INFO case statement"
  i_am_one = 1 # change this value to see different results

  case i_am_one
  when 10
    puts "the value of i_am_one is 10"
  when 9
    puts "the value of i_am_one is 9"
  when 5
    puts "the value of i_am_one is 5"
  when 1
    puts "the value of i_am_one is 1"
  else
    puts "Value wasn't cased."
  end
end

# ====================================================================================
#  comparison operators
# ====================================================================================

repl do
  puts "** INFO: Different types of comparisons"
  if 4 == 4
    puts "4 equals 4 (==)"
  end

  if 4 != 3
    puts "4 does not equal 3 (!=)"
  end

  if 3 < 4
    puts "3 is less than 4 (<)"
  end

  if 4 > 3
    puts "4 is greater than 3 (>)"
  end
end

# ====================================================================================
#  and/or conditionals
# ====================================================================================

repl do
  puts "** INFO: AND, OR operator (&&, ||)"
  if (4 > 3) || (3 < 4) || false
    puts "print this if 4 is greater than 3 OR 3 is less than 4 OR false is true (||)"
  end

  if (4 > 3) && (3 < 4)
    puts "print this if 4 is greater than 3 AND 3 is less than 4 (&&)"
  end
end

Learn Ruby Optional - Intermediate Ruby Primer - looping.txt

# ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/06_looping.txt
# ====================================================================================
#  Looping
# ====================================================================================
#
# Looping looks a whole lot different than other languages.
# But it's pretty awesome when you get used to it.

repl do
  puts "* RUBY PRIMER: Loops"
end

# ====================================================================================
#  times
# ====================================================================================

repl do
  puts "** INFO: ~Numeric#times~ (for loop)"
  3.times do |i|
    puts i
  end
end

# ====================================================================================
#  foreach
# ====================================================================================

repl do
  puts "** INFO: ~Array#each~ (for each loop)"
  array = ["a", "b", "c", "d"]
  array.each do |char|
    puts char
  end

  puts "** INFO: ~Array#each_with_index~ (for each loop)"
  array = ["a", "b", "c", "d"]
  array.each do |char, i|
    puts "index #{i}: #{char}"
  end
end

# ====================================================================================
#  ranges
# ====================================================================================

repl do
  puts "** INFO: range block exclusive (three dots)"
  (0...3).each do |i|
    puts i
  end

  puts "** INFO: range block inclusive (two dots)"
  (0..3).each do |i|
    puts i
  end
end

Learn Ruby Optional - Intermediate Ruby Primer - functions.txt

# ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/07_functions.txt
# ====================================================================================
# Functions
# ====================================================================================

# The last statement of a function is implictly returned. Parenthesis for functions
# are optional as long as the statement can be envaluated disambiguously.

repl do
  puts "* RUBY PRIMER: Functions"
end

# ====================================================================================
# Functions single parameter
# ====================================================================================

repl do
  puts "* INFO: Function with one parameter"

  # function definition
  def add_one_to n
    n + 1
  end

  # Parenthesis are optional in Ruby as long as the
  # parsing is disambiguous. Here are a couple of variations.
  # Generally speaking, don't put parenthesis is you don't have to.

  # Conventional Usage of Parenthesis.
  puts add_one_to(3)

  # DragonRuby's recommended use of parenthesis (inner function has parenthesis).
  puts (add_one_to 3)

  # Full parens.
  puts(add_one_to(3))

  # Outer function has parenthesis
  puts(add_one_to 3)
end

# ====================================================================================
# Functions with default parameter values
# ====================================================================================

repl do
  puts "* INFO: Function with default value"
  def function_with_default_value v = 10
    v * 10
  end

  puts "Passing the argument three yields: #{function_with_default_value 3}"
  puts "Passing no argument yields: #{function_with_default_value}"
end

# ====================================================================================
# Nil default parameter value and ||= operator.
# ====================================================================================

repl do
  puts "* INFO: Using the OR EQUAL operator (||=)"
  def function_with_nil_default_with_local a = nil
    result   = a
    result ||= "DEFAULT_VALUE_OF_A_IS_NIL_OR_FALSE"
    "value is #{result}."
  end

  puts "Passing 'hi' as the argument yields: #{function_with_nil_default_with_local 'hi'}"
  puts "Passing nil: #{function_with_nil_default_with_local}"
end

Learn Ruby Optional - Intermediate Ruby Primer - arrays.txt

# ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/08_arrays.txt
# ====================================================================================
# Arrays
# ====================================================================================

# Arrays are incredibly powerful in Ruby. Learn to use them well.

repl do
  puts "* RUBY PRIMER: ARRAYS"
end

# ====================================================================================
# Enumerable ranges and .to_a
# ====================================================================================

repl do
  puts "** INFO: Create an array with the numbers 1 to 10."
  one_to_ten = (1..10).to_a
  puts one_to_ten
end

# ====================================================================================
# Finding elements
# ====================================================================================

repl do
  puts "** INFO: Finding elements in an array using ~Array#find_all~."
  puts "Create a new array that only contains even numbers from the previous array."

  one_to_ten = (1..10).to_a
  evens = one_to_ten.find_all do |number|
    number % 2 == 0
  end

  puts evens
end

# ====================================================================================
# Rejecting elements
# ====================================================================================

repl do
  puts "** INFO: Removing elements in an array using ~Array#reject~."
  puts "Create a new array that rejects odd numbers."

  one_to_ten = (1..10).to_a
  also_even = one_to_ten.reject do |number|
    number % 2 != 0
  end

  puts also_even
end

# ====================================================================================
# Array transform using the map function.
# ====================================================================================

repl do
  puts "** INFO: Creating new derived values from an array using ~Array#map~."
  puts "Create an array that doubles every number."

  one_to_ten = (1..10).to_a
  doubled = one_to_ten.map do |number|
    number * 2
  end

  puts doubled
end

# ====================================================================================
# Combining array functions.
# ====================================================================================

repl do
  puts "** INFO: Combining ~Array#find_all~ along with ~Array#map~."
  puts "Create an array that selects only odd numbers and then multiply those by 10."

  one_to_ten = (1..10).to_a
  odd_doubled = one_to_ten.find_all do |number|
    number % 2 != 0
  end.map do |odd_number|
    odd_number * 10
  end

  puts odd_doubled
end

# ====================================================================================
# Product function.
# ====================================================================================

repl do
  puts "** INFO: Create all combinations of array values using ~Array#product~."
  puts "All two-item pairs of numbers 1 to 10."
  one_to_ten = (1..10).to_a
  all_combinations = one_to_ten.product(one_to_ten)
  puts all_combinations
end

# ====================================================================================
# Uniq and sort function.
# ====================================================================================

repl do
  puts "** INFO: Providing uniq values using ~Array#uniq~ and ~Array#sort~."
  puts "All uniq combinations of numbers regardless of order."
  puts "For example: [1, 2] is the same as [2, 1]."
  one_to_ten = (1..10).to_a
  uniq_combinations =
    one_to_ten.product(one_to_ten)
              .map do |unsorted_number|
                unsorted_number.sort
              end.uniq
  puts uniq_combinations
end

# ====================================================================================
# Example of an advanced array transform.
# ====================================================================================

repl do
  puts "** INFO: Advanced chaining. Combining ~Array's ~map~, ~find_all~, ~sort~, and ~sort_by~."
  puts "All unique Pythagorean Triples between 1 and 100 sorted by area of the triangle."

  one_to_hundred = (1..100).to_a

  triples =
    one_to_hundred.product(one_to_hundred).map do |width, height|
                [width, height, Math.sqrt(width ** 2 + height ** 2)]
              end.find_all do |_, _, hypotenuse|
                hypotenuse.to_i == hypotenuse
              end.map do |triangle|
                triangle.map(&:to_i)
              end.uniq do |triangle|
                triangle.sort
              end.map do |width, height, hypotenuse|
                [width, height, hypotenuse, (width * height) / 2]
              end.sort_by do |_, _, _, area|
                area
              end

  triples.each do |width, height, hypotenuse, _|
    puts "(#{width}, #{height}, #{hypotenuse})"
  end
end

# ====================================================================================
# Example of an sorting.
# ====================================================================================

repl do
  puts "** INFO: Implementing a custom sort function that operates on the ~Hash~ datatype."

  things_to_sort = [
    { type: :background, order: 1 },
    { type: :foreground, order: 1 },
    { type: :foreground, order: 2 }
  ]
  puts "*** Original array."
  puts things_to_sort

  puts "*** Simple sort using key."
  # For a simple sort, you can use sort_by
  results = things_to_sort.sort_by do |hash|
    hash[:order]
  end

  puts results

  puts "*** Custom sort."
  puts "**** Sorting process."
  # for a more complicated sort, you can provide a block that returns
  # -1, 0, 1 for a left and right operand
  results = things_to_sort.sort do |l, r|
    sort_result = 0
    puts "here is l: #{l}"
    puts "here is r: #{r || "nil"}"
    # if either value is nil/false return 0
    if !l || !r
      sort_result = 0
    # if the type of "left" is background and the
    # type of "right" is foreground, then return
    # -1 (which means "left" is less than "right"
    elsif l[:type] == :background && r[:type] == :foreground
      sort_result = -1
    # if the type of "left" is foreground and the
    # type of "right" is background, then return
    #  1 (which means "left" is greater than "right"
    elsif l[:type] == :foreground && r[:type] == :background
      sort_result = 1
    # if "left" and "right"'s type are the same, then
    # use the order as the tie breaker
    elsif l[:order] < r[:order]
      sort_result = -1
    elsif l[:order] > r[:order]
      sort_result = 1
    # returning 0 means both values are equal
    else
      sort_result = 0
    end
    sort_result
  end.to_a

  puts "**** Sort result."
  puts results
end

# ====================================================================================
# Api documention for Array that is worth commiting to memory because arrays are so
# awesome in Ruby: https://docs.ruby-lang.org/en/2.0.0/Array.html
# ====================================================================================

Learn Ruby Optional - Intermediate Ruby Primer - main.rb

# ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/main.rb
def tick args
  args.outputs.labels << [640, 380, "Open repl.rb in the text editor of your choice and follow the document.", 0, 1]
end

Learn Ruby Optional - Intermediate Ruby Primer - repl.rb

# ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/repl.rb
# Copy and paste the code inside of the txt files here.

Rendering Basics - Labels - main.rb

# ./samples/01_rendering_basics/01_labels/app/main.rb
=begin

APIs listing that haven't been encountered in a previous sample apps:

- args.outputs.labels: An array. Values in this array generate labels
  the screen.
- args.grid.(left|right|top|bottom): Pixel value for the boundaries of the virtual
  720 p screen (Dragon Ruby Game Toolkits's virtual resolution is always 1280x720).
- Numeric#shift_(left|right|up|down): Shifts the Numeric in the correct direction
  by adding or subracting.

=end

# Labels are used to represent text elements in DragonRuby

# An example of creating a label is:
# args.outputs.labels << [320, 640, "Example", 3, 1, 255, 0, 0, 200, manaspace.ttf]

# The code above does the following:
# 1. GET the place where labels go: args.outputs.labels
# 2. Request a new LABEL be ADDED: <<
# 3. The DEFINITION of a SOLID is the ARRAY:
#     [320, 640, "Example", 3,     1,   255,   0,    0,    200,  manaspace.ttf]
#     [ X ,  Y,    TEXT,   SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]


# The tick method is called by DragonRuby every frame
# args contains all the information regarding the game.
def tick args
  tick_instructions args, "Sample app shows different version of label sizes and alignments. And how to use hashes instead of arrays."
  # Here are some examples of simple labels, with the minimum number of parameters
  # Note that the default values for the other parameters are 0, except for Alpha which is 255 and Font Style which is the default font
  args.outputs.labels << [400, 620, "Here is a label with just an x, y, and text"]

  args.outputs.labels << [args.grid.left.shift_right(5), args.grid.top.shift_down(5), "This is a label located at the top left."]
  args.outputs.labels << [args.grid.left.shift_right(5), args.grid.bottom.shift_up(30), "This is a label located at the bottom left."]
  args.outputs.labels << [args.grid.right.shift_left(420), args.grid.top.shift_down(5), "This is a label located at the top right."]
  args.outputs.labels << [args.grid.right.shift_left(440), args.grid.bottom.shift_up(30), "This is a label located at the bottom right."]

  # Demonstration of the Size Parameter
  args.outputs.labels << [175 + 150, 610 - 50, "Smaller label.",  -2]
  args.outputs.labels << [175 + 150, 580 - 50, "Small label.",    -1]
  args.outputs.labels << [175 + 150, 550 - 50, "Medium label.",    0]
  args.outputs.labels << [175 + 150, 520 - 50, "Large label.",     1]
  args.outputs.labels << [175 + 150, 490 - 50, "Larger label.",    2]

  # Demonstration of the Align Parameter
  args.outputs.labels << [260 + 150, 345 - 50, "Left aligned.",    0, 2]
  args.outputs.labels << [260 + 150, 325 - 50, "Center aligned.",  0, 1]
  args.outputs.labels << [260 + 150, 305 - 50, "Right aligned.",   0, 0]

  # Demonstration of the RGBA parameters
  args.outputs.labels << [600  + 150, 590 - 50, "Red Label.",       0, 0, 255,   0,   0]
  args.outputs.labels << [600  + 150, 570 - 50, "Green Label.",     0, 0,   0, 255,   0]
  args.outputs.labels << [600  + 150, 550 - 50, "Blue Label.",      0, 0,   0,   0, 255]
  args.outputs.labels << [600  + 150, 530 - 50, "Faded Label.",     0, 0,   0,   0,   0, 128]

  # Demonstration of the Font parameter
  # In order to use a font of your choice, add its ttf file to the project folder, where the app folder is
  args.outputs.labels << [690 + 150, 330 - 20, "Custom font (Array)", 0, 1, 125, 0, 200, 255, "manaspc.ttf" ]
  args.outputs.primitives << { x: 690 + 150,
                               y: 330 - 50,
                               text: "Custom font (Hash)",
                               size_enum: 0,
                               alignment_enum: 1,
                               r: 125,
                               g: 0,
                               b: 200,
                               a: 255,
                               font: "manaspc.ttf" }.label!

  # Primitives can hold anything, and can be given a label in the following forms
  args.outputs.primitives << [690 + 150, 330 - 80, "Custom font (.primitives Array)", 0, 1, 125, 0, 200, 255, "manaspc.ttf" ].label

  args.outputs.primitives << { x: 690 + 150,
                               y: 330 - 110,
                               text: "Custom font (.primitives Hash)",
                               size_enum: 0,
                               alignment_enum: 1,
                               r: 125,
                               g: 0,
                               b: 200,
                               a: 255,
                               font: "manaspc.ttf" }.label!
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Rendering Basics - Labels Text Wrapping - main.rb

# ./samples/01_rendering_basics/01_labels_text_wrapping/app/main.rb
def tick args
  # create a really long string
  args.state.really_long_string =  "Lorem ipsum dolor sit amet, consectetur adipiscing elit. In vulputate viverra metus et vehicula. Aenean quis accumsan dolor. Nulla tempus, ex et lacinia elementum, nisi felis ullamcorper sapien, sed sagittis sem justo eu lectus. Etiam ut vehicula lorem, nec placerat ligula. Duis varius ultrices magna non sagittis. Aliquam et sem vel risus viverra hendrerit. Maecenas dapibus congue lorem, a blandit mauris feugiat sit amet."
  args.state.really_long_string += "\n"
  args.state.really_long_string += "Sed quis metus lacinia mi dapibus fermentum nec id nunc. Donec tincidunt ante a sem bibendum, eget ultricies ex mollis. Quisque venenatis erat quis pretium bibendum. Pellentesque vel laoreet nibh. Cras gravida nisi nec elit pulvinar, in feugiat leo blandit. Quisque sodales quam sed congue consequat. Vivamus placerat risus vitae ex feugiat viverra. In lectus arcu, pellentesque vel ipsum ac, dictum finibus enim. Quisque consequat leo in urna dignissim, eu tristique ipsum accumsan. In eros sem, iaculis ac rhoncus eu, laoreet vitae ipsum. In sodales, ante eu tempus vehicula, mi nulla luctus turpis, eu egestas leo sapien et mi."

  # length of characters on line
  max_character_length = 80

  # line height
  line_height = 25

  long_string = args.state.really_long_string

  # API: args.string.wrapped_lines string, max_character_length
  long_strings_split = args.string.wrapped_lines long_string, max_character_length

  # render a label for each line and offset by the line_height
  args.outputs.labels << long_strings_split.map_with_index do |s, i|
    {
      x: 60,
      y: 60.from_top - (i * line_height),
      text: s
    }
  end
end

Rendering Basics - Lines - main.rb

# ./samples/01_rendering_basics/02_lines/app/main.rb
=begin

APIs listing that haven't been encountered in a previous sample apps:

- args.outputs.lines: An array. Values in this array generate lines on
  the screen.
- args.state.tick_count: This property contains an integer value that
  represents the current frame. GTK renders at 60 FPS. A value of 0
  for args.state.tick_count represents the initial load of the game.

=end

# The parameters required for lines are:
# 1. The initial point (x, y)
# 2. The end point (x2, y2)
# 3. The rgba values for the color and transparency (r, g, b, a)

# An example of creating a line would be:
# args.outputs.lines << [100, 100, 300, 300, 255, 0, 255, 255]

# This would create a line from (100, 100) to (300, 300)
# The RGB code (255, 0, 255) would determine its color, a purple
# It would have an Alpha value of 255, making it completely opaque

def tick args
  tick_instructions args, "Sample app shows how to create lines."

  args.outputs.labels << [480, 620, "Lines (x, y, x2, y2, r, g, b, a)"]

  # Some simple lines
  args.outputs.lines  << [380, 450, 675, 450]
  args.outputs.lines  << [380, 410, 875, 410]

  # These examples utilize args.state.tick_count to change the length of the lines over time
  # args.state.tick_count is the ticks that have occurred in the game
  # This is accomplished by making either the starting or ending point based on the args.state.tick_count
  args.outputs.lines  << [380, 370, 875, 370, args.state.tick_count % 255, 0, 0, 255]
  args.outputs.lines  << [380, 330 - args.state.tick_count % 25, 875, 330, 0, 0, 0, 255]
  args.outputs.lines  << [380 + args.state.tick_count % 400, 290, 875, 290, 0, 0, 0, 255]
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Rendering Basics - Solids Borders - main.rb

# ./samples/01_rendering_basics/03_solids_borders/app/main.rb
=begin

APIs listing that haven't been encountered in a previous sample apps:

- args.outputs.solids: An array. Values in this array generate
  solid/filled rectangles on the screen.

=end

# Rects are outputted in DragonRuby as rectangles
# If filled in, they are solids
# If hollow, they are borders

# Solids are added to args.outputs.solids
# Borders are added to args.outputs.borders

# The parameters required for rects are:
# 1. The upper right corner (x, y)
# 2. The width (w)
# 3. The height (h)
# 4. The rgba values for the color and transparency (r, g, b, a)

# Here is an example of a rect definition:
# [100, 100, 400, 500, 0, 255, 0, 180]

# The example would create a rect from (100, 100)
# Extending 400 pixels across the x axis
# and 500 pixels across the y axis
# The rect would be green (0, 255, 0)
# and mostly opaque with some transparency (180)

# Whether the rect would be filled or not depends on if
# it is added to args.outputs.solids or args.outputs.borders


def tick args
  tick_instructions args, "Sample app shows how to create solid squares."
  args.outputs.labels << [460, 600, "Solids (x, y, w, h, r, g, b, a)"]
  args.outputs.solids << [470, 520, 50, 50]
  args.outputs.solids << [530, 520, 50, 50, 0, 0, 0]
  args.outputs.solids << [590, 520, 50, 50, 255, 0, 0]
  args.outputs.solids << [650, 520, 50, 50, 255, 0, 0, 128]
  args.outputs.solids << [710, 520, 50, 50, 0, 0, 0, 128 + args.state.tick_count % 128]


  args.outputs.labels <<  [460, 400, "Borders (x, y, w, h, r, g, b, a)"]
  args.outputs.borders << [470, 320, 50, 50]
  args.outputs.borders << [530, 320, 50, 50, 0, 0, 0]
  args.outputs.borders << [590, 320, 50, 50, 255, 0, 0]
  args.outputs.borders << [650, 320, 50, 50, 255, 0, 0, 128]
  args.outputs.borders << [710, 320, 50, 50, 0, 0, 0, 128 + args.state.tick_count % 128]
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Rendering Basics - Sprites - main.rb

# ./samples/01_rendering_basics/04_sprites/app/main.rb
=begin

APIs listing that haven't been encountered in a previous sample apps:

- args.outputs.sprites: An array. Values in this array generate
  sprites on the screen. The location of the sprite is assumed to
  be under the mygame/ directory (the exception being dragonruby.png).

=end


# For all other display outputs, Sprites are your solution
# Sprites import images and display them with a certain rectangular area
# The image can be of any usual format and should be located within the folder,
# similar to additional fonts.

# Sprites have the following parameters
# Rectangular area (x, y, width, height)
# The image (path)
# Rotation (angle)
# Alpha (a)

def tick args
  tick_instructions args, "Sample app shows how to render a sprite. Set its alpha, and rotate it."
  args.outputs.labels <<  [460, 600, "Sprites (x, y, w, h, path, angle, a)"]
  args.outputs.sprites << [460, 470, 128, 101, 'dragonruby.png']
  args.outputs.sprites << [610, 470, 128, 101, 'dragonruby.png', args.state.tick_count % 360]
  args.outputs.sprites << [760, 470, 128, 101, 'dragonruby.png', 0, args.state.tick_count % 255]
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Rendering Basics - Sounds - main.rb

# ./samples/01_rendering_basics/05_sounds/app/main.rb
=begin

 APIs Listing that haven't been encountered in previous sample apps:

 - sample: Chooses random element from array.
   In this sample app, the target note is set by taking a sample from the collection
   of available notes.

 Reminders:

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

 - args.outputs.labels: An array. The values generate a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.
=end

# This sample app allows users to test their musical skills by matching the piano sound that plays in each
# level to the correct note.

# Runs all the methods necessary for the game to function properly.
def tick args
  args.outputs.labels << [640, 360, "Click anywhere to play a random sound.", 0, 1]
  args.state.notes ||= [:C3, :D3, :E3, :F3, :G3, :A3, :B3, :C4]

  if args.inputs.mouse.click
    # Play a sound by adding a string to args.outputs.sounds
    args.outputs.sounds << "sounds/#{args.state.notes.sample}.wav" # sound of target note is output
  end
end

Input Basics - Keyboard - main.rb

# ./samples/02_input_basics/01_keyboard/app/main.rb
=begin

APIs listing that haven't been encountered in a previous sample apps:

- args.inputs.keyboard.key_up.KEY: The value of the properties will be set
  to the frame  that the key_up event occurred (the frame correlates
  to args.state.tick_count). Otherwise the value will be nil. For a
  full listing of keys, take a look at mygame/documentation/06-keyboard.md.
- args.state.PROPERTY: The state property on args is a dynamic
  structure. You can define ANY property here with ANY type of
  arbitrary nesting. Properties defined on args.state will be retained
  across frames. If you attempt access a property that doesn't exist
  on args.state, it will simply return nil (no exception will be thrown).

=end

# Along with outputs, inputs are also an essential part of video game development
# DragonRuby can take input from keyboards, mouse, and controllers.
# This sample app will cover keyboard input.

# args.inputs.keyboard.key_up.a will check to see if the a key has been pressed
# This will work with the other keys as well


def tick args
  tick_instructions args, "Sample app shows how keyboard events are registered and accessed.", 360
  # Notice how small_font accounts for all the remaining parameters
  args.outputs.labels << { x: 460, y: row_to_px(args, 0), text: "Current game time: #{args.state.tick_count}", size_enum: -1 }
  args.outputs.labels << { x: 460, y: row_to_px(args, 2), text: "Keyboard input: args.inputs.keyboard.key_up.h", size_enum: -1 }
  args.outputs.labels << { x: 460, y: row_to_px(args, 3), text: "Press \"h\" on the keyboard.", size_enum: -1 }

  # Input on a specifc key can be found through args.inputs.keyboard.key_up followed by the key
  if args.inputs.keyboard.key_up.h
    args.state.h_pressed_at = args.state.tick_count
  end

  # This code simplifies to if args.state.h_pressed_at has not been initialized, set it to false
  args.state.h_pressed_at ||= false

  if args.state.h_pressed_at
    args.outputs.labels << { x: 460, y: row_to_px(args, 4), text: "\"h\" was pressed at time: #{args.state.h_pressed_at}", size_enum: -1 }
  else
    args.outputs.labels << { x: 460, y: row_to_px(args, 4), text: "\"h\" has never been pressed.", size_enum: -1 }
  end

  tick_help_text args
end

def row_to_px args, row_number, y_offset = 20
  # This takes a row_number and converts it to pixels DragonRuby understands.
  # Row 0 starts 5 units below the top of the grid
  # Each row afterward is 20 units lower
  args.grid.top - 5 - (y_offset * row_number)
end

# Don't worry about understanding the code within this method just yet.
# This method shows you the help text within the game.
def tick_help_text args
  return unless args.state.h_pressed_at

  args.state.key_value_history      ||= {}
  args.state.key_down_value_history ||= {}
  args.state.key_held_value_history ||= {}
  args.state.key_up_value_history   ||= {}

  if (args.inputs.keyboard.key_down.truthy_keys.length > 0 ||
      args.inputs.keyboard.key_held.truthy_keys.length > 0 ||
      args.inputs.keyboard.key_up.truthy_keys.length > 0)
    args.state.help_available = true
    args.state.no_activity_debounce = nil
  else
    args.state.no_activity_debounce ||= 5.seconds
    args.state.no_activity_debounce -= 1
    if args.state.no_activity_debounce <= 0
      args.state.help_available = false
      args.state.key_value_history        = {}
      args.state.key_down_value_history   = {}
      args.state.key_held_value_history   = {}
      args.state.key_up_value_history     = {}
    end
  end

  args.outputs.labels << { x: 10, y: row_to_px(args, 6), text: "This is the api for the keys you've pressed:", size_enum: -1, r: 180 }

  if !args.state.help_available
    args.outputs.labels << [10, row_to_px(args, 7),  "Press a key and I'll show code to access the key and what value will be returned if you used the code.", small_font]
    return
  end

  args.outputs.labels << { x: 10 , y: row_to_px(args, 7), text: "args.inputs.keyboard",          size_enum: -2 }
  args.outputs.labels << { x: 330, y: row_to_px(args, 7), text: "args.inputs.keyboard.key_down", size_enum: -2 }
  args.outputs.labels << { x: 650, y: row_to_px(args, 7), text: "args.inputs.keyboard.key_held", size_enum: -2 }
  args.outputs.labels << { x: 990, y: row_to_px(args, 7), text: "args.inputs.keyboard.key_up",   size_enum: -2 }

  fill_history args, :key_value_history,      :down_or_held, nil
  fill_history args, :key_down_value_history, :down,        :key_down
  fill_history args, :key_held_value_history, :held,        :key_held
  fill_history args, :key_up_value_history,   :up,          :key_up

  render_help_labels args, :key_value_history,      :down_or_held, nil,      10
  render_help_labels args, :key_down_value_history, :down,        :key_down, 330
  render_help_labels args, :key_held_value_history, :held,        :key_held, 650
  render_help_labels args, :key_up_value_history,   :up,          :key_up,   990
end

def fill_history args, history_key, state_key, keyboard_method
  fill_single_history args, history_key, state_key, keyboard_method, :raw_key
  fill_single_history args, history_key, state_key, keyboard_method, :char
  args.inputs.keyboard.keys[state_key].each do |key_name|
    fill_single_history args, history_key, state_key, keyboard_method, key_name
  end
end

def fill_single_history args, history_key, state_key, keyboard_method, key_name
  current_value = args.inputs.keyboard.send(key_name)
  if keyboard_method
    current_value = args.inputs.keyboard.send(keyboard_method).send(key_name)
  end
  args.state.as_hash[history_key][key_name] ||= []
  args.state.as_hash[history_key][key_name] << current_value
  args.state.as_hash[history_key][key_name] = args.state.as_hash[history_key][key_name].reverse.uniq.take(3).reverse
end

def render_help_labels args, history_key, state_key, keyboard_method, x
  idx = 8
  args.outputs.labels << args.state
                           .as_hash[history_key]
                           .keys
                           .reverse
                           .map
                           .with_index do |k, i|
    v = args.state.as_hash[history_key][k]
    current_value = args.inputs.keyboard.send(k)
    if keyboard_method
      current_value = args.inputs.keyboard.send(keyboard_method).send(k)
    end
    idx += 2
    [
      { x: x, y: row_to_px(args, idx + 0, 16), text: "    .#{k} is #{current_value || "nil"}", size_enum: -2 },
      { x: x, y: row_to_px(args, idx + 1, 16), text: "       was #{v}", size_enum: -2 }
    ]
  end
end


def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << { x: 0,   y: y - 50, w: 1280, h: 60 }.solid!
  args.outputs.debug << { x: 640, y: y,      text: text,
                          size_enum: 1, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
  args.outputs.debug << { x: 640, y: y - 25, text: "(click to dismiss instructions)",
                          size_enum: -2, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
end

Input Basics - Moving A Sprite - main.rb

# ./samples/02_input_basics/01_moving_a_sprite/app/main.rb
def tick args
  # create a player and set default values
  # for the player's x, y, w (width), and h (height)
  args.state.player.x ||= 100
  args.state.player.y ||= 100
  args.state.player.w ||=  50
  args.state.player.h ||=  50

  # render the player to the screen
  args.outputs.sprites << { x: args.state.player.x,
                            y: args.state.player.y,
                            w: args.state.player.w,
                            h: args.state.player.h,
                            path: 'sprites/square/green.png' }

  # move the player around using the keyboard
  if args.inputs.up
    args.state.player.y += 10
  elsif args.inputs.down
    args.state.player.y -= 10
  end

  if args.inputs.left
    args.state.player.x -= 10
  elsif args.inputs.right
    args.state.player.x += 10
  end
end

$gtk.reset

Input Basics - Mouse - main.rb

# ./samples/02_input_basics/02_mouse/app/main.rb
=begin

APIs that haven't been encountered in a previous sample apps:

- args.inputs.mouse.click: This property will be set if the mouse was clicked.
- args.inputs.mouse.click.point.(x|y): The x and y location of the mouse.
- args.inputs.mouse.click.point.created_at: The frame the mouse click occurred in.
- args.inputs.mouse.click.point.created_at_elapsed: How many frames have passed
  since the click event.

Reminder:

- args.state.PROPERTY: The state property on args is a dynamic
  structure. You can define ANY property here with ANY type of
  arbitrary nesting. Properties defined on args.state will be retained
  across frames. If you attempt access a property that doesn't exist
  on args.state, it will simply return nil (no exception will be thrown).

=end

# This code demonstrates DragonRuby mouse input

# To see if the a mouse click occurred
# Use args.inputs.mouse.click
# Which returns a boolean

# To see where a mouse click occurred
# Use args.inputs.mouse.click.point.x AND
# args.inputs.mouse.click.point.y

# To see which frame the click occurred
# Use args.inputs.mouse.click.created_at

# To see how many frames its been since the click occurred
# Use args.inputs.mouse.click.created_at_elapsed

# Saving the click in args.state can be quite useful

def tick args
  tick_instructions args, "Sample app shows how mouse events are registered and how to measure elapsed time."
  x = 460

  args.outputs.labels << small_label(args, x, 11, "Mouse input: args.inputs.mouse")

  if args.inputs.mouse.click
    args.state.last_mouse_click = args.inputs.mouse.click
  end

  if args.state.last_mouse_click
    click = args.state.last_mouse_click
    args.outputs.labels << small_label(args, x, 12, "Mouse click happened at: #{click.created_at}")
    args.outputs.labels << small_label(args, x, 13, "Mouse clicked #{click.created_at_elapsed} ticks ago")
    args.outputs.labels << small_label(args, x, 14, "Mouse click location: #{click.point.x}, #{click.point.y}")
  else
    args.outputs.labels << small_label(args, x, 12, "Mouse click has not occurred yet.")
    args.outputs.labels << small_label(args, x, 13, "Please click mouse.")
  end
end

def small_label args, x, row, message
  # This method effectively combines the row_to_px and small_font methods
  # It changes the given row value to a DragonRuby pixel value
  # and adds the customization parameters
  { x: x, y: row_to_px(args, row), text: message, alignment_enum: -2 }
end

def row_to_px args, row_number
  args.grid.top.shift_down(5).shift_down(20 * row_number)
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << { x: 0,   y: y - 50, w: 1280, h: 60 }.solid!
  args.outputs.debug << { x: 640, y: y, text: text, size_enum: 1, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
  args.outputs.debug << { x: 640, y: y - 25, text: "(click to dismiss instructions)", size_enum: -2, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
end

Input Basics - Mouse Point To Rect - main.rb

# ./samples/02_input_basics/03_mouse_point_to_rect/app/main.rb
=begin

APIs that haven't been encountered in a previous sample apps:

- args.outputus.borders: An array. Values in this array will be rendered as
  unfilled rectangles on the screen.
- ARRAY#inside_rect?: An array with at least two values is considered a point. An array
  with at least four values is considered a rect. The inside_rect? function returns true
  or false depending on if the point is inside the rect.

  ```
  # Point:  x: 100, y: 100
  # Rect:   x: 0, y: 0, w: 500, h: 500
  # Result: true

  [100, 100].inside_rect? [0, 0, 500, 500]
  ```

  ```
  # Point:  x: 100, y: 100
  # Rect:   x: 300, y: 300, w: 100, h: 100
  # Result: false

  [100, 100].inside_rect? [300, 300, 100, 100]
  ```

- args.inputs.mouse.click.point.created_at: The frame the mouse click occurred in.
- args.inputs.mouse.click.point.created_at_elapsed: How many frames have passed
  since the click event.

=end

# To determine whether a point is in a rect
# Use point.inside_rect? rect

# This is useful to determine if a click occurred in a rect

def tick args
  tick_instructions args, "Sample app shows how to determing if a click happened inside a rectangle."

  x = 460

  args.outputs.labels << small_label(args, x, 15, "Click inside the blue box maybe ---->")

  box = { x: 785, y: 370, w: 50, h: 50, r: 0, g: 0, b: 170 }
  args.outputs.borders << box

  # Saves the most recent click into args.state
  # Unlike the other components of args,
  # args.state does not reset every tick.
  if args.inputs.mouse.click
    args.state.last_mouse_click = args.inputs.mouse.click
  end

  if args.state.last_mouse_click
    if args.state.last_mouse_click.point.inside_rect? box
      args.outputs.labels << small_label(args, x, 16, "Mouse click happened *inside* the box.")
    else
      args.outputs.labels << small_label(args, x, 16, "Mouse click happened *outside* the box.")
    end
  else
    args.outputs.labels << small_label(args, x, 16, "Mouse click has not occurred yet.")
  end
end

def small_label args, x, row, message
  { x: x, y: row_to_px(args, row), text: message, size_enum: -2 }
end

def row_to_px args, row_number
  args.grid.top.shift_down(5).shift_down(20 * row_number)
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << { x: 0,   y: y - 50, w: 1280, h: 60 }.solid!
  args.outputs.debug << { x: 640, y: y, text: text, size_enum: 1, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
  args.outputs.debug << { x: 640, y: y - 25, text: "(click to dismiss instructions)", size_enum: -2, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
end

Input Basics - Mouse Rect To Rect - main.rb

# ./samples/02_input_basics/04_mouse_rect_to_rect/app/main.rb
=begin

APIs that haven't been encountered in a previous sample apps:

- args.outputs.borders: An array. Values in this array will be rendered as
  unfilled rectangles on the screen.
- ARRAY#intersect_rect?: An array with at least four values is
  considered a rect. The intersect_rect? function returns true
  or false depending on if the two rectangles intersect.

  ```
  # Rect One: x: 100, y: 100, w: 100, h: 100
  # Rect Two: x: 0, y: 0, w: 500, h: 500
  # Result:   true

  [100, 100, 100, 100].intersect_rect? [0, 0, 500, 500]
  ```

  ```
  # Rect One: x: 100, y: 100, w: 10, h: 10
  # Rect Two: x: 500, y: 500, w: 10, h: 10
  # Result:   false

  [100, 100, 10, 10].intersect_rect? [500, 500, 10, 10]
  ```

=end

# Similarly, whether rects intersect can be found through
# rect1.intersect_rect? rect2

def tick args
  tick_instructions args, "Sample app shows how to determine if two rectangles intersect."
  x = 460

  args.outputs.labels << small_label(args, x, 3, "Click anywhere on the screen")
  # red_box = [460, 250, 355, 90, 170, 0, 0]
  # args.outputs.borders << red_box

  # args.state.box_collision_one and args.state.box_collision_two
  # Are given values of a solid when they should be rendered
  # They are stored in game so that they do not get reset every tick
  if args.inputs.mouse.click
    if !args.state.box_collision_one
      args.state.box_collision_one = { x: args.inputs.mouse.click.point.x - 25,
                                       y: args.inputs.mouse.click.point.y - 25,
                                       w: 125, h: 125,
                                       r: 180, g: 0, b: 0, a: 180 }
    elsif !args.state.box_collision_two
      args.state.box_collision_two = { x: args.inputs.mouse.click.point.x - 25,
                                       y: args.inputs.mouse.click.point.y - 25,
                                       w: 125, h: 125,
                                       r: 0, g: 0, b: 180, a: 180 }
    else
      args.state.box_collision_one = nil
      args.state.box_collision_two = nil
    end
  end

  if args.state.box_collision_one
    args.outputs.solids << args.state.box_collision_one
  end

  if args.state.box_collision_two
    args.outputs.solids << args.state.box_collision_two
  end

  if args.state.box_collision_one && args.state.box_collision_two
    if args.state.box_collision_one.intersect_rect? args.state.box_collision_two
      args.outputs.labels << small_label(args, x, 4, 'The boxes intersect.')
    else
      args.outputs.labels << small_label(args, x, 4, 'The boxes do not intersect.')
    end
  else
    args.outputs.labels << small_label(args, x, 4, '--')
  end
end

def small_label args, x, row, message
  { x: x, y: row_to_px(args, row), text: message, size_enum: -2 }
end

def row_to_px args, row_number
  args.grid.top - 5 - (20 * row_number)
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Input Basics - Controller - main.rb

# ./samples/02_input_basics/05_controller/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - args.current_controller.key_held.KEY: Will check to see if a specific key
   is being held down on the controller.
   If there is more than one controller being used, they can be differentiated by
   using names like controller_one and controller_two.

   For a full listing of buttons, take a look at mygame/documentation/08-controllers.md.

 Reminder:

 - args.state.PROPERTY: The state property on args is a dynamic
   structure. You can define ANY property here with ANY type of
   arbitrary nesting. Properties defined on args.state will be retained
   across frames. If you attempt to access a property that doesn't exist
   on args.state, it will simply return nil (no exception will be thrown).

   In this sample app, args.state.BUTTONS is an array that stores the buttons of the controller.
   The parameters of a button are:
   1. the position (x, y)
   2. the input key held on the controller
   3. the text or name of the button

=end

# This sample app provides a visual demonstration of a standard controller, including
# the placement and function of all buttons.

class ControllerDemo
  attr_accessor :inputs, :state, :outputs

  # Calls the methods necessary for the app to run successfully.
  def tick
    process_inputs
    render
  end

  # Starts with an empty collection of buttons.
  # Adds buttons that are on the controller to the collection.
  def process_inputs
    state.target  ||= :controller_one
    state.buttons = []

    if inputs.keyboard.key_down.tab
      if state.target == :controller_one
        state.target = :controller_two
      elsif state.target == :controller_two
        state.target = :controller_three
      elsif state.target == :controller_three
        state.target = :controller_four
      elsif state.target == :controller_four
        state.target = :controller_one
      end
    end

    state.buttons << { x: 100,  y: 500, active: current_controller.key_held.l1, text: "L1"}
    state.buttons << { x: 100,  y: 600, active: current_controller.key_held.l2, text: "L2"}
    state.buttons << { x: 1100, y: 500, active: current_controller.key_held.r1, text: "R1"}
    state.buttons << { x: 1100, y: 600, active: current_controller.key_held.r2, text: "R2"}
    state.buttons << { x: 540,  y: 450, active: current_controller.key_held.select, text: "Select"}
    state.buttons << { x: 660,  y: 450, active: current_controller.key_held.start, text: "Start"}
    state.buttons << { x: 200,  y: 300, active: current_controller.key_held.left, text: "Left"}
    state.buttons << { x: 300,  y: 400, active: current_controller.key_held.up, text: "Up"}
    state.buttons << { x: 400,  y: 300, active: current_controller.key_held.right, text: "Right"}
    state.buttons << { x: 300,  y: 200, active: current_controller.key_held.down, text: "Down"}
    state.buttons << { x: 800,  y: 300, active: current_controller.key_held.x, text: "X"}
    state.buttons << { x: 900,  y: 400, active: current_controller.key_held.y, text: "Y"}
    state.buttons << { x: 1000, y: 300, active: current_controller.key_held.a, text: "A"}
    state.buttons << { x: 900,  y: 200, active: current_controller.key_held.b, text: "B"}
    state.buttons << { x: 450 + current_controller.left_analog_x_perc * 100,
                       y: 100 + current_controller.left_analog_y_perc * 100,
                       active: current_controller.key_held.l3,
                       text: "L3" }
    state.buttons << { x: 750 + current_controller.right_analog_x_perc * 100,
                       y: 100 + current_controller.right_analog_y_perc * 100,
                       active: current_controller.key_held.r3,
                       text: "R3" }
  end

  # Gives each button a square shape.
  # If the button is being pressed or held (which means it is considered active),
  # the square is filled in. Otherwise, the button simply has a border.
  def render
    state.buttons.each do |b|
      rect = { x: b.x, y: b.y, w: 75, h: 75 }

      if b.active # if button is pressed
        outputs.solids << rect # rect is output as solid (filled in)
      else
        outputs.borders << rect # otherwise, output as border
      end

      # Outputs the text of each button using labels.
      outputs.labels << { x: b.x, y: b.y + 95, text: b.text } # add 95 to place label above button
    end

    outputs.labels << { x:  10, y: 60, text: "Left Analog x: #{current_controller.left_analog_x_raw} (#{current_controller.left_analog_x_perc * 100}%)" }
    outputs.labels << { x:  10, y: 30, text: "Left Analog y: #{current_controller.left_analog_y_raw} (#{current_controller.left_analog_y_perc * 100}%)" }
    outputs.labels << { x: 1270, y: 60, text: "Right Analog x: #{current_controller.right_analog_x_raw} (#{current_controller.right_analog_x_perc * 100}%)", alignment_enum: 2 }
    outputs.labels << { x: 1270, y: 30, text: "Right Analog y: #{current_controller.right_analog_y_raw} (#{current_controller.right_analog_y_perc * 100}%)" , alignment_enum: 2 }

    outputs.labels << { x: 640, y: 60, text: "Target: #{state.target} (press tab to go to next controller)", alignment_enum: 1 }
    outputs.labels << { x: 640, y: 30, text: "Connected: #{current_controller.connected}", alignment_enum: 1 }
  end

  def current_controller
    if state.target == :controller_one
      return inputs.controller_one
    elsif state.target == :controller_two
      return inputs.controller_two
    elsif state.target == :controller_three
      return inputs.controller_three
    elsif state.target == :controller_four
      return inputs.controller_four
    end
  end
end

$controller_demo = ControllerDemo.new

def tick args
  tick_instructions args, "Sample app shows how controller input is handled. You'll need to connect a USB controller."
  $controller_demo.inputs = args.inputs
  $controller_demo.state = args.state
  $controller_demo.outputs = args.outputs
  $controller_demo.tick
end

# Resets the app.
def r
  $gtk.reset
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Input Basics - Touch - main.rb

# ./samples/02_input_basics/06_touch/app/main.rb
def tick args
  args.outputs.background_color = [ 0, 0, 0 ]
  args.outputs.primitives << [640, 700, "Touch your screen.", 5, 1, 255, 255, 255].label

  # If you don't want to get fancy, you can just look for finger_one
  #  (and _two, if you like), which are assigned in the order new touches hit
  #  the screen. If not nil, they are touching right now, and are just
  #  references to specific items in the args.input.touch hash.
  # If finger_one lifts off, it will become nil, but finger_two, if it was
  #  touching, remains until it also lifts off. When all fingers lift off, the
  #  the next new touch will be finger_one again, but until then, new touches
  #  don't fill in earlier slots.
  if !args.inputs.finger_one.nil?
    args.outputs.primitives << { x: 640, y: 650, text: "Finger #1 is touching at (#{args.inputs.finger_one.x}, #{args.inputs.finger_one.y}).",
                                 size_enum: 5, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
  end
  if !args.inputs.finger_two.nil?
    args.outputs.primitives << { x: 640, y: 600, text: "Finger #2 is touching at (#{args.inputs.finger_two.x}, #{args.inputs.finger_two.y}).",
                                 size_enum: 5, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
  end

  # Here's the more flexible interface: this will report as many simultaneous
  #  touches as the system can handle, but it's a little more effort to track
  #  them. Each item in the args.input.touch hash has a unique key (an
  #  incrementing integer) that exists until the finger lifts off. You can
  #  tell which order the touches happened globally by the key value, or
  #  by the touch[id].touch_order field, which resets to zero each time all
  #  touches have lifted.

  args.state.colors ||= [
    0xFF0000, 0x00FF00, 0x1010FF, 0xFFFF00, 0xFF00FF, 0x00FFFF, 0xFFFFFF
  ]

  size = 100
  args.inputs.touch.each { |k,v|
    color = args.state.colors[v.touch_order % 7]
    r = (color & 0xFF0000) >> 16
    g = (color & 0x00FF00) >> 8
    b = (color & 0x0000FF)
    args.outputs.primitives << { x: v.x - (size / 2), y: v.y + (size / 2), w: size, h: size, r: r, g: g, b: b, a: 255 }.solid!
    args.outputs.primitives << { x: v.x, y: v.y + size, text: k.to_s, alignment_enum: 1 }.label!
  }
end

Input Basics - Managing Scenes - main.rb

# ./samples/02_input_basics/07_managing_scenes/app/main.rb
def tick args
  # initialize the scene to scene 1
  args.state.current_scene ||= :title_scene
  # capture the current scene to verify it didn't change through
  # the duration of tick
  current_scene = args.state.current_scene

  # tick whichever scene is current
  case current_scene
  when :title_scene
    tick_title_scene args
  when :game_scene
    tick_game_scene args
  when :game_over_scene
    tick_game_over_scene args
  end

  # make sure that the current_scene flag wasn't set mid tick
  if args.state.current_scene != current_scene
    raise "Scene was changed incorrectly. Set args.state.next_scene to change scenes."
  end

  # if next scene was set/requested, then transition the current scene to the next scene
  if args.state.next_scene
    args.state.current_scene = args.state.next_scene
    args.state.next_scene = nil
  end
end

def tick_title_scene args
  args.outputs.labels << { x: 640,
                           y: 360,
                           text: "Title Scene (click to go to game)",
                           alignment_enum: 1 }

  if args.inputs.mouse.click
    args.state.next_scene = :game_scene
  end
end

def tick_game_scene args
  args.outputs.labels << { x: 640,
                           y: 360,
                           text: "Game Scene (click to go to game over)",
                           alignment_enum: 1 }

  if args.inputs.mouse.click
    args.state.next_scene = :game_over_scene
  end
end

def tick_game_over_scene args
  args.outputs.labels << { x: 640,
                           y: 360,
                           text: "Game Over Scene (click to go to title)",
                           alignment_enum: 1 }

  if args.inputs.mouse.click
    args.state.next_scene = :title_scene
  end
end

Rendering Sprites - Animation Using Separate Pngs - main.rb

# ./samples/03_rendering_sprites/01_animation_using_separate_pngs/app/main.rb
=begin

 Reminders:

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

   In this sample app, we're using string interpolation to iterate through images in the
   sprites folder using their image path names.

 - args.outputs.sprites: An array. Values in this array generate sprites on the screen.
   The parameters are [X, Y, WIDTH, HEIGHT, IMAGE PATH]
   For more information about sprites, go to mygame/documentation/05-sprites.md.

 - args.outputs.labels: An array. Values in the array generate labels on the screen.
   The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.

 - args.inputs.keyboard.key_down.KEY: Determines if a key is in the down state, or pressed.
   Stores the frame that key was pressed on.
   For more information about the keyboard, go to mygame/documentation/06-keyboard.md.

=end

# This sample app demonstrates how sprite animations work.
# There are two sprites that animate forever and one sprite
# that *only* animates when you press the "f" key on the keyboard.

# This is the entry point to your game. The `tick` method
# executes at 60 frames per second. There are two methods
# in this tick "entry point": `looping_animation`, and the
# second method is `one_time_animation`.
def tick args
  # uncomment the line below to see animation play out in slow motion
  # args.gtk.slowmo! 6
  looping_animation args
  one_time_animation args
end

# This function shows how to animate a sprite that loops forever.
def looping_animation args
  # Here we define a few local variables that will be sent
  # into the magic function that gives us the correct sprite image
  # over time. There are four things we need in order to figure
  # out which sprite to show.

  # 1. When to start the animation.
  start_looping_at = 0

  # 2. The number of pngs that represent the full animation.
  number_of_sprites = 6

  # 3. How long to show each png.
  number_of_frames_to_show_each_sprite = 4

  # 4. Whether the animation should loop once, or forever.
  does_sprite_loop = true

  # With the variables defined above, we can get a number
  # which represents the sprite to show by calling the `frame_index` function.
  # In this case the number will be between 0, and 5 (you can see the sprites
  # in the ./sprites directory).
  sprite_index = start_looping_at.frame_index number_of_sprites,
                                              number_of_frames_to_show_each_sprite,
                                              does_sprite_loop

  # Now that we have `sprite_index, we can present the correct file.
  args.outputs.sprites << { x: 100, y: 100, w: 100, h: 100, path: "sprites/dragon_fly_#{sprite_index}.png" }

  # Try changing the numbers below to see how the animation changes:
  args.outputs.sprites << { x: 100, y: 200, w: 100, h: 100, path: "sprites/dragon_fly_#{0.frame_index 6, 4, true}.png" }
end

# This function shows how to animate a sprite that executes
# only once when the "f" key is pressed.
def one_time_animation args
  # This is just a label the shows instructions within the game.
  args.outputs.labels <<  { x: 220, y: 350, text: "(press f to animate)" }

  # If "f" is pressed on the keyboard...
  if args.inputs.keyboard.key_down.f
    # Print the frame that "f" was pressed on.
    puts "Hello from main.rb! The \"f\" key was in the down state on frame: #{args.state.tick_count}"

    # And MOST IMPORTANTLY set the point it time to start the animation,
    # equal to "now" which is represented as args.state.tick_count.

    # Also IMPORTANT, you'll notice that the value of when to start looping
    # is stored in `args.state`. This construct's values are retained across
    # executions of the `tick` method.
    args.state.start_looping_at = args.state.tick_count
  end

  # These are the same local variables that were defined
  # for the `looping_animation` function.
  number_of_sprites = 6
  number_of_frames_to_show_each_sprite = 4

  # Except this sprite does not loop again. If the animation time has passed,
  # then the frame_index function returns nil.
  does_sprite_loop = false

  if args.state.start_looping_at
    sprite_index = args.state
                       .start_looping_at
                       .frame_index number_of_sprites,
                                    number_of_frames_to_show_each_sprite,
                                    does_sprite_loop
  end

  # This line sets the frame index to zero, if
  # the animation duration has passed (frame_index returned nil).

  # Remeber: we are not looping forever here.
  sprite_index ||= 0

  # Present the sprite.
  args.outputs.sprites << { x: 100, y: 300, w: 100, h: 100, path: "sprites/dragon_fly_#{sprite_index}.png" }

  tick_instructions args, "Sample app shows how to use Numeric#frame_index and string interpolation to animate a sprite over time."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Rendering Sprites - Animation Using Sprite Sheet - main.rb

# ./samples/03_rendering_sprites/02_animation_using_sprite_sheet/app/main.rb
def tick args
  args.state.player.x ||= 100
  args.state.player.y ||= 100
  args.state.player.w ||= 64
  args.state.player.h ||= 64
  args.state.player.direction ||= 1

  args.state.player.is_moving = false

  # get the keyboard input and set player properties
  if args.inputs.keyboard.right
    args.state.player.x += 3
    args.state.player.direction = 1
    args.state.player.started_running_at ||= args.state.tick_count
  elsif args.inputs.keyboard.left
    args.state.player.x -= 3
    args.state.player.direction = -1
    args.state.player.started_running_at ||= args.state.tick_count
  end

  if args.inputs.keyboard.up
    args.state.player.y += 1
    args.state.player.started_running_at ||= args.state.tick_count
  elsif args.inputs.keyboard.down
    args.state.player.y -= 1
    args.state.player.started_running_at ||= args.state.tick_count
  end

  # if no arrow keys are being pressed, set the player as not moving
  if !args.inputs.keyboard.directional_vector
    args.state.player.started_running_at = nil
  end

  # wrap player around the stage
  if args.state.player.x > 1280
    args.state.player.x = -64
    args.state.player.started_running_at ||= args.state.tick_count
  elsif args.state.player.x < -64
    args.state.player.x = 1280
    args.state.player.started_running_at ||= args.state.tick_count
  end

  if args.state.player.y > 720
    args.state.player.y = -64
    args.state.player.started_running_at ||= args.state.tick_count
  elsif args.state.player.y < -64
    args.state.player.y = 720
    args.state.player.started_running_at ||= args.state.tick_count
  end

  # render player as standing or running
  if args.state.player.started_running_at
    args.outputs.sprites << running_sprite(args)
  else
    args.outputs.sprites << standing_sprite(args)
  end
  args.outputs.labels << [30, 700, "Use arrow keys to move around."]
end

def standing_sprite args
  {
    x: args.state.player.x,
    y: args.state.player.y,
    w: args.state.player.w,
    h: args.state.player.h,
    path: "sprites/horizontal-stand.png",
    flip_horizontally: args.state.player.direction > 0
  }
end

def running_sprite args
  if !args.state.player.started_running_at
    tile_index = 0
  else
    how_many_frames_in_sprite_sheet = 6
    how_many_ticks_to_hold_each_frame = 3
    should_the_index_repeat = true
    tile_index = args.state
                     .player
                     .started_running_at
                     .frame_index(how_many_frames_in_sprite_sheet,
                                  how_many_ticks_to_hold_each_frame,
                                  should_the_index_repeat)
  end

  {
    x: args.state.player.x,
    y: args.state.player.y,
    w: args.state.player.w,
    h: args.state.player.h,
    path: 'sprites/horizontal-run.png',
    tile_x: 0 + (tile_index * args.state.player.w),
    tile_y: 0,
    tile_w: args.state.player.w,
    tile_h: args.state.player.h,
    flip_horizontally: args.state.player.direction > 0,
  }
end

Rendering Sprites - Animation States - main.rb

# ./samples/03_rendering_sprites/03_animation_states/app/main.rb
class Game
  attr_gtk

  def defaults
    state.show_debug_layer  = true if state.tick_count == 0
    player.tile_size        = 64
    player.speed            = 3
    player.slash_frames     = 15
    player.x              ||= 50
    player.y              ||= 400
    player.dir_x          ||=  1
    player.dir_y          ||= -1
    player.is_moving      ||= false
    state.watch_list      ||= {}
    state.enemies         ||= []
  end

  def add_enemy
    state.enemies << { x: 1200 * rand, y: 600 * rand, w: 64, h: 64 }
  end

  def sprite_horizontal_run
    tile_index = 0.frame_index(6, 3, true)
    tile_index = 0 if !player.is_moving

    {
      x: player.x,
      y: player.y,
      w: player.tile_size,
      h: player.tile_size,
      path: 'sprites/horizontal-run.png',
      tile_x: 0 + (tile_index * player.tile_size),
      tile_y: 0,
      tile_w: player.tile_size,
      tile_h: player.tile_size,
      flip_horizontally: player.dir_x > 0,
      # a: 40
    }
  end

  def sprite_horizontal_stand
    {
      x: player.x,
      y: player.y,
      w: player.tile_size,
      h: player.tile_size,
      path: 'sprites/horizontal-stand.png',
      flip_horizontally: player.dir_x > 0,
      # a: 40
    }
  end

  def sprite_horizontal_slash
    tile_index   = player.slash_at.frame_index(5, player.slash_frames.idiv(5), false) || 0

    {
      x: player.x - 41.25,
      y: player.y - 41.25,
      w: 165,
      h: 165,
      path: 'sprites/horizontal-slash.png',
      tile_x: 0 + (tile_index * 128),
      tile_y: 0,
      tile_w: 128,
      tile_h: 128,
      flip_horizontally: player.dir_x > 0
    }
  end

  def render_player
    if player.slash_at
      outputs.sprites << sprite_horizontal_slash
    elsif player.is_moving
      outputs.sprites << sprite_horizontal_run
    else
      outputs.sprites << sprite_horizontal_stand
    end
  end

  def render_enemies
    outputs.borders << state.enemies
  end

  def render_debug_layer
    return if !state.show_debug_layer
    outputs.labels << state.watch_list.map.with_index do |(k, v), i|
       [30, 710 - i * 28, "#{k}: #{v || "(nil)"}"]
    end

    outputs.borders << player.slash_collision_rect
  end

  def slash_initiate?
    # buffalo usb controller has a button and b button swapped lol
    inputs.controller_one.key_down.a || inputs.keyboard.key_down.j
  end

  def input
    # player movement
    if slash_complete? && (vector = inputs.directional_vector)
      player.x += vector.x * player.speed
      player.y += vector.y * player.speed
    end
    player.slash_at = slash_initiate? if slash_initiate?
  end

  def calc_movement
    # movement
    if vector = inputs.directional_vector
      state.debug_label = vector
      player.dir_x = vector.x
      player.dir_y = vector.y
      player.is_moving = true
    else
      state.debug_label = vector
      player.is_moving = false
    end
  end

  def calc_slash
    # re-calc the location of the swords collision box
    if player.dir_x.positive?
      player.slash_collision_rect = [player.x + player.tile_size,
                                     player.y + player.tile_size.half - 10,
                                     40, 20]
    else
      player.slash_collision_rect = [player.x - 32 - 8,
                                     player.y + player.tile_size.half - 10,
                                     40, 20]
    end

    # recalc sword's slash state
    player.slash_at = nil if slash_complete?

    # determine collision if the sword is at it's point of damaging
    return unless slash_can_damage?

    state.enemies.reject! { |e| e.intersect_rect? player.slash_collision_rect }
  end

  def slash_complete?
    !player.slash_at || player.slash_at.elapsed?(player.slash_frames)
  end

  def slash_can_damage?
    # damage occurs half way into the slash animation
    return false if slash_complete?
    return false if (player.slash_at + player.slash_frames.idiv(2)) != state.tick_count
    return true
  end

  def calc
    # generate an enemy if there aren't any on the screen
    add_enemy if state.enemies.length == 0
    calc_movement
    calc_slash
  end

  # source is at http://github.com/amirrajan/dragonruby-link-to-the-past
  def tick
    defaults
    render_enemies
    render_player
    outputs.labels << [30, 30, "Gamepad: D-Pad to move. B button to attack."]
    outputs.labels << [30, 52, "Keyboard: WASD/Arrow keys to move. J to attack."]
    render_debug_layer
    input
    calc
  end

  def player
    state.player
  end
end

$game = Game.new

def tick args
  $game.args = args
  $game.tick
end

$gtk.reset

Rendering Sprites - Animation States Advanced - main.rb

# ./samples/03_rendering_sprites/03_animation_states_advanced/app/main.rb
class Game
  attr_gtk

  def request_action name, at: nil
    at ||= state.tick_count
    state.player.requested_action = name
    state.player.requested_action_at = at
  end

  def defaults
    state.player.x                  ||= 64
    state.player.y                  ||= 0
    state.player.dx                 ||= 0
    state.player.dy                 ||= 0
    state.player.action             ||= :standing
    state.player.action_at          ||= 0
    state.player.next_action_queue  ||= {}
    state.player.facing             ||= 1
    state.player.jump_at            ||= 0
    state.player.jump_count         ||= 0
    state.player.max_speed          ||= 1.0
    state.sabre.x                   ||= state.player.x
    state.sabre.y                   ||= state.player.y
    state.actions_lookup            ||= new_actions_lookup
  end

  def render
    outputs.background_color = [32, 32, 32]
    outputs[:scene].w = 128
    outputs[:scene].h = 128
    outputs[:scene].borders << { x: 0, y: 0, w: 128, h: 128, r: 255, g: 255, b: 255 }
    render_player
    render_sabre
    args.outputs.sprites << { x: 320, y: 0, w: 640, h: 640, path: :scene }
    args.outputs.labels << { x: 10, y: 100, text: "Controls:", r: 255, g: 255, b: 255, size_enum: -1 }
    args.outputs.labels << { x: 10, y: 80, text: "Move:   left/right", r: 255, g: 255, b: 255, size_enum: -1 }
    args.outputs.labels << { x: 10, y: 60, text: "Jump:   space | up | right click", r: 255, g: 255, b: 255, size_enum: -1 }
    args.outputs.labels << { x: 10, y: 40, text: "Attack: f     | j  | left click", r: 255, g: 255, b: 255, size_enum: -1 }
  end

  def render_sabre
    return if !state.sabre.is_active
    sabre_index = 0.frame_index count:    4,
                                hold_for: 2,
                                repeat:   true
    offset =  0
    offset = -8 if state.player.facing == -1
    outputs[:scene].sprites << { x: state.sabre.x + offset,
                        y: state.sabre.y, w: 16, h: 16, path: "sprites/sabre-throw/#{sabre_index}.png" }
  end

  def new_actions_lookup
    r = {
      slash_0: {
        frame_count: 6,
        interrupt_count: 4,
        path: "sprites/kenobi/slash-0/:index.png"
      },
      slash_1: {
        frame_count: 6,
        interrupt_count: 4,
        path: "sprites/kenobi/slash-1/:index.png"
      },
      throw_0: {
        frame_count: 8,
        throw_frame: 2,
        catch_frame: 6,
        path: "sprites/kenobi/slash-2/:index.png"
      },
      throw_1: {
        frame_count: 9,
        throw_frame: 2,
        catch_frame: 7,
        path: "sprites/kenobi/slash-3/:index.png"
      },
      throw_2: {
        frame_count: 9,
        throw_frame: 2,
        catch_frame: 7,
        path: "sprites/kenobi/slash-4/:index.png"
      },
      slash_5: {
        frame_count: 11,
        path: "sprites/kenobi/slash-5/:index.png"
      },
      slash_6: {
        frame_count: 8,
        interrupt_count: 6,
        path: "sprites/kenobi/slash-6/:index.png"
      }
    }

    r.each.with_index do |(k, v), i|
      v.name               ||= k
      v.index              ||= i

      v.hold_for           ||= 5
      v.duration           ||= v.frame_count * v.hold_for
      v.last_index         ||= v.frame_count - 1

      v.interrupt_count    ||= v.frame_count
      v.interrupt_duration ||= v.interrupt_count * v.hold_for

      v.repeat             ||= false
      v.next_action        ||= r[r.keys[i + 1]]
    end

    r
  end

  def render_player
    flip_horizontally = if state.player.facing == -1
                          true
                        else
                          false
                        end

    player_sprite = { x: state.player.x + 1 - 8,
                      y: state.player.y,
                      w: 16,
                      h: 16,
                      flip_horizontally: flip_horizontally }

    if state.player.action == :standing
      if state.player.y != 0
        if state.player.jump_count <= 1
          outputs[:scene].sprites << { **player_sprite, path: "sprites/kenobi/jumping.png" }
        else
          index = state.player.jump_at.frame_index count: 8, hold_for: 5, repeat: false
          index ||= 7
          outputs[:scene].sprites << { **player_sprite, path: "sprites/kenobi/second-jump/#{index}.png" }
        end
      elsif state.player.dx != 0
        index = state.player.action_at.frame_index count: 4, hold_for: 5, repeat: true
        outputs[:scene].sprites << { **player_sprite, path: "sprites/kenobi/run/#{index}.png" }
      else
        outputs[:scene].sprites << { **player_sprite, path: 'sprites/kenobi/standing.png'}
      end
    else
      v = state.actions_lookup[state.player.action]
      slash_frame_index = state.player.action_at.frame_index count:    v.frame_count,
                                                             hold_for: v.hold_for,
                                                             repeat:   v.repeat
      slash_frame_index ||= v.last_index
      slash_path          = v.path.sub ":index", slash_frame_index.to_s
      outputs[:scene].sprites << { **player_sprite, path: slash_path }
    end
  end

  def calc_input
    if state.player.next_action_queue.length > 2
      raise "Code in calc assums that key length of state.player.next_action_queue will never be greater than 2."
    end

    if inputs.controller_one.key_down.a ||
       inputs.mouse.button_left  ||
       inputs.keyboard.key_down.j ||
       inputs.keyboard.key_down.f
      request_action :attack
    end

    should_update_facing = false
    if state.player.action == :standing
      should_update_facing = true
    else
      key_0 = state.player.next_action_queue.keys[0]
      key_1 = state.player.next_action_queue.keys[1]
      if state.tick_count == key_0
        should_update_facing = true
      elsif state.tick_count == key_1
        should_update_facing = true
      elsif key_0 && key_1 && state.tick_count.between?(key_0, key_1)
        should_update_facing = true
      end
    end

    if should_update_facing && inputs.left_right.sign != state.player.facing.sign
      state.player.dx = 0

      if inputs.left
        state.player.facing = -1
      elsif inputs.right
        state.player.facing = 1
      end

      state.player.dx += 0.1 * inputs.left_right
    end

    if state.player.action == :standing
      state.player.dx += 0.1 * inputs.left_right
      if state.player.dx.abs > state.player.max_speed
        state.player.dx = state.player.max_speed * state.player.dx.sign
      end
    end

    was_jump_requested = inputs.keyboard.key_down.up ||
                         inputs.keyboard.key_down.w  ||
                         inputs.mouse.button_right  ||
                         inputs.controller_one.key_down.up ||
                         inputs.controller_one.key_down.b ||
                         inputs.keyboard.key_down.space

    can_jump = state.player.jump_at.elapsed_time > 20
    if state.player.jump_count <= 1
      can_jump = state.player.jump_at.elapsed_time > 10
    end

    if was_jump_requested && can_jump
      if state.player.action == :slash_6
        state.player.action = :standing
      end
      state.player.dy = 1
      state.player.jump_count += 1
      state.player.jump_at     = state.tick_count
    end
  end

  def calc
    calc_input
    calc_requested_action
    calc_next_action
    calc_sabre
    calc_player_movement

    if state.player.y <= 0 && state.player.dy < 0
      state.player.y = 0
      state.player.dy = 0
      state.player.jump_at = 0
      state.player.jump_count = 0
    end
  end

  def calc_player_movement
    state.player.x += state.player.dx
    state.player.y += state.player.dy
    state.player.dy -= 0.05
    if state.player.y <= 0
      state.player.y = 0
      state.player.dy = 0
      state.player.jump_at = 0
      state.player.jump_count = 0
    end

    if state.player.dx.abs < 0.09
      state.player.dx = 0
    end

    state.player.x = 8  if state.player.x < 8
    state.player.x = 120 if state.player.x > 120
  end

  def calc_requested_action
    return if !state.player.requested_action
    return if state.player.requested_action_at > state.tick_count

    player_action = state.player.action
    player_action_at = state.player.action_at

    # first attack
    if state.player.requested_action == :attack
      if player_action == :standing
        state.player.next_action_queue.clear
        state.player.next_action_queue[state.tick_count] = :slash_0
        state.player.next_action_queue[state.tick_count + state.actions_lookup.slash_0.duration] = :standing
      else
        current_action = state.actions_lookup[state.player.action]
        state.player.next_action_queue.clear
        queue_at = player_action_at + current_action.interrupt_duration
        queue_at = state.tick_count if queue_at < state.tick_count
        next_action = current_action.next_action
        next_action ||= { name: :standing,
                          duration: 4 }
        if next_action
        state.player.next_action_queue[queue_at] = next_action.name
        state.player.next_action_queue[player_action_at +
                                       current_action.interrupt_duration +
                                       next_action.duration] = :standing
        end
      end
    end

    state.player.requested_action = nil
    state.player.requested_action_at = nil
  end

  def calc_sabre
    can_throw_sabre = true
    sabre_throws = [:throw_0, :throw_1, :throw_2]
    if !sabre_throws.include? state.player.action
      state.sabre.facing = nil
      state.sabre.is_active = false
      return
    end

    current_action = state.actions_lookup[state.player.action]
    throw_at = state.player.action_at + (current_action.throw_frame) * 5
    catch_at = state.player.action_at + (current_action.catch_frame) * 5
    if !state.tick_count.between? throw_at, catch_at
      state.sabre.facing = nil
      state.sabre.is_active = false
      return
    end

    state.sabre.facing ||= state.player.facing

    state.sabre.is_active = true

    spline = [
      [  0, 0.25, 0.75, 1.0],
      [1.0, 0.75, 0.25,   0]
    ]

    throw_duration = catch_at - throw_at

    current_progress = args.easing.ease_spline throw_at,
                                               state.tick_count,
                                               throw_duration,
                                               spline

    farthest_sabre_x = 32
    state.sabre.y = state.player.y
    state.sabre.x = state.player.x + farthest_sabre_x * current_progress * state.sabre.facing
  end

  def calc_next_action
    return if !state.player.next_action_queue[state.tick_count]

    state.player.previous_action = state.player.action
    state.player.previous_action_at = state.player.action_at
    state.player.previous_action_ended_at = state.tick_count
    state.player.action = state.player.next_action_queue[state.tick_count]
    state.player.action_at = state.tick_count

    is_air_born = state.player.y != 0

    if state.player.action == :slash_0
      state.player.dy = 0 if state.player.dy > 0
      if is_air_born
        state.player.dy  = 0.5
      else
        state.player.dx += 0.25 * state.player.facing
      end
    elsif state.player.action == :slash_1
      state.player.dy = 0 if state.player.dy > 0
      if is_air_born
        state.player.dy  = 0.5
      else
        state.player.dx += 0.25 * state.player.facing
      end
    elsif state.player.action == :throw_0
      if is_air_born
        state.player.dy  = 1.0
      end

      state.player.dx += 0.5 * state.player.facing
    elsif state.player.action == :throw_1
      if is_air_born
        state.player.dy  = 1.0
      end

      state.player.dx += 0.5 * state.player.facing
    elsif state.player.action == :throw_2
      if is_air_born
        state.player.dy  = 1.0
      end

      state.player.dx += 0.5 * state.player.facing
    elsif state.player.action == :slash_5
      state.player.dy = 0 if state.player.dy < 0
      if is_air_born
        state.player.dy += 1.0
      else
        state.player.dy += 1.0
      end

      state.player.dx += 1.0 * state.player.facing
    elsif state.player.action == :slash_6
      state.player.dy = 0 if state.player.dy > 0
      if is_air_born
        state.player.dy  = -0.5
      end

      state.player.dx += 0.5 * state.player.facing
    end
  end

  def tick
    defaults
    calc
    render
  end
end

$game = Game.new

def tick args
  $game.args = args
  $game.tick
end

$gtk.reset

Rendering Sprites - Animation States Advanced - Metadata - ios_metadata.txt

# ./samples/03_rendering_sprites/03_animation_states_advanced/metadata/ios_metadata.txt
teamid=L7H57V9CRD
appid=com.scratchworkdevelopment.1bitanimate
appname=1-Bit Animate
version=1.0
devcert=iPhone Developer: Amirali Rajan (P2B6225J87)
prodcert=

Rendering Sprites - Color And Rotation - main.rb

# ./samples/03_rendering_sprites/04_color_and_rotation/app/main.rb
=begin
 APIs listing that haven't been encountered in previous sample apps:

 - merge: Returns a hash containing the contents of two original hashes.
   Merge does not allow duplicate keys, so the value of a repeated key
   will be overwritten.

   For example, if we had two hashes
   h1 = { "a" => 1, "b" => 2}
   h2 = { "b" => 3, "c" => 3}
   and we called the command
   h1.merge(h2)
   the result would the following hash
   { "a" => 1, "b" => 3, "c" => 3}.

 Reminders:

 - Hashes: Collection of unique keys and their corresponding values. The value can be found
   using their keys.
   In this sample app, we're using a hash to create a sprite.

 - args.outputs.sprites: An array. The values generate a sprite.
   The parameters are [X, Y, WIDTH, HEIGHT, PATH, ANGLE, ALPHA, RED, GREEN, BLUE]
   Before continuing with this sample app, it is HIGHLY recommended that you look
   at mygame/documentation/05-sprites.md.

 - args.inputs.keyboard.key_held.KEY: Determines if a key is being pressed.
   For more information about the keyboard, go to mygame/documentation/06-keyboard.md.

 - args.inputs.controller_one: Takes input from the controller based on what key is pressed.
   For more information about the controller, go to mygame/documentation/08-controllers.md.

 - num1.lesser(num2): Finds the lower value of the given options.

=end

# This sample app shows a car moving across the screen. It loops back around if it exceeds the dimensions of the screen,
# and also can be moved in different directions through keyboard input from the user.

# Calls the methods necessary for the game to run successfully.
def tick args
  default args
  render args.grid, args.outputs, args.state
  calc args.state
  process_inputs args
end

# Sets default values for the car sprite
# Initialization ||= only happens in the first frame
def default args
  args.state.sprite.width    = 19
  args.state.sprite.height   = 10
  args.state.sprite.scale    = 4
  args.state.max_speed       = 5
  args.state.x             ||= 100
  args.state.y             ||= 100
  args.state.speed         ||= 1
  args.state.angle         ||= 0
end

# Outputs sprite onto screen
def render grid, outputs, state
  outputs.solids  <<  [grid.rect, 70, 70, 70] # outputs gray background
  outputs.sprites <<  [destination_rect(state), # sets first four parameters of car sprite
  'sprites/86.png', # image path of car
  state.angle,
  opacity, # transparency
  saturation,
  source_rect(state), # sprite sub division/tile (tile x, y, w, h)
  false, false,  # don't flip sprites
  rotation_anchor]

  # also look at the create_sprite helper method
  #
  # For example:
  #
  # dest   = destination_rect(state)
  # source = source_rect(state),
  # outputs.sprites << create_sprite(
  #   'sprites/86.png',
  #   x: dest.x,
  #   y: dest.y,
  #   w: dest.w,
  #   h: dest.h,
  #   angle: state.angle,
  #   source_x: source.x,
  #   source_y: source.y,
  #   source_w: source.w,
  #   source_h: source.h,
  #   flip_h: false,
  #   flip_v: false,
  #   rotation_anchor_x: 0.7,
  #   rotation_anchor_y: 0.5
  # )
end

# Creates sprite by setting values inside of a hash
def create_sprite path, options = {}
  options = {

    # dest x, y, w, h
    x: 0,
    y: 0,
    w: 100,
    h: 100,

    # angle, rotation
    angle: 0,
    rotation_anchor_x: 0.5,
    rotation_anchor_y: 0.5,

    # color saturation (red, green, blue), transparency
    r: 255,
    g: 255,
    b: 255,
    a: 255,

    # source x, y, width, height
    source_x: 0,
    source_y: 0,
    source_w: -1,
    source_h: -1,

    # flip horiztonally, flip vertically
    flip_h: false,
    flip_v: false,

  }.merge options

  [
    options[:x], options[:y], options[:w], options[:h], # dest rect keys
    path,
    options[:angle], options[:a], options[:r], options[:g], options[:b], # angle, color, alpha
    options[:source_x], options[:source_y], options[:source_w], options[:source_h], # source rect keys
    options[:flip_h], options[:flip_v], # flip
    options[:rotation_anchor_x], options[:rotation_anchor_y], # rotation anchor
  ] # hash keys contain corresponding values
end

# Calls the calc_pos and calc_wrap methods.
def calc state
  calc_pos state
  calc_wrap state
end

# Changes sprite's position on screen
# Vectors have magnitude and direction, so the incremented x and y values give the car direction
def calc_pos state
  state.x     += state.angle.vector_x * state.speed # increments x by product of angle's x vector and speed
  state.y     += state.angle.vector_y * state.speed # increments y by product of angle's y vector and speed
  state.speed *= 1.1 # scales speed up
  state.speed  = state.speed.lesser(state.max_speed) # speed is either current speed or max speed, whichever has a lesser value (ensures that the car doesn't go too fast or exceed the max speed)
end

# The screen's dimensions are 1280x720. If the car goes out of scope,
# it loops back around on the screen.
def calc_wrap state

  # car returns to left side of screen if it disappears on right side of screen
  # sprite.width refers to tile's size, which is multipled by scale (4) to make it bigger
  state.x = -state.sprite.width * state.sprite.scale if state.x - 20 > 1280

  # car wraps around to right side of screen if it disappears on the left side
  state.x = 1280 if state.x + state.sprite.width * state.sprite.scale + 20 < 0

  # car wraps around to bottom of screen if it disappears at the top of the screen
  # if you subtract 520 pixels instead of 20 pixels, the car takes longer to reappear (try it!)
  state.y = 0    if state.y - 20 > 720 # if 20 pixels less than car's y position is greater than vertical scope

  # car wraps around to top of screen if it disappears at the bottom of the screen
  state.y = 720  if state.y + state.sprite.height * state.sprite.scale + 20 < 0
end

# Changes angle of sprite based on user input from keyboard or controller
def process_inputs args

  # NOTE: increasing the angle doesn't mean that the car will continue to go
  # in a specific direction. The angle is increasing, which means that if the
  # left key was kept in the "down" state, the change in the angle would cause
  # the car to go in a counter-clockwise direction and form a circle (360 degrees)
  if args.inputs.keyboard.key_held.left # if left key is pressed
    args.state.angle += 2 # car's angle is incremented by 2

  # The same applies to decreasing the angle. If the right key was kept in the
  # "down" state, the decreasing angle would cause the car to go in a clockwise
  # direction and form a circle (360 degrees)
  elsif args.inputs.keyboard.key_held.right # if right key is pressed
    args.state.angle -= 2 # car's angle is decremented by 2

  # Input from a controller can also change the angle of the car
  elsif args.inputs.controller_one.left_analog_x_perc != 0
    args.state.angle += 2 * args.inputs.controller_one.left_analog_x_perc * -1
  end
end

# A sprite's center of rotation can be altered
# Increasing either of these numbers would dramatically increase the
# car's drift when it turns!
def rotation_anchor
  [0.7, 0.5]
end

# Sets opacity value of sprite to 255 so that it is not transparent at all
# Change it to 0 and you won't be able to see the car sprite on the screen
def opacity
  255
end

# Sets the color of the sprite to white.
def saturation
  [255, 255, 255]
end

# Sets definition of destination_rect (used to define the car sprite)
def destination_rect state
  [state.x, state.y,
  state.sprite.width  * state.sprite.scale, # multiplies by 4 to set size
  state.sprite.height * state.sprite.scale]
end

# Portion of a sprite (a tile)
# Sub division of sprite is denoted as a rectangle directly related to original size of .png
# Tile is located at bottom left corner within a 19x10 pixel rectangle (based on sprite.width, sprite.height)
def source_rect state
  [0, 0, state.sprite.width, state.sprite.height]
end

Physics And Collisions - Simple - main.rb

# ./samples/04_physics_and_collisions/01_simple/app/main.rb
=begin

 Reminders:
 - ARRAY#intersect_rect?: Returns true or false depending on if the two rectangles intersect.

 - args.outputs.solids: An array. The values generate a solid.
   The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]

=end

# This sample app shows collisions between two boxes.

# Runs methods needed for game to run properly.
def tick args
  tick_instructions args, "Sample app shows how to move a square over time and determine collision."
  defaults args
  render args
  calc args
end

# Sets default values.
def defaults args
  # These values represent the moving box.
  args.state.moving_box_speed   = 10
  args.state.moving_box_size    = 100
  args.state.moving_box_dx    ||=  1
  args.state.moving_box_dy    ||=  1
  args.state.moving_box       ||= [0, 0, args.state.moving_box_size, args.state.moving_box_size] # moving_box_size is set as the width and height

  # These values represent the center box.
  args.state.center_box ||= [540, 260, 200, 200, 180]
  args.state.center_box_collision ||= false # initially no collision
end

def render args
  # If the game state denotes that a collision has occured,
  # render a solid square, otherwise render a border instead.
  if args.state.center_box_collision
    args.outputs.solids << args.state.center_box
  else
    args.outputs.borders << args.state.center_box
  end

  # Then render the moving box.
  args.outputs.solids << args.state.moving_box
end

# Generally in a pipeline for a game engine, you have rendering,
# game simulation (calculation), and input processing.
# This fuction represents the game simulation.
def calc args
  position_moving_box args
  determine_collision_center_box args
end

# Changes the position of the moving box on the screen by multiplying the change in x (dx) and change in y (dy) by the speed,
# and adding it to the current position.
# dx and dy are positive if the box is moving right and up, respectively
# dx and dy are negative if the box is moving left and down, respectively
def position_moving_box args
  args.state.moving_box.x += args.state.moving_box_dx * args.state.moving_box_speed
  args.state.moving_box.y += args.state.moving_box_dy * args.state.moving_box_speed

  # 1280x720 are the virtual pixels you work with (essentially 720p).
  screen_width  = 1280
  screen_height = 720

  # Position of the box is denoted by the bottom left hand corner, in
  # that case, we have to subtract the width of the box so that it stays
  # in the scene (you can try deleting the subtraction to see how it
  # impacts the box's movement).
  if args.state.moving_box.x > screen_width - args.state.moving_box_size
    args.state.moving_box_dx = -1 # moves left
  elsif args.state.moving_box.x < 0
    args.state.moving_box_dx =  1 # moves right
  end

  # Here, we're making sure the moving box remains within the vertical scope of the screen
  if args.state.moving_box.y > screen_height - args.state.moving_box_size # if the box moves too high
    args.state.moving_box_dy = -1 # moves down
  elsif args.state.moving_box.y < 0 # if the box moves too low
    args.state.moving_box_dy =  1 # moves up
  end
end

def determine_collision_center_box args
  # Collision is handled by the engine. You simply have to call the
  # `intersect_rect?` function.
  if args.state.moving_box.intersect_rect? args.state.center_box # if the two boxes intersect
    args.state.center_box_collision = true # then a collision happened
  else
    args.state.center_box_collision = false # otherwise, no collision happened
  end
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Physics And Collisions - Simple Aabb Collision - main.rb

# ./samples/04_physics_and_collisions/01_simple_aabb_collision/app/main.rb
def tick args
  # define terrain of 32x32 sized squares
  args.state.terrain ||= [
    { x: 640,          y: 360,          w: 32, h: 32, path: 'sprites/square/blue.png' },
    { x: 640,          y: 360 - 32,     w: 32, h: 32, path: 'sprites/square/blue.png' },
    { x: 640,          y: 360 - 32 * 2, w: 32, h: 32, path: 'sprites/square/blue.png' },
    { x: 640 + 32,     y: 360 - 32 * 2, w: 32, h: 32, path: 'sprites/square/blue.png' },
    { x: 640 + 32 * 2, y: 360 - 32 * 2, w: 32, h: 32, path: 'sprites/square/blue.png' },
  ]

  # define player
  args.state.player ||= {
    x: 600,
    y: 360,
    w: 32,
    h: 32,
    dx: 0,
    dy: 0,
    path: 'sprites/square/red.png'
  }

  # render terrain and player
  args.outputs.sprites << args.state.terrain
  args.outputs.sprites << args.state.player

  # set dx and dy based on inputs
  args.state.player.dx = args.inputs.left_right * 2
  args.state.player.dy = args.inputs.up_down * 2

  # check for collisions on the x and y axis independently

  # increment the player's position by dx
  args.state.player.x += args.state.player.dx

  # check for collision on the x axis first
  collision = args.state.terrain.find { |t| t.intersect_rect? args.state.player }

  # if there is a collision, move the player to the edge of the collision
  # based on the direction of the player's movement and set the player's
  # dx to 0
  if collision
    if args.state.player.dx > 0
      args.state.player.x = collision.x - args.state.player.w
    elsif args.state.player.dx < 0
      args.state.player.x = collision.x + collision.w
    end
    args.state.player.dx = 0
  end

  # increment the player's position by dy
  args.state.player.y += args.state.player.dy

  # check for collision on the y axis next
  collision = args.state.terrain.find { |t| t.intersect_rect? args.state.player }

  # if there is a collision, move the player to the edge of the collision
  # based on the direction of the player's movement and set the player's
  # dy to 0
  if collision
    if args.state.player.dy > 0
      args.state.player.y = collision.y - args.state.player.h
    elsif args.state.player.dy < 0
      args.state.player.y = collision.y + collision.h
    end
    args.state.player.dy = 0
  end
end

Physics And Collisions - Simple Aabb Collision With Map Editor - main.rb

# ./samples/04_physics_and_collisions/01_simple_aabb_collision_with_map_editor/app/main.rb
# the sample app is an expansion of ./01_simple_aabb_collision
# but includes an in game map editor that saves map data to disk
def tick args
  # if it's the first tick, read the terrain data from disk
  # and create the player
  if args.state.tick_count == 0
    args.state.terrain = read_terrain_data args

    args.state.player = {
      x: 320,
      y: 320,
      w: 32,
      h: 32,
      dx: 0,
      dy: 0,
      path: 'sprites/square/red.png'
    }
  end

  # tick the game (where input and aabb collision is processed)
  tick_game args

  # tick the map editor
  tick_map_editor args
end

def tick_game args
  # render terrain and player
  args.outputs.sprites << args.state.terrain
  args.outputs.sprites << args.state.player

  # set dx and dy based on inputs
  args.state.player.dx = args.inputs.left_right * 2
  args.state.player.dy = args.inputs.up_down * 2

  # check for collisions on the x and y axis independently

  # increment the player's position by dx
  args.state.player.x += args.state.player.dx

  # check for collision on the x axis first
  collision = args.state.terrain.find { |t| t.intersect_rect? args.state.player }

  # if there is a collision, move the player to the edge of the collision
  # based on the direction of the player's movement and set the player's
  # dx to 0
  if collision
    if args.state.player.dx > 0
      args.state.player.x = collision.x - args.state.player.w
    elsif args.state.player.dx < 0
      args.state.player.x = collision.x + collision.w
    end
    args.state.player.dx = 0
  end

  # increment the player's position by dy
  args.state.player.y += args.state.player.dy

  # check for collision on the y axis next
  collision = args.state.terrain.find { |t| t.intersect_rect? args.state.player }

  # if there is a collision, move the player to the edge of the collision
  # based on the direction of the player's movement and set the player's
  # dy to 0
  if collision
    if args.state.player.dy > 0
      args.state.player.y = collision.y - args.state.player.h
    elsif args.state.player.dy < 0
      args.state.player.y = collision.y + collision.h
    end
    args.state.player.dy = 0
  end
end

def tick_map_editor args
  # determine the location of the mouse, but
  # aligned to the grid
  grid_aligned_mouse_rect = {
    x: args.inputs.mouse.x.idiv(32) * 32,
    y: args.inputs.mouse.y.idiv(32) * 32,
    w: 32,
    h: 32
  }

  # determine if there's a tile at the grid aligned mouse location
  existing_terrain = args.state.terrain.find { |t| t.intersect_rect? grid_aligned_mouse_rect }

  # if there is, then render a red square to denote that
  # the tile will be deleted
  if existing_terrain
    args.outputs.sprites << {
      x: args.inputs.mouse.x.idiv(32) * 32,
      y: args.inputs.mouse.y.idiv(32) * 32,
      w: 32,
      h: 32,
      path: "sprites/square/red.png",
      a: 128
    }
  else
    # otherwise, render a blue square to denote that
    # a tile will be added
    args.outputs.sprites << {
      x: args.inputs.mouse.x.idiv(32) * 32,
      y: args.inputs.mouse.y.idiv(32) * 32,
      w: 32,
      h: 32,
      path: "sprites/square/blue.png",
      a: 128
    }
  end

  # if the mouse is clicked, then add or remove a tile
  if args.inputs.mouse.click
    if existing_terrain
      args.state.terrain.delete existing_terrain
    else
      args.state.terrain << { **grid_aligned_mouse_rect, path: "sprites/square/blue.png" }
    end

    # once the terrain state has been updated
    # save the terrain data to disk
    write_terrain_data args
  end
end

def read_terrain_data args
  # create the terrain data file if it doesn't exist
  contents = args.gtk.read_file "data/terrain.txt"
  if !contents
    args.gtk.write_file "data/terrain.txt", ""
  end

  # read the terrain data from disk which is a csv
  args.gtk.read_file('data/terrain.txt').split("\n").map do |line|
    x, y, w, h = line.split(',').map(&:to_i)
    { x: x, y: y, w: w, h: h, path: 'sprites/square/blue.png' }
  end
end

def write_terrain_data args
  terrain_csv = args.state.terrain.map { |t| "#{t.x},#{t.y},#{t.w},#{t.h}" }.join "\n"
  args.gtk.write_file 'data/terrain.txt', terrain_csv
end

Physics And Collisions - Simple Aabb Collision With Map Editor - Data - terrain.txt

# ./samples/04_physics_and_collisions/01_simple_aabb_collision_with_map_editor/data/terrain.txt

Physics And Collisions - Moving Objects - main.rb

# ./samples/04_physics_and_collisions/02_moving_objects/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - Hashes: Collection of unique keys and their corresponding values. The value can be found
   using their keys.

   For example, if we have a "numbers" hash that stores numbers in English as the
   key and numbers in Spanish as the value, we'd have a hash that looks like this...
   numbers = { "one" => "uno", "two" => "dos", "three" => "tres" }
   and on it goes.

   Now if we wanted to find the corresponding value of the "one" key, we could say
   puts numbers["one"]
   which would print "uno" to the console.

 - num1.greater(num2): Returns the greater value.
   For example, if we have the command
   puts 4.greater(3)
   the number 4 would be printed to the console since it has a greater value than 3.
   Similar to lesser, which returns the lesser value.

 - num1.lesser(num2): Finds the lower value of the given options.
   For example, in the statement
   a = 4.lesser(3)
   3 has a lower value than 4, which means that the value of a would be set to 3,
   but if the statement had been
   a = 4.lesser(5)
   4 has a lower value than 5, which means that the value of a would be set to 4.

 - reject: Removes elements from a collection if they meet certain requirements.
   For example, you can derive an array of odd numbers from an original array of
   numbers 1 through 10 by rejecting all elements that are even (or divisible by 2).

 - find_all: Finds all values that satisfy specific requirements.
   For example, you can find all elements of a collection that are divisible by 2
   or find all objects that have intersected with another object.

 - abs: Returns the absolute value.
   For example, the command
   (-30).abs
   would return 30 as a result.

 - map: Ruby method used to transform data; used in arrays, hashes, and collections.
   Can be used to perform an action on every element of a collection, such as multiplying
   each element by 2 or declaring every element as a new entity.

 Reminders:

 - args.inputs.keyboard.KEY: Determines if a key has been pressed.
   For more information about the keyboard, take a look at mygame/documentation/06-keyboard.md.

 - ARRAY#intersect_rect?: Returns true or false depending on if the two rectangles intersect.

 - args.outputs.solids: An array. The values generate a solid.
   The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]
   For more information about solids, go to mygame/documentation/03-solids-and-borders.md.

=end

# Calls methods needed for game to run properly
def tick args
  tick_instructions args, "Use LEFT and RIGHT arrow keys to move and SPACE to jump."
  defaults args
  render args
  calc args
  input args
end

# sets default values and creates empty collections
# initialization only happens in the first frame
def defaults args
  fiddle args
  args.state.enemy.hammers ||= []
  args.state.enemy.hammer_queue ||= []
  args.state.tick_count = args.state.tick_count
  args.state.bridge_top = 128
  args.state.player.x  ||= 0                        # initializes player's properties
  args.state.player.y  ||= args.state.bridge_top
  args.state.player.w  ||= 64
  args.state.player.h  ||= 64
  args.state.player.dy ||= 0
  args.state.player.dx ||= 0
  args.state.enemy.x   ||= 800                      # initializes enemy's properties
  args.state.enemy.y   ||= 0
  args.state.enemy.w   ||= 128
  args.state.enemy.h   ||= 128
  args.state.enemy.dy  ||= 0
  args.state.enemy.dx  ||= 0
  args.state.game_over_at ||= 0
end

# sets enemy, player, hammer values
def fiddle args
  args.state.gravity                     = -0.3
  args.state.enemy_jump_power            = 10       # sets enemy values
  args.state.enemy_jump_interval         = 60
  args.state.hammer_throw_interval       = 40       # sets hammer values
  args.state.hammer_launch_power_default = 5
  args.state.hammer_launch_power_near    = 2
  args.state.hammer_launch_power_far     = 7
  args.state.hammer_upward_launch_power  = 15
  args.state.max_hammers_per_volley      = 10
  args.state.gap_between_hammers         = 10
  args.state.player_jump_power           = 10       # sets player values
  args.state.player_jump_power_duration  = 10
  args.state.player_max_run_speed        = 10
  args.state.player_speed_slowdown_rate  = 0.9
  args.state.player_acceleration         = 1
  args.state.hammer_size                 = 32
end

# outputs objects onto the screen
def render args
  args.outputs.solids << 20.map_with_index do |i| # uses 20 squares to form bridge
    # sets x by multiplying 64 to index to find pixel value (places all squares side by side)
    # subtracts 64 from bridge_top because position is denoted by bottom left corner
    [i * 64, args.state.bridge_top - 64, 64, 64]
  end

  args.outputs.solids << [args.state.x, args.state.y, args.state.w, args.state.h, 255, 0, 0]
  args.outputs.solids << [args.state.player.x, args.state.player.y, args.state.player.w, args.state.player.h, 255, 0, 0] # outputs player onto screen (red box)
  args.outputs.solids << [args.state.enemy.x, args.state.enemy.y, args.state.enemy.w, args.state.enemy.h, 0, 255, 0] # outputs enemy onto screen (green box)
  args.outputs.solids << args.state.enemy.hammers # outputs enemy's hammers onto screen
end

# Performs calculations to move objects on the screen
def calc args

  # Since velocity is the change in position, the change in x increases by dx. Same with y and dy.
  args.state.player.x  += args.state.player.dx
  args.state.player.y  += args.state.player.dy

  # Since acceleration is the change in velocity, the change in y (dy) increases every frame
  args.state.player.dy += args.state.gravity

  # player's y position is either current y position or y position of top of
  # bridge, whichever has a greater value
  # ensures that the player never goes below the bridge
  args.state.player.y  = args.state.player.y.greater(args.state.bridge_top)

  # player's x position is either the current x position or 0, whichever has a greater value
  # ensures that the player doesn't go too far left (out of the screen's scope)
  args.state.player.x  = args.state.player.x.greater(0)

  # player is not falling if it is located on the top of the bridge
  args.state.player.falling = false if args.state.player.y == args.state.bridge_top
  args.state.player.rect = [args.state.player.x, args.state.player.y, args.state.player.h, args.state.player.w] # sets definition for player

  args.state.enemy.x += args.state.enemy.dx # velocity; change in x increases by dx
  args.state.enemy.y += args.state.enemy.dy # same with y and dy

  # ensures that the enemy never goes below the bridge
  args.state.enemy.y  = args.state.enemy.y.greater(args.state.bridge_top)

  # ensures that the enemy never goes too far left (outside the screen's scope)
  args.state.enemy.x  = args.state.enemy.x.greater(0)

  # objects that go up must come down because of gravity
  args.state.enemy.dy += args.state.gravity

  args.state.enemy.y  = args.state.enemy.y.greater(args.state.bridge_top)

  #sets definition of enemy
  args.state.enemy.rect = [args.state.enemy.x, args.state.enemy.y, args.state.enemy.h, args.state.enemy.w]

  if args.state.enemy.y == args.state.bridge_top # if enemy is located on the top of the bridge
    args.state.enemy.dy = 0 # there is no change in y
  end

  # if 60 frames have passed and the enemy is not moving vertically
  if args.state.tick_count.mod_zero?(args.state.enemy_jump_interval) && args.state.enemy.dy == 0
    args.state.enemy.dy = args.state.enemy_jump_power # the enemy jumps up
  end

  # if 40 frames have passed or 5 frames have passed since the game ended
  if args.state.tick_count.mod_zero?(args.state.hammer_throw_interval) || args.state.game_over_at.elapsed_time == 5
    # rand will return a number greater than or equal to 0 and less than given variable's value (since max is excluded)
    # that is why we're adding 1, to include the max possibility
    volley_dx   = (rand(args.state.hammer_launch_power_default) + 1) * -1 # horizontal movement (follow order of operations)

    # if the horizontal distance between the player and enemy is less than 128 pixels
    if (args.state.player.x - args.state.enemy.x).abs < 128
      # the change in x won't be that great since the enemy and player are closer to each other
      volley_dx = (rand(args.state.hammer_launch_power_near) + 1) * -1
    end

    # if the horizontal distance between the player and enemy is greater than 300 pixels
    if (args.state.player.x - args.state.enemy.x).abs > 300
      # change in x will be more drastic since player and enemy are so far apart
      volley_dx = (rand(args.state.hammer_launch_power_far) + 1) * -1 # more drastic change
    end

    (rand(args.state.max_hammers_per_volley) + 1).map_with_index do |i|
      args.state.enemy.hammer_queue << { # stores hammer values in a hash
        x: args.state.enemy.x,
        w: args.state.hammer_size,
        h: args.state.hammer_size,
        dx: volley_dx, # change in horizontal position
        # multiplication operator takes precedence over addition operator
        throw_at: args.state.tick_count + i * args.state.gap_between_hammers
      }
    end
  end

  # add elements from hammer_queue collection to the hammers collection by
  # finding all hammers that were thrown before the current frame (have already been thrown)
  args.state.enemy.hammers += args.state.enemy.hammer_queue.find_all do |h|
    h[:throw_at] < args.state.tick_count
  end

  args.state.enemy.hammers.each do |h| # sets values for all hammers in collection
    h[:y]  ||= args.state.enemy.y + 130
    h[:dy] ||= args.state.hammer_upward_launch_power
    h[:dy]  += args.state.gravity # acceleration is change in gravity
    h[:x]   += h[:dx] # incremented by change in position
    h[:y]   += h[:dy]
    h[:rect] = [h[:x], h[:y], h[:w], h[:h]] # sets definition of hammer's rect
  end

  # reject hammers that have been thrown before current frame (have already been thrown)
  args.state.enemy.hammer_queue = args.state.enemy.hammer_queue.reject do |h|
    h[:throw_at] < args.state.tick_count
  end

  # any hammers with a y position less than 0 are rejected from the hammers collection
  # since they have gone too far down (outside the scope's screen)
  args.state.enemy.hammers = args.state.enemy.hammers.reject { |h| h[:y] < 0 }

  # if there are any hammers that intersect with (or hit) the player,
  # the reset_player method is called (so the game can start over)
  if args.state.enemy.hammers.any? { |h| h[:rect].intersect_rect?(args.state.player.rect) }
    reset_player args
  end

  # if the enemy's rect intersects with (or hits) the player,
  # the reset_player method is called (so the game can start over)
  if args.state.enemy.rect.intersect_rect? args.state.player.rect
    reset_player args
  end
end

# Resets the player by changing its properties back to the values they had at initialization
def reset_player args
  args.state.player.x = 0
  args.state.player.y = args.state.bridge_top
  args.state.player.dy = 0
  args.state.player.dx = 0
  args.state.enemy.hammers.clear # empties hammer collection
  args.state.enemy.hammer_queue.clear # empties hammer_queue
  args.state.game_over_at = args.state.tick_count # game_over_at set to current frame (or passage of time)
end

# Processes input from the user to move the player
def input args
  if args.inputs.keyboard.space # if the user presses the space bar
    args.state.player.jumped_at ||= args.state.tick_count # jumped_at is set to current frame

    # if the time that has passed since the jump is less than the player's jump duration and
    # the player is not falling
    if args.state.player.jumped_at.elapsed_time < args.state.player_jump_power_duration && !args.state.player.falling
      args.state.player.dy = args.state.player_jump_power # change in y is set to power of player's jump
    end
  end

  # if the space bar is in the "up" state (or not being pressed down)
  if args.inputs.keyboard.key_up.space
    args.state.player.jumped_at = nil # jumped_at is empty
    args.state.player.falling = true # the player is falling
  end

  if args.inputs.keyboard.left # if left key is pressed
    args.state.player.dx -= args.state.player_acceleration # dx decreases by acceleration (player goes left)
    # dx is either set to current dx or the negative max run speed (which would be -10),
    # whichever has a greater value
    args.state.player.dx = args.state.player.dx.greater(-args.state.player_max_run_speed)
  elsif args.inputs.keyboard.right # if right key is pressed
    args.state.player.dx += args.state.player_acceleration # dx increases by acceleration (player goes right)
    # dx is either set to current dx or max run speed (which would be 10),
    # whichever has a lesser value
    args.state.player.dx = args.state.player.dx.lesser(args.state.player_max_run_speed)
  else
    args.state.player.dx *= args.state.player_speed_slowdown_rate # dx is scaled down
  end
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.space ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Physics And Collisions - Entities - main.rb

# ./samples/04_physics_and_collisions/03_entities/app/main.rb
=begin

 Reminders:

 - map: Ruby method used to transform data; used in arrays, hashes, and collections.
   Can be used to perform an action on every element of a collection, such as multiplying
   each element by 2 or declaring every element as a new entity.

 - reject: Removes elements from a collection if they meet certain requirements.
   For example, you can derive an array of odd numbers from an original array of
   numbers 1 through 10 by rejecting all elements that are even (or divisible by 2).

 - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
   In this sample app, new_entity is used to define the properties of enemies and bullets.
   (Remember, you can use state to define ANY property and it will be retained across frames.)

 - args.outputs.labels: An array. The values generate a label on the screen.
   The parameters are [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]

 - ARRAY#intersect_rect?: Returns true or false depending on if the two rectangles intersect.

 - args.inputs.mouse.click.point.(x|y): The x and y location of the mouse.

=end

# This sample app shows enemies that contain an id value and the time they were created.
# These enemies can be removed by shooting at them with bullets.

# Calls all methods necessary for the game to function properly.
def tick args
  tick_instructions args, "Sample app shows how to use args.state.new_entity along with collisions. CLICK to shoot a bullet."
  defaults args
  render args
  calc args
  process_inputs args
end

# Sets default values
# Enemies and bullets start off as empty collections
def defaults args
  args.state.enemies ||= []
  args.state.bullets ||= []
end

# Provides each enemy in enemies collection with rectangular border,
# as well as a label showing id and when they were created
def render args
  # When you're calling a method that takes no arguments, you can use this & syntax on map.
  # Numbers are being added to x and y in order to keep the text within the enemy's borders.
  args.outputs.borders << args.state.enemies.map(&:rect)
  args.outputs.labels  << args.state.enemies.flat_map do |enemy|
    [
      [enemy.x + 4, enemy.y + 29, "id: #{enemy.entity_id}", -3, 0],
      [enemy.x + 4, enemy.y + 17, "created_at: #{enemy.created_at}", -3, 0] # frame enemy was created
    ]
  end

  # Outputs bullets in bullets collection as rectangular solids
  args.outputs.solids << args.state.bullets.map(&:rect)
end

# Calls all methods necessary for performing calculations
def calc args
  add_new_enemies_if_needed args
  move_bullets args
  calculate_collisions args
  remove_bullets_of_screen args
end

# Adds enemies to the enemies collection and sets their values
def add_new_enemies_if_needed args
  return if args.state.enemies.length >= 10 # if 10 or more enemies, enemies are not added
  return unless args.state.bullets.length == 0 # if user has not yet shot bullet, no enemies are added

  args.state.enemies += (10 - args.state.enemies.length).map do # adds enemies so there are 10 total
    args.state.new_entity(:enemy) do |e| # each enemy is declared as a new entity
      e.x = 640 + 500 * rand # each enemy is given random position on screen
      e.y = 600 * rand + 50
      e.rect = [e.x, e.y, 130, 30] # sets definition for enemy's rect
    end
  end
end

# Moves bullets across screen
# Sets definition of the bullets
def move_bullets args
  args.state.bullets.each do |bullet| # perform action on each bullet in collection
    bullet.x += bullet.speed # increment x by speed (bullets fly horizontally across screen)

    # By randomizing the value that increments bullet.y, the bullet does not fly straight up and out
    # of the scope of the screen. Try removing what follows bullet.speed, or changing 0.25 to 1.25 to
    # see what happens to the bullet's movement.
    bullet.y += bullet.speed.*(0.25).randomize(:ratio, :sign)
    bullet.rect = [bullet.x, bullet.y, bullet.size, bullet.size] # sets definition of bullet's rect
  end
end

# Determines if a bullet hits an enemy
def calculate_collisions args
  args.state.bullets.each do |bullet| # perform action on every bullet and enemy in collections
    args.state.enemies.each do |enemy|
      # if bullet has not exploded yet and the bullet hits an enemy
      if !bullet.exploded && bullet.rect.intersect_rect?(enemy.rect)
        bullet.exploded = true # bullet explodes
        enemy.dead = true # enemy is killed
      end
    end
  end

  # All exploded bullets are rejected or removed from the bullets collection
  # and any dead enemy is rejected from the enemies collection.
  args.state.bullets = args.state.bullets.reject(&:exploded)
  args.state.enemies = args.state.enemies.reject(&:dead)
end

# Bullets are rejected from bullets collection once their position exceeds the width of screen
def remove_bullets_of_screen args
  args.state.bullets = args.state.bullets.reject { |bullet| bullet.x > 1280 } # screen width is 1280
end

# Calls fire_bullet method
def process_inputs args
  fire_bullet args
end

# Once mouse is clicked by the user to fire a bullet, a new bullet is added to bullets collection
def fire_bullet args
  return unless args.inputs.mouse.click # return unless mouse is clicked
  args.state.bullets << args.state.new_entity(:bullet) do |bullet| # new bullet is declared a new entity
    bullet.y = args.inputs.mouse.click.point.y # set to the y value of where the mouse was clicked
    bullet.x = 0 # starts on the left side of the screen
    bullet.size = 10
    bullet.speed = 10 * rand + 2 # speed of a bullet is randomized
    bullet.rect = [bullet.x, bullet.y, bullet.size, bullet.size] # definition is set
  end
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.space ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Physics And Collisions - Box Collision - main.rb

# ./samples/04_physics_and_collisions/04_box_collision/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - first: Returns the first element of the array.
   For example, if we have an array
   numbers = [1, 2, 3, 4, 5]
   and we call first by saying
   numbers.first
   the number 1 will be returned because it is the first element of the numbers array.

 - num1.idiv(num2): Divides two numbers and returns an integer.
   For example,
   16.idiv(3) = 5, because 16 / 3 is 5.33333 returned as an integer.
   16.idiv(4) = 4, because 16 / 4 is 4 and already has no decimal.

 Reminders:

 - find_all: Finds all values that satisfy specific requirements.

 - ARRAY#intersect_rect?: An array with at least four values is
   considered a rect. The intersect_rect? function returns true
   or false depending on if the two rectangles intersect.

 - reject: Removes elements from a collection if they meet certain requirements.

=end

# This sample app allows users to create tiles and place them anywhere on the screen as obstacles.
# The player can then move and maneuver around them.

class PoorManPlatformerPhysics
  attr_accessor :grid, :inputs, :state, :outputs

  # Calls all methods necessary for the app to run successfully.
  def tick
    defaults
    render
    calc
    process_inputs
  end

  # Sets default values for variables.
  # The ||= sign means that the variable will only be set to the value following the = sign if the value has
  # not already been set before. Intialization happens only in the first frame.
  def defaults
    state.tile_size               = 64
    state.gravity                 = -0.2
    state.previous_tile_size    ||= state.tile_size
    state.x                     ||= 0
    state.y                     ||= 800
    state.dy                    ||= 0
    state.dx                    ||= 0
    state.world                 ||= []
    state.world_lookup          ||= {}
    state.world_collision_rects ||= []
  end

  # Outputs solids and borders of different colors for the world and collision_rects collections.
  def render

    # Sets a black background on the screen (Comment this line out and the background will become white.)
    # Also note that black is the default color for when no color is assigned.
    outputs.solids << grid.rect

    # The position, size, and color (white) are set for borders given to the world collection.
    # Try changing the color by assigning different numbers (between 0 and 255) to the last three parameters.
    outputs.borders << state.world.map do |x, y|
      [x * state.tile_size,
       y * state.tile_size,
       state.tile_size,
       state.tile_size, 255, 255, 255]
    end

    # The top, bottom, and sides of the borders for collision_rects are different colors.
    outputs.borders << state.world_collision_rects.map do |e|
      [
        [e[:top],                             0, 170,   0], # top is a shade of green
        [e[:bottom],                          0, 100, 170], # bottom is a shade of greenish-blue
        [e[:left_right],                    170,   0,   0], # left and right are a shade of red
      ]
    end

    # Sets the position, size, and color (a shade of green) of the borders of only the player's
    # box and outputs it. If you change the 180 to 0, the player's box will be black and you
    # won't be able to see it (because it will match the black background).
    outputs.borders << [state.x,
                        state.y,
                        state.tile_size,
                        state.tile_size,  0, 180, 0]
  end

  # Calls methods needed to perform calculations.
  def calc
    calc_world_lookup
    calc_player
  end

  # Performs calculations on world_lookup and sets values.
  def calc_world_lookup

    # If the tile size isn't equal to the previous tile size,
    # the previous tile size is set to the tile size,
    # and world_lookup hash is set to empty.
    if state.tile_size != state.previous_tile_size
      state.previous_tile_size = state.tile_size
      state.world_lookup = {} # empty hash
    end

    # return if the world_lookup hash has keys (or, in other words, is not empty)
    # return unless the world collection has values inside of it (or is not empty)
    return if state.world_lookup.keys.length > 0
    return unless state.world.length > 0

    # Starts with an empty hash for world_lookup.
    # Searches through the world and finds the coordinates that exist.
    state.world_lookup = {}
    state.world.each { |x, y| state.world_lookup[[x, y]] = true }

    # Assigns world_collision_rects for every sprite drawn.
    state.world_collision_rects =
      state.world_lookup
          .keys
          .map do |coord_x, coord_y|
            s = state.tile_size
            # multiply by tile size so the grid coordinates; sets pixel value
            # don't forget that position is denoted by bottom left corner
            # set x = coord_x or y = coord_y and see what happens!
            x = s * coord_x
            y = s * coord_y
            {
              # The values added to x, y, and s position the world_collision_rects so they all appear
              # stacked (on top of world rects) but don't directly overlap.
              # Remove these added values and mess around with the rect placement!
              args:       [coord_x, coord_y],
              left_right: [x,     y + 4, s,     s - 6], # hash keys and values
              top:        [x + 4, y + 6, s - 8, s - 6],
              bottom:     [x + 1, y - 1, s - 2, s - 8],
            }
          end
  end

  # Performs calculations to change the x and y values of the player's box.
  def calc_player

    # Since acceleration is the change in velocity, the change in y (dy) increases every frame.
    # What goes up must come down because of gravity.
    state.dy += state.gravity

    # Calls the calc_box_collision and calc_edge_collision methods.
    calc_box_collision
    calc_edge_collision

    # Since velocity is the change in position, the change in y increases by dy. Same with x and dx.
    state.y += state.dy
    state.x += state.dx

    # Scales dx down.
    state.dx *= 0.8
  end

  # Calls methods needed to determine collisions between player and world_collision rects.
  def calc_box_collision
    return unless state.world_lookup.keys.length > 0 # return unless hash has atleast 1 key
    collision_floor!
    collision_left!
    collision_right!
    collision_ceiling!
  end

  # Finds collisions between the bottom of the player's rect and the top of a world_collision_rect.
  def collision_floor!
    return unless state.dy <= 0 # return unless player is going down or is as far down as possible
    player_rect = [state.x, state.y - 0.1, state.tile_size, state.tile_size] # definition of player

    # Goes through world_collision_rects to find all intersections between the bottom of player's rect and
    # the top of a world_collision_rect (hence the "-0.1" above)
    floor_collisions = state.world_collision_rects
                           .find_all { |r| r[:top].intersect_rect?(player_rect, collision_tollerance) }
                           .first

    return unless floor_collisions # return unless collision occurred
    state.y = floor_collisions[:top].top # player's y is set to the y of the top of the collided rect
    state.dy = 0 # if a collision occurred, the player's rect isn't moving because its path is blocked
  end

  # Finds collisions between the player's left side and the right side of a world_collision_rect.
  def collision_left!
    return unless state.dx < 0 # return unless player is moving left
    player_rect = [state.x - 0.1, state.y, state.tile_size, state.tile_size]

    # Goes through world_collision_rects to find all intersections beween the player's left side and the
    # right side of a world_collision_rect.
    left_side_collisions = state.world_collision_rects
                               .find_all { |r| r[:left_right].intersect_rect?(player_rect, collision_tollerance) }
                               .first

    return unless left_side_collisions # return unless collision occurred

    # player's x is set to the value of the x of the collided rect's right side
    state.x = left_side_collisions[:left_right].right
    state.dx = 0 # player isn't moving left because its path is blocked
  end

  # Finds collisions between the right side of the player and the left side of a world_collision_rect.
  def collision_right!
    return unless state.dx > 0 # return unless player is moving right
    player_rect = [state.x + 0.1, state.y, state.tile_size, state.tile_size]

    # Goes through world_collision_rects to find all intersections between the player's right side
    # and the left side of a world_collision_rect (hence the "+0.1" above)
    right_side_collisions = state.world_collision_rects
                                .find_all { |r| r[:left_right].intersect_rect?(player_rect, collision_tollerance) }
                                .first

    return unless right_side_collisions # return unless collision occurred

    # player's x is set to the value of the collided rect's left, minus the size of a rect
    # tile size is subtracted because player's position is denoted by bottom left corner
    state.x = right_side_collisions[:left_right].left - state.tile_size
    state.dx = 0 # player isn't moving right because its path is blocked
  end

  # Finds collisions between the top of the player's rect and the bottom of a world_collision_rect.
  def collision_ceiling!
    return unless state.dy > 0 # return unless player is moving up
    player_rect = [state.x, state.y + 0.1, state.tile_size, state.tile_size]

    # Goes through world_collision_rects to find intersections between the bottom of a
    # world_collision_rect and the top of the player's rect (hence the "+0.1" above)
    ceil_collisions = state.world_collision_rects
                          .find_all { |r| r[:bottom].intersect_rect?(player_rect, collision_tollerance) }
                          .first

    return unless ceil_collisions # return unless collision occurred

    # player's y is set to the bottom y of the rect it collided with, minus the size of a rect
    state.y = ceil_collisions[:bottom].y - state.tile_size
    state.dy = 0 # if a collision occurred, the player isn't moving up because its path is blocked
  end

  # Makes sure the player remains within the screen's dimensions.
  def calc_edge_collision

    #Ensures that the player doesn't fall below the map.
    if state.y < 0
      state.y = 0
      state.dy = 0

    #Ensures that the player doesn't go too high.
    # Position of player is denoted by bottom left hand corner, which is why we have to subtract the
    # size of the player's box (so it remains visible on the screen)
    elsif state.y > 720 - state.tile_size # if the player's y position exceeds the height of screen
      state.y = 720 - state.tile_size # the player will remain as high as possible while staying on screen
      state.dy = 0
    end

    # Ensures that the player remains in the horizontal range that it is supposed to.
    if state.x >= 1280 - state.tile_size && state.dx > 0 # if player moves too far right
      state.x = 1280 - state.tile_size # player will remain as right as possible while staying on screen
      state.dx = 0
    elsif state.x <= 0 && state.dx < 0 # if player moves too far left
      state.x = 0 # player will remain as left as possible while remaining on screen
      state.dx = 0
    end
  end

  # Processes input from the user on the keyboard.
  def process_inputs
    if inputs.mouse.down
      state.world_lookup = {}
      x, y = to_coord inputs.mouse.down.point  # gets x, y coordinates for the grid

      if state.world.any? { |loc| loc == [x, y] }  # checks if coordinates duplicate
        state.world = state.world.reject { |loc| loc == [x, y] }  # erases tile space
      else
        state.world << [x, y] # If no duplicates, adds to world collection
      end
    end

    # Sets dx to 0 if the player lets go of arrow keys.
    if inputs.keyboard.key_up.right
      state.dx = 0
    elsif inputs.keyboard.key_up.left
      state.dx = 0
    end

    # Sets dx to 3 in whatever direction the player chooses.
    if inputs.keyboard.key_held.right # if right key is pressed
      state.dx =  3
    elsif inputs.keyboard.key_held.left # if left key is pressed
      state.dx = -3
    end

    #Sets dy to 5 to make the player ~fly~ when they press the space bar
    if inputs.keyboard.key_held.space
      state.dy = 5
    end
  end

  def to_coord point

    # Integer divides (idiv) point.x to turn into grid
    # Then, you can just multiply each integer by state.tile_size later so the grid coordinates.
    [point.x.idiv(state.tile_size), point.y.idiv(state.tile_size)]
  end

  # Represents the tolerance for a collision between the player's rect and another rect.
  def collision_tollerance
    0.0
  end
end

$platformer_physics = PoorManPlatformerPhysics.new

def tick args
  $platformer_physics.grid    = args.grid
  $platformer_physics.inputs  = args.inputs
  $platformer_physics.state    = args.state
  $platformer_physics.outputs = args.outputs
  $platformer_physics.tick
  tick_instructions args, "Sample app shows platformer collisions. CLICK to place box. ARROW keys to move around. SPACE to jump."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Physics And Collisions - Box Collision 2 - main.rb

# ./samples/04_physics_and_collisions/05_box_collision_2/app/main.rb
=begin
 APIs listing that haven't been encountered in previous sample apps:

 - times: Performs an action a specific number of times.
   For example, if we said
   5.times puts "Hello DragonRuby",
   then we'd see the words "Hello DragonRuby" printed on the console 5 times.

 - split: Divides a string into substrings based on a delimiter.
   For example, if we had a command
   "DragonRuby is awesome".split(" ")
   then the result would be
   ["DragonRuby", "is", "awesome"] because the words are separated by a space delimiter.

 - join: Opposite of split; converts each element of array to a string separated by delimiter.
   For example, if we had a command
   ["DragonRuby","is","awesome"].join(" ")
   then the result would be
   "DragonRuby is awesome".

 Reminders:

 - to_s: Returns a string representation of an object.
   For example, if we had
   500.to_s
   the string "500" would be returned.
   Similar to to_i, which returns an integer representation of an object.

 - elapsed_time: How many frames have passed since the click event.

 - args.outputs.labels: An array. Values in the array generate labels on the screen.
   The parameters are: [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.

 - inputs.mouse.down: Determines whether or not the mouse is being pressed down.
   The position of the mouse when it is pressed down can be found using inputs.mouse.down.point.(x|y).

 - first: Returns the first element of the array.

 - num1.idiv(num2): Divides two numbers and returns an integer.

 - find_all: Finds all values that satisfy specific requirements.

 - ARRAY#intersect_rect?: Returns true or false depending on if two rectangles intersect.

 - reject: Removes elements from a collection if they meet certain requirements.

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

=end

MAP_FILE_PATH = 'app/map.txt' # the map.txt file in the app folder contains exported map

class MetroidvaniaStarter
  attr_accessor :grid, :inputs, :state, :outputs, :gtk

  # Calls methods needed to run the game properly.
  def tick
    defaults
    render
    calc
    process_inputs
  end

  # Sets all the default variables.
  # '||' states that initialization occurs only in the first frame.
  def defaults
    state.tile_size                = 64
    state.gravity                  = -0.2
    state.player_width             = 60
    state.player_height            = 64
    state.collision_tolerance      = 0.0
    state.previous_tile_size     ||= state.tile_size
    state.x                      ||= 0
    state.y                      ||= 800
    state.dy                     ||= 0
    state.dx                     ||= 0
    attempt_load_world_from_file
    state.world_lookup           ||= { }
    state.world_collision_rects  ||= []
    state.mode                   ||= :creating # alternates between :creating and :selecting for sprite selection
    state.select_menu            ||= [0, 720, 1280, 720]
    #=======================================IMPORTANT=======================================#
    # When adding sprites, please label them "image1.png", "image2.png", image3".png", etc.
    # Once you have done that, adjust "state.sprite_quantity" to how many sprites you have.
    #=======================================================================================#
    state.sprite_quantity        ||= 20 # IMPORTANT TO ALTER IF SPRITES ADDED IF YOU ADD MORE SPRITES
    state.sprite_coords          ||= []
    state.banner_coords          ||= [640, 680 + 720]
    state.sprite_selected        ||= 1
    state.map_saved_at           ||= 0

    # Sets all the cordinate values for the sprite selection screen into a grid
    # Displayed when 's' is pressed by player to access sprites
    if state.sprite_coords == [] # if sprite_coords is an empty array
      count = 1
      temp_x = 165 # sets a starting x and y position for display
      temp_y = 500 + 720
      state.sprite_quantity.times do # for the number of sprites you have
        state.sprite_coords += [[temp_x, temp_y, count]] # add element to sprite_coords array
        temp_x += 100 # increment temp_x
        count += 1 # increment count
        if temp_x > 1280 - (165 + 50) # if exceeding specific horizontal width on screen
          temp_x = 165 # a new row of sprites starts
          temp_y -= 75 # new row of sprites starts 75 units lower than the previous row
        end
      end
    end
  end

  # Places sprites
  def render

    # Sets the x, y, width, height, and image path for each sprite in the world collection.
    outputs.sprites << state.world.map do |x, y, sprite|
      [x * state.tile_size, # multiply by size so grid coordinates; pixel value of location
       y * state.tile_size,
       state.tile_size,
       state.tile_size,
       'sprites/image' + sprite.to_s + '.png'] # uses concatenation to create unique image path
    end

    # Outputs sprite for the player by setting x, y, width, height, and image path
    outputs.sprites << [state.x,
                        state.y,
                        state.player_width,
                        state.player_height,'sprites/player.png']

    # Outputs labels as primitives in top right of the screen
    outputs.primitives << [920, 700, 'Press \'s\' to access sprites.', 1, 0].label
    outputs.primitives << [920, 675, 'Click existing sprite to delete.', 1, 0].label

    outputs.primitives << [920, 640, '<- and -> to move.', 1, 0].label
    outputs.primitives << [920, 615, 'Press and hold space to jump.', 1, 0].label

    outputs.primitives << [920, 580, 'Press \'e\' to export current map.', 1, 0].label

    # if the map is saved and less than 120 frames have passed, the label is displayed
    if state.map_saved_at > 0 && state.map_saved_at.elapsed_time < 120
      outputs.primitives << [920, 555, 'Map has been exported!', 1, 0, 50, 100, 50].label
    end

    # If player hits 's', following appears
    if state.mode == :selecting
      # White background for sprite selection
      outputs.primitives << [state.select_menu, 255, 255, 255].solid

      # Select tile label at the top of the screen
      outputs.primitives << [state.banner_coords.x, state.banner_coords.y, "Select Sprite (sprites located in \"sprites\" folder)", 10, 1, 0, 0, 0, 255].label

      # Places sprites in locations calculated in the defaults function
      outputs.primitives << state.sprite_coords.map do |x, y, order|
        [x, y, 50, 50, 'sprites/image' + order.to_s + ".png"].sprite
      end
    end

    # Creates sprite following mouse to help indicate which sprite you have selected
    # 10 is subtracted from the mouse's x position so that the sprite is not covered by the mouse icon
    outputs.primitives << [inputs.mouse.position.x - 10, inputs.mouse.position.y,
                           10, 10, 'sprites/image' + state.sprite_selected.to_s + ".png"].sprite
  end

  # Calls methods that perform calculations
  def calc
    calc_in_game
    calc_sprite_selection
  end

  # Calls methods that perform calculations (if in creating mode)
  def calc_in_game
    return unless state.mode == :creating
    calc_world_lookup
    calc_player
  end

  def calc_world_lookup
    # If the tile size isn't equal to the previous tile size,
    # the previous tile size is set to the tile size,
    # and world_lookup hash is set to empty.
    if state.tile_size != state.previous_tile_size
      state.previous_tile_size = state.tile_size
      state.world_lookup = {}
    end

    # return if world_lookup is not empty or if world is empty
    return if state.world_lookup.keys.length > 0
    return unless state.world.length > 0

    # Searches through the world and finds the coordinates that exist
    state.world_lookup = {}
    state.world.each { |x, y| state.world_lookup[[x, y]] = true }

    # Assigns collision rects for every sprite drawn
    state.world_collision_rects =
      state.world_lookup
           .keys
           .map do |coord_x, coord_y|
             s = state.tile_size
             # Multiplying by s (the size of a tile) ensures that the rect is
             # placed exactly where you want it to be placed (causes grid to coordinate)
             # How many pixels horizontally across and vertically up and down
             x = s * coord_x
             y = s * coord_y
             {
               args:       [coord_x, coord_y],
               left_right: [x,     y + 4, s,     s - 6], # hash keys and values
               top:        [x + 4, y + 6, s - 8, s - 6],
               bottom:     [x + 1, y - 1, s - 2, s - 8],
             }
           end
  end

  # Calculates movement of player and calls methods that perform collision calculations
  def calc_player
    state.dy += state.gravity  # what goes up must come down because of gravity
    calc_box_collision
    calc_edge_collision
    state.y  += state.dy       # Since velocity is the change in position, the change in y increases by dy
    state.x  += state.dx       # Ditto line above but dx and x
    state.dx *= 0.8            # Scales dx down
  end

  # Calls methods that determine whether the player collides with any world_collision_rects.
  def calc_box_collision
    return unless state.world_lookup.keys.length > 0 # return unless hash has atleast 1 key
    collision_floor
    collision_left
    collision_right
    collision_ceiling
  end

  # Finds collisions between the bottom of the player's rect and the top of a world_collision_rect.
  def collision_floor
    return unless state.dy <= 0 # return unless player is going down or is as far down as possible
    player_rect = [state.x, next_y, state.tile_size, state.tile_size] # definition of player

    # Runs through all the sprites on the field and finds all intersections between player's
    # bottom and the top of a rect.
    floor_collisions = state.world_collision_rects
                         .find_all { |r| r[:top].intersect_rect?(player_rect, state.collision_tolerance) }
                         .first

    return unless floor_collisions # performs following changes if a collision has occurred
    state.y = floor_collisions[:top].top # y of player is set to the y of the colliding rect's top
    state.dy = 0 # no change in y because the player's path is blocked
  end

  # Finds collisions between the player's left side and the right side of a world_collision_rect.
  def collision_left
    return unless state.dx < 0 # return unless player is moving left
    player_rect = [next_x, state.y, state.tile_size, state.tile_size]

    # Runs through all the sprites on the field and finds all intersections between the player's left side
    # and the right side of a rect.
    left_side_collisions = state.world_collision_rects
                             .find_all { |r| r[:left_right].intersect_rect?(player_rect, state.collision_tolerance) }
                             .first

    return unless left_side_collisions # return unless collision occurred
    state.x = left_side_collisions[:left_right].right # sets player's x to the x of the colliding rect's right side
    state.dx = 0 # no change in x because the player's path is blocked
  end

  # Finds collisions between the right side of the player and the left side of a world_collision_rect.
  def collision_right
    return unless state.dx > 0 # return unless player is moving right
    player_rect = [next_x, state.y, state.tile_size, state.tile_size]

    # Runs through all the sprites on the field and finds all intersections between the  player's
    # right side and the left side of a rect.
    right_side_collisions = state.world_collision_rects
                              .find_all { |r| r[:left_right].intersect_rect?(player_rect, state.collision_tolerance) }
                              .first

    return unless right_side_collisions # return unless collision occurred
    state.x = right_side_collisions[:left_right].left - state.tile_size # player's x is set to the x of colliding rect's left side (minus tile size since x is the player's bottom left corner)
    state.dx = 0 # no change in x because the player's path is blocked
  end

  # Finds collisions between the top of the player's rect and the bottom of a world_collision_rect.
  def collision_ceiling
    return unless state.dy > 0 # return unless player is moving up
    player_rect = [state.x, next_y, state.player_width, state.player_height]

    # Runs through all the sprites on the field and finds all intersections between the player's top
    # and the bottom of a rect.
    ceil_collisions = state.world_collision_rects
                        .find_all { |r| r[:bottom].intersect_rect?(player_rect, state.collision_tolerance) }
                        .first

    return unless ceil_collisions # return unless collision occurred
    state.y = ceil_collisions[:bottom].y - state.tile_size # player's y is set to the y of the colliding rect's bottom (minus tile size)
    state.dy = 0 # no change in y because the player's path is blocked
  end

  # Makes sure the player remains within the screen's dimensions.
  def calc_edge_collision
    # Ensures that player doesn't fall below the map
    if next_y < 0 && state.dy < 0 # if player is moving down and is about to fall (next_y) below the map's scope
      state.y = 0 # 0 is the lowest the player can be while staying on the screen
      state.dy = 0
    # Ensures player doesn't go insanely high
    elsif next_y > 720 - state.tile_size && state.dy > 0 # if player is moving up, about to exceed map's scope
      state.y = 720 - state.tile_size # if we don't subtract tile_size, we won't be able to see the player on the screen
      state.dy = 0
    end

    # Ensures that player remains in the horizontal range its supposed to
    if state.x >= 1280 - state.tile_size && state.dx > 0 # if the player is moving too far right
      state.x = 1280 - state.tile_size # farthest right the player can be while remaining in the screen's scope
      state.dx = 0
    elsif state.x <= 0 && state.dx < 0 # if the player is moving too far left
      state.x = 0 # farthest left the player can be while remaining in the screen's scope
      state.dx = 0
    end
  end

  def calc_sprite_selection
    # Does the transition to bring down the select sprite screen
    if state.mode == :selecting && state.select_menu.y != 0
      state.select_menu.y = 0  # sets y position of select menu (shown when 's' is pressed)
      state.banner_coords.y = 680 # sets y position of Select Sprite banner
      state.sprite_coords = state.sprite_coords.map do |x, y, w, h|
        [x, y - 720, w, h] # sets definition of sprites (change '-' to '+' and the sprites can't be seen)
      end
    end

    # Does the transition to leave the select sprite screen
    if state.mode == :creating  && state.select_menu.y != 720
      state.select_menu.y = 720 # sets y position of select menu (menu is retreated back up)
      state.banner_coords.y = 1000 # sets y position of Select Sprite banner
      state.sprite_coords = state.sprite_coords.map do |x, y, w, h|
        [x, y + 720, w, h] # sets definition of all elements in collection
      end
    end
  end

  def process_inputs
    # If the state.mode is back and if the menu has retreated back up
    # call methods that process user inputs
    if state.mode == :creating
      process_inputs_player_movement
      process_inputs_place_tile
    end

    # For each sprite_coordinate added, check what sprite was selected
    if state.mode == :selecting
      state.sprite_coords.map do |x, y, order| # goes through all sprites in collection
        # checks that a specific sprite was pressed based on x, y position
        if inputs.mouse.down && # the && (and) sign means ALL statements must be true for the evaluation to be true
           inputs.mouse.down.point.x >= x      && # x is greater than or equal to sprite's x and
           inputs.mouse.down.point.x <= x + 50 && # x is less than or equal to 50 pixels to the right
           inputs.mouse.down.point.y >= y      && # y is greater than or equal to sprite's y
           inputs.mouse.down.point.y <= y + 50 # y is less than or equal to 50 pixels up
          state.sprite_selected = order # sprite is chosen
        end
      end
    end

    inputs_export_stage
    process_inputs_show_available_sprites
  end

  # Moves the player based on the keys they press on their keyboard
  def process_inputs_player_movement
    # Sets dx to 0 if the player lets go of arrow keys (player won't move left or right)
    if inputs.keyboard.key_up.right
      state.dx = 0
    elsif inputs.keyboard.key_up.left
      state.dx = 0
    end

    # Sets dx to 3 in whatever direction the player chooses when they hold down (or press) the left or right keys
    if inputs.keyboard.key_held.right
      state.dx =  3
    elsif inputs.keyboard.key_held.left
      state.dx = -3
    end

    # Sets dy to 5 to make the player ~fly~ when they press the space bar on their keyboard
    if inputs.keyboard.key_held.space
      state.dy = 5
    end
  end

  # Adds tile in the place the user holds down the mouse
  def process_inputs_place_tile
    if inputs.mouse.down # if mouse is pressed
      state.world_lookup = {}
      x, y = to_coord inputs.mouse.down.point # gets x, y coordinates for the grid

      # Checks if any coordinates duplicate (already exist in world)
      if state.world.any? { |existing_x, existing_y, n| existing_x == x && existing_y == y }
        #erases existing tile space by rejecting them from world
        state.world = state.world.reject do |existing_x, existing_y, n|
          existing_x == x && existing_y == y
        end
      else
        state.world << [x, y, state.sprite_selected] # If no duplicates, add the sprite
      end
    end
  end

  # Stores/exports world collection's info (coordinates, sprite number) into a file
  def inputs_export_stage
    if inputs.keyboard.key_down.e # if "e" is pressed
      export_string = state.world.map do |x, y, sprite_number| # stores world info in a string
        "#{x},#{y},#{sprite_number}"                           # using string interpolation
      end
      gtk.write_file(MAP_FILE_PATH, export_string.join("\n")) # writes string into a file
      state.map_saved_at = state.tick_count # frame number (passage of time) when the map was saved
    end
  end

  def process_inputs_show_available_sprites
    # Based on keyboard input, the entity (:creating and :selecting) switch
    if inputs.keyboard.key_held.s && state.mode == :creating # if "s" is pressed and currently creating
      state.mode = :selecting # will change to selecting
      inputs.keyboard.clear # VERY IMPORTANT! If not present, it'll flicker between on and off
    elsif inputs.keyboard.key_held.s && state.mode == :selecting # if "s" is pressed and currently selecting
      state.mode = :creating # will change to creating
      inputs.keyboard.clear # VERY IMPORTANT! If not present, it'll flicker between on and off
    end
  end

  # Loads the world collection by reading from the map.txt file in the app folder
  def attempt_load_world_from_file
    return if state.world # return if the world collection is already populated
    state.world ||= [] # initialized as an empty collection
    exported_world = gtk.read_file(MAP_FILE_PATH) # reads the file using the path mentioned at top of code
    return unless exported_world # return unless the file read was successful
    state.world = exported_world.each_line.map do |l| # perform action on each line of exported_world
        l.split(',').map(&:to_i) # calls split using ',' as a delimiter, and invokes .map on the collection,
                                 # calling to_i (converts to integers) on each element
    end
  end

  # Adds the change in y to y to determine the next y position of the player.
  def next_y
    state.y + state.dy
  end

  # Determines next x position of player
  def next_x
    if state.dx < 0 # if the player moves left
      return state.x - (state.tile_size - state.player_width) # subtracts since the change in x is negative (player is moving left)
    else
      return state.x + (state.tile_size - state.player_width) # adds since the change in x is positive (player is moving right)
    end
  end

  def to_coord point
    # Integer divides (idiv) point.x to turn into grid
    # Then, you can just multiply each integer by state.tile_size
    # later and huzzah. Grid coordinates
    [point.x.idiv(state.tile_size), point.y.idiv(state.tile_size)]
  end
end

$metroidvania_starter = MetroidvaniaStarter.new

def tick args
    $metroidvania_starter.grid    = args.grid
    $metroidvania_starter.inputs  = args.inputs
    $metroidvania_starter.state   = args.state
    $metroidvania_starter.outputs = args.outputs
    $metroidvania_starter.gtk     = args.gtk
    $metroidvania_starter.tick
end

Physics And Collisions - Box Collision 3 - main.rb

# ./samples/04_physics_and_collisions/06_box_collision_3/app/main.rb
class Game
  attr_gtk

  def tick
    defaults
    render
    input_edit_map
    input_player
    calc_player
  end

  def defaults
    state.gravity           = -0.4
    state.drag              = 0.15
    state.tile_size         = 32
    state.player.size       = 16
    state.player.jump_power = 12

    state.tiles                 ||= []
    state.player.y              ||= 800
    state.player.x              ||= 100
    state.player.dy             ||= 0
    state.player.dx             ||= 0
    state.player.jumped_down_at ||= 0
    state.player.jumped_at      ||= 0

    calc_player_rect if !state.player.rect
  end

  def render
    outputs.labels << [10, 10.from_top, "tile: click to add a tile, hold X key and click to delete a tile."]
    outputs.labels << [10, 35.from_top, "move: use left and right to move, space to jump, down and space to jump down."]
    outputs.labels << [10, 55.from_top, "      You can jump through or jump down through tiles with a height of 1."]
    outputs.background_color = [80, 80, 80]
    outputs.sprites << tiles.map(&:sprite)
    outputs.sprites << (player.rect.merge path: 'sprites/square/green.png')

    mouse_overlay = {
      x: (inputs.mouse.x.ifloor state.tile_size),
      y: (inputs.mouse.y.ifloor state.tile_size),
      w: state.tile_size,
      h: state.tile_size,
      a: 100
    }

    mouse_overlay = mouse_overlay.merge r: 255 if state.delete_mode

    if state.mouse_held
      outputs.primitives << mouse_overlay.border!
    else
      outputs.primitives << mouse_overlay.solid!
    end
  end

  def input_edit_map
    state.mouse_held = true  if inputs.mouse.down
    state.mouse_held = false if inputs.mouse.up

    if inputs.keyboard.x
      state.delete_mode = true
    elsif inputs.keyboard.key_up.x
      state.delete_mode = false
    end

    return unless state.mouse_held

    ordinal = { x: (inputs.mouse.x.idiv state.tile_size),
                y: (inputs.mouse.y.idiv state.tile_size) }

    found = find_tile ordinal
    if !found && !state.delete_mode
      tiles << (state.new_entity :tile, ordinal)
      recompute_tiles
    elsif found && state.delete_mode
      tiles.delete found
      recompute_tiles
    end
  end

  def input_player
    player.dx += inputs.left_right

    if inputs.keyboard.key_down.space && inputs.keyboard.down
      player.dy             = player.jump_power * -1
      player.jumped_at      = 0
      player.jumped_down_at = state.tick_count
    elsif inputs.keyboard.key_down.space
      player.dy             = player.jump_power
      player.jumped_at      = state.tick_count
      player.jumped_down_at = 0
    end
  end

  def calc_player
    calc_player_rect
    calc_below
    calc_left
    calc_right
    calc_above
    calc_player_dy
    calc_player_dx
    reset_player if player_off_stage?
  end

  def calc_player_rect
    player.rect      = current_player_rect
    player.next_rect = player.rect.merge x: player.x + player.dx,
                                         y: player.y + player.dy
    player.prev_rect = player.rect.merge x: player.x - player.dx,
                                         y: player.y - player.dy
  end

  def calc_below
    return unless player.dy <= 0
    tiles_below = find_tiles { |t| t.rect.top <= player.prev_rect.y }
    collision = find_colliding_tile tiles_below, (player.rect.merge y: player.next_rect.y)
    return unless collision
    if collision.neighbors.b == :none && player.jumped_down_at.elapsed_time < 10
      player.dy = -1
    else
      player.y  = collision.rect.y + state.tile_size
      player.dy = 0
    end
  end

  def calc_left
    return unless player.dx < 0
    tiles_left = find_tiles { |t| t.rect.right <= player.prev_rect.left }
    collision = find_colliding_tile tiles_left, (player.rect.merge x: player.next_rect.x)
    return unless collision
    player.x  = collision.rect.right
    player.dx = 0
  end

  def calc_right
    return unless player.dx > 0
    tiles_right = find_tiles { |t| t.rect.left >= player.prev_rect.right }
    collision = find_colliding_tile tiles_right, (player.rect.merge x: player.next_rect.x)
    return unless collision
    player.x  = collision.rect.left - player.rect.w
    player.dx = 0
  end

  def calc_above
    return unless player.dy > 0
    tiles_above = find_tiles { |t| t.rect.y >= player.prev_rect.y }
    collision = find_colliding_tile tiles_above, (player.rect.merge y: player.next_rect.y)
    return unless collision
    return if collision.neighbors.t == :none
    player.dy = 0
    player.y  = collision.rect.bottom - player.rect.h
  end

  def calc_player_dx
    player.dx  = player.dx.clamp(-5,  5)
    player.dx *= 0.9
    player.x  += player.dx
  end

  def calc_player_dy
    player.y  += player.dy
    player.dy += state.gravity
    player.dy += player.dy * state.drag ** 2 * -1
  end

  def reset_player
    player.x  = 100
    player.y  = 720
    player.dy = 0
  end

  def recompute_tiles
    tiles.each do |t|
      t.w = state.tile_size
      t.h = state.tile_size
      t.neighbors = tile_neighbors t, tiles

      t.rect = [t.x * state.tile_size,
                t.y * state.tile_size,
                state.tile_size,
                state.tile_size].rect.to_hash

      sprite_sub_path = t.neighbors.mask.map { |m| flip_bit m }.join("")

      t.sprite = {
        x: t.x * state.tile_size,
        y: t.y * state.tile_size,
        w: state.tile_size,
        h: state.tile_size,
        path: "sprites/tile/wall-#{sprite_sub_path}.png"
      }
    end
  end

  def flip_bit bit
    return 0 if bit == 1
    return 1
  end

  def player
    state.player
  end

  def player_off_stage?
    player.rect.top < grid.bottom ||
    player.rect.right < grid.left ||
    player.rect.left > grid.right
  end

  def current_player_rect
    { x: player.x, y: player.y, w: player.size, h: player.size }
  end

  def tiles
    state.tiles
  end

  def find_tile ordinal
    tiles.find { |t| t.x == ordinal.x && t.y == ordinal.y }
  end

  def find_tiles &block
    tiles.find_all(&block)
  end

  def find_colliding_tile tiles, target
    tiles.find { |t| t.rect.intersect_rect? target }
  end

  def tile_neighbors tile, other_points
    t = find_tile x: tile.x + 0, y: tile.y + 1
    r = find_tile x: tile.x + 1, y: tile.y + 0
    b = find_tile x: tile.x + 0, y: tile.y - 1
    l = find_tile x: tile.x - 1, y: tile.y + 0

    tile_t, tile_r, tile_b, tile_l = 0

    tile_t = 1 if t
    tile_r = 1 if r
    tile_b = 1 if b
    tile_l = 1 if l

    state.new_entity :neighbors, mask: [tile_t, tile_r, tile_b, tile_l],
                                 t:    t ? :some : :none,
                                 b:    b ? :some : :none,
                                 l:    l ? :some : :none,
                                 r:    r ? :some : :none
  end
end

def tick args
  $game ||= Game.new
  $game.args = args
  $game.tick
end

Physics And Collisions - Jump Physics - main.rb

# ./samples/04_physics_and_collisions/07_jump_physics/app/main.rb
=begin

 Reminders:

 - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
   For example, if we want to create a new button, we would declare it as a new entity and
   then define its properties. (Remember, you can use state to define ANY property and it will
   be retained across frames.)

 - args.outputs.solids: An array. The values generate a solid.
   The parameters for a solid are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]
   For more information about solids, go to mygame/documentation/03-solids-and-borders.md.

 - num1.greater(num2): Returns the greater value.

 - Hashes: Collection of unique keys and their corresponding values. The value can be found
   using their keys.

 - ARRAY#inside_rect?: Returns true or false depending on if the point is inside the rect.

=end

# This sample app is a game that requires the user to jump from one platform to the next.
# As the player successfully clears platforms, they become smaller and move faster.

class VerticalPlatformer
  attr_gtk

  # declares vertical platformer as new entity
  def s
    state.vertical_platformer ||= state.new_entity(:vertical_platformer)
    state.vertical_platformer
  end

  # creates a new platform using a hash
  def new_platform hash
    s.new_entity_strict(:platform, hash) # platform key
  end

  # calls methods needed for game to run properly
  def tick
    defaults
    render
    calc
    input
  end

  def init_game
    s.platforms ||= [ # initializes platforms collection with two platforms using hashes
      new_platform(x: 0, y: 0, w: 700, h: 32, dx: 1, speed: 0, rect: nil),
      new_platform(x: 0, y: 300, w: 700, h: 32, dx: 1, speed: 0, rect: nil), # 300 pixels higher
    ]

    s.tick_count  = args.state.tick_count
    s.gravity     = -0.3 # what goes up must come down because of gravity
    s.player.platforms_cleared ||= 0 # counts how many platforms the player has successfully cleared
    s.player.x  ||= 0           # sets player values
    s.player.y  ||= 100
    s.player.w  ||= 64
    s.player.h  ||= 64
    s.player.dy ||= 0           # change in position
    s.player.dx ||= 0
    s.player_jump_power           = 15
    s.player_jump_power_duration  = 10
    s.player_max_run_speed        = 5
    s.player_speed_slowdown_rate  = 0.9
    s.player_acceleration         = 1
    s.camera ||= { y: -100 } # shows view on screen (as the player moves upward, the camera does too)
  end

  # Sets default values
  def defaults
    init_game
  end

  # Outputs objects onto the screen
  def render
    outputs.solids << s.platforms.map do |p| # outputs platforms onto screen
      [p.x + 300, p.y - s.camera[:y], p.w, p.h] # add 300 to place platform in horizontal center
      # don't forget, position of platform is denoted by bottom left hand corner
    end

    # outputs player using hash
    outputs.solids << {
      x: s.player.x + 300, # player positioned on top of platform
      y: s.player.y - s.camera[:y],
      w: s.player.w,
      h: s.player.h,
      r: 100,              # color saturation
      g: 100,
      b: 200
    }
  end

  # Performs calculations
  def calc
    s.platforms.each do |p| # for each platform in the collection
      p.rect = [p.x, p.y, p.w, p.h] # set the definition
    end

    # sets player point by adding half the player's width to the player's x
    s.player.point = [s.player.x + s.player.w.half, s.player.y] # change + to - and see what happens!

    # search the platforms collection to find if the player's point is inside the rect of a platform
    collision = s.platforms.find { |p| s.player.point.inside_rect? p.rect }

    # if collision occurred and player is moving down (or not moving vertically at all)
    if collision && s.player.dy <= 0
      s.player.y = collision.rect.y + collision.rect.h - 2 # player positioned on top of platform
      s.player.dy = 0 if s.player.dy < 0 # player stops moving vertically
      if !s.player.platform
        s.player.dx = 0 # no horizontal movement
      end
      # changes horizontal position of player by multiplying collision change in x (dx) by speed and adding it to current x
      s.player.x += collision.dx * collision.speed
      s.player.platform = collision # player is on the platform that it collided with (or landed on)
      if s.player.falling # if player is falling
        s.player.dx = 0  # no horizontal movement
      end
      s.player.falling = false
      s.player.jumped_at = nil
    else
      s.player.platform = nil # player is not on a platform
      s.player.y  += s.player.dy # velocity is the change in position
      s.player.dy += s.gravity # acceleration is the change in velocity; what goes up must come down
    end

    s.platforms.each do |p| # for each platform in the collection
      p.x += p.dx * p.speed # x is incremented by product of dx and speed (causes platform to move horizontally)
      # changes platform's x so it moves left and right across the screen (between -300 and 300 pixels)
      if p.x < -300 # if platform goes too far left
        p.dx *= -1 # dx is scaled down
        p.x = -300 # as far left as possible within scope
      elsif p.x > (1000 - p.w) # if platform's x is greater than 300
        p.dx *= -1
        p.x = (1000 - p.w) # set to 300 (as far right as possible within scope)
      end
    end

    delta = (s.player.y - s.camera[:y] - 100) # used to position camera view

    if delta > -200
      s.camera[:y] += delta * 0.01 # allows player to see view as they move upwards
      s.player.x  += s.player.dx # velocity is change in position; change in x increases by dx

      # searches platform collection to find platforms located more than 300 pixels above the player
      has_platforms = s.platforms.find { |p| p.y > (s.player.y + 300) }
      if !has_platforms # if there are no platforms 300 pixels above the player
        width = 700 - (700 * (0.1 * s.player.platforms_cleared)) # the next platform is smaller than previous
        s.player.platforms_cleared += 1 # player successfully cleared another platform
        last_platform = s.platforms[-1] # platform just cleared becomes last platform
        # another platform is created 300 pixels above the last platform, and this
        # new platform has a smaller width and moves faster than all previous platforms
        s.platforms << new_platform(x: (700 - width) * rand, # random x position
                                    y: last_platform.y + 300,
                                    w: width,
                                    h: 32,
                                    dx: 1.randomize(:sign), # random change in x
                                    speed: 2 * s.player.platforms_cleared,
                                    rect: nil)
      end
    else
      # game over
      s.as_hash.clear # otherwise clear the hash (no new platform is necessary)
      init_game
    end
  end

  # Takes input from the user to move the player
  def input
    if inputs.keyboard.space # if the space bar is pressed
      s.player.jumped_at ||= s.tick_count # set to current frame

      # if the time that has passed since the jump is less than the duration of a jump (10 frames)
      # and the player is not falling
      if s.player.jumped_at.elapsed_time < s.player_jump_power_duration && !s.player.falling
        s.player.dy = s.player_jump_power # player jumps up
      end
    end

    if inputs.keyboard.key_up.space # if space bar is in "up" state
      s.player.falling = true # player is falling
    end

    if inputs.keyboard.left # if left key is pressed
      s.player.dx -= s.player_acceleration # player's position changes, decremented by acceleration
      s.player.dx = s.player.dx.greater(-s.player_max_run_speed) # dx is either current dx or -5, whichever is greater
    elsif inputs.keyboard.right # if right key is pressed
      s.player.dx += s.player_acceleration # player's position changes, incremented by acceleration
      s.player.dx  = s.player.dx.lesser(s.player_max_run_speed) # dx is either current dx or 5, whichever is lesser
    else
      s.player.dx *= s.player_speed_slowdown_rate # scales dx down
    end
  end
end

$game = VerticalPlatformer.new

def tick args
  $game.args = args
  $game.tick
end

Physics And Collisions - Bouncing On Collision - ball.rb

# ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/ball.rb
GRAVITY = -0.08

class Ball
    attr_accessor :velocity, :center, :radius, :collision_enabled

    def initialize args
        #Start the ball in the top center
        #@x = args.grid.w / 2
        #@y = args.grid.h - 20

        @velocity = {x: 0, y: 0}
        #@width =  20
        #@height = @width
        @radius = 20.0 / 2.0
        @center = {x: (args.grid.w / 2), y: (args.grid.h)}

        #@left_wall = (args.state.board_width + args.grid.w / 8)
        #@right_wall = @left_wall + args.state.board_width
        @left_wall = 0
        @right_wall = $args.grid.right

        @max_velocity = 7
        @collision_enabled = true
    end

    #Move the ball according to its velocity
    def update args
      @center.x += @velocity.x
      @center.y += @velocity.y
      @velocity.y += GRAVITY

      alpha = 0.2
      if @center.y-@radius <= 0
        @velocity.y  = (@velocity.y.abs*0.7).abs
        @velocity.x  = (@velocity.x.abs*0.9).abs * ((@velocity.x < 0) ? -1 : 1)

        if @velocity.y.abs() < alpha
          @velocity.y=0
        end
        if @velocity.x.abs() < alpha
          @velocity.x=0
        end
      end

      if @center.x > args.grid.right+@radius*2
        @center.x = 0-@radius
      elsif @center.x< 0-@radius*2
        @center.x = args.grid.right + @radius
      end
    end

    def wallBounds args
        #if @x < @left_wall || @x + @width > @right_wall
            #@velocity.x *= -1.1
            #if @velocity.x > @max_velocity
                #@velocity.x = @max_velocity
            #elsif @velocity.x < @max_velocity * -1
                #@velocity.x = @max_velocity * -1
            #end
        #end
        #if @y < 0 || @y + @height > args.grid.h
            #@velocity.y *= -1.1
            #if @velocity.y > @max_velocity
                #@velocity.y = @max_velocity
            #elsif @velocity.y < @max_velocity * -1
                #@velocity.y = @max_velocity * -1
            #end
        #end
    end

    #render the ball to the screen
    def draw args
        #args.outputs.solids << [@x, @y, @width, @height, 255, 255, 0];
        args.outputs.sprites << [
          @center.x-@radius,
          @center.y-@radius,
          @radius*2,
          @radius*2,
          "sprites/circle-white.png",
          0,
          255,
          255,    #r
          0,    #g
          255   #b
        ]
    end
  end

Physics And Collisions - Bouncing On Collision - block.rb

# ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/block.rb
DEGREES_TO_RADIANS = Math::PI / 180

class Block
  def initialize(x, y, block_size, rotation)
    @x = x
    @y = y
    @block_size = block_size
    @rotation = rotation

    #The repel velocity?
    @velocity = {x: 2, y: 0}

    horizontal_offset = (3 * block_size) * Math.cos(rotation * DEGREES_TO_RADIANS)
    vertical_offset = block_size * Math.sin(rotation * DEGREES_TO_RADIANS)

    if rotation >= 0
      theta = 90 - rotation
      #The line doesn't visually line up exactly with the edge of the sprite, so artificially move it a bit
      modifier = 5
      x_offset = modifier * Math.cos(theta * DEGREES_TO_RADIANS)
      y_offset = modifier * Math.sin(theta * DEGREES_TO_RADIANS)
      @x1 = @x - x_offset
      @y1 = @y + y_offset
      @x2 = @x1 + horizontal_offset
      @y2 = @y1 + (vertical_offset * 3)

      @imaginary_line = [ @x1, @y1, @x2, @y2 ]
    else
      theta = 90 + rotation
      x_offset = @block_size * Math.cos(theta * DEGREES_TO_RADIANS)
      y_offset = @block_size * Math.sin(theta * DEGREES_TO_RADIANS)
      @x1 = @x + x_offset
      @y1 = @y + y_offset + 19
      @x2 = @x1 + horizontal_offset
      @y2 = @y1 + (vertical_offset * 3)

      @imaginary_line = [ @x1, @y1, @x2, @y2 ]
    end

  end

  def draw args
    args.outputs.sprites << [
      @x,
      @y,
      @block_size*3,
      @block_size,
      "sprites/square-green.png",
      @rotation
    ]

    args.outputs.lines << @imaginary_line
    args.outputs.solids << @debug_shape
  end

  def multiply_matricies
  end

  def calc args
    if collision? args
        collide args
    end
  end

  #Determine if the ball and block are touching
  def collision? args
    #The minimum area enclosed by the center of the ball and the 2 corners of the block
    #If the area ever drops below this value, we know there is a collision
    min_area = ((@block_size * 3) * args.state.ball.radius) / 2

    #https://www.mathopenref.com/coordtrianglearea.html
    ax = @x1
    ay = @y1
    bx = @x2
    by = @y2
    cx = args.state.ball.center.x
    cy = args.state.ball.center.y

    current_area = (ax*(by-cy)+bx*(cy-ay)+cx*(ay-by))/2

    collision = false
    if @rotation >= 0
      if (current_area < min_area &&
        current_area > 0 &&
        args.state.ball.center.y > @y1 &&
        args.state.ball.center.x < @x2)

        collision = true
      end
    else
      if (current_area < min_area &&
        current_area > 0 &&
        args.state.ball.center.y > @y2 &&
        args.state.ball.center.x > @x1)

      collision = true
      end
    end

    return collision
  end

  def collide args
    #Slope of the block
    slope = (@y2 - @y1) / (@x2 - @x1)

    #Create a unit vector and tilt it (@rotation) number of degrees
    x = -Math.cos(@rotation * DEGREES_TO_RADIANS)
    y = Math.sin(@rotation * DEGREES_TO_RADIANS)

    #Find the vector that is perpendicular to the slope
    perpVect = { x: x, y: y }
    mag  = (perpVect.x**2 + perpVect.y**2)**0.5                                 # find the magniude of the perpVect
    perpVect = {x: perpVect.x/(mag), y: perpVect.y/(mag)}                       # divide the perpVect by the magniude to make it a unit vector

    previousPosition = {                                                        # calculate an ESTIMATE of the previousPosition of the ball
      x:args.state.ball.center.x-args.state.ball.velocity.x,
      y:args.state.ball.center.y-args.state.ball.velocity.y
    }

    velocityMag = (args.state.ball.velocity.x**2 + args.state.ball.velocity.y**2)**0.5 # the current velocity magnitude of the ball
    theta_ball = Math.atan2(args.state.ball.velocity.y, args.state.ball.velocity.x)         #the angle of the ball's velocity
    theta_repel = (180 * DEGREES_TO_RADIANS) - theta_ball + (@rotation * DEGREES_TO_RADIANS)

    fbx = velocityMag * Math.cos(theta_ball)                                    #the x component of the ball's velocity
    fby = velocityMag * Math.sin(theta_ball)                                    #the y component of the ball's velocity

    frx = velocityMag * Math.cos(theta_repel)                                       #the x component of the repel's velocity | magnitude is set to twice of fbx
    fry = velocityMag * Math.sin(theta_repel)                                       #the y component of the repel's velocity | magnitude is set to twice of fby

    args.state.display_value = velocityMag
    fsumx = fbx+frx                                                             #sum of x forces
    fsumy = fby+fry                                                             #sum of y forces
    fr = velocityMag                                                            #fr is the resulting magnitude
    thetaNew = Math.atan2(fsumy, fsumx)                                         #thetaNew is the resulting angle

    xnew = fr*Math.cos(thetaNew)                                                #resulting x velocity
    ynew = fr*Math.sin(thetaNew)                                                #resulting y velocity

    dampener = 0.3
    ynew *= dampener * 0.5

    #If the bounce is very low, that means the ball is rolling and we don't want to dampenen the X velocity
    if ynew > -0.1
      xnew *= dampener
    end

    #Add the sine component of gravity back in (X component)
    gravity_x = 4 * Math.sin(@rotation * DEGREES_TO_RADIANS)
    xnew += gravity_x

    args.state.ball.velocity.x = -xnew
    args.state.ball.velocity.y = -ynew

    #Set the position of the ball to the previous position so it doesn't warp throught the block
    args.state.ball.center.x = previousPosition.x
    args.state.ball.center.y = previousPosition.y
  end
end

Physics And Collisions - Bouncing On Collision - cannon.rb

# ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/cannon.rb
class Cannon
  def initialize args
    @pointA = {x: args.grid.right/2,y: args.grid.top}
    @pointB = {x: args.inputs.mouse.x, y: args.inputs.mouse.y}
  end
  def update args
    activeBall = args.state.ball
    @pointB = {x: args.inputs.mouse.x, y: args.inputs.mouse.y}

    if args.inputs.mouse.click
      alpha = 0.01
      activeBall.velocity.y = (@pointB.y - @pointA.y) * alpha
      activeBall.velocity.x = (@pointB.x - @pointA.x) * alpha
      activeBall.center = {x: (args.grid.w / 2), y: (args.grid.h)}
    end
  end
  def render args
    args.outputs.lines << [@pointA.x, @pointA.y, @pointB.x, @pointB.y]
  end
end

Physics And Collisions - Bouncing On Collision - main.rb

# ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/main.rb
INFINITY= 10**10

require 'app/vector2d.rb'
require 'app/peg.rb'
require 'app/block.rb'
require 'app/ball.rb'
require 'app/cannon.rb'


#Method to init default values
def defaults args
  args.state.pegs ||= []
  args.state.blocks ||= []
  args.state.cannon ||= Cannon.new args
  args.state.ball ||= Ball.new args
  args.state.horizontal_offset ||= 0
  init_pegs args
  init_blocks args

  args.state.display_value ||= "test"
end

begin :default_methods
  def init_pegs args
    num_horizontal_pegs = 14
    num_rows = 5

    return unless args.state.pegs.count < num_rows * num_horizontal_pegs

    block_size = 32
    block_spacing = 50
    total_width = num_horizontal_pegs * (block_size + block_spacing)
    starting_offset = (args.grid.w - total_width) / 2 + block_size

    for i in (0...num_rows)
      for j in (0...num_horizontal_pegs)
        row_offset = 0
        if i % 2 == 0
          row_offset = 20
        else
          row_offset = -20
        end
        args.state.pegs.append(Peg.new(j * (block_size+block_spacing) + starting_offset + row_offset, (args.grid.h - block_size * 2) - (i * block_size * 2)-90, block_size))
      end
    end

  end

  def init_blocks args
    return unless args.state.blocks.count < 10

    #Sprites are rotated in degrees, but the Ruby math functions work on radians
    radians_to_degrees = Math::PI / 180

    block_size = 25
    #Rotation angle (in degrees) of the blocks
    rotation = 30
    vertical_offset = block_size * Math.sin(rotation * radians_to_degrees)
    horizontal_offset = (3 * block_size) * Math.cos(rotation * radians_to_degrees)
    center = args.grid.w / 2

    for i in (0...5)
      #Create a ramp of blocks. Not going to be perfect because of the float to integer conversion and anisotropic to isotropic coversion
      args.state.blocks.append(Block.new((center + 100 + (i * horizontal_offset)).to_i, 100 + (vertical_offset * i) + (i * block_size), block_size, rotation))
      args.state.blocks.append(Block.new((center - 100 - (i * horizontal_offset)).to_i, 100 + (vertical_offset * i) + (i * block_size), block_size, -rotation))
    end
  end
end

#Render loop
def render args
  args.outputs.borders << args.state.game_area
  render_pegs args
  render_blocks args
  args.state.cannon.render args
  args.state.ball.draw args
end

begin :render_methods
  #Draw the pegs in a grid pattern
  def render_pegs args
    args.state.pegs.each do |peg|
      peg.draw args
    end
  end

  def render_blocks args
    args.state.blocks.each do |block|
      block.draw args
    end
  end

end

#Calls all methods necessary for performing calculations
def calc args
  args.state.pegs.each do |peg|
    peg.calc args
  end

  args.state.blocks.each do |block|
    block.calc args
  end

  args.state.ball.update args
  args.state.cannon.update args
end

begin :calc_methods

end

def tick args
  defaults args
  render args
  calc args
end

Physics And Collisions - Bouncing On Collision - peg.rb

# ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/peg.rb
class Peg
  def initialize(x, y, block_size)
    @x = x                    # x cordinate of the LEFT side of the peg
    @y = y                    # y cordinate of the RIGHT side of the peg
    @block_size = block_size  # diameter of the peg

    @radius = @block_size/2.0 # radius of the peg
    @center = {               # cordinatees of the CENTER of the peg
      x: @x+@block_size/2.0,
      y: @y+@block_size/2.0
    }

    @r = 255 # color of the peg
    @g = 0
    @b = 0

    @velocity = {x: 2, y: 0}
  end

  def draw args
    args.outputs.sprites << [ # draw the peg according to the @x, @y, @radius, and the RGB
      @x,
      @y,
      @radius*2.0,
      @radius*2.0,
      "sprites/circle-white.png",
      0,
      255,
      @r,    #r
      @g,    #g
      @b   #b
    ]
  end


  def calc args
    if collisionWithBounce? args # if the is a collision with the bouncing ball
      collide args
      @r = 0
      @b = 0
      @g = 255
    else
    end
  end


  # do two circles (the ball and this peg) intersect
  def collisionWithBounce? args
    squareDistance = (  # the squared distance between the ball's center and this peg's center
      (args.state.ball.center.x - @center.x) ** 2.0 +
      (args.state.ball.center.y - @center.y) ** 2.0
    )
    radiusSum = (  # the sum of the radius squared of the this peg and the ball
      (args.state.ball.radius + @radius) ** 2.0
    )
    # if the squareDistance is less or equal to radiusSum, then there is a radial intersection between the ball and this peg
    return (squareDistance <= radiusSum)
  end

  # ! The following links explain the getRepelMagnitude function !
  # https://raw.githubusercontent.com/DragonRuby/dragonruby-game-toolkit-physics/master/docs/docImages/LinearCollider_4.png
  # https://raw.githubusercontent.com/DragonRuby/dragonruby-game-toolkit-physics/master/docs/docImages/LinearCollider_5.png
  # https://github.com/DragonRuby/dragonruby-game-toolkit-physics/blob/master/docs/LinearCollider.md
  def getRepelMagnitude (args, fbx, fby, vrx, vry, ballMag)
    a = fbx ; b = vrx ; c = fby
    d = vry ; e = ballMag
    if b**2 + d**2 == 0
      #unexpected
    end

    x1 = (-a*b+-c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 + d**2 - a**2 * d**2)**0.5)/(b**2 + d**2)
    x2 = -((a*b + c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 * d**2 - a**2 * d**2)**0.5)/(b**2 + d**2))

    err = 0.00001
    o = ((fbx + x1*vrx)**2 + (fby + x1*vry)**2 ) ** 0.5
    p = ((fbx + x2*vrx)**2 + (fby + x2*vry)**2 ) ** 0.5
    r = 0

    if (ballMag >= o-err and ballMag <= o+err)
      r = x1
    elsif (ballMag >= p-err and ballMag <= p+err)
      r = x2
    else
      #unexpected
    end

    if (args.state.ball.center.x > @center.x)
      return x2*-1
    end

    return x2

    #return r
  end

  #this sets the new velocity of the ball once it has collided with this peg
  def collide args
    normalOfRCCollision = [                                                     #this is the normal of the collision in COMPONENT FORM
      {x: @center.x, y: @center.y},                                             #see https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.mathscard.co.uk%2Fonline%2Fcircle-coordinate-geometry%2F&psig=AOvVaw2GcD-e2-nJR_IUKpw3hO98&ust=1605731315521000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCMjBo7e1iu0CFQAAAAAdAAAAABAD
      {x: args.state.ball.center.x, y: args.state.ball.center.y},
    ]

    normalSlope = (                                                             #normalSlope is the slope of normalOfRCCollision
      (normalOfRCCollision[1].y - normalOfRCCollision[0].y) /
      (normalOfRCCollision[1].x - normalOfRCCollision[0].x)
    )
    slope = normalSlope**-1.0 * -1                                              # slope is the slope of the tangent
    # args.state.display_value = slope
    pointA = {                                                                  # pointA and pointB are using the var slope to tangent in COMPONENT FORM
      x: args.state.ball.center.x-1,
      y: -(slope-args.state.ball.center.y)
    }
    pointB = {
      x: args.state.ball.center.x+1,
      y: slope+args.state.ball.center.y
    }

    perpVect = {x: pointB.x - pointA.x, y:pointB.y - pointA.y}                  # perpVect is to be VECTOR of the perpendicular tangent
    mag  = (perpVect.x**2 + perpVect.y**2)**0.5                                 # find the magniude of the perpVect
    perpVect = {x: perpVect.x/(mag), y: perpVect.y/(mag)}                       # divide the perpVect by the magniude to make it a unit vector
    perpVect = {x: -perpVect.y, y: perpVect.x}                                  # swap the x and y and multiply by -1 to make the vector perpendicular
    args.state.display_value = perpVect
    if perpVect.y > 0                                                           #ensure perpVect points upward
      perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
    end

    previousPosition = {                                                        # calculate an ESTIMATE of the previousPosition of the ball
      x:args.state.ball.center.x-args.state.ball.velocity.x,
      y:args.state.ball.center.y-args.state.ball.velocity.y
    }

    yInterc = pointA.y + -slope*pointA.x
    if slope == INFINITY                                                        # the perpVect presently either points in the correct dirrection or it is 180 degrees off we need to correct this
      if previousPosition.x < pointA.x
        perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
        yInterc = -INFINITY
      end
    elsif previousPosition.y < slope*previousPosition.x + yInterc               # check if ball is bellow or above the collider to determine if perpVect is - or +
      perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
    end

    velocityMag =                                                               # the current velocity magnitude of the ball
      (args.state.ball.velocity.x**2 + args.state.ball.velocity.y**2)**0.5
    theta_ball=
      Math.atan2(args.state.ball.velocity.y,args.state.ball.velocity.x)         #the angle of the ball's velocity
    theta_repel=
      Math.atan2(args.state.ball.center.y,args.state.ball.center.x)             #the angle of the repelling force(perpVect)

    fbx = velocityMag * Math.cos(theta_ball)                                    #the x component of the ball's velocity
    fby = velocityMag * Math.sin(theta_ball)                                    #the y component of the ball's velocity
    repelMag = getRepelMagnitude(                                               # the magniude of the collision vector
      args,
      fbx,
      fby,
      perpVect.x,
      perpVect.y,
      (args.state.ball.velocity.x**2 + args.state.ball.velocity.y**2)**0.5
    )
    frx = repelMag* Math.cos(theta_repel)                                       #the x component of the repel's velocity | magnitude is set to twice of fbx
    fry = repelMag* Math.sin(theta_repel)                                       #the y component of the repel's velocity | magnitude is set to twice of fby

    fsumx = fbx+frx                            # sum of x forces
    fsumy = fby+fry                            # sum of y forces
    fr = velocityMag                           # fr is the resulting magnitude
    thetaNew = Math.atan2(fsumy, fsumx)        # thetaNew is the resulting angle
    xnew = fr*Math.cos(thetaNew)               # resulting x velocity
    ynew = fr*Math.sin(thetaNew)               # resulting y velocity
    if (args.state.ball.center.x >= @center.x) # this is necessary for the ball colliding on the right side of the peg
      xnew=xnew.abs
    end

    args.state.ball.velocity.x = xnew                                           # set the x-velocity to the new velocity
    if args.state.ball.center.y > @center.y                                     # if the ball is above the middle of the peg we need to temporarily ignore some of the gravity
      args.state.ball.velocity.y = ynew + GRAVITY * 0.01
    else
      args.state.ball.velocity.y = ynew - GRAVITY * 0.01                        # if the ball is bellow the middle of the peg we need to temporarily increase the power of the gravity
    end

    args.state.ball.center.x+= args.state.ball.velocity.x                       # update the position of the ball so it never looks like the ball is intersecting the circle
    args.state.ball.center.y+= args.state.ball.velocity.y
  end
end

Physics And Collisions - Bouncing On Collision - vector2d.rb

# ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/vector2d.rb
class Vector2d
    attr_accessor :x, :y

    def initialize x=0, y=0
      @x=x
      @y=y
    end

    #returns a vector multiplied by scalar x
    #x [float] scalar
    def mult x
      r = Vector2d.new(0,0)
      r.x=@x*x
      r.y=@y*x
      r
    end

    # vect [Vector2d] vector to copy
    def copy vect
      Vector2d.new(@x, @y)
    end

    #returns a new vector equivalent to this+vect
    #vect [Vector2d] vector to add to self
    def add vect
      Vector2d.new(@x+vect.x,@y+vect.y)
    end

    #returns a new vector equivalent to this-vect
    #vect [Vector2d] vector to subtract to self
    def sub vect
      Vector2d.new(@x-vect.c, @y-vect.y)
    end

    #return the magnitude of the vector
    def mag
      ((@x**2)+(@y**2))**0.5
    end

    #returns a new normalize version of the vector
    def normalize
      Vector2d.new(@x/mag, @y/mag)
    end

    #TODO delet?
    def distABS vect
      (((vect.x-@x)**2+(vect.y-@y)**2)**0.5).abs()
    end
  end

Physics And Collisions - Arbitrary Collision - ball.rb

# ./samples/04_physics_and_collisions/09_arbitrary_collision/app/ball.rb

class Ball
    attr_accessor :velocity, :child, :parent, :number, :leastChain
    attr_reader :x, :y, :hypotenuse, :width, :height

    def initialize args, number, leastChain, parent, child
        #Start the ball in the top center
        @number = number
        @leastChain = leastChain
        @x = args.grid.w / 2
        @y = args.grid.h - 20

        @velocity = Vector2d.new(2, -2)
        @width =  10
        @height = 10

        @left_wall = (args.state.board_width + args.grid.w / 8)
        @right_wall = @left_wall + args.state.board_width

        @max_velocity = MAX_VELOCITY

        @child = child
        @parent = parent

        @past = [{x: @x, y: @y}]
        @next = nil
    end

    def reassignLeastChain (lc=nil)
      if (lc == nil)
        lc = @number
      end
      @leastChain = lc
      if (parent != nil)
        @parent.reassignLeastChain(lc)
      end

    end

    def makeLeader args
      if isLeader
        return
      end
      @parent.reassignLeastChain
      args.state.ballParents.push(self)
      @parent = nil

    end

    def isLeader
      return (parent == nil)
    end

    def receiveNext (p)
      #trace!
      if parent != nil
        @x = p[:x]
        @y = p[:y]
        @velocity = p[:velocity]
        #puts @x.to_s + "|" + @y.to_s + "|"+@velocity.to_s
        @past.append(p)
        if (@past.length >= BALL_DISTANCE)
          if (@child != nil)
            @child.receiveNext(@past[0])
            @past.shift
          end
        end
      end
    end

    #Move the ball according to its velocity
    def update args

        if isLeader
          wallBounds args
          @x += @velocity.x
          @y += @velocity.y
          @past.append({x: @x, y: @y, velocity: @velocity})
          #puts @past

          if (@past.length >= BALL_DISTANCE)
            if (@child != nil)
              @child.receiveNext(@past[0])
              @past.shift
            end
          end

        else
          puts "unexpected"
          raise "unexpected"
        end
    end

    def wallBounds args
        b= false
        if @x < @left_wall
          @velocity.x = @velocity.x.abs() * 1
          b=true
        elsif @x + @width > @right_wall
          @velocity.x = @velocity.x.abs() * -1
          b=true
        end
        if @y < 0
          @velocity.y = @velocity.y.abs() * 1
          b=true
        elsif @y + @height > args.grid.h
          @velocity.y = @velocity.y.abs() * -1
          b=true
        end
        mag = (@velocity.x**2.0 + @velocity.y**2.0)**0.5
        if (b == true && mag < MAX_VELOCITY)
          @velocity.x*=1.1;
          @velocity.y*=1.1;
        end

    end

    #render the ball to the screen
    def draw args

        #update args
        #args.outputs.solids << [@x, @y, @width, @height, 255, 255, 0];
        #args.outputs.sprits << {
          #x: @x,
          #y: @y,
          #w: @width,
          #h: @height,
          #path: "sprites/ball10.png"
        #}
        #args.outputs.sprites <<[@x, @y, @width, @height, "sprites/ball10.png"]
        args.outputs.sprites << {x: @x, y: @y, w: @width, h: @height, path:"sprites/ball10.png" }
    end

    def getDraw args
      #wallBounds args
      #update args
      #args.outputs.labels << [@x, @y, @number.to_s + "|" + @leastChain.to_s]
      return [@x, @y, @width, @height, "sprites/ball10.png"]
    end

    def getPoints args
      points = [
        {x:@x+@width/2, y: @y},
        {x:@x+@width, y:@y+@height/2},
        {x:@x+@width/2,y:@y+@height},
        {x:@x,y:@y+@height/2}
      ]
      #psize = 5.0
      #for p in points
        #args.outputs.solids << [p.x-psize/2.0, p.y-psize/2.0, psize, psize, 0, 0, 0];
      #end
      return points
    end

    def serialize
      {x: @x, y:@y}
    end

    def inspect
      serialize.to_s
    end

    def to_s
      serialize.to_s
    end
  end

Physics And Collisions - Arbitrary Collision - blocks.rb

# ./samples/04_physics_and_collisions/09_arbitrary_collision/app/blocks.rb
MAX_COUNT=100

def universalUpdateOne args, shape
  didHit = false
  hitters = []
  #puts shape.to_s
  toCollide = nil
  for b in args.state.balls
    if [b.x, b.y, b.width, b.height].intersect_rect?(shape.bold)
      didSquare = false
      for s in shape.squareColliders
        if (s.collision?(args, b))
          didSquare = true
          didHit = true
          #s.collide(args, b)
          toCollide = s
          #hitter = b
          hitters.append(b)
        end #end if
      end #end for
      if (didSquare == false)
        for c in shape.colliders
          #puts args.state.ball.velocity
          if c.collision?(args, b.getPoints(args),b)
            #c.collide args, b
            toCollide = c
            didHit = true
            hitters.append(b)
          end #end if
        end #end for
      end #end if
    end#end if
  end#end for
  if (didHit)
    shape.count=0
    hitters = hitters.uniq
    for hitter in hitters
      hitter.makeLeader args
      #toCollide.collide(args, hitter)
      if shape.home == "squares"
        args.state.squares.delete(shape)
      elsif shape.home == "tshapes"
        args.state.tshapes.delete(shape)
      else shape.home == "lines"
        args.state.lines.delete(shape)
      end
    end

    #puts "HIT!" + hitter.number
  end
end

def universalUpdate args, shape
  #puts shape.home
  if (shape.count <= 1)
    universalUpdateOne args, shape
    return
  end

  didHit = false
  hitter = nil
  for b in args.state.ballParents
    if [b.x, b.y, b.width, b.height].intersect_rect?(shape.bold)
      didSquare = false
      for s in shape.squareColliders
        if (s.collision?(args, b))
          didSquare = true
          didHit = true
          s.collide(args, b)
          hitter = b
        end
      end
      if (didSquare == false)
        for c in shape.colliders
          #puts args.state.ball.velocity
          if c.collision?(args, b.getPoints(args),b)
            c.collide args, b
            didHit = true
            hitter = b
          end
        end
      end
    end
  end
  if (didHit)
    shape.count=shape.count-1
    shape.damageCount.append([(hitter.leastChain+1 - hitter.number)-1, args.state.tick_count])

  end
  i=0
  while i < shape.damageCount.length
    if shape.damageCount[i][0] <= 0
      shape.damageCount.delete_at(i)
      i-=1
    elsif shape.damageCount[i][1].elapsed_time > BALL_DISTANCE and shape.damageCount[i][0] > 1
      shape.count-=1
      shape.damageCount[i][0]-=1
      shape.damageCount[i][1] = args.state.tick_count
    end
    i+=1
  end
end


class Square
   attr_accessor :count, :x, :y, :home, :bold, :squareColliders, :colliders, :damageCount
   def initialize(args, x, y, block_size, orientation, block_offset)
        @x = x * block_size
        @y = y * block_size
        @block_size = block_size
        @block_offset = block_offset
        @orientation = orientation
        @damageCount = []
        @home = 'squares'


        Kernel.srand()
        @r = rand(255)
        @g = rand(255)
        @b = rand(255)

        @count = rand(MAX_COUNT)+1

        x_offset = (args.state.board_width + args.grid.w / 8) + @block_offset / 2
        @x_adjusted = @x + x_offset
        @y_adjusted = @y
        @size_adjusted = @block_size * 2 - @block_offset

        hypotenuse=args.state.ball_hypotenuse
        @bold = [(@x_adjusted-hypotenuse/2)-1, (@y_adjusted-hypotenuse/2)-1, @size_adjusted + hypotenuse + 2, @size_adjusted + hypotenuse + 2]

        @points = [
          {x:@x_adjusted, y:@y_adjusted},
          {x:@x_adjusted+@size_adjusted, y:@y_adjusted},
          {x:@x_adjusted+@size_adjusted, y:@y_adjusted+@size_adjusted},
          {x:@x_adjusted, y:@y_adjusted+@size_adjusted}
        ]
        @squareColliders = [
          SquareCollider.new(@points[0].x,@points[0].y,{x:-1,y:-1}),
          SquareCollider.new(@points[1].x-COLLISIONWIDTH,@points[1].y,{x:1,y:-1}),
          SquareCollider.new(@points[2].x-COLLISIONWIDTH,@points[2].y-COLLISIONWIDTH,{x:1,y:1}),
          SquareCollider.new(@points[3].x,@points[3].y-COLLISIONWIDTH,{x:-1,y:1}),
        ]
        @colliders = [
          LinearCollider.new(@points[0],@points[1], :neg),
          LinearCollider.new(@points[1],@points[2], :neg),
          LinearCollider.new(@points[2],@points[3], :pos),
          LinearCollider.new(@points[0],@points[3], :pos)
        ]
   end

   def draw(args)
    #Offset the coordinates to the edge of the game area
    x_offset = (args.state.board_width + args.grid.w / 8) + @block_offset / 2
    #args.outputs.solids << [@x + x_offset, @y, @block_size * 2 - @block_offset, @block_size * 2 - @block_offset, @r, @g, @b]
    args.outputs.solids <<{x: (@x + x_offset), y: (@y), w: (@block_size * 2 - @block_offset), h: (@block_size * 2 - @block_offset), r: @r , g: @g , b: @b }
    #args.outputs.solids << @bold.append([255,0,0])
    args.outputs.labels << [@x + x_offset + (@block_size * 2 - @block_offset)/2, (@y) + (@block_size * 2 - @block_offset)/2, @count.to_s]

   end

   def update args
     universalUpdate args, self
   end
end

class TShape
    attr_accessor :count, :x, :y, :home, :bold, :squareColliders, :colliders, :damageCount
    def initialize(args, x, y, block_size, orientation, block_offset)
        @x = x * block_size
        @y = y * block_size
        @block_size = block_size
        @block_offset = block_offset
        @orientation = orientation
        @damageCount = []
        @home = "tshapes"

        Kernel.srand()
        @r = rand(255)
        @g = rand(255)
        @b = rand(255)

        @count = rand(MAX_COUNT)+1


        @shapePoints = getShapePoints(args)
        minX={x:INFINITY, y:0}
        minY={x:0, y:INFINITY}
        maxX={x:-INFINITY, y:0}
        maxY={x:0, y:-INFINITY}
        for p in @shapePoints
          if p.x < minX.x
            minX = p
          end
          if p.x > maxX.x
            maxX = p
          end
          if p.y < minY.y
            minY = p
          end
          if p.y > maxY.y
            maxY = p
          end
        end


        hypotenuse=args.state.ball_hypotenuse

        @bold = [(minX.x-hypotenuse/2)-1, (minY.y-hypotenuse/2)-1, -((minX.x-hypotenuse/2)-1)+(maxX.x + hypotenuse + 2), -((minY.y-hypotenuse/2)-1)+(maxY.y + hypotenuse + 2)]
    end
    def getShapePoints(args)
      points=[]
      x_offset = (args.state.board_width + args.grid.w / 8) + (@block_offset / 2)

      if @orientation == :right
          #args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
          #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 2, @block_size, @r, @g, @b]
          points = [
            {x:@x + x_offset, y:@y},
            {x:(@x + x_offset)+(@block_size - @block_offset), y:@y},
            {x:(@x + x_offset)+(@block_size - @block_offset),y:@y + @block_size},
            {x:(@x + x_offset)+ @block_size * 2,y:@y + @block_size},
            {x:(@x + x_offset)+ @block_size * 2,y:@y + @block_size+@block_size},
            {x:(@x + x_offset)+(@block_size - @block_offset),y:@y + @block_size+@block_size},
            {x:(@x + x_offset)+(@block_size - @block_offset), y:@y+ @block_size * 3 - @block_offset},
            {x:@x + x_offset , y:@y+ @block_size * 3 - @block_offset}
          ]
          @squareColliders = [
            SquareCollider.new(points[0].x,points[0].y,{x:-1,y:-1}),
            SquareCollider.new(points[1].x-COLLISIONWIDTH,points[1].y,{x:1,y:-1}),
            SquareCollider.new(points[2].x,points[2].y-COLLISIONWIDTH,{x:1,y:-1}),
            SquareCollider.new(points[3].x-COLLISIONWIDTH,points[3].y,{x:1,y:-1}),
            SquareCollider.new(points[4].x-COLLISIONWIDTH,points[4].y-COLLISIONWIDTH,{x:1,y:1}),
            SquareCollider.new(points[5].x,points[5].y,{x:1,y:1}),
            SquareCollider.new(points[6].x-COLLISIONWIDTH,points[6].y-COLLISIONWIDTH,{x:1,y:1}),
            SquareCollider.new(points[7].x,points[7].y-COLLISIONWIDTH,{x:-1,y:1}),
          ]
          @colliders = [
            LinearCollider.new(points[0],points[1], :neg),
            LinearCollider.new(points[1],points[2], :neg),
            LinearCollider.new(points[2],points[3], :neg),
            LinearCollider.new(points[3],points[4], :neg),
            LinearCollider.new(points[4],points[5], :pos),
            LinearCollider.new(points[5],points[6], :neg),
            LinearCollider.new(points[6],points[7], :pos),
            LinearCollider.new(points[0],points[7], :pos)
          ]
      elsif @orientation == :up
          #args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
          #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size, @block_size * 2, @r, @g, @b]
          points = [
            {x:@x + x_offset, y:@y},
            {x:(@x + x_offset)+(@block_size * 3 - @block_offset), y:@y},
            {x:(@x + x_offset)+(@block_size * 3 - @block_offset), y:@y+(@block_size - @block_offset)},
            {x:@x + x_offset + @block_size + @block_size, y:@y+(@block_size - @block_offset)},
            {x:@x + x_offset + @block_size + @block_size, y:@y+@block_size*2},
            {x:@x + x_offset + @block_size, y:@y+@block_size*2},
            {x:@x + x_offset + @block_size, y:@y+(@block_size - @block_offset)},
            {x:@x + x_offset, y:@y+(@block_size - @block_offset)}
          ]
          @squareColliders = [
            SquareCollider.new(points[0].x,points[0].y,{x:-1,y:-1}),
            SquareCollider.new(points[1].x-COLLISIONWIDTH,points[1].y,{x:1,y:-1}),
            SquareCollider.new(points[2].x-COLLISIONWIDTH,points[2].y-COLLISIONWIDTH,{x:1,y:1}),
            SquareCollider.new(points[3].x,points[3].y,{x:1,y:1}),
            SquareCollider.new(points[4].x-COLLISIONWIDTH,points[4].y-COLLISIONWIDTH,{x:1,y:1}),
            SquareCollider.new(points[5].x,points[5].y-COLLISIONWIDTH,{x:-1,y:1}),
            SquareCollider.new(points[6].x-COLLISIONWIDTH,points[6].y,{x:-1,y:1}),
            SquareCollider.new(points[7].x,points[7].y-COLLISIONWIDTH,{x:-1,y:1}),
          ]
          @colliders = [
            LinearCollider.new(points[0],points[1], :neg),
            LinearCollider.new(points[1],points[2], :neg),
            LinearCollider.new(points[2],points[3], :pos),
            LinearCollider.new(points[3],points[4], :neg),
            LinearCollider.new(points[4],points[5], :pos),
            LinearCollider.new(points[5],points[6], :neg),
            LinearCollider.new(points[6],points[7], :pos),
            LinearCollider.new(points[0],points[7], :pos)
          ]
      elsif @orientation == :left
          #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
          #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 2 - @block_offset, @block_size - @block_offset, @r, @g, @b]
          xh = @x + x_offset
          #points = [
            #{x:@x + x_offset, y:@y},
            #{x:(@x + x_offset)+(@block_size - @block_offset), y:@y},
            #{x:(@x + x_offset)+(@block_size - @block_offset),y:@y + @block_size},
            #{x:(@x + x_offset)+ @block_size * 2,y:@y + @block_size},
            #{x:(@x + x_offset)+ @block_size * 2,y:@y + @block_size+@block_size},
            #{x:(@x + x_offset)+(@block_size - @block_offset),y:@y + @block_size+@block_size},
            #{x:(@x + x_offset)+(@block_size - @block_offset), y:@y+ @block_size * 3 - @block_offset},
            #{x:@x + x_offset , y:@y+ @block_size * 3 - @block_offset}
          #]
          points = [
            {x:@x + x_offset + @block_size, y:@y},
            {x:@x + x_offset + @block_size + (@block_size - @block_offset), y:@y},
            {x:@x + x_offset + @block_size + (@block_size - @block_offset),y:@y+@block_size*3- @block_offset},
            {x:@x + x_offset + @block_size, y:@y+@block_size*3- @block_offset},
            {x:@x + x_offset+@block_size, y:@y+@block_size*2- @block_offset},
            {x:@x + x_offset, y:@y+@block_size*2- @block_offset},
            {x:@x + x_offset, y:@y+@block_size},
            {x:@x + x_offset+@block_size, y:@y+@block_size}
          ]
          @squareColliders = [
            SquareCollider.new(points[0].x,points[0].y,{x:-1,y:-1}),
            SquareCollider.new(points[1].x-COLLISIONWIDTH,points[1].y,{x:1,y:-1}),
            SquareCollider.new(points[2].x-COLLISIONWIDTH,points[2].y-COLLISIONWIDTH,{x:1,y:1}),
            SquareCollider.new(points[3].x,points[3].y-COLLISIONWIDTH,{x:-1,y:1}),
            SquareCollider.new(points[4].x-COLLISIONWIDTH,points[4].y,{x:-1,y:1}),
            SquareCollider.new(points[5].x,points[5].y-COLLISIONWIDTH,{x:-1,y:1}),
            SquareCollider.new(points[6].x,points[6].y,{x:-1,y:-1}),
            SquareCollider.new(points[7].x-COLLISIONWIDTH,points[7].y-COLLISIONWIDTH,{x:-1,y:-1}),
          ]
          @colliders = [
            LinearCollider.new(points[0],points[1], :neg),
            LinearCollider.new(points[1],points[2], :neg),
            LinearCollider.new(points[2],points[3], :pos),
            LinearCollider.new(points[3],points[4], :neg),
            LinearCollider.new(points[4],points[5], :pos),
            LinearCollider.new(points[5],points[6], :neg),
            LinearCollider.new(points[6],points[7], :neg),
            LinearCollider.new(points[0],points[7], :pos)
          ]
      elsif @orientation == :down
          #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
          #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size - @block_offset, @block_size * 2 - @block_offset, @r, @g, @b]

          points = [
            {x:@x + x_offset, y:@y+(@block_size*2)-@block_offset},
            {x:@x + x_offset+ @block_size*3-@block_offset, y:@y+(@block_size*2)-@block_offset},
            {x:@x + x_offset+ @block_size*3-@block_offset, y:@y+(@block_size)},
            {x:@x + x_offset+ @block_size*2-@block_offset, y:@y+(@block_size)},
            {x:@x + x_offset+ @block_size*2-@block_offset, y:@y},#
            {x:@x + x_offset+ @block_size, y:@y},#
            {x:@x + x_offset + @block_size, y:@y+(@block_size)},
            {x:@x + x_offset, y:@y+(@block_size)}
          ]
          @squareColliders = [
            SquareCollider.new(points[0].x,points[0].y-COLLISIONWIDTH,{x:-1,y:1}),
            SquareCollider.new(points[1].x-COLLISIONWIDTH,points[1].y-COLLISIONWIDTH,{x:1,y:1}),
            SquareCollider.new(points[2].x-COLLISIONWIDTH,points[2].y,{x:1,y:-1}),
            SquareCollider.new(points[3].x,points[3].y-COLLISIONWIDTH,{x:1,y:-1}),
            SquareCollider.new(points[4].x-COLLISIONWIDTH,points[4].y,{x:1,y:-1}),
            SquareCollider.new(points[5].x,points[5].y,{x:-1,y:-1}),
            SquareCollider.new(points[6].x-COLLISIONWIDTH,points[6].y-COLLISIONWIDTH,{x:-1,y:-1}),
            SquareCollider.new(points[7].x,points[7].y,{x:-1,y:-1}),
          ]
          @colliders = [
            LinearCollider.new(points[0],points[1], :pos),
            LinearCollider.new(points[1],points[2], :pos),
            LinearCollider.new(points[2],points[3], :neg),
            LinearCollider.new(points[3],points[4], :pos),
            LinearCollider.new(points[4],points[5], :neg),
            LinearCollider.new(points[5],points[6], :pos),
            LinearCollider.new(points[6],points[7], :neg),
            LinearCollider.new(points[0],points[7], :neg)
          ]
      end
      return points
    end

    def draw(args)
        #Offset the coordinates to the edge of the game area
        x_offset = (args.state.board_width + args.grid.w / 8) + (@block_offset / 2)

        if @orientation == :right
            #args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
            args.outputs.solids << {x: (@x + x_offset), y: @y, w: @block_size - @block_offset, h: (@block_size * 3 - @block_offset), r: @r , g: @g, b: @b}
            #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 2, @block_size, @r, @g, @b]
            args.outputs.solids << {x: (@x + x_offset), y: (@y + @block_size), w: (@block_size * 2), h: (@block_size), r: @r , g: @g, b: @b }
        elsif @orientation == :up
            #args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
            args.outputs.solids << {x: (@x + x_offset), y: (@y), w: (@block_size * 3 - @block_offset), h: (@block_size - @block_offset), r: @r , g: @g, b: @b}
            #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size, @block_size * 2, @r, @g, @b]
            args.outputs.solids << {x: (@x + x_offset + @block_size), y: (@y), w: (@block_size), h: (@block_size * 2), r: @r , g: @g, b: @b}
        elsif @orientation == :left
            #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
            args.outputs.solids << {x: (@x + x_offset + @block_size), y: (@y), w: (@block_size - @block_offset), h: (@block_size * 3 - @block_offset), r: @r , g: @g, b: @b}
            #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 2 - @block_offset, @block_size - @block_offset, @r, @g, @b]
            args.outputs.solids << {x: (@x + x_offset), y: (@y + @block_size), w: (@block_size * 2 - @block_offset), h: (@block_size - @block_offset), r: @r , g: @g, b: @b}
        elsif @orientation == :down
            #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
            args.outputs.solids << {x: (@x + x_offset), y: (@y + @block_size), w: (@block_size * 3 - @block_offset), h: (@block_size - @block_offset), r: @r , g: @g, b: @b}
            #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size - @block_offset, @block_size * 2 - @block_offset, @r, @g, @b]
            args.outputs.solids << {x: (@x + x_offset + @block_size), y: (@y), w: (@block_size - @block_offset), h: ( @block_size * 2 - @block_offset), r: @r , g: @g, b: @b}
        end

        #psize = 5.0
        #for p in @shapePoints
          #args.outputs.solids << [p.x-psize/2, p.y-psize/2, psize, psize, 0, 0, 0]
        #end
        args.outputs.labels << [@x + x_offset + (@block_size * 2 - @block_offset)/2, (@y) + (@block_size * 2 - @block_offset)/2, @count.to_s]

    end

    def updateOne_old args
      didHit = false
      hitter = nil
      toCollide = nil
      for b in args.state.balls
        if [b.x, b.y, b.width, b.height].intersect_rect?(@bold)
          didSquare = false
          for s in @squareColliders
            if (s.collision?(args, b))
              didSquare = true
              didHit = true
              #s.collide(args, b)
              toCollide = s
              hitter = b
              break
            end
          end
          if (didSquare == false)
            for c in @colliders
              #puts args.state.ball.velocity
              if c.collision?(args, b.getPoints(args),b)
                #c.collide args, b
                toCollide = c
                didHit = true
                hitter = b
                break
              end
            end
          end
        end
        if didHit
          break
        end
      end
      if (didHit)
        @count=0
        hitter.makeLeader args
        #toCollide.collide(args, hitter)
        args.state.tshapes.delete(self)
        #puts "HIT!" + hitter.number
      end
    end

    def update_old args
      if (@count == 1)
        updateOne args
        return
      end
      didHit = false
      hitter = nil
      for b in args.state.ballParents
        if [b.x, b.y, b.width, b.height].intersect_rect?(@bold)
          didSquare = false
          for s in @squareColliders
            if (s.collision?(args, b))
              didSquare = true
              didHit=true
              s.collide(args, b)
              hitter = b
            end
          end
          if (didSquare == false)
            for c in @colliders
              #puts args.state.ball.velocity
              if c.collision?(args, b.getPoints(args), b)
                c.collide args, b
                didHit=true
                hitter = b
              end
            end
          end
        end
      end
      if (didHit)
        @count=@count-1
        @damageCount.append([(hitter.leastChain+1 - hitter.number)-1, args.state.tick_count])

        if (@count == 0)
          args.state.tshapes.delete(self)
          return
        end
      end
      i=0

      while i < @damageCount.length
        if @damageCount[i][0] <= 0
          @damageCount.delete_at(i)
          i-=1
        elsif @damageCount[i][1].elapsed_time > BALL_DISTANCE
          @count-=1
          @damageCount[i][0]-=1
        end
        if (@count == 0)
          args.state.tshapes.delete(self)
          return
        end
        i+=1
      end
    end #end update

    def update args
      universalUpdate args, self
    end

end

class Line
    attr_accessor :count, :x, :y, :home, :bold, :squareColliders, :colliders, :damageCount
    def initialize(args, x, y, block_size, orientation, block_offset)
        @x = x * block_size
        @y = y * block_size
        @block_size = block_size
        @block_offset = block_offset
        @orientation = orientation
        @damageCount = []
        @home = "lines"

        Kernel.srand()
        @r = rand(255)
        @g = rand(255)
        @b = rand(255)

        @count = rand(MAX_COUNT)+1

        @shapePoints = getShapePoints(args)
        minX={x:INFINITY, y:0}
        minY={x:0, y:INFINITY}
        maxX={x:-INFINITY, y:0}
        maxY={x:0, y:-INFINITY}
        for p in @shapePoints
          if p.x < minX.x
            minX = p
          end
          if p.x > maxX.x
            maxX = p
          end
          if p.y < minY.y
            minY = p
          end
          if p.y > maxY.y
            maxY = p
          end
        end


        hypotenuse=args.state.ball_hypotenuse

        @bold = [(minX.x-hypotenuse/2)-1, (minY.y-hypotenuse/2)-1, -((minX.x-hypotenuse/2)-1)+(maxX.x + hypotenuse + 2), -((minY.y-hypotenuse/2)-1)+(maxY.y + hypotenuse + 2)]
    end

    def getShapePoints(args)
      points=[]
      x_offset = (args.state.board_width + args.grid.w / 8) + (@block_offset / 2)

      if @orientation == :right
        #args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
        xa =@x + x_offset
        ya =@y
        wa =@block_size * 3 - @block_offset
        ha =(@block_size - @block_offset)
      elsif @orientation == :up
        #args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
        xa =@x + x_offset
        ya =@y
        wa =@block_size - @block_offset
        ha =@block_size * 3 - @block_offset

      elsif @orientation == :left
        #args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
        xa =@x + x_offset
        ya =@y
        wa =@block_size * 3 - @block_offset
        ha =@block_size - @block_offset
      elsif @orientation == :down
        #args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
        xa =@x + x_offset
        ya =@y
        wa =@block_size - @block_offset
        ha =@block_size * 3 - @block_offset
      end
      points = [
        {x: xa, y:ya},
        {x: xa + wa,y:ya},
        {x: xa + wa,y:ya+ha},
        {x: xa, y:ya+ha},
      ]
      @squareColliders = [
        SquareCollider.new(points[0].x,points[0].y,{x:-1,y:-1}),
        SquareCollider.new(points[1].x-COLLISIONWIDTH,points[1].y,{x:1,y:-1}),
        SquareCollider.new(points[2].x-COLLISIONWIDTH,points[2].y-COLLISIONWIDTH,{x:1,y:1}),
        SquareCollider.new(points[3].x,points[3].y-COLLISIONWIDTH,{x:-1,y:1}),
      ]
      @colliders = [
        LinearCollider.new(points[0],points[1], :neg),
        LinearCollider.new(points[1],points[2], :neg),
        LinearCollider.new(points[2],points[3], :pos),
        LinearCollider.new(points[0],points[3], :pos),
      ]
      return points
    end

    def update args
      universalUpdate args, self
    end

    def draw(args)
        x_offset = (args.state.board_width + args.grid.w / 8) + @block_offset / 2

        if @orientation == :right
            args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
        elsif @orientation == :up
            args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
        elsif @orientation == :left
            args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
        elsif @orientation == :down
            args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
        end

        args.outputs.labels << [@x + x_offset + (@block_size * 2 - @block_offset)/2, (@y) + (@block_size * 2 - @block_offset)/2, @count.to_s]

    end
end

Physics And Collisions - Arbitrary Collision - linear_collider.rb

# ./samples/04_physics_and_collisions/09_arbitrary_collision/app/linear_collider.rb

COLLISIONWIDTH=8

class LinearCollider
  attr_reader :pointA, :pointB
  def initialize (pointA, pointB, mode,collisionWidth=COLLISIONWIDTH)
    @pointA = pointA
    @pointB = pointB
    @mode = mode
    @collisionWidth = collisionWidth

    if (@pointA.x > @pointB.x)
      @pointA, @pointB = @pointB, @pointA
    end

    @linearCollider_collision_once = false
  end

  def collisionSlope args
    if (@pointB.x-@pointA.x == 0)
      return INFINITY
    end
    return (@pointB.y - @pointA.y) / (@pointB.x - @pointA.x)
  end


  def collision? (args, points, ball=nil)

    slope = collisionSlope args
    result = false

    # calculate a vector with a magnitude of (1/2)collisionWidth and a direction perpendicular to the collision line
    vect=nil;mag=nil;vect=nil;
    if @mode == :both
      vect = {x: @pointB.x - @pointA.x, y:@pointB.y - @pointA.y}
      mag  = (vect.x**2 + vect.y**2)**0.5
      vect = {y: -1*(vect.x/(mag))*@collisionWidth*0.5, x: (vect.y/(mag))*@collisionWidth*0.5}
    else
      vect = {x: @pointB.x - @pointA.x, y:@pointB.y - @pointA.y}
      mag  = (vect.x**2 + vect.y**2)**0.5
      vect = {y: -1*(vect.x/(mag))*@collisionWidth, x: (vect.y/(mag))*@collisionWidth}
    end

    rpointA=nil;rpointB=nil;rpointC=nil;rpointD=nil;
    if @mode == :pos
      rpointA = {x:@pointA.x + vect.x, y:@pointA.y + vect.y}
      rpointB = {x:@pointB.x + vect.x, y:@pointB.y + vect.y}
      rpointC = {x:@pointB.x, y:@pointB.y}
      rpointD = {x:@pointA.x, y:@pointA.y}
    elsif @mode == :neg
      rpointA = {x:@pointA.x, y:@pointA.y}
      rpointB = {x:@pointB.x, y:@pointB.y}
      rpointC = {x:@pointB.x - vect.x, y:@pointB.y - vect.y}
      rpointD = {x:@pointA.x - vect.x, y:@pointA.y - vect.y}
    elsif @mode == :both
      rpointA = {x:@pointA.x + vect.x, y:@pointA.y + vect.y}
      rpointB = {x:@pointB.x + vect.x, y:@pointB.y + vect.y}
      rpointC = {x:@pointB.x - vect.x, y:@pointB.y - vect.y}
      rpointD = {x:@pointA.x - vect.x, y:@pointA.y - vect.y}
    end
    #four point rectangle



    if ball != nil
      xs = [rpointA.x,rpointB.x,rpointC.x,rpointD.x]
      ys = [rpointA.y,rpointB.y,rpointC.y,rpointD.y]
      correct = 1
      rect1 = [ball.x, ball.y, ball.width, ball.height]
      #$r1 = rect1
      rect2 = [xs.min-correct,ys.min-correct,(xs.max-xs.min)+correct*2,(ys.max-ys.min)+correct*2]
      #$r2 = rect2
      if rect1.intersect_rect?(rect2) == false
        return false
      end
    end


    #area of a triangle
    triArea = -> (a,b,c) { ((a.x * (b.y - c.y) + b.x * (c.y - a.y) + c.x * (a.y - b.y))/2.0).abs }

    #if at least on point is in the rectangle then collision? is true - otherwise false
    for point in points
      #Check whether a given point lies inside a rectangle or not:
      #if the sum of the area of traingls, PAB, PBC, PCD, PAD equal the area of the rec, then an intersection has occured
      areaRec =  triArea.call(rpointA, rpointB, rpointC)+triArea.call(rpointA, rpointC, rpointD)
      areaSum = [
        triArea.call(point, rpointA, rpointB),triArea.call(point, rpointB, rpointC),
        triArea.call(point, rpointC, rpointD),triArea.call(point, rpointA, rpointD)
      ].inject(0){|sum,x| sum + x }
      e = 0.0001 #allow for minor error
      if areaRec>= areaSum-e and areaRec<= areaSum+e
        result = true
        #return true
        break
      end
    end

    #args.outputs.lines << [@pointA.x, @pointA.y, @pointB.x, @pointB.y,     000, 000, 000]
    #args.outputs.lines << [rpointA.x, rpointA.y, rpointB.x, rpointB.y,     255, 000, 000]
    #args.outputs.lines << [rpointC.x, rpointC.y, rpointD.x, rpointD.y,     000, 000, 255]


    #puts (rpointA.x.to_s + " " +  rpointA.y.to_s + " " + rpointB.x.to_s + " "+ rpointB.y.to_s)
    return result
  end #end collision?

  def getRepelMagnitude (fbx, fby, vrx, vry, ballMag)
    a = fbx ; b = vrx ; c = fby
    d = vry ; e = ballMag
    if b**2 + d**2 == 0
      #unexpected
    end
    x1 = (-a*b+-c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 + d**2 - a**2 * d**2)**0.5)/(b**2 + d**2)
    x2 = -((a*b + c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 * d**2 - a**2 * d**2)**0.5)/(b**2 + d**2))
    err = 0.00001
    o = ((fbx + x1*vrx)**2 + (fby + x1*vry)**2 ) ** 0.5
    p = ((fbx + x2*vrx)**2 + (fby + x2*vry)**2 ) ** 0.5
    r = 0
    if (ballMag >= o-err and ballMag <= o+err)
      r = x1
    elsif (ballMag >= p-err and ballMag <= p+err)
      r = x2
    else
      #unexpected
    end
    return r
  end

  def collide args, ball
    slope = collisionSlope args

    # perpVect: normal vector perpendicular to collision
    perpVect = {x: @pointB.x - @pointA.x, y:@pointB.y - @pointA.y}
    mag  = (perpVect.x**2 + perpVect.y**2)**0.5
    perpVect = {x: perpVect.x/(mag), y: perpVect.y/(mag)}
    perpVect = {x: -perpVect.y, y: perpVect.x}
    if perpVect.y > 0 #ensure perpVect points upward
      perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
    end
    previousPosition = {
      x:ball.x-ball.velocity.x,
      y:ball.y-ball.velocity.y
    }
    yInterc = @pointA.y + -slope*@pointA.x
    if slope == INFINITY
      if previousPosition.x < @pointA.x
        perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
        yInterc = -INFINITY
      end
    elsif previousPosition.y < slope*previousPosition.x + yInterc #check if ball is bellow or above the collider to determine if perpVect is - or +
      perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
    end

    velocityMag = (ball.velocity.x**2 + ball.velocity.y**2)**0.5
    theta_ball=Math.atan2(ball.velocity.y,ball.velocity.x) #the angle of the ball's velocity
    theta_repel=Math.atan2(perpVect.y,perpVect.x) #the angle of the repelling force(perpVect)

    fbx = velocityMag * Math.cos(theta_ball) #the x component of the ball's velocity
    fby = velocityMag * Math.sin(theta_ball) #the y component of the ball's velocity

    #the magnitude of the repelling force
    repelMag = getRepelMagnitude(fbx, fby, perpVect.x, perpVect.y, (ball.velocity.x**2 + ball.velocity.y**2)**0.5)
    frx = repelMag* Math.cos(theta_repel) #the x component of the repel's velocity | magnitude is set to twice of fbx
    fry = repelMag* Math.sin(theta_repel) #the y component of the repel's velocity | magnitude is set to twice of fby

    fsumx = fbx+frx #sum of x forces
    fsumy = fby+fry #sum of y forces
    fr = velocityMag#fr is the resulting magnitude
    thetaNew = Math.atan2(fsumy, fsumx)  #thetaNew is the resulting angle
    xnew = fr*Math.cos(thetaNew)#resulting x velocity
    ynew = fr*Math.sin(thetaNew)#resulting y velocity
    if (velocityMag < MAX_VELOCITY)
      ball.velocity =  Vector2d.new(xnew*1.1, ynew*1.1)
    else
      ball.velocity =  Vector2d.new(xnew, ynew)
    end

  end
end

Physics And Collisions - Arbitrary Collision - main.rb

# ./samples/04_physics_and_collisions/09_arbitrary_collision/app/main.rb
INFINITY= 10**10
MAX_VELOCITY = 8.0
BALL_COUNT = 90
BALL_DISTANCE = 20
require 'app/vector2d.rb'
require 'app/blocks.rb'
require 'app/ball.rb'
require 'app/rectangle.rb'
require 'app/linear_collider.rb'
require 'app/square_collider.rb'



#Method to init default values
def defaults args
  args.state.board_width ||= args.grid.w / 4
  args.state.board_height ||= args.grid.h
  args.state.game_area ||= [(args.state.board_width + args.grid.w / 8), 0, args.state.board_width, args.grid.h]
  args.state.balls ||= []
  args.state.num_balls ||= 0
  args.state.ball_created_at ||= args.state.tick_count
  args.state.ball_hypotenuse = (10**2 + 10**2)**0.5
  args.state.ballParents ||= []

  init_blocks args
  init_balls args
end

begin :default_methods
  def init_blocks args
    block_size = args.state.board_width / 8
    #Space inbetween each block
    block_offset = 4

    args.state.squares ||=[
      Square.new(args, 2, 0, block_size, :right, block_offset),
      Square.new(args, 5, 0, block_size, :right, block_offset),
      Square.new(args, 6, 7, block_size, :right, block_offset)
    ]


    #Possible orientations are :right, :left, :up, :down


    args.state.tshapes ||= [
      TShape.new(args, 0, 6, block_size, :left, block_offset),
      TShape.new(args, 3, 3, block_size, :down, block_offset),
      TShape.new(args, 0, 3, block_size, :right, block_offset),
      TShape.new(args, 0, 11, block_size, :up, block_offset)
    ]

    args.state.lines ||= [
      Line.new(args,3, 8, block_size, :down, block_offset),
      Line.new(args, 7, 3, block_size, :up, block_offset),
      Line.new(args, 3, 7, block_size, :right, block_offset)
    ]

    #exit()
  end

  def init_balls args
    return unless args.state.num_balls < BALL_COUNT


    #only create a new ball every 10 ticks
    return unless args.state.ball_created_at.elapsed_time > 10

    if (args.state.num_balls == 0)
      args.state.balls.append(Ball.new(args,args.state.num_balls,BALL_COUNT-1, nil, nil))
      args.state.ballParents = [args.state.balls[0]]
    else
      args.state.balls.append(Ball.new(args,args.state.num_balls,BALL_COUNT-1, args.state.balls.last, nil) )
      args.state.balls[-2].child = args.state.balls[-1]
    end
    args.state.ball_created_at = args.state.tick_count
    args.state.num_balls += 1
  end
end

#Render loop
def render args
  bgClr = {r:10, g:10, b:200}
  bgClr = {r:255-30, g:255-30, b:255-30}

  args.outputs.solids << [0, 0, $args.grid.right, $args.grid.top, bgClr[:r], bgClr[:g], bgClr[:b]];
  args.outputs.borders << args.state.game_area

  render_instructions args
  render_shapes args

  render_balls args

  #args.state.rectangle.draw args

  args.outputs.sprites << [$args.grid.right-(args.state.board_width + args.grid.w / 8), 0, $args.grid.right, $args.grid.top, "sprites/square-white-2.png", 0, 255, bgClr[:r], bgClr[:g], bgClr[:b]]
  args.outputs.sprites << [0, 0, (args.state.board_width + args.grid.w / 8), $args.grid.top, "sprites/square-white-2.png", 0, 255, bgClr[:r], bgClr[:g], bgClr[:b]]

end

begin :render_methods
  def render_instructions args
    #gtk.current_framerate
    args.outputs.labels << [20, $args.grid.top-20, "FPS: " + $gtk.current_framerate.to_s]
    if (args.state.balls != nil && args.state.balls[0] != nil)
        bx =  args.state.balls[0].velocity.x
        by =  args.state.balls[0].velocity.y
        bmg = (bx**2.0 + by**2.0)**0.5
        args.outputs.labels << [20, $args.grid.top-20-20, "V: " + bmg.to_s ]
    end


  end

  def render_shapes args
    for s in args.state.squares
      s.draw args
    end

    for l in args.state.lines
      l.draw args
    end

    for t in args.state.tshapes
      t.draw args
    end


  end

  def render_balls args
    #args.state.balls.each do |ball|
      #ball.draw args
    #end

    args.outputs.sprites << args.state.balls.map do |ball|
      ball.getDraw args
    end
  end
end

#Calls all methods necessary for performing calculations
def calc args
  for b in args.state.ballParents
    b.update args
  end

  for s in args.state.squares
    s.update args
  end

  for l in args.state.lines
    l.update args
  end

  for t in args.state.tshapes
    t.update args
  end



end

begin :calc_methods

end

def tick args
  defaults args
  render args
  calc args
end

Physics And Collisions - Arbitrary Collision - paddle.rb

# ./samples/04_physics_and_collisions/09_arbitrary_collision/app/paddle.rb
class Paddle
  attr_accessor :enabled

  def initialize ()
    @x=WIDTH/2
    @y=100
    @width=100
    @height=20
    @speed=10

    @xyCollision  = LinearCollider.new({x: @x,y: @y+@height+5}, {x: @x+@width, y: @y+@height+5})
    @xyCollision2 = LinearCollider.new({x: @x,y: @y}, {x: @x+@width, y: @y}, :pos)
    @xyCollision3 = LinearCollider.new({x: @x,y: @y}, {x: @x, y: @y+@height+5})
    @xyCollision4 = LinearCollider.new({x: @x+@width,y: @y}, {x: @x+@width, y: @y+@height+5}, :pos)

    @enabled = true
  end

  def update args
    @xyCollision.resetPoints({x: @x,y: @y+@height+5}, {x: @x+@width, y: @y+@height+5})
    @xyCollision2.resetPoints({x: @x,y: @y}, {x: @x+@width, y: @y})
    @xyCollision3.resetPoints({x: @x,y: @y}, {x: @x, y: @y+@height+5})
    @xyCollision4.resetPoints({x: @x+@width,y: @y}, {x: @x+@width, y: @y+@height+5})

    @xyCollision.update  args
    @xyCollision2.update args
    @xyCollision3.update args
    @xyCollision4.update args

    args.inputs.keyboard.key_held.left  ||= false
    args.inputs.keyboard.key_held.right  ||= false

    if not (args.inputs.keyboard.key_held.left == args.inputs.keyboard.key_held.right)
      if args.inputs.keyboard.key_held.left && @enabled
        @x-=@speed
      elsif args.inputs.keyboard.key_held.right && @enabled
        @x+=@speed
      end
    end

    xmin =WIDTH/4
    xmax = 3*(WIDTH/4)
    @x = (@x+@width > xmax) ? xmax-@width : (@x<xmin) ? xmin : @x;
  end

  def render args
    args.outputs.solids << [@x,@y,@width,@height,255,0,0];
  end

  def rect
    [@x, @y, @width, @height]
  end
end

Physics And Collisions - Arbitrary Collision - rectangle.rb

# ./samples/04_physics_and_collisions/09_arbitrary_collision/app/rectangle.rb
class Rectangle
  def initialize args

    @image = "sprites/roundSquare_white.png"
    @width  = 160.0
    @height = 80.0
    @x=$args.grid.right/2.0 - @width/2.0
    @y=$args.grid.top/2.0 - @height/2.0

    @xtmp = @width  * (1.0/10.0)
    @ytmp = @height * (1.0/10.0)

    #ball0 = args.state.balls[0]
    #hypotenuse = (args.state.balls[0].width**2 + args.state.balls[0].height**2)**0.5
    hypotenuse=args.state.ball_hypotenuse
    @boldXY = {x:(@x-hypotenuse/2)-1, y:(@y-hypotenuse/2)-1}
    @boldWidth = @width + hypotenuse + 2
    @boldHeight = @height + hypotenuse + 2
    @bold = [(@x-hypotenuse/2)-1,(@y-hypotenuse/2)-1,@width + hypotenuse + 2,@height + hypotenuse + 2]


    @points = [
      {x:@x,        y:@y+@ytmp},
      {x:@x+@xtmp,        y:@y},
      {x:@x+@width-@xtmp, y:@y},
      {x:@x+@width, y:@y+@ytmp},
      {x:@x+@width, y:@y+@height-@ytmp},#
      {x:@x+@width-@xtmp, y:@y+@height},
      {x:@x+@xtmp,        y:@y+@height},
      {x:@x,        y:@y+@height-@ytmp}
    ]

    @colliders = []
    #i = 0
    #while i < @points.length-1
      #@colliders.append(LinearCollider.new(@points[i],@points[i+1],:pos))
      #i+=1
    #end
    @colliders.append(LinearCollider.new(@points[0],@points[1], :neg))
    @colliders.append(LinearCollider.new(@points[1],@points[2], :neg))
    @colliders.append(LinearCollider.new(@points[2],@points[3], :neg))
    @colliders.append(LinearCollider.new(@points[3],@points[4], :neg))
    @colliders.append(LinearCollider.new(@points[4],@points[5], :pos))
    @colliders.append(LinearCollider.new(@points[5],@points[6], :pos))
    @colliders.append(LinearCollider.new(@points[6],@points[7], :pos))
    @colliders.append(LinearCollider.new(@points[0],@points[7], :pos))

  end

  def update args

    for b in args.state.balls
      if [b.x, b.y, b.width, b.height].intersect_rect?(@bold)
        for c in @colliders
          if c.collision?(args, b.getPoints(args),b)
            c.collide args, b
          end
        end
      end
    end
  end

  def draw args
    args.outputs.sprites << [
      @x,                                       # X
      @y,                                       # Y
      @width,                                   # W
      @height,                                  # H
      @image,                                   # PATH
      0,                                        # ANGLE
      255,                                      # ALPHA
      219,                                      # RED_SATURATION
      112,                                      # GREEN_SATURATION
      147                                       # BLUE_SATURATION
    ]
    #args.outputs.sprites << [@x, @y, @width, @height, "sprites/roundSquare_small_black.png"]
  end

  def serialize
  	{x: @x, y:@y}
  end

  def inspect
  	serialize.to_s
  end

  def to_s
  	serialize.to_s
  end
end

Physics And Collisions - Arbitrary Collision - square_collider.rb

# ./samples/04_physics_and_collisions/09_arbitrary_collision/app/square_collider.rb

class SquareCollider
  def initialize x,y,direction,size=COLLISIONWIDTH
    @x = x
    @y = y
    @size = size
    @direction = direction

  end
  def collision? args, ball
    #args.outputs.solids <<  [@x, @y, @size, @size,     000, 255, 255]


    return [@x,@y,@size,@size].intersect_rect?([ball.x,ball.y,ball.width,ball.height])
  end

  def collide args, ball
    vmag = (ball.velocity.x**2.0 +ball.velocity.y**2.0)**0.5
    a = ((2.0**0.5)*vmag)/2.0
    if vmag < MAX_VELOCITY
      ball.velocity.x = (a) * @direction.x * 1.1
      ball.velocity.y = (a) * @direction.y * 1.1
    else
      ball.velocity.x = (a) * @direction.x
      ball.velocity.y = (a) * @direction.y
    end

  end
end

Physics And Collisions - Arbitrary Collision - vector2d.rb

# ./samples/04_physics_and_collisions/09_arbitrary_collision/app/vector2d.rb
class Vector2d
    attr_accessor :x, :y

    def initialize x=0, y=0
      @x=x
      @y=y
    end

    #returns a vector multiplied by scalar x
    #x [float] scalar
    def mult x
      r = Vector2d.new(0,0)
      r.x=@x*x
      r.y=@y*x
      r
    end

    # vect [Vector2d] vector to copy
    def copy vect
      Vector2d.new(@x, @y)
    end

    #returns a new vector equivalent to this+vect
    #vect [Vector2d] vector to add to self
    def add vect
      Vector2d.new(@x+vect.x,@y+vect.y)
    end

    #returns a new vector equivalent to this-vect
    #vect [Vector2d] vector to subtract to self
    def sub vect
      Vector2d.new(@x-vect.c, @y-vect.y)
    end

    #return the magnitude of the vector
    def mag
      ((@x**2)+(@y**2))**0.5
    end

    #returns a new normalize version of the vector
    def normalize
      Vector2d.new(@x/mag, @y/mag)
    end

    #TODO delet?
    def distABS vect
      (((vect.x-@x)**2+(vect.y-@y)**2)**0.5).abs()
    end
  end

Physics And Collisions - Collision With Object Removal - ball.rb

# ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/ball.rb
class Ball
  #TODO limit accessors?
  attr_accessor :xy, :width, :height, :velocity


  #@xy [Vector2d] x,y position
  #@velocity [Vector2d] velocity of ball
  def initialize
    @xy = Vector2d.new(WIDTH/2,500)
    @velocity = Vector2d.new(4,-4)
    @width =  20
    @height = 20
  end

  #move the ball according to its velocity
  def update args
    @xy.x+=@velocity.x
    @xy.y+=@velocity.y
  end

  #render the ball to the screen
  def render args
    args.outputs.solids << [@xy.x,@xy.y,@width,@height,255,0,255];
    #args.outputs.labels << [20,HEIGHT-50,"velocity: " +@velocity.x.to_s+","+@velocity.y.to_s + "   magnitude:" + @velocity.mag.to_s]
  end

  def rect
    [@xy.x,@xy.y,@width,@height]
  end

end

Physics And Collisions - Collision With Object Removal - linear_collider.rb

# ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/linear_collider.rb
#The LinearCollider (theoretically) produces collisions upon a line segment defined point.y two x,y cordinates

class LinearCollider

  #start [Array of length 2] start of the line segment as a x,y cordinate
  #last [Array of length 2] end of the line segment as a x,y cordinate

  #inorder for the LinearCollider to be functional the line segment must be said to have a thickness
  #(as it is unlikly that a colliding object will land exactly on the linesegment)

  #extension defines if the line's thickness extends negatively or positively
  #extension :pos     extends positively
  #extension :neg     extends negatively

  #thickness [float] how thick the line should be (should always be atleast as large as the magnitude of the colliding object)
  def initialize (pointA, pointB, extension=:neg, thickness=10)
    @pointA = pointA
    @pointB = pointB
    @thickness = thickness
    @extension = extension

    @pointAExtended={
      x: @pointA.x + @thickness*(@extension == :neg ? -1 : 1),
      y: @pointA.y + @thickness*(@extension == :neg ? -1 : 1)
    }
    @pointBExtended={
      x: @pointB.x + @thickness*(@extension == :neg ? -1 : 1),
      y: @pointB.y + @thickness*(@extension == :neg ? -1 : 1)
    }

  end

  def resetPoints(pointA,pointB)
    @pointA = pointA
    @pointB = pointB

    @pointAExtended={
      x:@pointA.x + @thickness*(@extension == :neg ? -1 : 1),
      y:@pointA.y + @thickness*(@extension == :neg ? -1 : 1)
    }
    @pointBExtended={
      x:@pointB.x + @thickness*(@extension == :neg ? -1 : 1),
      y:@pointB.y + @thickness*(@extension == :neg ? -1 : 1)
    }
  end

  #TODO: Ugly function
  def slope (pointA, pointB)
    return (pointB.x==pointA.x) ? INFINITY : (pointB.y+-pointA.y)/(pointB.x+-pointA.x)
  end

  #TODO: Ugly function
  def intercept(pointA, pointB)
    if (slope(pointA, pointB) == INFINITY)
      -INFINITY
    elsif slope(pointA, pointB) == -1*INFINITY
      INFINITY
    else
      pointA.y+-1.0*(slope(pointA, pointB)*pointA.x)
    end
  end

  def calcY(pointA, pointB, x)
    return slope(pointA, pointB)*x + intercept(pointA, pointB)
  end

  #test if a collision has occurred
  def isCollision? (point)
    #INFINITY slop breaks down when trying to determin collision, ergo it requires a special test
    if slope(@pointA, @pointB) ==  INFINITY &&
      point.x >= [@pointA.x,@pointB.x].min+(@extension == :pos ? -@thickness : 0) &&
      point.x <= [@pointA.x,@pointB.x].max+(@extension == :neg ?  @thickness : 0) &&
      point.y >= [@pointA.y,@pointB.y].min && point.y <= [@pointA.y,@pointB.y].max
        return true
    end

    isNegInLine   = @extension == :neg &&
                    point.y <= slope(@pointA, @pointB)*point.x+intercept(@pointA,@pointB) &&
                    point.y >= point.x*slope(@pointAExtended, @pointBExtended)+intercept(@pointAExtended,@pointBExtended)
    isPosInLine   = @extension == :pos &&
                    point.y >= slope(@pointA, @pointB)*point.x+intercept(@pointA,@pointB) &&
                    point.y <= point.x*slope(@pointAExtended, @pointBExtended)+intercept(@pointAExtended,@pointBExtended)
    isInBoxBounds = point.x >= [@pointA.x,@pointB.x].min &&
                    point.x <= [@pointA.x,@pointB.x].max &&
                    point.y >= [@pointA.y,@pointB.y].min+(@extension == :neg ? -@thickness : 0) &&
                    point.y <= [@pointA.y,@pointB.y].max+(@extension == :pos ? @thickness : 0)

    return isInBoxBounds && (isNegInLine || isPosInLine)

  end

  def getRepelMagnitude (fbx, fby, vrx, vry, args)
    a = fbx ; b = vrx ; c = fby
    d = vry ; e = args.state.ball.velocity.mag

    if b**2 + d**2 == 0
      puts "magnitude error"
    end

    x1 = (-a*b+-c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 + d**2 - a**2 * d**2)**0.5)/(b**2 + d**2)
    x2 = -((a*b + c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 * d**2 - a**2 * d**2)**0.5)/(b**2 + d**2))
    return ((a+x1*b)**2 + (c+x1*d)**2 == e**2) ? x1 : x2
  end

  def update args
    #each of the four points on the square ball - NOTE simple to extend to a circle
    points= [ {x: args.state.ball.xy.x,                          y: args.state.ball.xy.y},
              {x: args.state.ball.xy.x+args.state.ball.width,    y: args.state.ball.xy.y},
              {x: args.state.ball.xy.x,                          y: args.state.ball.xy.y+args.state.ball.height},
              {x: args.state.ball.xy.x+args.state.ball.width,    y: args.state.ball.xy.y + args.state.ball.height}
            ]

    #for each point p in points
    for point in points
      #isCollision.md has more information on this section
      #TODO: section can certainly be simplifyed
      if isCollision?(point)
        u = Vector2d.new(1.0,((slope(@pointA, @pointB)==0) ? INFINITY : -1/slope(@pointA, @pointB))*1.0).normalize #normal perpendicular (to line segment) vector

        #the vector with the repeling force can be u or -u depending of where the ball was coming from in relation to the line segment
        previousBallPosition=Vector2d.new(point.x-args.state.ball.velocity.x,point.y-args.state.ball.velocity.y)
        choiceA = (u.mult(1))
        choiceB =  (u.mult(-1))
        vectorRepel = nil

        if (slope(@pointA, @pointB))!=INFINITY && u.y < 0
          choiceA, choiceB = choiceB, choiceA
        end
        vectorRepel = (previousBallPosition.y > calcY(@pointA, @pointB, previousBallPosition.x)) ? choiceA : choiceB

        #vectorRepel = (previousBallPosition.y > slope(@pointA, @pointB)*previousBallPosition.x+intercept(@pointA,@pointB)) ? choiceA : choiceB)
        if (slope(@pointA, @pointB) == INFINITY) #slope INFINITY breaks down in the above test, ergo it requires a custom test
          vectorRepel = (previousBallPosition.x > @pointA.x) ? (u.mult(1)) : (u.mult(-1))
        end
        #puts ("     " + $t[0].to_s + "," + $t[1].to_s + "    " + $t[2].to_s + "," + $t[3].to_s + "     " + "   " + u.x.to_s + "," + u.y.to_s)
        #vectorRepel now has the repeling force

        mag = args.state.ball.velocity.mag
        theta_ball=Math.atan2(args.state.ball.velocity.y,args.state.ball.velocity.x) #the angle of the ball's velocity
        theta_repel=Math.atan2(vectorRepel.y,vectorRepel.x) #the angle of the repeling force
        #puts ("theta:" + theta_ball.to_s + " " + theta_repel.to_s) #theta okay

        fbx = mag * Math.cos(theta_ball) #the x component of the ball's velocity
        fby = mag * Math.sin(theta_ball) #the y component of the ball's velocity

        repelMag = getRepelMagnitude(fbx, fby, vectorRepel.x, vectorRepel.y, args)

        frx = repelMag* Math.cos(theta_repel) #the x component of the repel's velocity | magnitude is set to twice of fbx
        fry = repelMag* Math.sin(theta_repel) #the y component of the repel's velocity | magnitude is set to twice of fby

        fsumx = fbx+frx #sum of x forces
        fsumy = fby+fry #sum of y forces
        fr = mag#fr is the resulting magnitude
        thetaNew = Math.atan2(fsumy, fsumx)  #thetaNew is the resulting angle
        xnew = fr*Math.cos(thetaNew) #resulting x velocity
        ynew = fr*Math.sin(thetaNew) #resulting y velocity

        args.state.ball.velocity = Vector2d.new(xnew,ynew)
        #args.state.ball.xy.add(args.state.ball.velocity)
        break #no need to check the other points ?
      else
      end
    end
  end #end update

end

Physics And Collisions - Collision With Object Removal - main.rb

# ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/main.rb
# coding: utf-8
INFINITY= 10**10
WIDTH=1280
HEIGHT=720

require 'app/vector2d.rb'
require 'app/paddle.rb'
require 'app/ball.rb'
require 'app/linear_collider.rb'

#Method to init default values
def defaults args
  args.state.game_board ||= [(args.grid.w / 2 - args.grid.w / 4), 0, (args.grid.w / 2), args.grid.h]
  args.state.bricks ||= []
  args.state.num_bricks ||= 0
  args.state.game_over_at ||= 0
  args.state.paddle ||= Paddle.new
  args.state.ball   ||= Ball.new
  args.state.westWall  ||= LinearCollider.new({x: args.grid.w/4,      y: 0},          {x: args.grid.w/4,      y: args.grid.h}, :pos)
  args.state.eastWall  ||= LinearCollider.new({x: 3*args.grid.w*0.25, y: 0},          {x: 3*args.grid.w*0.25, y: args.grid.h})
  args.state.southWall ||= LinearCollider.new({x: 0,                  y: 0},          {x: args.grid.w,        y: 0})
  args.state.northWall ||= LinearCollider.new({x: 0,                  y:args.grid.h}, {x: args.grid.w,        y: args.grid.h}, :pos)

  #args.state.testWall ||= LinearCollider.new({x:0 , y:0},{x:args.grid.w, y:args.grid.h})
end

#Render loop
def render args
  render_instructions args
  render_board args
  render_bricks args
end

begin :render_methods
  #Method to display the instructions of the game
  def render_instructions args
    args.outputs.labels << [225, args.grid.h - 30, "← and → to move the paddle left and right",  0, 1]
  end

  def render_board args
    args.outputs.borders << args.state.game_board
  end

  def render_bricks args
    args.outputs.solids << args.state.bricks.map(&:rect)
  end
end

#Calls all methods necessary for performing calculations
def calc args
  add_new_bricks args
  reset_game args
  calc_collision args
  win_game args

  args.state.westWall.update args
  args.state.eastWall.update args
  args.state.southWall.update args
  args.state.northWall.update args
  args.state.paddle.update args
  args.state.ball.update args

  #args.state.testWall.update args

  args.state.paddle.render args
  args.state.ball.render args
end

begin :calc_methods
  def add_new_bricks args
    return if args.state.num_bricks > 40

    #Width of the game board is 640px
    brick_width = (args.grid.w / 2) / 10
    brick_height = brick_width / 2

    (4).map_with_index do |y|
      #Make a box that is 10 bricks wide and 4 bricks tall
      args.state.bricks += (10).map_with_index do |x|
        args.state.new_entity(:brick) do |b|
          b.x = x * brick_width + (args.grid.w / 2 - args.grid.w / 4)
          b.y = args.grid.h - ((y + 1) * brick_height)
          b.rect = [b.x + 1, b.y - 1, brick_width - 2, brick_height - 2, 235, 50 * y, 52]

          #Add linear colliders to the brick
          b.collider_bottom = LinearCollider.new([(b.x-2), (b.y-5)], [(b.x+brick_width+1), (b.y-5)], :pos, brick_height)
          b.collider_right = LinearCollider.new([(b.x+brick_width+1), (b.y-5)], [(b.x+brick_width+1), (b.y+brick_height+1)], :pos)
          b.collider_left = LinearCollider.new([(b.x-2), (b.y-5)], [(b.x-2), (b.y+brick_height+1)], :neg)
          b.collider_top = LinearCollider.new([(b.x-2), (b.y+brick_height+1)], [(b.x+brick_width+1), (b.y+brick_height+1)], :neg)

          # @xyCollision  = LinearCollider.new({x: @x,y: @y+@height}, {x: @x+@width, y: @y+@height})
          # @xyCollision2 = LinearCollider.new({x: @x,y: @y}, {x: @x+@width, y: @y}, :pos)
          # @xyCollision3 = LinearCollider.new({x: @x,y: @y}, {x: @x, y: @y+@height})
          # @xyCollision4 = LinearCollider.new({x: @x+@width,y: @y}, {x: @x+@width, y: @y+@height}, :pos)

          b.broken = false

          args.state.num_bricks += 1
        end
      end
    end
  end

  def reset_game args
    if args.state.ball.xy.y < 20 && args.state.game_over_at.elapsed_time > 60
      #Freeze the ball
      args.state.ball.velocity.x = 0
      args.state.ball.velocity.y = 0
      #Freeze the paddle
      args.state.paddle.enabled = false

      args.state.game_over_at = args.state.tick_count
    end

    if args.state.game_over_at.elapsed_time < 60 && args.state.tick_count > 60 && args.state.bricks.count != 0
      #Display a "Game over" message
      args.outputs.labels << [100, 100, "GAME OVER", 10]
    end

    #If 60 frames have passed since the game ended, restart the game
    if args.state.game_over_at != 0 && args.state.game_over_at.elapsed_time == 60
      # FIXME: only put value types in state
      args.state.ball = Ball.new

      # FIXME: only put value types in state
      args.state.paddle = Paddle.new

      args.state.bricks = []
      args.state.num_bricks = 0
    end
  end

  def calc_collision args
    #Remove the brick if it is hit with the ball
    ball = args.state.ball
    ball_rect = [ball.xy.x, ball.xy.y, 20, 20]

    #Loop through each brick to see if the ball is colliding with it
    args.state.bricks.each do |b|
      if b.rect.intersect_rect?(ball_rect)
        #Run the linear collider for the brick if there is a collision
        b[:collider_bottom].update args
        b[:collider_right].update args
        b[:collider_left].update args
        b[:collider_top].update args

        b.broken = true
      end
    end

    args.state.bricks = args.state.bricks.reject(&:broken)
  end

  def win_game args
    if args.state.bricks.count == 0 && args.state.game_over_at.elapsed_time > 60
      #Freeze the ball
      args.state.ball.velocity.x = 0
      args.state.ball.velocity.y = 0
      #Freeze the paddle
      args.state.paddle.enabled = false

      args.state.game_over_at = args.state.tick_count
    end

    if args.state.game_over_at.elapsed_time < 60 && args.state.tick_count > 60 && args.state.bricks.count == 0
      #Display a "Game over" message
      args.outputs.labels << [100, 100, "CONGRATULATIONS!", 10]
    end
  end

end

def tick args
  defaults args
  render args
  calc args

  #args.outputs.lines << [0, 0, args.grid.w, args.grid.h]

  #$tc+=1
  #if $tc == 5
    #$train << [args.state.ball.xy.x, args.state.ball.xy.y]
    #$tc = 0
  #end
  #for t in $train

    #args.outputs.solids << [t[0],t[1],5,5,255,0,0];
  #end
end

Physics And Collisions - Collision With Object Removal - paddle.rb

# ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/paddle.rb
class Paddle
  attr_accessor :enabled

  def initialize ()
    @x=WIDTH/2
    @y=100
    @width=100
    @height=20
    @speed=10

    @xyCollision  = LinearCollider.new({x: @x,y: @y+@height+5}, {x: @x+@width, y: @y+@height+5})
    @xyCollision2 = LinearCollider.new({x: @x,y: @y}, {x: @x+@width, y: @y}, :pos)
    @xyCollision3 = LinearCollider.new({x: @x,y: @y}, {x: @x, y: @y+@height+5})
    @xyCollision4 = LinearCollider.new({x: @x+@width,y: @y}, {x: @x+@width, y: @y+@height+5}, :pos)

    @enabled = true
  end

  def update args
    @xyCollision.resetPoints({x: @x,y: @y+@height+5}, {x: @x+@width, y: @y+@height+5})
    @xyCollision2.resetPoints({x: @x,y: @y}, {x: @x+@width, y: @y})
    @xyCollision3.resetPoints({x: @x,y: @y}, {x: @x, y: @y+@height+5})
    @xyCollision4.resetPoints({x: @x+@width,y: @y}, {x: @x+@width, y: @y+@height+5})

    @xyCollision.update  args
    @xyCollision2.update args
    @xyCollision3.update args
    @xyCollision4.update args

    args.inputs.keyboard.key_held.left  ||= false
    args.inputs.keyboard.key_held.right  ||= false

    if not (args.inputs.keyboard.key_held.left == args.inputs.keyboard.key_held.right)
      if args.inputs.keyboard.key_held.left && @enabled
        @x-=@speed
      elsif args.inputs.keyboard.key_held.right && @enabled
        @x+=@speed
      end
    end

    xmin =WIDTH/4
    xmax = 3*(WIDTH/4)
    @x = (@x+@width > xmax) ? xmax-@width : (@x<xmin) ? xmin : @x;
  end

  def render args
    args.outputs.solids << [@x,@y,@width,@height,255,0,0];
  end

  def rect
    [@x, @y, @width, @height]
  end
end

Physics And Collisions - Collision With Object Removal - tests.rb

# ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/tests.rb
# For advanced users:
# You can put some quick verification tests here, any method
# that starts with the `test_` will be run when you save this file.

# Here is an example test and game

# To run the test: ./dragonruby mygame --eval app/tests.rb --no-tick

class MySuperHappyFunGame
  attr_gtk

  def tick
    outputs.solids << [100, 100, 300, 300]
  end
end

def test_universe args, assert
  game = MySuperHappyFunGame.new
  game.args = args
  game.tick
  assert.true!  args.outputs.solids.length == 1, "failure: a solid was not added after tick"
  assert.false! 1 == 2, "failure: some how, 1 equals 2, the world is ending"
  puts "test_universe completed successfully"
end

puts "running tests"
$gtk.reset 100
$gtk.log_level = :off
$gtk.tests.start

Physics And Collisions - Collision With Object Removal - vector2d.rb

# ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/vector2d.rb

class Vector2d
  attr_accessor :x, :y

  def initialize x=0, y=0
    @x=x
    @y=y
  end

  #returns a vector multiplied by scalar x
  #x [float] scalar
  def mult x
    r = Vector2d.new(0,0)
    r.x=@x*x
    r.y=@y*x
    r
  end

  # vect [Vector2d] vector to copy
  def copy vect
    Vector2d.new(@x, @y)
  end

  #returns a new vector equivalent to this+vect
  #vect [Vector2d] vector to add to self
  def add vect
    Vector2d.new(@x+vect.x,@y+vect.y)
  end

  #returns a new vector equivalent to this-vect
  #vect [Vector2d] vector to subtract to self
  def sub vect
    Vector2d.new(@x-vect.c, @y-vect.y)
  end

  #return the magnitude of the vector
  def mag
    ((@x**2)+(@y**2))**0.5
  end

  #returns a new normalize version of the vector
  def normalize
    Vector2d.new(@x/mag, @y/mag)
  end

  #TODO delet?
  def distABS vect
    (((vect.x-@x)**2+(vect.y-@y)**2)**0.5).abs()
  end
end

Physics And Collisions - Bouncing Ball With Gravity - main.rb

# ./samples/04_physics_and_collisions/11_bouncing_ball_with_gravity/app/main.rb
include MatrixFunctions

class BouncingBall
  attr_gtk

  def tick
    defaults
    render
    input
    calc

    reset_ball if args.inputs.keyboard.key_down.r

    args.state.debug = !args.state.debug if inputs.keyboard.key_down.g
    debug if args.state.debug
  end

  def defaults
    args.state.rest ||= false
    args.state.debug ||= false

    state.walls ||= [
      { x: 50.from_left, y: 50.from_bottom, x2: 50.from_left, y2: 50.from_top },
      { x: 50.from_left, y: 50.from_bottom, x2: 50.from_right, y2: 50.from_bottom },
      { x: 50.from_left, y: 50.from_top, x2: 50.from_right, y2: 50.from_top },
      { x: 50.from_right, y: 50.from_bottom, x2: 50.from_right, y2: 50.from_top },
    ]

    state.ball ||= { x: 250, y: 250, w: 50, h: 50, path: 'circle-white.png' }
    state.ball_old_x ||= state.ball[:x]
    state.ball_old_y ||= state.ball[:y]
    state.ball_vector ||= vec2(0, 0)

    state.stick_length = 200
    state.stick_angle ||= 0
    state.stick_power ||= 0

    # Prevent consecutive bounces on the same normal vector
    # Solves issue where ball gets stuck on a wall
    state.prevent_collision ||= {}

    state.physics.gravity = 0.4
    state.physics.restitution = 0.80
    state.physics.friction = 0.70
  end

  def render
    outputs.lines << state.walls
    outputs.sprites << state.ball
    render_stick
    render_point_one
  end

  def render_stick
    stick_vec_x = Math.cos(state.stick_angle.to_radians)
    stick_vec_y = Math.sin(state.stick_angle.to_radians)
    ball_center_x = state.ball[:x] + (state.ball[:w] / 2)
    ball_center_y = state.ball[:y] + (state.ball[:h] / 2)
    # Draws the line starting 15% of stick_length away from the ball
    outputs.lines << {
      x: ball_center_x + (stick_vec_x * state.stick_length * -0.15),
      y: ball_center_y + (stick_vec_y * state.stick_length * -0.15),
      w: stick_vec_x * state.stick_length * -1,
      h: stick_vec_y * state.stick_length * -1,
    }
  end

  def render_point_one
    return unless state.point_one

    outputs.lines << { x: state.point_one.x, y: state.point_one.y,
                       x2: inputs.mouse.x, y2: inputs.mouse.y,
                       r: 255 }
  end

  def input
    input_stick
    input_lines
    state.point_one = nil if inputs.keyboard.key_down.escape
  end

  def input_stick
    if inputs.keyboard.key_up.space
      hit_ball
      state.stick_power = 0
    end

    if inputs.keyboard.key_held.space
      state.stick_power += 1 unless state.stick_power >= 50
      outputs.labels << [100, 100, state.stick_power]
    end

    state.stick_angle += inputs.keyboard.left_right
  end

  def input_lines
    return unless inputs.mouse.click

    if state.point_one
      x = snap(state.point_one.x)
      y = snap(state.point_one.y)
      x2 = snap(inputs.mouse.click.x)
      y2 = snap(inputs.mouse.click.y)
      state.walls << { x: x, y: y, x2: x2, y2: y2 }
      state.point_one = nil
    else
      state.point_one = inputs.mouse.click.point
    end
  end

  # FIX: does not snap negative numbers properly
  def snap value
    snap_number = 10
    min = value.to_i.idiv(snap_number) * snap_number
    max = min + snap_number
    result = (max - value).abs < (min - value).abs ? max : min
    puts "SNAP: #{ value } --> #{ result }" if state.debug
    result
  end

  def hit_ball
    vec_x = Math.cos(state.stick_angle.to_radians) * state.stick_power
    vec_y = Math.sin(state.stick_angle.to_radians) * state.stick_power
    state.ball_vector = vec2(vec_x, vec_y)
    state.rest = false
  end

  def entropy
    state.ball_vector[:x].abs + state.ball_vector[:y].abs
  end

  # Ball is resting if
  # entropy is low, ball is touching a line
  # the line is not steep and the ball is above the line
  def ball_is_resting?(walls, true_normal)
    entropy < 1.5 && !walls.empty? && true_normal[:y] > 0.96
  end

  def calc
    walls = []
    state.walls.each do |wall|
      if line_intersect_rect?(wall, state.ball)
        walls << wall unless state.prevent_collision.key?(wall)
      end
    end

    state.prevent_collision = {}
    walls.each { |w| state.prevent_collision[w] = true }

    normals = walls.map { |w| compute_proper_normal(w) }
    true_normal = normals.inject { |a, b| normalize(vector_add(a, b)) }

    unless state.rest
      state.ball_vector = collision(true_normal) unless walls.empty?
      state.ball_old_x = state.ball[:x]
      state.ball_old_y = state.ball[:y]
      state.ball[:x] += state.ball_vector[:x]
      state.ball[:y] += state.ball_vector[:y]
      state.ball_vector[:y] -= state.physics.gravity

      if ball_is_resting?(walls, true_normal)
        state.ball[:y] += 1
        state.rest = true
      end
    end
  end

  # Line segment intersects rect if it intersects
  # any of the lines that make up the rect
  # This doesn't cover the case where the line is completely within the rect
  def line_intersect_rect?(line, rect)
    rect_to_lines(rect).each do |rect_line|
      return true if segments_intersect?(line, rect_line)
    end

    false
  end

  # https://stackoverflow.com/questions/573084/
  def collision(normal_vector)
    dot_product = dot(state.ball_vector, normal_vector)
    normal_square = dot(normal_vector, normal_vector)
    perpendicular = vector_multiply(normal_vector, (dot_product / normal_square))
    parallel = vector_minus(state.ball_vector, perpendicular)
    perpendicular = vector_multiply(perpendicular, state.physics.restitution)
    parallel = vector_multiply(parallel, state.physics.friction)
    vector_minus(parallel, perpendicular)
  end

  # https://stackoverflow.com/questions/1243614/
  def compute_normals(line)
    h = line[:y2] - line[:y]
    w = line[:x2] - line[:x]
    a = normalize vec2(-h, w)
    b = normalize vec2(h, -w)
    [a, b]
  end

  # https://stackoverflow.com/questions/3838319/
  # Get the normal vector that points at the ball from the center of the line
  def compute_proper_normal(line)
    normals = compute_normals(line)
    ball_center_x = state.ball_old_x + (state.ball[:w] / 2)
    ball_center_y = state.ball_old_y + (state.ball[:h] / 2)
    v1 = vec2(line[:x2] - line[:x], line[:y2] - line[:y])
    v2 = vec2(line[:x2] - ball_center_x, line[:y2] - ball_center_y)
    cp = v1[:x] * v2[:y] - v1[:y] * v2[:x]
    cp < 0 ? normals[0] : normals[1]
  end

  def vector_multiply(vector, value)
    vec2(vector[:x] * value, vector[:y] * value)
  end

  def vector_minus(vec_a, vec_b)
    vec2(vec_a[:x] - vec_b[:x], vec_a[:y] - vec_b[:y])
  end

  def vector_add a, b
    vec2(a[:x] + b[:x], a[:y] + b[:y])
  end

  # The lines composing the boundaries of a rectangle
  def rect_to_lines(rect)
    x = rect[:x]
    y = rect[:y]
    x2 = rect[:x] + rect[:w]
    y2 = rect[:y] + rect[:h]
    [{ x: x, y: y, x2: x2, y2: y },
     { x: x, y: y, x2: x, y2: y2 },
     { x: x2, y: y, x2: x2, y2: y2 },
     { x: x, y: y2, x2: x2, y2: y2 }]
  end

  # This is different from args.geometry.line_intersect
  # This considers line segments instead of lines
  # http://jeffreythompson.org/collision-detection/line-line.php
  def segments_intersect?(line_one, line_two)
    x1 = line_one[:x]
    y1 = line_one[:y]
    x2 = line_one[:x2]
    y2 = line_one[:y2]

    x3 = line_two[:x]
    y3 = line_two[:y]
    x4 = line_two[:x2]
    y4 = line_two[:y2]

    uA = ((x4-x3)*(y1-y3) - (y4-y3)*(x1-x3)) / ((y4-y3)*(x2-x1) - (x4-x3)*(y2-y1))
    uB = ((x2-x1)*(y1-y3) - (y2-y1)*(x1-x3)) / ((y4-y3)*(x2-x1) - (x4-x3)*(y2-y1))

    uA >= 0 && uA <= 1 && uB >= 0 && uB <= 1
  end

  def reset_ball
    state.ball = nil
    state.ball_vector = nil
    state.rest = false
  end

  def debug
    outputs.labels << { x: 50.from_left, y: 50.from_top, text: "Entropy: #{entropy}"}
  end
end


def tick args
  $game ||= BouncingBall.new
  $game.args = args
  $game.tick
end

Physics And Collisions - Ramp Collision - main.rb

# ./samples/04_physics_and_collisions/12_ramp_collision/app/main.rb
# sample app shows how to do ramp collision
# based off of the writeup here:
# http://higherorderfun.com/blog/2012/05/20/the-guide-to-implementing-2d-platformers/

# NOTE: at the bottom of the file you'll find $gtk.reset_and_replay "replay.txt"
#       whenever you make changes to this file, a replay will automatically run so you can
#       see how your changes affected the game. Comment out the line at the bottom if you
#       don't want the replay to autmatically run.

# toolbar interaction is in a seperate file
require 'app/toolbar.rb'

def tick args
  tick_toolbar args
  tick_game args
end

def tick_game args
  game_defaults args
  game_input args
  game_calc args
  game_render args
end

def game_input args
  # if space is pressed or held (signifying a jump)
  if args.inputs.keyboard.space
    # change the player's dy to the jump power if the
    # player is not currently touching a ceiling
    if !args.state.player.on_ceiling
      args.state.player.dy = args.state.player.jump_power
      args.state.player.on_floor = false
      args.state.player.jumping = true
    end
  else
    # if the space key is released, then jumping is false
    # and the player will no longer be on the ceiling
    args.state.player.jumping = false
    args.state.player.on_ceiling = false
  end

  # set the player's dx value to the left/right input
  # NOTE: that the speed of the player's dx movement has
  #       a sensitive relation ship with collision detection.
  #       If you increase the speed of the player, you may
  #       need to tweak the collision code to compensate for
  #       the extra horizontal speed.
  args.state.player.dx = args.inputs.left_right * 2
end

def game_render args
  # for each terrain entry, render the line that represents the connection
  # from the tile's left_height to the tile's right_height
  args.outputs.primitives << args.state.terrain.map { |t| t.line }

  # determine if the player sprite needs to be flipped hoizontally
  flip_horizontally = args.state.player.facing == -1

  # render the player
  args.outputs.sprites << args.state.player.merge(flip_horizontally: flip_horizontally)

  args.outputs.labels << {
    x: 640,
    y: 100,
    alignment_enum: 1,
    text: "Left and Right to move player. Space to jump. Use the toolbar at the top to add more terrain."
  }

  args.outputs.labels << {
    x: 640,
    y: 60,
    alignment_enum: 1,
    text: "Click any existing terrain on the map to delete it."
  }
end

def game_calc args
  # set the direction the player is facing based on the
  # the dx value of the player
  if args.state.player.dx > 0
    args.state.player.facing = 1
  elsif args.state.player.dx < 0
    args.state.player.facing = -1
  end

  # preform the calcuation of ramp collision
  calc_collision args

  # reset the player if the go off screen
  calc_off_screen args
end

def game_defaults args
  # how much gravity is in the game
  args.state.gravity ||= 0.1

  # initialized the player to the center of the screen
  args.state.player ||= {
    x: 640,
    y: 360,
    w: 16,
    h: 16,
    dx: 0,
    dy: 0,
    jump_power: 3,
    path: 'sprites/square/blue.png',
    on_floor: false,
    on_ceiling: false,
    facing: 1
  }
end

def calc_collision args
  # increment the players x position by the dx value
  args.state.player.x += args.state.player.dx

  # if the player is not on the floor
  if !args.state.player.on_floor
    # then apply gravity
    args.state.player.dy -= args.state.gravity
    # clamp the max dy value to -12 to 12
    args.state.player.dy = args.state.player.dy.clamp(-12, 12)

    # update the player's y position by the dy value
    args.state.player.y += args.state.player.dy
  end

  # get all colisions between the player and the terrain
  collisions = args.state.geometry.find_all_intersect_rect args.state.player, args.state.terrain

  # if there are no collisions, then the player is not on the floor or ceiling
  # return from the method since there is nothing more to process
  if collisions.length == 0
    args.state.player.on_floor = false
    args.state.player.on_ceiling = false
    return
  end

  # set a local variable to the player since
  # we'll be accessing it a lot
  player = args.state.player

  # sort the collisions by the distance from the collision's center to the player's center
  sorted_collisions = collisions.sort_by do |collision|
    player_center = player.x + player.w / 2
    collision_center = collision.x + collision.w / 2
    (player_center - collision_center).abs
  end

  # define a one pixel wide rectangle that represents the center of the player
  # we'll use this value to determine the location of the player's feet on
  # a ramp
  player_center_rect = {
    x: player.x + player.w / 2 - 0.5,
    y: player.y,
    w: 1,
    h: player.h
  }

  # for each collision...
  sorted_collisions.each do |collision|
    # if the player doesn't intersect with the collision,
    # then set the player's on_floor and on_ceiling values to false
    # and continue to the next collision
    if !collision.intersect_rect? player_center_rect
      player.on_floor = false
      player.on_ceiling = false
      next
    end

    if player.dy < 0
      # if the player is falling
      # the percentage of the player's center relative to the collision
      # is a difference from the collision to the player (as opposed to the player to the collision)
      perc = (collision.x - player_center_rect.x) / player.w
      height_of_slope = collision.tile.left_height - collision.tile.right_height

      new_y = (collision.y + collision.tile.left_height + height_of_slope * perc)
      diff = new_y - player.y

      if diff < 0
        # if the current fall rate of the player is less than the difference
        # of the player's new y position and the player's current y position
        # then don't set the player's y position to the new y position
        # and wait for another application of gravity to bring the player a little
        # closer
        if player.dy.abs >= diff.abs
          # if the player's current fall speed can cover the distance to the
          # new y position, then set the player's y position to the new y position
          # and mark them as being on the floor so that gravity no longer get's processed
          player.y = new_y
          player.on_floor = true

          # given the player's speed, set the player's dy to a value that will
          # keep them from bouncing off the floor when the ramp is steep
          # NOTE: if you change the player's speed, then this value will need to be adjusted
          #       to keep the player from bouncing off the floor
          player.dy = -1
        end
      elsif diff > 0 && diff < 8
        # there's a small edge case where collision may be processed from
        # below the terrain (eg when the player is jumping up and hitting the
        # ramp from below). The moment when jump is released, the player's dy
        # value could result in the player tunneling through the terrain,
        # and get popped on to the top side.

        # testing to make sure the distance that will be displaced is less than
        # 8 pixels will keep this tunneling from happening
        player.y = new_y
        player.on_floor = true

        # given the player's speed, set the player's dy to a value that will
        # keep them from bouncing off the floor when the ramp is steep
        # NOTE: if you change the player's speed, then this value will need to be adjusted
        #       to keep the player from bouncing off the floor
        player.dy = -1
      end
    elsif player.dy > 0
      # if the player is jumping
      # the percentage of the player's center relative to the collision
      # is a difference is reversed from the player to the collision (as opposed to the player to the collision)
      perc = (player_center_rect.x - collision.x) / player.w

      # the height of the slope is also reversed when approaching the collision from the bottom
      height_of_slope = collision.tile.right_height - collision.tile.left_height

      new_y = collision.y + collision.tile.left_height + height_of_slope * perc

      # since this collision is being processed from below, the difference
      # between the current players position and the new y position is
      # based off of the player's top position (their head)
      player_top = player.y + player.h

      diff = new_y - player_top

      # we also need to calculate the difference between the player's bottom
      # and the new position. This will be used to determine if the player
      # can jump from the new_y position
      diff_bottom = new_y - player.y


      # if the player's current rising speed can cover the distance to the
      # new y position, then set the player's y position to the new y position
      # an mark them as being on the floor so that gravity no longer get's processed
      can_cover_distance_to_new_y = player.dy >= diff.abs && player.dy.sign == diff.sign

      # another scenario that needs to be covered is if the player's top is already passed
      # the new_y position (their rising speed made them partially clip through the collision)
      player_top_above_new_y = player_top > new_y

      # if either of the conditions above is true then we want to set the player's y position
      if can_cover_distance_to_new_y || player_top_above_new_y
        # only set the player's y position to the new y position if the player's
        # cannot escape the collision by jumping up from the new_y position
        if diff_bottom >= player.jump_power
          player.y = new_y.floor - player.h

          # after setting the new_y position, we need to determine if the player
          # if the player is touching the ceiling or not
          # touching the ceiling disables the ability for the player to jump/increase
          # their dy value any more than it already is
          if player.jumping
            # disable jumping if the player is currently moving upwards
            player.on_ceiling = true

            # NOTE: if you change the player's speed, then this value will need to be adjusted
            #       to keep the player from bouncing off the ceiling as they move right and left
            player.dy = 1
          else
            # if the player is not currently jumping, then set their dy to 0
            # so they can immediately start falling after the collision
            # this also means that they are no longer on the ceiling and can jump again
            player.dy = 0
            player.on_ceiling = false
          end
        end
      end
    end
  end
end

def calc_off_screen args
  below_screen = args.state.player.y + args.state.player.h < 0
  above_screen = args.state.player.y > 720 + args.state.player.h
  off_screen_left = args.state.player.x + args.state.player.w < 0
  off_screen_right = args.state.player.x > 1280

  # if the player is off the screen, then reset them to the top of the screen
  if below_screen || above_screen || off_screen_left || off_screen_right
    args.state.player.x = 640
    args.state.player.y = 720
    args.state.player.dy = 0
    args.state.player.on_floor = false
  end
end

$gtk.reset_and_replay "replay.txt", speed: 2

Physics And Collisions - Ramp Collision - toolbar.rb

# ./samples/04_physics_and_collisions/12_ramp_collision/app/toolbar.rb
def tick_toolbar args
  # ================================================
  # tollbar defaults
  # ================================================
  if !args.state.toolbar
    # these are the tiles you can select from
    tile_definitions = [
      { name: "16-12", left_height: 16, right_height: 12  },
      { name: "12-8",  left_height: 12, right_height: 8   },
      { name: "8-4",   left_height: 8,  right_height: 4   },
      { name: "4-0",   left_height: 4,  right_height: 0   },
      { name: "0-4",   left_height: 0,  right_height: 4   },
      { name: "4-8",   left_height: 4,  right_height: 8   },
      { name: "8-12",  left_height: 8,  right_height: 12  },
      { name: "12-16", left_height: 12, right_height: 16  },

      { name: "16-8",  left_height: 16, right_height: 8   },
      { name: "8-0",   left_height: 8,  right_height: 0   },
      { name: "0-8",   left_height: 0,  right_height: 8   },
      { name: "8-16",  left_height: 8,  right_height: 16  },

      { name: "0-0",   left_height: 0,  right_height: 0   },
      { name: "8-8",   left_height: 8,  right_height: 8   },
      { name: "16-16", left_height: 16, right_height: 16  },
    ]

    # toolbar data representation which will be used to render the toolbar.
    # the buttons array will be used to render the buttons
    # the toolbar_rect will be used to restrict the creation of tiles
    # within the toolbar area
    args.state.toolbar = {
      toolbar_rect: nil,
      buttons: []
    }

    # for each tile definition, create a button
    args.state.toolbar.buttons = tile_definitions.map_with_index do |spec, index|
      left_height  = spec.left_height
      right_height = spec.right_height
      button_size  = 48
      column_size  = 15
      column_padding = 2
      column = index % column_size
      column_padding = column * column_padding
      margin = 10
      row = index.idiv(column_size)
      row_padding = row * 2
      x = margin + column_padding + (column * button_size)
      y = (margin + button_size + row_padding + (row * button_size)).from_top

      # when a tile is added, the data of this button will be used
      # to construct the terrain

      # each tile has an x, y, w, h which represents the bounding box
      # of the button.
      # the button also contains the left_height and right_height which is
      # important when determining collision of the ramps
      {
        name: spec.name,
        left_height: left_height,
        right_height: right_height,
        button_rect: {
          x: x,
          y: y,
          w: 48,
          h: 48
        }
      }
    end

    # with the buttons populated, compute the bounding box of the entire
    # toolbar (again this will be used to restrict the creation of tiles)
    min_x = args.state.toolbar.buttons.map { |t| t.button_rect.x }.min
    min_y = args.state.toolbar.buttons.map { |t| t.button_rect.y }.min

    max_x = args.state.toolbar.buttons.map { |t| t.button_rect.x }.max
    max_y = args.state.toolbar.buttons.map { |t| t.button_rect.y }.max

    args.state.toolbar.rect = {
      x: min_x - 10,
      y: min_y - 10,
      w: max_x - min_x + 10 + 64,
      h: max_y - min_y + 10 + 64
    }
  end

  # set the selected tile to the last button in the toolbar
  args.state.selected_tile ||= args.state.toolbar.buttons.last

  # ================================================
  # starting terrain generation
  # ================================================
  if !args.state.terrain
    world = [
      { row: 14, col: 25, name: "0-8"   },
      { row: 14, col: 26, name: "8-16"  },
      { row: 15, col: 27, name: "0-8"   },
      { row: 15, col: 28, name: "8-16"  },
      { row: 16, col: 29, name: "0-8"   },
      { row: 16, col: 30, name: "8-16"  },
      { row: 17, col: 31, name: "0-8"   },
      { row: 17, col: 32, name: "8-16"  },
      { row: 18, col: 33, name: "0-8"   },
      { row: 18, col: 34, name: "8-16"  },
      { row: 18, col: 35, name: "16-12" },
      { row: 18, col: 36, name: "12-8"  },
      { row: 18, col: 37, name: "8-4"   },
      { row: 18, col: 38, name: "4-0"   },
      { row: 18, col: 39, name: "0-0"   },
      { row: 18, col: 40, name: "0-0"   },
      { row: 18, col: 41, name: "0-0"   },
      { row: 18, col: 42, name: "0-4"   },
      { row: 18, col: 43, name: "4-8"   },
      { row: 18, col: 44, name: "8-12"  },
      { row: 18, col: 45, name: "12-16" },
    ]

    args.state.terrain = world.map do |tile|
      template = tile_by_name(args, tile.name)
      next if !template
      grid_rect = grid_rect_for(tile.row, tile.col)
      new_terrain_definition(grid_rect, template)
    end
  end

  # ================================================
  # toolbar input and rendering
  # ================================================
  # store the mouse position alligned to the tile grid
  mouse_grid_aligned_rect = grid_aligned_rect args.inputs.mouse, 16

  # determine if the mouse intersects the toolbar
  mouse_intersects_toolbar = args.state.toolbar.rect.intersect_rect? args.inputs.mouse

  # determine if the mouse intersects a toolbar button
  toolbar_button = args.state.toolbar.buttons.find { |t| t.button_rect.intersect_rect? args.inputs.mouse }

  # determine if the mouse click occurred over a tile in the terrain
  terrain_tile = args.geometry.find_intersect_rect mouse_grid_aligned_rect, args.state.terrain


  # if a mouse click occurs....
  if args.inputs.mouse.click
    if toolbar_button
      # if a toolbar button was clicked, set the currently selected tile to the toolbar tile
      args.state.selected_tile = toolbar_button
    elsif terrain_tile
      # if a tile was clicked, delete it from the terrain
      args.state.terrain.delete terrain_tile
    elsif !args.state.toolbar.rect.intersect_rect? args.inputs.mouse
      # if the mouse was not clicked in the toolbar area
      # add a new terrain based off of the information in the selected tile
      args.state.terrain << new_terrain_definition(mouse_grid_aligned_rect, args.state.selected_tile)
    end
  end

  # render a light blue background for the toolbar button that is currently
  # being hovered over (if any)
  if toolbar_button
    args.outputs.primitives << toolbar_button.button_rect.merge(primitive_marker: :solid, a: 10, b: 255)
  end

  # put a blue background around the currently selected tile
  args.outputs.primitives << args.state.selected_tile.button_rect.merge(primitive_marker: :solid, b: 255)

  if !mouse_intersects_toolbar
    if terrain_tile
      # if the mouse is hoving over an existing terrain tile, render a red border around the
      # tile to signify that it will be deleted if the mouse is clicked
      args.outputs.borders << terrain_tile.merge(a: 255, r: 255)
    else
      # if the mouse is not hovering over an existing terrain tile, render the currently
      # selected tile at the mouse position
      grid_aligned_rect = grid_aligned_rect args.inputs.mouse, 16

      args.outputs.solids << {
        **grid_aligned_rect,
        a: 30,
        g: 128
      }

      args.outputs.lines << {
        x:  grid_aligned_rect.x,
        y:  grid_aligned_rect.y + args.state.selected_tile.left_height,
        x2: grid_aligned_rect.x + grid_aligned_rect.w,
        y2: grid_aligned_rect.y + args.state.selected_tile.right_height,
      }
    end
  end

  # render each toolbar button using two primitives, a border to denote
  # the click area of the button, and a line to denote the terrain that
  # will be created when the button is clicked
  args.outputs.primitives << args.state.toolbar.buttons.map do |toolbar_tile|
    primitives = []
    scale = toolbar_tile.button_rect.w / 16

    primitive_type = :border

    [
      {
        **toolbar_tile.button_rect,
        primitive_marker: primitive_type,
        a: 64,
      },
      {
        x:  toolbar_tile.button_rect.x,
        y:  toolbar_tile.button_rect.y + toolbar_tile.left_height * scale,
        x2: toolbar_tile.button_rect.x + toolbar_tile.button_rect.w,
        y2: toolbar_tile.button_rect.y + toolbar_tile.right_height * scale
      }
    ]
  end
end

# ================================================
# helper methods
#=================================================

# converts a row and column on the grid to
# a rect
def grid_rect_for row, col
  { x: col * 16, y: row * 16, w: 16, h: 16 }
end

# find a tile by name
def tile_by_name args, name
  args.state.toolbar.buttons.find { |b| b.name == name }
end

# data structure containing terrain information
# specifcially tile.left_height and tile.right_height
def new_terrain_definition grid_rect, tile
  grid_rect.merge(
    tile: tile,
    line: {
      x:  grid_rect.x,
      y:  grid_rect.y + tile.left_height,
      x2: grid_rect.x + grid_rect.w,
      y2: grid_rect.y + tile.right_height
    }
  )
end

# helper method that returns a grid aligned rect given
# an arbitrary rect and a grid size
def grid_aligned_rect point, size
  grid_aligned_x = point.x - (point.x % size)
  grid_aligned_y = point.y - (point.y % size)
  { x: grid_aligned_x.to_i, y: grid_aligned_y.to_i, w: size.to_i, h: size.to_i }
end

Mouse - Mouse Click - main.rb

# ./samples/05_mouse/01_mouse_click/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - product: Returns an array of all combinations of elements from all arrays.

   For example, [1,2].product([1,2]) would return the following array...
   [[1,1], [1,2], [2,1], [2,2]]
   More than two arrays can be given to product and it will still work,
   such as [1,2].product([1,2],[3,4]). What would product return in this case?

   Answer:
   [[1,1,3],[1,1,4],[1,2,3],[1,2,4],[2,1,3],[2,1,4],[2,2,3],[2,2,4]]

 - num1.fdiv(num2): Returns the float division (will have a decimal) of the two given numbers.
   For example, 5.fdiv(2) = 2.5 and 5.fdiv(5) = 1.0

 - yield: Allows you to call a method with a code block and yield to that block.

 Reminders:

 - ARRAY#inside_rect?: Returns true or false depending on if the point is inside the rect.

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

 - args.inputs.mouse.click: This property will be set if the mouse was clicked.

 - Ternary operator (?): Will evaluate a statement (just like an if statement)
   and perform an action if the result is true or another action if it is false.

 - reject: Removes elements from a collection if they meet certain requirements.

 - args.outputs.borders: An array. The values generate a border.
   The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]
   For more information about borders, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.labels: An array. The values generate a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.

=end

# This sample app is a classic game of Tic Tac Toe.

class TicTacToe
  attr_accessor :_, :state, :outputs, :inputs, :grid, :gtk

  # Starts the game with player x's turn and creates an array (to_a) for space combinations.
  # Calls methods necessary for the game to run properly.
  def tick
    init_new_game
    render_board
    input_board
  end

  def init_new_game
    state.current_turn       ||= :x
    state.space_combinations ||= [-1, 0, 1].product([-1, 0, 1]).to_a

    state.spaces             ||= {}

    state.space_combinations.each do |x, y|
      state.spaces[x]    ||= {}
      state.spaces[x][y] ||= state.new_entity(:space)
    end
  end

  # Uses borders to create grid squares for the game's board. Also outputs the game pieces using labels.
  def render_board
    square_size = 80

    # Positions the game's board in the center of the screen.
    # Try removing what follows grid.w_half or grid.h_half and see how the position changes!
    board_left = grid.w_half - square_size * 1.5
    board_top  = grid.h_half - square_size * 1.5

    # At first glance, the add(1) looks pretty trivial. But if you remove it,
    # you'll see that the positioning of the board would be skewed without it!
    # Or if you put 2 in the parenthesis, the pieces will be placed in the wrong squares
    # due to the change in board placement.
    outputs.borders << all_spaces do |x, y, space| # outputs borders for all board spaces
      space.border ||= [
        board_left + x.add(1) * square_size, # space.border is initialized using this definition
        board_top  + y.add(1) * square_size,
        square_size,
        square_size
      ]
    end

    # Again, the calculations ensure that the piece is placed in the center of the grid square.
    # Remove the '- 20' and the piece will be placed at the top of the grid square instead of the center.
    outputs.labels << filled_spaces do |x, y, space| # put label in each filled space of board
          label board_left + x.add(1) * square_size + square_size.fdiv(2),
          board_top  + y.add(1) * square_size + square_size - 20,
          space.piece # text of label, either "x" or "o"
    end

    # Uses a label to output whether x or o won, or if a draw occurred.
    # If the game is ongoing, a label shows whose turn it currently is.
    outputs.labels << if state.x_won
                        label grid.w_half, grid.top - 80, "x won" # the '-80' positions the label 80 pixels lower than top
                      elsif state.o_won
                        label grid.w_half, grid.top - 80, "o won" # grid.w_half positions the label in the center horizontally
                      elsif state.draw
                        label grid.w_half, grid.top - 80, "a draw"
                      else # if no one won and the game is ongoing
                        label grid.w_half, grid.top - 80, "turn: #{state.current_turn}"
                      end
  end

  # Calls the methods responsible for handling user input and determining the winner.
  # Does nothing unless the mouse is clicked.
  def input_board
    return unless inputs.mouse.click
    input_place_piece
    input_restart_game
    determine_winner
  end

  # Handles user input for placing pieces on the board.
  def input_place_piece
    return if state.game_over

    # Checks to find the space that the mouse was clicked inside of, and makes sure the space does not already
    # have a piece in it.
    __, __, space = all_spaces.find do |__, __, space|
      inputs.mouse.click.point.inside_rect?(space.border) && !space.piece
    end

    # The piece that goes into the space belongs to the player whose turn it currently is.
    return unless space
    space.piece = state.current_turn

    # This ternary operator statement allows us to change the current player's turn.
    # If it is currently x's turn, it becomes o's turn. If it is not x's turn, it become's x's turn.
    state.current_turn = state.current_turn == :x ? :o : :x
  end

  # Resets the game.
  def input_restart_game
    return unless state.game_over
    gtk.reset
    init_new_game
  end

  # Checks if x or o won the game.
  # If neither player wins and all nine squares are filled, a draw happens.
  # Once a player is chosen as the winner or a draw happens, the game is over.
  def determine_winner
    state.x_won = won? :x # evaluates to either true or false (boolean values)
    state.o_won = won? :o
    state.draw = true if filled_spaces.length == 9 && !state.x_won && !state.o_won
    state.game_over = state.x_won || state.o_won || state.draw
  end

  # Determines if a player won by checking if there is a horizontal match or vertical match.
  # Horizontal_match and vertical_match have boolean values. If either is true, the game has been won.
  def won? piece
    # performs action on all space combinations
    won = [[-1, 0, 1]].product([-1, 0, 1]).map do |xs, y|

      # Checks if the 3 grid spaces with the same y value (or same row) and
      # x values that are next to each other have pieces that belong to the same player.
      # Remember, the value of piece is equal to the current turn (which is the player).
      horizontal_match = state.spaces[xs[0]][y].piece == piece &&
                         state.spaces[xs[1]][y].piece == piece &&
                         state.spaces[xs[2]][y].piece == piece

      # Checks if the 3 grid spaces with the same x value (or same column) and
      # y values that are next to each other have pieces that belong to the same player.
      # The && represents an "and" statement: if even one part of the statement is false,
      # the entire statement evaluates to false.
      vertical_match = state.spaces[y][xs[0]].piece == piece &&
                       state.spaces[y][xs[1]].piece == piece &&
                       state.spaces[y][xs[2]].piece == piece

      horizontal_match || vertical_match # if either is true, true is returned
    end

    # Sees if there is a diagonal match, starting from the bottom left and ending at the top right.
    # Is added to won regardless of whether the statement is true or false.
    won << (state.spaces[-1][-1].piece == piece && # bottom left
            state.spaces[ 0][ 0].piece == piece && # center
            state.spaces[ 1][ 1].piece == piece)   # top right

    # Sees if there is a diagonal match, starting at the bottom right and ending at the top left
    # and is added to won.
    won << (state.spaces[ 1][-1].piece == piece && # bottom right
            state.spaces[ 0][ 0].piece == piece && # center
            state.spaces[-1][ 1].piece == piece)   # top left

    # Any false statements (meaning false diagonal matches) are rejected from won
    won.reject_false.any?
  end

  # Defines filled spaces on the board by rejecting all spaces that do not have game pieces in them.
  # The ! before a statement means "not". For example, we are rejecting any space combinations that do
  # NOT have pieces in them.
  def filled_spaces
    state.space_combinations
      .reject { |x, y| !state.spaces[x][y].piece } # reject spaces with no pieces in them
      .map do |x, y|
        if block_given?
          yield x, y, state.spaces[x][y]
        else
          [x, y, state.spaces[x][y]] # sets definition of space
        end
    end
  end

  # Defines all spaces on the board.
  def all_spaces
    if !block_given?
      state.space_combinations.map do |x, y|
        [x, y, state.spaces[x][y]] # sets definition of space
      end
    else # if a block is given (block_given? is true)
      state.space_combinations.map do |x, y|
        yield x, y, state.spaces[x][y] # yield if a block is given
      end
    end
  end

  # Sets values for a label, such as the position, value, size, alignment, and color.
  def label x, y, value
    [x, y + 10, value, 20, 1, 0, 0, 0]
  end
end

$tic_tac_toe = TicTacToe.new

def tick args
  $tic_tac_toe._       = args
  $tic_tac_toe.state   = args.state
  $tic_tac_toe.outputs = args.outputs
  $tic_tac_toe.inputs  = args.inputs
  $tic_tac_toe.grid    = args.grid
  $tic_tac_toe.gtk     = args.gtk
  $tic_tac_toe.tick
  tick_instructions args, "Sample app shows how to work with mouse clicks."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Mouse - Mouse Move - main.rb

# ./samples/05_mouse/02_mouse_move/app/main.rb
=begin

 Reminders:

 - num1.greater(num2): Returns the greater value.
   For example, if we have the command
   puts 4.greater(3)
   the number 4 would be printed to the console since it has a greater value than 3.
   Similar to lesser, which returns the lesser value.

 - find_all: Finds all elements of a collection that meet certain requirements.
   For example, in this sample app, we're using find_all to find all zombies that have intersected
   or hit the player's sprite since these zombies have been killed.

 - args.inputs.keyboard.key_down.KEY: Determines if a key is being held or pressed.
   Stores the frame the "down" event occurred.
   For more information about the keyboard, go to mygame/documentation/06-keyboard.md.

 - args.outputs.sprites: An array. The values generate a sprite.
   The parameters are [X, Y, WIDTH, HEIGHT, PATH, ANGLE, ALPHA, RED, GREEN, BLUE]
   For more information about sprites, go to mygame/documentation/05-sprites.md.

 - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
   When we want to create a new object, we can declare it as a new entity and then define
   its properties. (Remember, you can use state to define ANY property and it will
   be retained across frames.)

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

 - map: Ruby method used to transform data; used in arrays, hashes, and collections.
   Can be used to perform an action on every element of a collection, such as multiplying
   each element by 2 or declaring every element as a new entity.

 - sample: Chooses a random element from the array.

 - reject: Removes elements that meet certain requirements.
   In this sample app, we're removing/rejecting zombies that reach the center of the screen. We're also
   rejecting zombies that were killed more than 30 frames ago.

=end

# This sample app allows users to move around the screen in order to kill zombies. Zombies appear from every direction so the goal
# is to kill the zombies as fast as possible!

class ProtectThePuppiesFromTheZombies
  attr_accessor :grid, :inputs, :state, :outputs

  # Calls the methods necessary for the game to run properly.
  def tick
    defaults
    render
    calc
    input
  end

  # Sets default values for the zombies and for the player.
  # Initialization happens only in the first frame.
  def defaults
    state.flash_at               ||= 0
    state.zombie_min_spawn_rate  ||= 60
    state.zombie_spawn_countdown ||= random_spawn_countdown state.zombie_min_spawn_rate
    state.zombies                ||= []
    state.killed_zombies         ||= []

    # Declares player as a new entity and sets its properties.
    # The player begins the game in the center of the screen, not moving in any direction.
    state.player ||= state.new_entity(:player, { x: 640,
                                               y: 360,
                                               attack_angle: 0,
                                               dx: 0,
                                               dy: 0 })
  end

  # Outputs a gray background.
  # Calls the methods needed to output the player, zombies, etc onto the screen.
  def render
    outputs.solids << [grid.rect, 100, 100, 100]
    render_zombies
    render_killed_zombies
    render_player
    render_flash
  end

  # Outputs the zombies on the screen and sets values for the sprites, such as the position, width, height, and animation.
  def render_zombies
    outputs.sprites << state.zombies.map do |z| # performs action on all zombies in the collection
      z.sprite = [z.x, z.y, 4 * 3, 8 * 3, animation_sprite(z)].sprite # sets definition for sprite, calls animation_sprite method
      z.sprite
    end
  end

  # Outputs sprites of killed zombies, and displays a slash image to show that a zombie has been killed.
  def render_killed_zombies
    outputs.sprites << state.killed_zombies.map do |z| # performs action on all killed zombies in collection
      z.sprite = [z.x,
                  z.y,
                  4 * 3,
                  8 * 3,
                  animation_sprite(z, z.death_at), # calls animation_sprite method
                  0, # angle
                  255 * z.death_at.ease(30, :flip)].sprite # transparency of a zombie changes when they die
                  # change the value of 30 and see what happens when a zombie is killed

      # Sets values to output the slash over the zombie's sprite when a zombie is killed.
      # The slash is tilted 45 degrees from the angle of the player's attack.
      # Change the 3 inside scale_rect to 30 and the slash will be HUGE! Scale_rect positions
      # the slash over the killed zombie's sprite.
      [z.sprite, [z.sprite.rect, 'sprites/slash.png', 45 + state.player.attack_angle_on_click, z.sprite.a].scale_rect(3, 0.5, 0.5)]
    end
  end

  # Outputs the player sprite using the images in the sprites folder.
  def render_player
    state.player_sprite = [state.player.x,
                           state.player.y,
                          4 * 3,
                          8 * 3, "sprites/player-#{animation_index(state.player.created_at_elapsed)}.png"] # string interpolation
    outputs.sprites << state.player_sprite

    # Outputs a small red square that previews the angles that the player can attack in.
    # It can be moved in a perfect circle around the player to show possible movements.
    # Change the 60 in the parenthesis and see what happens to the movement of the red square.
    outputs.solids <<  [state.player.x + state.player.attack_angle.vector_x(60),
                        state.player.y + state.player.attack_angle.vector_y(60),
                        3, 3, 255, 0, 0]
  end

  # Renders flash as a solid. The screen turns white for 10 frames when a zombie is killed.
  def render_flash
    return if state.flash_at.elapsed_time > 10 # return if more than 10 frames have passed since flash.
    # Transparency gradually changes (or eases) during the 10 frames of flash.
    outputs.primitives << [grid.rect, 255, 255, 255, 255 * state.flash_at.ease(10, :flip)].solid
  end

  # Calls all methods necessary for performing calculations.
  def calc
    calc_spawn_zombie
    calc_move_zombies
    calc_player
    calc_kill_zombie
  end

  # Decreases the zombie spawn countdown by 1 if it has a value greater than 0.
  def calc_spawn_zombie
    if state.zombie_spawn_countdown > 0
      state.zombie_spawn_countdown -= 1
      return
    end

    # New zombies are created, positioned on the screen, and added to the zombies collection.
    state.zombies << state.new_entity(:zombie) do |z| # each zombie is declared a new entity
      if rand > 0.5
        z.x = grid.rect.w.randomize(:ratio) # random x position on screen (within grid scope)
        z.y = [-10, 730].sample # y position is set to either -10 or 730 (randomly chosen)
        # the possible values exceed the screen's scope so zombies appear to be coming from far away
      else
        z.x = [-10, 1290].sample # x position is set to either -10 or 1290 (randomly chosen)
        z.y = grid.rect.w.randomize(:ratio) # random y position on screen
      end
    end

    # Calls random_spawn_countdown method (determines how fast new zombies appear)
    state.zombie_spawn_countdown = random_spawn_countdown state.zombie_min_spawn_rate
    state.zombie_min_spawn_rate -= 1
    # set to either the current zombie_min_spawn_rate or 0, depending on which value is greater
    state.zombie_min_spawn_rate  = state.zombie_min_spawn_rate.greater(0)
  end

  # Moves all zombies towards the center of the screen.
  # All zombies that reach the center (640, 360) are rejected from the zombies collection and disappear.
  def calc_move_zombies
    state.zombies.each do |z| # for each zombie in the collection
      z.y = z.y.towards(360, 0.1) # move the zombie towards the center (640, 360) at a rate of 0.1
      z.x = z.x.towards(640, 0.1) # change 0.1 to 1.1 and see how much faster the zombies move to the center
    end
    state.zombies = state.zombies.reject { |z| z.y == 360 && z.x == 640 } # remove zombies that are in center
  end

  # Calculates the position and movement of the player on the screen.
  def calc_player
    state.player.x += state.player.dx # changes x based on dx (change in x)
    state.player.y += state.player.dy # changes y based on dy (change in y)

    state.player.dx *= 0.9 # scales dx down
    state.player.dy *= 0.9 # scales dy down

    # Compares player's x to 1280 to find lesser value, then compares result to 0 to find greater value.
    # This ensures that the player remains within the screen's scope.
    state.player.x = state.player.x.lesser(1280).greater(0)
    state.player.y = state.player.y.lesser(720).greater(0) # same with player's y
  end

  # Finds all zombies that intersect with the player's sprite. These zombies are removed from the zombies collection
  # and added to the killed_zombies collection since any zombie that intersects with the player is killed.
  def calc_kill_zombie

    # Find all zombies that intersect with the player. They are considered killed.
    killed_this_frame = state.zombies.find_all { |z| z.sprite && (z.sprite.intersect_rect? state.player_sprite) }
    state.zombies = state.zombies - killed_this_frame # remove newly killed zombies from zombies collection
    state.killed_zombies += killed_this_frame # add newly killed zombies to killed zombies

    if killed_this_frame.length > 0 # if atleast one zombie was killed in the frame
      state.flash_at = state.tick_count # flash_at set to the frame when the zombie was killed
    # Don't forget, the rendered flash lasts for 10 frames after the zombie is killed (look at render_flash method)
    end

    # Sets the tick_count (passage of time) as the value of the death_at variable for each killed zombie.
    # Death_at stores the frame a zombie was killed.
    killed_this_frame.each do |z|
      z.death_at = state.tick_count
    end

    # Zombies are rejected from the killed_zombies collection depending on when they were killed.
    # They are rejected if more than 30 frames have passed since their death.
    state.killed_zombies = state.killed_zombies.reject { |z| state.tick_count - z.death_at > 30 }
  end

  # Uses input from the user to move the player around the screen.
  def input

    # If the "a" key or left key is pressed, the x position of the player decreases.
    # Otherwise, if the "d" key or right key is pressed, the x position of the player increases.
    if inputs.keyboard.key_held.a || inputs.keyboard.key_held.left
      state.player.x -= 5
    elsif inputs.keyboard.key_held.d || inputs.keyboard.key_held.right
      state.player.x += 5
    end

    # If the "w" or up key is pressed, the y position of the player increases.
    # Otherwise, if the "s" or down key is pressed, the y position of the player decreases.
    if inputs.keyboard.key_held.w || inputs.keyboard.key_held.up
      state.player.y += 5
    elsif inputs.keyboard.key_held.s || inputs.keyboard.key_held.down
      state.player.y -= 5
    end

    # Sets the attack angle so the player can move and attack in the precise direction it wants to go.
    # If the mouse is moved, the attack angle is changed (based on the player's position and mouse position).
    # Attack angle also contributes to the position of red square.
    if inputs.mouse.moved
      state.player.attack_angle = inputs.mouse.position.angle_from [state.player.x, state.player.y]
    end

    if inputs.mouse.click && state.player.dx < 0.5 && state.player.dy < 0.5
      state.player.attack_angle_on_click = inputs.mouse.position.angle_from [state.player.x, state.player.y]
      state.player.attack_angle = state.player.attack_angle_on_click # player's attack angle is set
      state.player.dx = state.player.attack_angle.vector_x(25) # change in player's position
      state.player.dy = state.player.attack_angle.vector_y(25)
    end
  end

  # Sets the zombie spawn's countdown to a random number.
  # How fast zombies appear (change the 60 to 6 and too many zombies will appear at once!)
  def random_spawn_countdown minimum
    10.randomize(:ratio, :sign).to_i + 60
  end

  # Helps to iterate through the images in the sprites folder by setting the animation index.
  # 3 frames is how long to show an image, and 6 is how many images to flip through.
  def animation_index at
    at.idiv(3).mod(6)
  end

  # Animates the zombies by using the animation index to go through the images in the sprites folder.
  def animation_sprite zombie, at = nil
    at ||= zombie.created_at_elapsed # how long it is has been since a zombie was created
    index = animation_index at
    "sprites/zombie-#{index}.png" # string interpolation to iterate through images
  end
end

$protect_the_puppies_from_the_zombies = ProtectThePuppiesFromTheZombies.new

def tick args
  $protect_the_puppies_from_the_zombies.grid    = args.grid
  $protect_the_puppies_from_the_zombies.inputs  = args.inputs
  $protect_the_puppies_from_the_zombies.state    = args.state
  $protect_the_puppies_from_the_zombies.outputs = args.outputs
  $protect_the_puppies_from_the_zombies.tick
  tick_instructions args, "How to get the mouse position and translate it to an x, y position using .vector_x and .vector_y. CLICK to play."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Mouse - Mouse Move Paint App - main.rb

# ./samples/05_mouse/03_mouse_move_paint_app/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - Floor: Method that returns an integer number smaller than or equal to the original with no decimal.

   For example, if we have a variable, a = 13.7, and we called floor on it, it would look like this...
   puts a.floor()
   which would print out 13.
   (There is also a ceil method, which returns an integer number greater than or equal to the original
   with no decimal. If we had called ceil on the variable a, the result would have been 14.)

 Reminders:

 - Hashes: Collection of unique keys and their corresponding values. The value can be found
   using their keys.

   For example, if we have a "numbers" hash that stores numbers in English as the
   key and numbers in Spanish as the value, we'd have a hash that looks like this...
   numbers = { "one" => "uno", "two" => "dos", "three" => "tres" }
   and on it goes.

   Now if we wanted to find the corresponding value of the "one" key, we could say
   puts numbers["one"]
   which would print "uno" to the console.

 - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
   In this sample app, new_entity is used to create a new button that clears the grid.
   (Remember, you can use state to define ANY property and it will be retained across frames.)

 - args.inputs.mouse.click.point.(x|y): The x and y location of the mouse.

 - args.inputs.mouse.click.point.created_at: The frame the mouse click occurred in.

 - args.outputs.labels: An array. The values in the array generate a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.

 - ARRAY#inside_rect?: Returns true or false depending on if the point is inside the rect.

=end

# This sample app shows an empty grid that the user can paint on.
# To paint, the user must keep their mouse presssed and drag it around the grid.
# The "clear" button allows users to clear the grid so they can start over.

class PaintApp
  attr_accessor :inputs, :state, :outputs, :grid, :args

  # Runs methods necessary for the game to function properly.
  def tick
    print_title
    add_grid
    check_click
    draw_buttons
  end

  # Prints the title onto the screen by using a label.
  # Also separates the title from the grid with a line as a horizontal separator.
  def print_title
    args.outputs.labels << [ 640, 700, 'Paint!', 0, 1 ]
    outputs.lines << horizontal_separator(660, 0, 1280)
  end

  # Sets the starting position, ending position, and color for the horizontal separator.
  # The starting and ending positions have the same y values.
  def horizontal_separator y, x, x2
    [x, y, x2, y, 150, 150, 150]
  end

  # Sets the starting position, ending position, and color for the vertical separator.
  # The starting and ending positions have the same x values.
  def vertical_separator x, y, y2
    [x, y, x, y2, 150, 150, 150]
  end

  # Outputs a border and a grid containing empty squares onto the screen.
  def add_grid

    # Sets the x, y, height, and width of the grid.
    # There are 31 horizontal lines and 31 vertical lines in the grid.
    # Feel free to count them yourself before continuing!
    x, y, h, w = 640 - 500/2, 640 - 500, 500, 500 # calculations done so the grid appears in screen's center
    lines_h = 31
    lines_v = 31

    # Sets values for the grid's border, grid lines, and filled squares.
    # The filled_squares variable is initially set to an empty array.
    state.grid_border ||= [ x, y, h, w ] # definition of grid's outer border
    state.grid_lines ||= draw_grid(x, y, h, w, lines_h, lines_v) # calls draw_grid method
    state.filled_squares ||= [] # there are no filled squares until the user fills them in

    # Outputs the grid lines, border, and filled squares onto the screen.
    outputs.lines.concat state.grid_lines
    outputs.borders << state.grid_border
    outputs.solids << state.filled_squares
  end

  # Draws the grid by adding in vertical and horizontal separators.
  def draw_grid x, y, h, w, lines_h, lines_v

    # The grid starts off empty.
    grid = []

    # Calculates the placement and adds horizontal lines or separators into the grid.
    curr_y = y # start at the bottom of the box
    dist_y = h / (lines_h + 1) # finds distance to place horizontal lines evenly throughout 500 height of grid
    lines_h.times do
      curr_y += dist_y # increment curr_y by the distance between the horizontal lines
      grid << horizontal_separator(curr_y, x, x + w - 1) # add a separator into the grid
    end

    # Calculates the placement and adds vertical lines or separators into the grid.
    curr_x = x # now start at the left of the box
    dist_x = w / (lines_v + 1) # finds distance to place vertical lines evenly throughout 500 width of grid
    lines_v.times do
      curr_x += dist_x # increment curr_x by the distance between the vertical lines
      grid << vertical_separator(curr_x, y + 1, y  + h) # add separator
    end

    # paint_grid uses a hash to assign values to keys.
    state.paint_grid ||= {"x" => x, "y" => y, "h" => h, "w" => w, "lines_h" => lines_h,
                          "lines_v" => lines_v, "dist_x" => dist_x,
                          "dist_y" => dist_y }

    return grid
  end

  # Checks if the user is keeping the mouse pressed down and sets the mouse_hold variable accordingly using boolean values.
  # If the mouse is up, the user cannot drag the mouse.
  def check_click
    if inputs.mouse.down #is mouse up or down?
      state.mouse_held = true # mouse is being held down
    elsif inputs.mouse.up # if mouse is up
    state.mouse_held = false # mouse is not being held down or dragged
      state.mouse_dragging = false
    end

    if state.mouse_held &&    # mouse needs to be down
      !inputs.mouse.click &&     # must not be first click
      ((inputs.mouse.previous_click.point.x - inputs.mouse.position.x).abs > 15) # Need to move 15 pixels before "drag"
      state.mouse_dragging = true
    end

    # If the user clicks their mouse inside the grid, the search_lines method is called with a click input type.
    if ((inputs.mouse.click) && (inputs.mouse.click.point.inside_rect? state.grid_border))
      search_lines(inputs.mouse.click.point, :click)

    # If the user drags their mouse inside the grid, the search_lines method is called with a drag input type.
    elsif ((state.mouse_dragging) && (inputs.mouse.position.inside_rect? state.grid_border))
      search_lines(inputs.mouse.position, :drag)
    end
  end

  # Sets the definition of a grid box and handles user input to fill in or clear grid boxes.
  def search_lines (point, input_type)
    point.x -= state.paint_grid["x"] # subtracts the value assigned to the "x" key in the paint_grid hash
    point.y -= state.paint_grid["y"] # subtracts the value assigned to the "y" key in the paint_grid hash

    # Remove code following the .floor and see what happens when you try to fill in grid squares
    point.x = (point.x / state.paint_grid["dist_x"]).floor * state.paint_grid["dist_x"]
    point.y = (point.y / state.paint_grid["dist_y"]).floor * state.paint_grid["dist_y"]

    point.x += state.paint_grid["x"]
    point.y += state.paint_grid["y"]

    # Sets definition of a grid box, meaning its x, y, width, and height.
    # Floor is called on the point.x and point.y variables.
    # Ceil method is called on values of the distance hash keys, setting the width and height of a box.
    grid_box = [ point.x.floor, point.y.floor, state.paint_grid["dist_x"].ceil, state.paint_grid["dist_y"].ceil ]

    if input_type == :click # if user clicks their mouse
      if state.filled_squares.include? grid_box # if grid box is already filled in
        state.filled_squares.delete grid_box # box is cleared and removed from filled_squares
      else
        state.filled_squares << grid_box # otherwise, box is filled in and added to filled_squares
      end
    elsif input_type == :drag # if user drags mouse
      unless state.filled_squares.include? grid_box # unless the grid box dragged over is already filled in
        state.filled_squares << grid_box # the box is filled in and added to filled_squares
      end
    end
  end

  # Creates and outputs a "Clear" button on the screen using a label and a border.
  # If the button is clicked, the filled squares are cleared, making the filled_squares collection empty.
  def draw_buttons
    x, y, w, h = 390, 50, 240, 50
    state.clear_button        ||= state.new_entity(:button_with_fade)

    # The x and y positions are set to display the label in the center of the button.
    # Try changing the first two parameters to simply x, y and see what happens to the text placement!
    state.clear_button.label  ||= [x + w.half, y + h.half + 10, "Clear", 0, 1] # placed in center of border
    state.clear_button.border ||= [x, y, w, h]

    # If the mouse is clicked inside the borders of the clear button,
    # the filled_squares collection is emptied and the squares are cleared.
    if inputs.mouse.click && inputs.mouse.click.point.inside_rect?(state.clear_button.border)
      state.clear_button.clicked_at = inputs.mouse.click.created_at # time (frame) the click occurred
      state.filled_squares.clear
      inputs.mouse.previous_click = nil
    end

    outputs.labels << state.clear_button.label
    outputs.borders << state.clear_button.border

    # When the clear button is clicked, the color of the button changes
    # and the transparency changes, as well. If you change the time from
    # 0.25.seconds to 1.25.seconds or more, the change will last longer.
    if state.clear_button.clicked_at
      outputs.solids << [x, y, w, h, 0, 180, 80, 255 * state.clear_button.clicked_at.ease(0.25.seconds, :flip)]
    end
  end
end

$paint_app = PaintApp.new

def tick args
  $paint_app.inputs = args.inputs
  $paint_app.state = args.state
  $paint_app.grid = args.grid
  $paint_app.args = args
  $paint_app.outputs = args.outputs
  $paint_app.tick
  tick_instructions args, "How to create a simple paint app. CLICK and HOLD to draw."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Mouse - Coordinate Systems - main.rb

# ./samples/05_mouse/04_coordinate_systems/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - args.inputs.mouse.click.position: Coordinates of the mouse's position on the screen.
   Unlike args.inputs.mouse.click.point, the mouse does not need to be pressed down for
   position to know the mouse's coordinates.
   For more information about the mouse, go to mygame/documentation/07-mouse.md.

 Reminders:

 - args.inputs.mouse.click: This property will be set if the mouse was clicked.

 - args.inputs.mouse.click.point.(x|y): The x and y location of the mouse.

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

   In this sample app, string interpolation is used to show the current position of the mouse
   in a label.

 - args.outputs.labels: An array that generates a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.

 - args.outputs.solids: An array that generates a solid.
   The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE, ALPHA]
   For more information about solids, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.lines: An array that generates a line.
   The parameters are [X, Y, X2, Y2, RED, GREEN, BLUE, ALPHA]
   For more information about lines, go to mygame/documentation/04-lines.md.

=end

# This sample app shows a coordinate system or grid. The user can move their mouse around the screen and the
# coordinates of their position on the screen will be displayed. Users can choose to view one quadrant or
# four quadrants by pressing the button.

def tick args

  # The addition and subtraction in the first two parameters of the label and solid
  # ensure that the outputs don't overlap each other. Try removing them and see what happens.
  pos = args.inputs.mouse.position # stores coordinates of mouse's position
  args.outputs.labels << [pos.x + 10, pos.y + 10, "#{pos}"] # outputs label of coordinates
  args.outputs.solids << [pos.x -  2, pos.y - 2, 5, 5] # outputs small blackk box placed where mouse is hovering

  button = [0, 0, 370, 50] # sets definition of toggle button
  args.outputs.borders << button # outputs button as border (not filled in)
  args.outputs.labels << [10, 35, "click here toggle coordinate system"] # label of button
  args.outputs.lines << [    0, -720,    0, 720] # vertical line dividing quadrants
  args.outputs.lines << [-1280,    0, 1280,   0] # horizontal line dividing quadrants

  if args.inputs.mouse.click # if the user clicks the mouse
    pos = args.inputs.mouse.click.point # pos's value is point where user clicked (coordinates)
    if pos.inside_rect? button # if the click occurred inside the button
      if args.grid.name == :bottom_left # if the grid shows bottom left as origin
        args.grid.origin_center! # origin will be shown in center
      else
        args.grid.origin_bottom_left! # otherwise, the view will change to show bottom left as origin
      end
    end
  end

  tick_instructions args, "Sample app shows the two supported coordinate systems in Game Toolkit."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Mouse - Clicking Buttons - main.rb

# ./samples/05_mouse/05_clicking_buttons/app/main.rb
def tick args
  # create buttons
  args.state.buttons ||= [
    create_button(args, id: :button_1, row: 0, col: 0, text: "button 1"),
    create_button(args, id: :button_2, row: 1, col: 0, text: "button 2"),
    create_button(args, id: :clear,    row: 2, col: 0, text: "clear")
  ]

  # render button's border and label
  args.outputs.primitives << args.state.buttons.map do |b|
    b.primitives
  end

  # render center label if the text is set
  if args.state.center_label_text
    args.outputs.labels << { x: 640,
                             y: 360,
                             text: args.state.center_label_text,
                             alignment_enum: 1,
                             vertical_alignment_enum: 1 }
  end

  # if the mouse is clicked, see if the mouse click intersected
  # with a button
  if args.inputs.mouse.click
    button = args.state.buttons.find do |b|
      args.inputs.mouse.intersect_rect? b
    end

    # update the center label text based on button clicked
    case button.id
    when :button_1
      args.state.center_label_text = "button 1 was clicked"
    when :button_2
      args.state.center_label_text = "button 2 was clicked"
    when :clear
      args.state.center_label_text = nil
    end
  end
end

def create_button args, id:, row:, col:, text:;
  # args.layout.rect(row:, col:, w:, h:) is method that will
  # return a rectangle inside of a grid with 12 rows and 24 columns
  rect = args.layout.rect row: row, col: col, w: 3, h: 1

  # get senter of rect for label
  center = args.geometry.rect_center_point rect

  {
    id: id,
    x: rect.x,
    y: rect.y,
    w: rect.w,
    h: rect.h,
    primitives: [
      {
        x: rect.x,
        y: rect.y,
        w: rect.w,
        h: rect.h,
        primitive_marker: :border
      },
      {
        x: center.x,
        y: center.y,
        text: text,
        size_enum: -1,
        alignment_enum: 1,
        vertical_alignment_enum: 1,
        primitive_marker: :label
      }
    ]
  }
end

$gtk.reset

Save Load - Reading Writing Files - main.rb

# ./samples/06_save_load/00_reading_writing_files/app/main.rb
# APIs covered:
#   args.gtk.write_file "file-1.txt", args.state.tick_count.to_s
#   args.gtk.append_file "file-1.txt", args.state.tick_count.to_s

#   stat = args.gtk.stat_file "file-1.txt"

#   contents = args.gtk.read_file "file-1.txt"

#   args.gtk.delete_file "file-1.txt"
#   args.gtk.delete_file_if_exist "file-1.txt"

#   root_files = args.gtk.list_files ""
#   app_files  = args.gtk.list_files "app"

def tick args
  # create buttons
  args.state.buttons ||= [
    create_button(args, id: :write_file_1,  row: 0, col: 0, text: "write file-1.txt"),
    create_button(args, id: :append_file_1, row: 1, col: 0, text: "append file-1.txt"),
    create_button(args, id: :delete_file_1, row: 2, col: 0, text: "delete file-1.txt"),

    create_button(args, id: :read_file_1,   row: 0, col: 3, text: "read file-1.txt"),
    create_button(args, id: :stat_file_1,   row: 1, col: 3, text: "stat file-1.txt"),
    create_button(args, id: :list_files,    row: 2, col: 3, text: "list files"),
  ]

  # render button's border and label
  args.outputs.primitives << args.state.buttons.map do |b|
    b.primitives
  end

  # render center label if the text is set
  if args.state.center_label_text
    long_string = args.state.center_label_text
    max_character_length = 80
    long_strings_split = args.string.wrapped_lines long_string, max_character_length
    line_height = 23
    offset = (long_strings_split.length / 2) * line_height
    args.outputs.labels << long_strings_split.map_with_index do |s, i|
      {
        x: 400,
        y: 60.from_top - (i * line_height),
        text: s
      }
    end
  end

  # if the mouse is clicked, see if the mouse click intersected
  # with a button
  if args.inputs.mouse.click
    button = args.state.buttons.find do |b|
      args.inputs.mouse.intersect_rect? b
    end

    # update the center label text based on button clicked
    case button.id
    when :write_file_1
      args.gtk.write_file("file-1.txt", args.state.tick_count.to_s + "\n")

      args.state.center_label_text = ""
      args.state.center_label_text += "* Success (#{args.state.tick_count}):\n"
      args.state.center_label_text += "  Click \"read file-1.txt\" to see the contents.\n"
      args.state.center_label_text += "\n"
      args.state.center_label_text += "** Sample Code\n"
      args.state.center_label_text += "   args.gtk.write_file(\"file-1.txt\", args.state.tick_count.to_s + \"\\n\")\n"
    when :append_file_1
      args.gtk.append_file("file-1.txt", args.state.tick_count.to_s + "\n")

      args.state.center_label_text = ""
      args.state.center_label_text += "* Success (#{args.state.tick_count}):\n"
      args.state.center_label_text += "  Click \"read file-1.txt\" to see the contents.\n"
      args.state.center_label_text += "\n"
      args.state.center_label_text += "** Sample Code\n"
      args.state.center_label_text += "   args.gtk.append_file(\"file-1.txt\", args.state.tick_count.to_s + \"\\n\")\n"
    when :stat_file_1
      stat = args.gtk.stat_file "file-1.txt"

      args.state.center_label_text = ""
      args.state.center_label_text += "* Stat File (#{args.state.tick_count})\n"
      args.state.center_label_text += "#{stat || "nil (file does not exist)"}"
      args.state.center_label_text += "\n"
      args.state.center_label_text += "\n"
      args.state.center_label_text += "** Sample Code\n"
      args.state.center_label_text += "   args.gtk.stat_files(\"file-1.txt\")\n"
    when :read_file_1
      contents = args.gtk.read_file("file-1.txt")

      args.state.center_label_text = ""
      if contents
        args.state.center_label_text += "* Contents (#{args.state.tick_count}):\n"
        args.state.center_label_text += contents
        args.state.center_label_text += "\n"
        args.state.center_label_text += "** Sample Code\n"
        args.state.center_label_text += "   contents = args.gtk.read_file(\"file-1.txt\")\n"
      else
        args.state.center_label_text += "* Contents (#{args.state.tick_count}):\n"
        args.state.center_label_text += "Contents of file was nil. Click stat file-1.txt for file information."
        args.state.center_label_text += "\n"
        args.state.center_label_text += "** Sample Code\n"
        args.state.center_label_text += "   contents = args.gtk.read_file(\"file-1.txt\")\n"
      end
    when :delete_file_1
      args.state.center_label_text = ""

      if args.gtk.stat_file "file-1.txt"
        args.gtk.delete_file "file-1.txt"
        args.state.center_label_text += "* Delete File\n"
        args.state.center_label_text += "file-1.txt was deleted. Click \"list files\" or \"stat file-1.txt\" for more info."
        args.state.center_label_text += "\n"
        args.state.center_label_text += "\n"
        args.state.center_label_text += "** Sample Code\n"
        args.state.center_label_text += "   args.gtk.delete_file(\"file-1.txt\")\n"
      else
        args.state.center_label_text = ""
        args.state.center_label_text += "* Delete File\n"
        args.state.center_label_text += "File does not exist. Click \"write file-1.txt\" or \"append file-1.txt\" to create file."
        args.state.center_label_text += "\n"
        args.state.center_label_text += "\n"
        args.state.center_label_text += "** Sample Code\n"
        args.state.center_label_text += "   if args.gtk.stat_file(\"file-1.txt\") ...\n"
      end
    when :list_files
      root_files = args.gtk.list_files ""
      app_files  = args.gtk.list_files "app"

      args.state.center_label_text = ""
      args.state.center_label_text += "** Root Files (#{args.state.tick_count}):\n"
      args.state.center_label_text += root_files.join "\n"
      args.state.center_label_text += "\n"
      args.state.center_label_text += "\n"
      args.state.center_label_text += "** App Files (#{args.state.tick_count}):\n"
      args.state.center_label_text += app_files.join "\n"
      args.state.center_label_text += "\n"
      args.state.center_label_text += "\n"
      args.state.center_label_text += "** Sample Code\n"
      args.state.center_label_text += "   root_files = args.gtk.list_files(\"\")\n"
      args.state.center_label_text += "   app_files = args.gtk.list_files(\"app\")\n"
    end
  end
end

def create_button args, id:, row:, col:, text:;
  # args.layout.rect(row:, col:, w:, h:) is method that will
  # return a rectangle inside of a grid with 12 rows and 24 columns
  rect = args.layout.rect row: row, col: col, w: 3, h: 1

  # get senter of rect for label
  center = args.geometry.rect_center_point rect

  {
    id: id,
    x: rect.x,
    y: rect.y,
    w: rect.w,
    h: rect.h,
    primitives: [
      {
        x: rect.x,
        y: rect.y,
        w: rect.w,
        h: rect.h,
        primitive_marker: :border
      },
      {
        x: center.x,
        y: center.y,
        text: text,
        size_enum: -2,
        alignment_enum: 1,
        vertical_alignment_enum: 1,
        primitive_marker: :label
      }
    ]
  }
end

$gtk.reset

Save Load - Save Load Game - main.rb

# ./samples/06_save_load/01_save_load_game/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - Symbol (:): Ruby object with a name and an internal ID. Symbols are useful
   because with a given symbol name, you can refer to the same object throughout
   a Ruby program.

   In this sample app, we're using symbols for our buttons. We have buttons that
   light fires, save, load, etc. Each of these buttons has a distinct symbol like
   :light_fire, :save_game, :load_game, etc.

 - to_sym: Returns the symbol corresponding to the given string; creates the symbol
   if it does not already exist.
   For example,
   'car'.to_sym
   would return the symbol :car.

 - last: Returns the last element of an array.

 Reminders:

 - num1.lesser(num2): finds the lower value of the given options.
   For example, in the statement
   a = 4.lesser(3)
   3 has a lower value than 4, which means that the value of a would be set to 3,
   but if the statement had been
   a = 4.lesser(5)
   4 has a lower value than 5, which means that the value of a would be set to 4.

 - num1.fdiv(num2): returns the float division (will have a decimal) of the two given numbers.
   For example, 5.fdiv(2) = 2.5 and 5.fdiv(5) = 1.0

 - String interpolation: uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

 - args.outputs.labels: An array. Values generate a label.
   Parameters are [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information, go to mygame/documentation/02-labels.md.

 - ARRAY#inside_rect?: An array with at least two values is considered a point. An array
   with at least four values is considered a rect. The inside_rect? function returns true
   or false depending on if the point is inside the rect.

=end

# This code allows users to perform different tasks, such as saving and loading the game.
# Users also have options to reset the game and light a fire.

class TextedBasedGame

  # Contains methods needed for game to run properly.
  # Increments tick count by 1 each time it runs (60 times in a single second)
  def tick
    default
    show_intro
    state.engine_tick_count += 1
    tick_fire
  end

  # Sets default values.
  # The ||= ensures that a variable's value is only set to the value following the = sign
  # if the value has not already been set before. Intialization happens only in the first frame.
  def default
    state.engine_tick_count ||= 0
    state.active_module     ||= :room
    state.fire_progress     ||= 0
    state.fire_ready_in     ||= 10
    state.previous_fire     ||= :dead
    state.fire              ||= :dead
  end

  def show_intro
    return unless state.engine_tick_count == 0 # return unless the game just started
    set_story_line "awake." # calls set_story_line method, sets to "awake"
  end

  # Sets story line.
  def set_story_line story_line
    state.story_line    = story_line # story line set to value of parameter
    state.active_module = :alert # active module set to alert
  end

  # Clears story line.
  def clear_storyline
    state.active_module = :none # active module set to none
    state.story_line = nil # story line is cleared, set to nil (or empty)
  end

  # Determines fire progress (how close the fire is to being ready to light).
  def tick_fire
    return if state.active_module == :alert # return if active module is alert
    state.fire_progress += 1 # increment fire progress
    # fire_ready_in is 10. The fire_progress is either the current value or 10, whichever has a lower value.
    state.fire_progress = state.fire_progress.lesser(state.fire_ready_in)
  end

  # Sets the value of fire (whether it is dead or roaring), and the story line
  def light_fire
    return unless fire_ready? # returns unless the fire is ready to be lit
    state.fire = :roaring # fire is lit, set to roaring
    state.fire_progress = 0 # the fire progress returns to 0, since the fire has been lit
    if state.fire != state.previous_fire
      set_story_line "the fire is #{state.fire}." # the story line is set using string interpolation
      state.previous_fire = state.fire
    end
  end

  # Checks if the fire is ready to be lit. Returns a boolean value.
  def fire_ready?
    # If fire_progress (value between 0 and 10) is equal to fire_ready_in (value of 10),
    # the fire is ready to be lit.
    state.fire_progress == state.fire_ready_in
  end

  # Divides the value of the fire_progress variable by 10 to determine how close the user is to
  # being able to light a fire.
  def light_fire_progress
    state.fire_progress.fdiv(10) # float division
  end

  # Defines fire as the state.fire variable.
  def fire
    state.fire
  end

  # Sets the title of the room.
  def room_title
    return "a room that is dark" if state.fire == :dead # room is dark if the fire is dead
    return "a room that is lit" # room is lit if the fire is not dead
  end

  # Sets the active_module to room.
  def go_to_room
    state.active_module = :room
  end

  # Defines active_module as the state.active_module variable.
  def active_module
    state.active_module
  end

  # Defines story_line as the state.story_line variable.
  def story_line
    state.story_line
  end

  # Update every 60 frames (or every second)
  def should_tick?
    state.tick_count.mod_zero?(60)
  end

  # Sets the value of the game state provider.
  def initialize game_state_provider
    @game_state_provider = game_state_provider
  end

  # Defines the game state.
  # Any variable prefixed with an @ symbol is an instance variable.
  def state
    @game_state_provider.state
  end

  # Saves the state of the game in a text file called game_state.txt.
  def save
    $gtk.serialize_state('game_state.txt', state)
  end

  # Loads the game state from the game_state.txt text file.
  # If the load is unsuccessful, the user is informed since the story line indicates the failure.
  def load
    parsed_state = $gtk.deserialize_state('game_state.txt')
    if !parsed_state
      set_story_line "no game to load. press save first."
    else
      $gtk.args.state = parsed_state
    end
  end

  # Resets the game.
  def reset
    $gtk.reset
  end
end

class TextedBasedGamePresenter
  attr_accessor :state, :outputs, :inputs

  # Creates empty collection called highlights.
  # Calls methods necessary to run the game.
  def tick
    state.layout.highlights ||= []
    game.tick if game.should_tick?
    render
    process_input
  end

  # Outputs a label of the tick count (passage of time) and calls all render methods.
  def render
    outputs.labels << [10, 30, state.tick_count]
    render_alert
    render_room
    render_highlights
  end

  # Outputs a label onto the screen that shows the story line, and also outputs a "close" button.
  def render_alert
    return unless game.active_module == :alert

    outputs.labels << [640, 480, game.story_line, 5, 1]  # outputs story line label
    outputs.primitives << button(:alert_dismiss, 490, 380, "close")  # positions "close" button under story line
  end

  def render_room
    return unless game.active_module == :room
    outputs.labels << [640, 700, game.room_title, 4, 1] # outputs room title label at top of screen

    # The parameters for these outputs are (symbol, x, y, text, value/percentage) and each has a y value
    # that positions it 60 pixels lower than the previous output.

    # outputs the light_fire_progress bar, uses light_fire_progress for its percentage (which changes bar's appearance)
    outputs.primitives << progress_bar(:light_fire, 490, 600, "light fire", game.light_fire_progress)
    outputs.primitives << button(       :save_game, 490, 540, "save") # outputs save button
    outputs.primitives << button(       :load_game, 490, 480, "load") # outputs load button
    outputs.primitives << button(      :reset_game, 490, 420, "reset") # outputs reset button
    outputs.labels << [640, 30, "the fire is #{game.fire}", 0, 1] # outputs fire label at bottom of screen
  end

  # Outputs a collection of highlights using an array to set their values, and also rejects certain values from the collection.
  def render_highlights
    state.layout.highlights.each do |h| # for each highlight in the collection
        h.lifetime -= 1 # decrease the value of its lifetime
      end

      outputs.solids << state.layout.highlights.map do |h| # outputs highlights collection
        [h.x, h.y, h.w, h.h, h.color, 255 * h.lifetime / h.max_lifetime] # sets definition for each highlight
        # transparency changes; divide lifetime by max_lifetime, multiply result by 255
      end

      # reject highlights from collection that have no remaining lifetime
      state.layout.highlights = state.layout.highlights.reject { |h| h.lifetime <= 0 }
  end

  # Checks whether or not a button was clicked.
  # Returns a boolean value.
  def process_input
    button = button_clicked? # calls button_clicked? method
  end

  # Returns a boolean value.
  # Finds the button that was clicked from the button list and determines what method to call.
  # Adds a highlight to the highlights collection.
  def button_clicked?
    return nil unless click_pos # return nil unless click_pos holds coordinates of mouse click
      button = @button_list.find do |k, v| # goes through button_list to find button clicked
        click_pos.inside_rect? v[:primitives].last.rect # was the mouse clicked inside the rect of button?
      end
      return unless button # return unless a button was clicked
      method_to_call = "#{button[0]}_clicked".to_sym # sets method_to_call to symbol (like :save_game or :load_game)
      if self.respond_to? method_to_call # returns true if self responds to the given method (method actually exists)
        border = button[1][:primitives].last # sets border definition using value of last key in button list hash

        # declares each highlight as a new entity, sets properties
        state.layout.highlights << state.new_entity(:highlight) do |h|
            h.x = border.x
            h.y = border.y
            h.w = border.w
            h.h = border.h
            h.max_lifetime = 10
            h.lifetime = h.max_lifetime
            h.color = [120, 120, 180] # sets color to shade of purple
          end

          self.send method_to_call # invoke method identified by symbol
        else # otherwise, if self doesn't respond to given method
          border = button[1][:primitives].last # sets border definition using value of last key in hash

          # declares each highlight as a new entity, sets properties
          state.layout.highlights << state.new_entity(:highlight) do |h|
            h.x = border.x
            h.y = border.y
            h.w = border.w
            h.h = border.h
            h.max_lifetime = 4 # different max_lifetime than the one set if respond_to? had been true
            h.lifetime = h.max_lifetime
            h.color = [120, 80, 80] # sets color to dark color
          end

          # instructions for users on how to add the missing method_to_call to the code
          puts "It looks like #{method_to_call} doesn't exists on TextedBasedGamePresenter. Please add this method:"
          puts "Just copy the code below and put it in the #{TextedBasedGamePresenter} class definition."
          puts ""
          puts "```"
          puts "class TextedBasedGamePresenter <--- find this class and put the method below in it"
          puts ""
          puts "  def #{method_to_call}"
          puts "    puts 'Yay that worked!'"
          puts "  end"
          puts ""
          puts "end <-- make sure to put the #{method_to_call} method in between the `class` word and the final `end` statement."
          puts "```"
          puts ""
      end
  end

  # Returns the position of the mouse when it is clicked.
  def click_pos
    return nil unless inputs.mouse.click # returns nil unless the mouse was clicked
    return inputs.mouse.click.point # returns location of mouse click (coordinates)
  end

  # Creates buttons for the button_list and sets their values using a hash (uses symbols as keys)
  def button id, x, y, text
    @button_list[id] ||= { # assigns values to hash keys
      id: id,
      text: text,
      primitives: [
        [x + 10, y + 30, text, 2, 0].label, # positions label inside border
        [x, y, 300, 50].border,             # sets definition of border
      ]
    }

    @button_list[id][:primitives] # returns label and border for buttons
  end

  # Creates a progress bar (used for lighting the fire) and sets its values.
  def progress_bar id, x, y, text, percentage
    @button_list[id] = { # assigns values to hash keys
      id: id,
      text: text,
      primitives: [
        [x, y, 300, 50, 100, 100, 100].solid, # sets definition for solid (which fills the bar with gray)
        [x + 10, y + 30, text, 2, 0].label, # sets definition for label, positions inside border
        [x, y, 300, 50].border, # sets definition of border
      ]
    }

    # Fills progress bar based on percentage. If the fire was ready to be lit (100%) and we multiplied by
    # 100, only 1/3 of the bar would only be filled in. 200 would cause only 2/3 to be filled in.
    @button_list[id][:primitives][0][2] = 300 * percentage
    @button_list[id][:primitives]
  end

  # Defines the game.
  def game
    @game
  end

  # Initalizes the game and creates an empty list of buttons.
  def initialize
    @game = TextedBasedGame.new self
    @button_list ||= {}
  end

  # Clears the storyline and takes the user to the room.
  def alert_dismiss_clicked
    game.clear_storyline
    game.go_to_room
  end

  # Lights the fire when the user clicks the "light fire" option.
  def light_fire_clicked
    game.light_fire
  end

  # Saves the game when the user clicks the "save" option.
  def save_game_clicked
    game.save
  end

  # Resets the game when the user clicks the "reset" option.
  def reset_game_clicked
    game.reset
  end

  # Loads the game when the user clicks the "load" option.
  def load_game_clicked
    game.load
  end
end

$text_based_rpg = TextedBasedGamePresenter.new

def tick args
  $text_based_rpg.state = args.state
  $text_based_rpg.outputs = args.outputs
  $text_based_rpg.inputs = args.inputs
  $text_based_rpg.tick
end

Advanced Audio - Audio Mixer - main.rb

# ./samples/07_advanced_audio/01_audio_mixer/app/main.rb
# these are the properties that you can sent on args.audio
def spawn_new_sound args, name, path
  # Spawn randomly in an area that won't be covered by UI.
  screenx = (rand * 600.0) + 200.0
  screeny = (rand * 400.0) + 100.0

  id = new_sound_id! args
  # you can hang anything on the audio hashes you want, so we store the
  #  actual screen position in here for convenience.
  args.audio[id] = {
    name: name,
    input: path,
    screenx: screenx,
    screeny: screeny,
    x: ((screenx / 1279.0) * 2.0) - 1.0,  # scale to -1.0 - 1.0 range
    y: ((screeny / 719.0) * 2.0) - 1.0,   # scale to -1.0 - 1.0 range
    z: 0.0,
    gain: 1.0,
    pitch: 1.0,
    looping: true,
    paused: false
  }

  args.state.selected = id
end

# these are values you can change on the ~args.audio~ data structure
def input_panel args
  return unless args.state.panel
  return if args.state.dragging

  audio_entry = args.audio[args.state.selected]
  results = args.state.panel

  if args.state.mouse_state == :held && args.inputs.mouse.position.inside_rect?(results.pitch_slider_rect.rect)
    audio_entry.pitch = 2.0 * ((args.inputs.mouse.x - results.pitch_slider_rect.x).to_f / (results.pitch_slider_rect.w - 1.0))
  elsif args.state.mouse_state == :held && args.inputs.mouse.position.inside_rect?(results.playtime_slider_rect.rect)
    audio_entry.playtime = audio_entry.length_ * ((args.inputs.mouse.x - results.playtime_slider_rect.x).to_f / (results.playtime_slider_rect.w - 1.0))
  elsif args.state.mouse_state == :held && args.inputs.mouse.position.inside_rect?(results.gain_slider_rect.rect)
    audio_entry.gain = (args.inputs.mouse.x - results.gain_slider_rect.x).to_f / (results.gain_slider_rect.w - 1.0)
  elsif args.inputs.mouse.click && args.inputs.mouse.position.inside_rect?(results.looping_checkbox_rect.rect)
    audio_entry.looping = !audio_entry.looping
  elsif args.inputs.mouse.click && args.inputs.mouse.position.inside_rect?(results.paused_checkbox_rect.rect)
    audio_entry.paused = !audio_entry.paused
  elsif args.inputs.mouse.click && args.inputs.mouse.position.inside_rect?(results.delete_button_rect.rect)
    args.audio.delete args.state.selected
  end
end

def render_sources args
  args.outputs.primitives << args.audio.keys.map do |k|
    s = args.audio[k]

    isselected = (k == args.state.selected)

    color = isselected ? [ 0, 255, 0, 255 ] : [ 0, 0, 255, 255 ]
    [
      [s.screenx, s.screeny, args.state.boxsize, args.state.boxsize, *color].solid,

      {
        x: s.screenx + args.state.boxsize.half,
        y: s.screeny,
        text: s.name,
        r: 255,
        g: 255,
        b: 255,
        alignment_enum: 1
      }.label!
    ]
  end
end

def playtime_str t
  return "" unless t
  minutes = (t / 60.0).floor
  seconds = t - (minutes * 60.0).to_f
  return minutes.to_s + ':' + seconds.floor.to_s + ((seconds - seconds.floor).to_s + "000")[1..3]
end

def label_with_drop_shadow x, y, text
  [
    { x: x + 1, y: y + 1, text: text, vertical_alignment_enum: 1, alignment_enum: 1, r:   0, g:   0, b:   0 }.label!,
    { x: x + 2, y: y + 0, text: text, vertical_alignment_enum: 1, alignment_enum: 1, r:   0, g:   0, b:   0 }.label!,
    { x: x + 0, y: y + 1, text: text, vertical_alignment_enum: 1, alignment_enum: 1, r: 200, g: 200, b: 200 }.label!
  ]
end

def check_box opts = {}
  checkbox_template = opts.args.layout.rect(w: 0.5, h: 0.5, col: 2)
  final_rect = checkbox_template.center_inside_rect_y(opts.args.layout.rect(row: opts.row, col: opts.col))
  color = { r:   0, g:   0, b:   0 }
  color = { r: 255, g: 255, b: 255 } if opts.checked

  {
    rect: final_rect,
    primitives: [
      (final_rect.to_solid color)
    ]
  }
end

def progress_bar opts = {}
  outer_rect  = opts.args.layout.rect(row: opts.row, col: opts.col, w: 5, h: 1)
  color = opts.percentage * 255
  baseline_progress_bar = opts.args
                              .layout
                              .rect(w: 5, h: 0.5)

  final_rect = baseline_progress_bar.center_inside_rect(outer_rect)
  center = final_rect.rect_center_point

  {
    rect: final_rect,
    primitives: [
      final_rect.merge(r: color, g: color, b: color, a: 128).solid!,
      label_with_drop_shadow(center.x, center.y, opts.text)
    ]
  }
end

def panel_primitives args, audio_entry
  results = { primitives: [] }

  return results unless audio_entry

  # this uses DRGTK's layout apis to layout the controls
  # imagine the screen is split into equal cells (24 cells across, 12 cells up and down)
  # args.layout.rect returns a hash which we merge values with to create primitives
  # using args.layout.rect removes the need for pixel pushing

  # args.outputs.debug << args.layout.debug_primitives(r: 255, g: 255, b: 255)

  white_color = { r: 255, g: 255, b: 255 }
  label_style = white_color.merge(vertical_alignment_enum: 1)

  # panel background
  results.primitives << args.layout.rect(row: 0, col: 0, w: 7, h: 6, include_col_gutter: true, include_row_gutter: true)
                                   .border!(r: 255, g: 255, b: 255)

  # title
  results.primitives << args.layout.point(row: 0, col: 3.5, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text:           "Source #{args.state.selected} (#{args.audio[args.state.selected].name})",
                                          size_enum:      3,
                                          alignment_enum: 1)

  # seperator line
  results.primitives << args.layout.rect(row: 1, col: 0, w: 7, h: 0)
                                   .line!(white_color)

  # screen location
  results.primitives << args.layout.point(row: 1.0, col: 0, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "screen:")

  results.primitives << args.layout.point(row: 1.0, col: 2, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "(#{audio_entry.screenx.to_i}, #{audio_entry.screeny.to_i})")

  # position
  results.primitives << args.layout.point(row: 1.5, col: 0, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "position:")

  results.primitives << args.layout.point(row: 1.5, col: 2, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "(#{audio_entry[:x].round(5).to_s[0..6]}, #{audio_entry[:y].round(5).to_s[0..6]})")

  results.primitives << args.layout.point(row: 2.0, col: 0, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "pitch:")

  results.pitch_slider_rect = progress_bar(row: 2.0, col: 2,
                                           percentage: audio_entry.pitch / 2.0,
                                           text: "#{audio_entry.pitch.to_sf}",
                                           args: args)

  results.primitives << results.pitch_slider_rect.primitives

  results.primitives << args.layout.point(row: 2.5, col: 0, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "playtime:")

  results.playtime_slider_rect = progress_bar(args: args,
                                              row:  2.5,
                                              col:  2,
                                              percentage: (audio_entry.playtime || 1) / (audio_entry.length_ || 1),
                                              text: "#{playtime_str(audio_entry.playtime)} / #{playtime_str(audio_entry.length_)}")

  results.primitives << results.playtime_slider_rect.primitives

  results.primitives << args.layout.point(row: 3.0, col: 0, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "gain:")

  results.gain_slider_rect = progress_bar(args: args,
                                          row:  3.0,
                                          col:  2,
                                          percentage: audio_entry.gain,
                                          text: "#{audio_entry.gain.to_sf}")

  results.primitives << results.gain_slider_rect.primitives


  results.primitives << args.layout.point(row: 3.5, col: 0, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "looping:")

  checkbox_template = args.layout.rect(w: 0.5, h: 0.5, col: 2)

  results.looping_checkbox_rect = check_box(args: args, row: 3.5, col: 2, checked: audio_entry.looping)
  results.primitives << results.looping_checkbox_rect.primitives

  results.primitives << args.layout.point(row: 4.0, col: 0, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "paused:")

  checkbox_template = args.layout.rect(w: 0.5, h: 0.5, col: 2)

  results.paused_checkbox_rect = check_box(args: args, row: 4.0, col: 2, checked: !audio_entry.paused)
  results.primitives << results.paused_checkbox_rect.primitives

  results.delete_button_rect = { rect: args.layout.rect(row: 5, col: 0, w: 7, h: 1) }

  results.primitives << results.delete_button_rect.to_solid(r: 180)

  results.primitives << args.layout.point(row: 5, col: 3.5, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "DELETE", alignment_enum: 1)

  return results
end

def render_panel args
  args.state.panel = nil
  audio_entry = args.audio[args.state.selected]
  return unless audio_entry

  mouse_down = (args.state.mouse_held >= 0)
  args.state.panel = panel_primitives args, audio_entry
  args.outputs.primitives << args.state.panel.primitives
end

def new_sound_id! args
  args.state.sound_id ||= 0
  args.state.sound_id  += 1
  args.state.sound_id
end

def render_launcher args
  args.outputs.primitives << args.state.spawn_sound_buttons.map(&:primitives)
end

def render_ui args
  render_launcher args
  render_panel args
end

def tick args
  defaults args
  render args
  input args
end

def input args
  if !args.audio[args.state.selected]
    args.state.selected = nil
    args.state.dragging = nil
  end

  # spawn button and node interaction
  if args.inputs.mouse.click
    spawn_sound_button = args.state.spawn_sound_buttons.find { |b| args.inputs.mouse.inside_rect? b.rect }

    audio_click_key, audio_click_value = args.audio.find do |k, v|
      args.inputs.mouse.inside_rect? [v.screenx, v.screeny, args.state.boxsize, args.state.boxsize]
    end

    if spawn_sound_button
      args.state.selected = nil
      spawn_new_sound args, spawn_sound_button.name, spawn_sound_button.path
    elsif audio_click_key
      args.state.selected = audio_click_key
    end
  end

  if args.state.mouse_state == :held && args.state.selected
    v = args.audio[args.state.selected]
    if args.inputs.mouse.inside_rect? [v.screenx, v.screeny, args.state.boxsize, args.state.boxsize]
      args.state.dragging = args.state.selected
    end

    if args.state.dragging
      s = args.audio[args.state.selected]
      # you can hang anything on the audio hashes you want, so we store the
      #  actual screen position so it doesn't scale weirdly vs your mouse.
      s.screenx = args.inputs.mouse.x - (args.state.boxsize / 2)
      s.screeny = args.inputs.mouse.y - (args.state.boxsize / 2)

      s.screeny = 50 if s.screeny < 50
      s.screeny = (719 - args.state.boxsize) if s.screeny > (719 - args.state.boxsize)
      s.screenx = 0 if s.screenx < 0
      s.screenx = (1279 - args.state.boxsize) if s.screenx > (1279 - args.state.boxsize)

      s.x = ((s.screenx / 1279.0) * 2.0) - 1.0  # scale to -1.0 - 1.0 range
      s.y = ((s.screeny / 719.0) * 2.0) - 1.0   # scale to -1.0 - 1.0 range
    end
  elsif args.state.mouse_state == :released
    args.state.dragging = nil
  end

  input_panel args
end

def defaults args
  args.state.mouse_state      ||= :released
  args.state.dragging_source  ||= false
  args.state.selected         ||= 0
  args.state.next_sound_index ||= 0
  args.state.boxsize          ||= 30
  args.state.sound_files      ||= [
    { name: :tada,   path: "sounds/tada.wav"   },
    { name: :splash, path: "sounds/splash.wav" },
    { name: :drum,   path: "sounds/drum.mp3"   },
    { name: :spring, path: "sounds/spring.wav" },
    { name: :music,  path: "sounds/music.ogg"  }
  ]

  # generate buttons based off the sound collection above
  args.state.spawn_sound_buttons ||= begin
    # create a group of buttons
    # column centered (using col_offset to calculate the column offset)
    # where each item is 2 columns apart
    rects = args.layout.rect_group row:   11,
                                   col_offset: {
                                     count: args.state.sound_files.length,
                                     w:     2
                                   },
                                   dcol:  2,
                                   w:     2,
                                   h:     1,
                                   group: args.state.sound_files

    # now that you have the rects
    # construct the metadata for the buttons
    rects.map do |rect|
      {
        rect: rect,
        name: rect.name,
        path: rect.path,
        primitives: [
          rect.to_border(r: 255, g: 255, b: 255),
          rect.to_label(x: rect.center_x,
                        y: rect.center_y,
                        text: "#{rect.name}",
                        alignment_enum: 1,
                        vertical_alignment_enum: 1,
                        r: 255, g: 255, b: 255)
        ]
      }
    end
  end

  if args.inputs.mouse.up
    args.state.mouse_state = :released
    args.state.dragging_source = false
  elsif args.inputs.mouse.down
    args.state.mouse_state = :held
  end

  args.outputs.background_color = [ 0, 0, 0, 255 ]
end

def render args
  render_ui args
  render_sources args
end

Advanced Audio - Audio Mixer - server_ip_address.txt

# ./samples/07_advanced_audio/01_audio_mixer/app/server_ip_address.txt
192.168.1.65

Advanced Audio - Sound Synthesis - main.rb

# ./samples/07_advanced_audio/02_sound_synthesis/app/main.rb
begin # region: top level tick methods
  def tick args
    defaults args
    render args
    input args
    process_audio_queue args
  end

  def defaults args
    args.state.sine_waves      ||= {}
    args.state.square_waves    ||= {}
    args.state.saw_tooth_waves ||= {}
    args.state.triangle_waves  ||= {}
    args.state.audio_queue     ||= []
    args.state.buttons         ||= [
      (frequency_buttons args),
      (sine_wave_note_buttons args),
      (bell_buttons args),
      (square_wave_note_buttons args),
      (saw_tooth_wave_note_buttons args),
      (triangle_wave_note_buttons args),
    ].flatten
  end

  def render args
    args.outputs.borders << args.state.buttons.map { |b| b[:border] }
    args.outputs.labels  << args.state.buttons.map { |b| b[:label]  }
    args.outputs.labels  << args.layout
                              .rect(row: 0, col: 11.5)
                              .yield_self { |r| r.merge y: r.y + r.h }
                              .merge(text: "This is a Pro only feature. Click here to watch the YouTube video if you are on the Standard License.",
                                     alignment_enum: 1)
  end


  def input args
    args.state.buttons.each do |b|
      if args.inputs.mouse.click && (args.inputs.mouse.click.inside_rect? b[:rect])
        parameter_string = (b.slice :frequency, :note, :octave).map { |k, v| "#{k}: #{v}" }.join ", "
        args.gtk.notify! "#{b[:method_to_call]} #{parameter_string}"
        send b[:method_to_call], args, b
      end
    end

    if args.inputs.mouse.click && (args.inputs.mouse.click.inside_rect? (args.layout.rect(row: 0).yield_self { |r| r.merge y: r.y + r.h.half, h: r.h.half }))
      args.gtk.openurl 'https://www.youtube.com/watch?v=zEzovM5jT-k&ab_channel=AmirRajan'
    end
  end

  def process_audio_queue args
    to_queue = args.state.audio_queue.find_all { |v| v[:queue_at] <= args.tick_count }
    args.state.audio_queue -= to_queue
    to_queue.each { |a| args.audio[a[:id]] = a }

    args.audio.find_all { |k, v| v[:decay_rate] }
      .each     { |k, v| v[:gain] -= v[:decay_rate] }

    sounds_to_stop = args.audio
                       .find_all { |k, v| v[:stop_at] && args.state.tick_count >= v[:stop_at] }
                       .map { |k, v| k }

    sounds_to_stop.each { |k| args.audio.delete k }
  end
end

begin # region: button definitions, ui layout, callback functions
  def button args, opts
    button_def = opts.merge rect: (args.layout.rect (opts.merge w: 2, h: 1))

    button_def[:border] = button_def[:rect].merge r: 0, g: 0, b: 0

    label_offset_x = 5
    label_offset_y = 30

    button_def[:label]  = button_def[:rect].merge text: opts[:text],
                                                  size_enum: -2.5,
                                                  x: button_def[:rect].x + label_offset_x,
                                                  y: button_def[:rect].y + label_offset_y

    button_def
  end

  def play_sine_wave args, sender
    queue_sine_wave args,
                    frequency: sender[:frequency],
                    duration: 1.seconds,
                    fade_out: true
  end

  def play_note args, sender
    method_to_call = :queue_sine_wave
    method_to_call = :queue_square_wave    if sender[:type] == :square
    method_to_call = :queue_saw_tooth_wave if sender[:type] == :saw_tooth
    method_to_call = :queue_triangle_wave  if sender[:type] == :triangle
    method_to_call = :queue_bell           if sender[:type] == :bell

    send method_to_call, args,
         frequency: (frequency_for note: sender[:note], octave: sender[:octave]),
         duration: 1.seconds,
         fade_out: true
  end

  def frequency_buttons args
    [
      (button args,
              row: 4.0, col: 0, text: "300hz",
              frequency: 300,
              method_to_call: :play_sine_wave),
      (button args,
              row: 5.0, col: 0, text: "400hz",
              frequency: 400,
              method_to_call: :play_sine_wave),
      (button args,
              row: 6.0, col: 0, text: "500hz",
              frequency: 500,
              method_to_call: :play_sine_wave),
    ]
  end

  def sine_wave_note_buttons args
    [
      (button args,
              row: 1.5, col: 2, text: "Sine C4",
              note: :c, octave: 4, type: :sine, method_to_call: :play_note),
      (button args,
              row: 2.5, col: 2, text: "Sine D4",
              note: :d, octave: 4, type: :sine, method_to_call: :play_note),
      (button args,
              row: 3.5, col: 2, text: "Sine E4",
              note: :e, octave: 4, type: :sine, method_to_call: :play_note),
      (button args,
              row: 4.5, col: 2, text: "Sine F4",
              note: :f, octave: 4, type: :sine, method_to_call: :play_note),
      (button args,
              row: 5.5, col: 2, text: "Sine G4",
              note: :g, octave: 4, type: :sine, method_to_call: :play_note),
      (button args,
              row: 6.5, col: 2, text: "Sine A5",
              note: :a, octave: 5, type: :sine, method_to_call: :play_note),
      (button args,
              row: 7.5, col: 2, text: "Sine B5",
              note: :b, octave: 5, type: :sine, method_to_call: :play_note),
      (button args,
              row: 8.5, col: 2, text: "Sine C5",
              note: :c, octave: 5, type: :sine, method_to_call: :play_note),
    ]
  end

  def square_wave_note_buttons args
    [
      (button args,
              row: 1.5, col: 6, text: "Square C4",
              note: :c, octave: 4, type: :square, method_to_call: :play_note),
      (button args,
              row: 2.5, col: 6, text: "Square D4",
              note: :d, octave: 4, type: :square, method_to_call: :play_note),
      (button args,
              row: 3.5, col: 6, text: "Square E4",
              note: :e, octave: 4, type: :square, method_to_call: :play_note),
      (button args,
              row: 4.5, col: 6, text: "Square F4",
              note: :f, octave: 4, type: :square, method_to_call: :play_note),
      (button args,
              row: 5.5, col: 6, text: "Square G4",
              note: :g, octave: 4, type: :square, method_to_call: :play_note),
      (button args,
              row: 6.5, col: 6, text: "Square A5",
              note: :a, octave: 5, type: :square, method_to_call: :play_note),
      (button args,
              row: 7.5, col: 6, text: "Square B5",
              note: :b, octave: 5, type: :square, method_to_call: :play_note),
      (button args,
              row: 8.5, col: 6, text: "Square C5",
              note: :c, octave: 5, type: :square, method_to_call: :play_note),
    ]
  end
  def saw_tooth_wave_note_buttons args
    [
      (button args,
              row: 1.5, col: 8, text: "Saw C4",
              note: :c, octave: 4, type: :saw_tooth, method_to_call: :play_note),
      (button args,
              row: 2.5, col: 8, text: "Saw D4",
              note: :d, octave: 4, type: :saw_tooth, method_to_call: :play_note),
      (button args,
              row: 3.5, col: 8, text: "Saw E4",
              note: :e, octave: 4, type: :saw_tooth, method_to_call: :play_note),
      (button args,
              row: 4.5, col: 8, text: "Saw F4",
              note: :f, octave: 4, type: :saw_tooth, method_to_call: :play_note),
      (button args,
              row: 5.5, col: 8, text: "Saw G4",
              note: :g, octave: 4, type: :saw_tooth, method_to_call: :play_note),
      (button args,
              row: 6.5, col: 8, text: "Saw A5",
              note: :a, octave: 5, type: :saw_tooth, method_to_call: :play_note),
      (button args,
              row: 7.5, col: 8, text: "Saw B5",
              note: :b, octave: 5, type: :saw_tooth, method_to_call: :play_note),
      (button args,
              row: 8.5, col: 8, text: "Saw C5",
              note: :c, octave: 5, type: :saw_tooth, method_to_call: :play_note),
    ]
  end

  def triangle_wave_note_buttons args
    [
      (button args,
              row: 1.5, col: 10, text: "Triangle C4",
              note: :c, octave: 4, type: :triangle, method_to_call: :play_note),
      (button args,
              row: 2.5, col: 10, text: "Triangle D4",
              note: :d, octave: 4, type: :triangle, method_to_call: :play_note),
      (button args,
              row: 3.5, col: 10, text: "Triangle E4",
              note: :e, octave: 4, type: :triangle, method_to_call: :play_note),
      (button args,
              row: 4.5, col: 10, text: "Triangle F4",
              note: :f, octave: 4, type: :triangle, method_to_call: :play_note),
      (button args,
              row: 5.5, col: 10, text: "Triangle G4",
              note: :g, octave: 4, type: :triangle, method_to_call: :play_note),
      (button args,
              row: 6.5, col: 10, text: "Triangle A5",
              note: :a, octave: 5, type: :triangle, method_to_call: :play_note),
      (button args,
              row: 7.5, col: 10, text: "Triangle B5",
              note: :b, octave: 5, type: :triangle, method_to_call: :play_note),
      (button args,
              row: 8.5, col: 10, text: "Triangle C5",
              note: :c, octave: 5, type: :triangle, method_to_call: :play_note),
    ]
  end

  def bell_buttons args
    [
      (button args,
              row: 1.5, col: 4, text: "Bell C4",
              note: :c, octave: 4, type: :bell, method_to_call: :play_note),
      (button args,
              row: 2.5, col: 4, text: "Bell D4",
              note: :d, octave: 4, type: :bell, method_to_call: :play_note),
      (button args,
              row: 3.5, col: 4, text: "Bell E4",
              note: :e, octave: 4, type: :bell, method_to_call: :play_note),
      (button args,
              row: 4.5, col: 4, text: "Bell F4",
              note: :f, octave: 4, type: :bell, method_to_call: :play_note),
      (button args,
              row: 5.5, col: 4, text: "Bell G4",
              note: :g, octave: 4, type: :bell, method_to_call: :play_note),
      (button args,
              row: 6.5, col: 4, text: "Bell A5",
              note: :a, octave: 5, type: :bell, method_to_call: :play_note),
      (button args,
              row: 7.5, col: 4, text: "Bell B5",
              note: :b, octave: 5, type: :bell, method_to_call: :play_note),
      (button args,
              row: 8.5, col: 4, text: "Bell C5",
              note: :c, octave: 5, type: :bell, method_to_call: :play_note),
    ]
  end
end

begin # region: wave generation
  begin # sine wave
    def defaults_sine_wave_for
      { frequency: 440, sample_rate: 48000 }
    end

    def sine_wave_for opts = {}
      opts = defaults_sine_wave_for.merge opts
      frequency   = opts[:frequency]
      sample_rate = opts[:sample_rate]
      period_size = (sample_rate.fdiv frequency).ceil
      period_size.map_with_index do |i|
        Math::sin((2.0 * Math::PI) / (sample_rate.to_f / frequency.to_f) * i)
      end.to_a
    end

    def defaults_queue_sine_wave
      { frequency: 440, duration: 60, gain: 1.0, fade_out: false, queue_in: 0 }
    end

    def queue_sine_wave args, opts = {}
      opts        = defaults_queue_sine_wave.merge opts
      frequency   = opts[:frequency]
      sample_rate = 48000

      sine_wave = sine_wave_for frequency: frequency, sample_rate: sample_rate
      args.state.sine_waves[frequency] ||= sine_wave_for frequency: frequency, sample_rate: sample_rate

      proc = lambda do
        generate_audio_data args.state.sine_waves[frequency], sample_rate
      end

      audio_state = new_audio_state args, opts
      audio_state[:input] = [1, sample_rate, proc]
      queue_audio args, audio_state: audio_state, wave: sine_wave
    end
  end

  begin # region: square wave
    def defaults_square_wave_for
      { frequency: 440, sample_rate: 48000 }
    end

    def square_wave_for opts = {}
      opts = defaults_square_wave_for.merge opts
      sine_wave = sine_wave_for opts
      sine_wave.map do |v|
        if v >= 0
          1.0
        else
          -1.0
        end
      end.to_a
    end

    def defaults_queue_square_wave
      { frequency: 440, duration: 60, gain: 0.3, fade_out: false, queue_in: 0 }
    end

    def queue_square_wave args, opts = {}
      opts        = defaults_queue_square_wave.merge opts
      frequency   = opts[:frequency]
      sample_rate = 48000

      square_wave = square_wave_for frequency: frequency, sample_rate: sample_rate
      args.state.square_waves[frequency] ||= square_wave_for frequency: frequency, sample_rate: sample_rate

      proc = lambda do
        generate_audio_data args.state.square_waves[frequency], sample_rate
      end

      audio_state = new_audio_state args, opts
      audio_state[:input] = [1, sample_rate, proc]
      queue_audio args, audio_state: audio_state, wave: square_wave
    end
  end

  begin # region: saw tooth wave
    def defaults_saw_tooth_wave_for
      { frequency: 440, sample_rate: 48000 }
    end

    def saw_tooth_wave_for opts = {}
      opts = defaults_saw_tooth_wave_for.merge opts
      sine_wave = sine_wave_for opts
      period_size = sine_wave.length
      sine_wave.map_with_index do |v, i|
        (((i % period_size).fdiv period_size) * 2) - 1
      end
    end

    def defaults_queue_saw_tooth_wave
      { frequency: 440, duration: 60, gain: 0.3, fade_out: false, queue_in: 0 }
    end

    def queue_saw_tooth_wave args, opts = {}
      opts        = defaults_queue_saw_tooth_wave.merge opts
      frequency   = opts[:frequency]
      sample_rate = 48000

      saw_tooth_wave = saw_tooth_wave_for frequency: frequency, sample_rate: sample_rate
      args.state.saw_tooth_waves[frequency] ||= saw_tooth_wave_for frequency: frequency, sample_rate: sample_rate

      proc = lambda do
        generate_audio_data args.state.saw_tooth_waves[frequency], sample_rate
      end

      audio_state = new_audio_state args, opts
      audio_state[:input] = [1, sample_rate, proc]
      queue_audio args, audio_state: audio_state, wave: saw_tooth_wave
    end
  end

  begin # region: triangle wave
    def defaults_triangle_wave_for
      { frequency: 440, sample_rate: 48000 }
    end

    def triangle_wave_for opts = {}
      opts = defaults_saw_tooth_wave_for.merge opts
      sine_wave = sine_wave_for opts
      period_size = sine_wave.length
      sine_wave.map_with_index do |v, i|
        ratio = (i.fdiv period_size)
        if ratio <= 0.5
          (ratio * 4) - 1
        else
          ratio -= 0.5
          1 - (ratio * 4)
        end
      end
    end

    def defaults_queue_triangle_wave
      { frequency: 440, duration: 60, gain: 1.0, fade_out: false, queue_in: 0 }
    end

    def queue_triangle_wave args, opts = {}
      opts        = defaults_queue_triangle_wave.merge opts
      frequency   = opts[:frequency]
      sample_rate = 48000

      triangle_wave = triangle_wave_for frequency: frequency, sample_rate: sample_rate
      args.state.triangle_waves[frequency] ||= triangle_wave_for frequency: frequency, sample_rate: sample_rate

      proc = lambda do
        generate_audio_data args.state.triangle_waves[frequency], sample_rate
      end

      audio_state = new_audio_state args, opts
      audio_state[:input] = [1, sample_rate, proc]
      queue_audio args, audio_state: audio_state, wave: triangle_wave
    end
  end

  begin # region: bell
    def defaults_queue_bell
      { frequency: 440, duration: 1.seconds, queue_in: 0 }
    end

    def queue_bell args, opts = {}
      (bell_to_sine_waves (defaults_queue_bell.merge opts)).each { |b| queue_sine_wave args, b }
    end

    def bell_harmonics
      [
        { frequency_ratio: 0.5, duration_ratio: 1.00 },
        { frequency_ratio: 1.0, duration_ratio: 0.80 },
        { frequency_ratio: 2.0, duration_ratio: 0.60 },
        { frequency_ratio: 3.0, duration_ratio: 0.40 },
        { frequency_ratio: 4.2, duration_ratio: 0.25 },
        { frequency_ratio: 5.4, duration_ratio: 0.20 },
        { frequency_ratio: 6.8, duration_ratio: 0.15 }
      ]
    end

    def defaults_bell_to_sine_waves
      { frequency: 440, duration: 1.seconds, queue_in: 0 }
    end

    def bell_to_sine_waves opts = {}
      opts = defaults_bell_to_sine_waves.merge opts
      bell_harmonics.map do |b|
        {
          frequency: opts[:frequency] * b[:frequency_ratio],
          duration:  opts[:duration] * b[:duration_ratio],
          queue_in:  opts[:queue_in],
          gain:      (1.fdiv bell_harmonics.length),
          fade_out:  true
        }
      end
    end
  end

  begin # audio entity construction
    def generate_audio_data sine_wave, sample_rate
      sample_size = (sample_rate.fdiv (1000.fdiv 60)).ceil
      copy_count  = (sample_size.fdiv sine_wave.length).ceil
      sine_wave * copy_count
    end

    def defaults_new_audio_state
      { frequency: 440, duration: 60, gain: 1.0, fade_out: false, queue_in: 0 }
    end

    def new_audio_state args, opts = {}
      opts        = defaults_new_audio_state.merge opts
      decay_rate  = 0
      decay_rate  = 1.fdiv(opts[:duration]) * opts[:gain] if opts[:fade_out]
      frequency   = opts[:frequency]
      sample_rate = 48000

      {
        id:               (new_id! args),
        frequency:        frequency,
        sample_rate:      48000,
        stop_at:          args.tick_count + opts[:queue_in] + opts[:duration],
        gain:             opts[:gain].to_f,
        queue_at:         args.state.tick_count + opts[:queue_in],
        decay_rate:       decay_rate,
        pitch:            1.0,
        looping:          true,
        paused:           false
      }
    end

    def queue_audio args, opts = {}
      graph_wave args, opts[:wave], opts[:audio_state][:frequency]
      args.state.audio_queue << opts[:audio_state]
    end

    def new_id! args
      args.state.audio_id ||= 0
      args.state.audio_id  += 1
    end

    def graph_wave args, wave, frequency
      if args.state.tick_count != args.state.graphed_at
        args.outputs.static_lines.clear
        args.outputs.static_sprites.clear
      end

      wave = wave

      r, g, b = frequency.to_i % 85,
                frequency.to_i % 170,
                frequency.to_i % 255

      starting_rect = args.layout.rect(row: 5, col: 13)
      x_scale    = 10
      y_scale    = 100
      max_points = 25

      points = wave
      if wave.length > max_points
        resolution = wave.length.idiv max_points
        points = wave.find_all.with_index { |y, i| (i % resolution == 0) }
      end

      args.outputs.static_lines << points.map_with_index do |y, x|
        next_y = points[x + 1]

        if next_y
          {
            x:  starting_rect.x + (x * x_scale),
            y:  starting_rect.y + starting_rect.h.half + y_scale * y,
            x2: starting_rect.x + ((x + 1) * x_scale),
            y2: starting_rect.y + starting_rect.h.half + y_scale * next_y,
            r:  r,
            g:  g,
            b:  b
          }
        end
      end

      args.outputs.static_sprites << points.map_with_index do |y, x|
        {
          x:  (starting_rect.x + (x * x_scale)) - 2,
          y:  (starting_rect.y + starting_rect.h.half + y_scale * y) - 2,
          w:  4,
          h:  4,
          path: 'sprites/square-white.png',
          r: r,
          g: g,
          b: b
        }
      end

      args.state.graphed_at = args.state.tick_count
    end
  end

  begin # region: musical note mapping
    def defaults_frequency_for
      { note: :a, octave: 5, sharp:  false, flat:   false }
    end

    def frequency_for opts = {}
      opts = defaults_frequency_for.merge opts
      octave_offset_multiplier  = opts[:octave] - 5
      note = note_frequencies_octave_5[opts[:note]]
      if octave_offset_multiplier < 0
        note = note * 1 / (octave_offset_multiplier.abs + 1)
      elsif octave_offset_multiplier > 0
        note = note * (octave_offset_multiplier.abs + 1) / 1
      end
      note
    end

    def note_frequencies_octave_5
      {
        a: 440.0,
        a_sharp: 466.16, b_flat: 466.16,
        b: 493.88,
        c: 523.25,
        c_sharp: 554.37, d_flat: 587.33,
        d: 587.33,
        d_sharp: 622.25, e_flat: 659.25,
        e: 659.25,
        f: 698.25,
        f_sharp: 739.99, g_flat: 739.99,
        g: 783.99,
        g_sharp: 830.61, a_flat: 830.61
      }
    end
  end
end

$gtk.reset

Advanced Rendering - Labels With Wrapped Text - main.rb

# ./samples/07_advanced_rendering/00_labels_with_wrapped_text/app/main.rb
def tick args
  # defaults
  args.state.scroll_location  ||= 0
  args.state.textbox.messages ||= []
  args.state.textbox.scroll   ||= 0

  # render
  args.outputs.background_color = [0, 0, 0, 255]
  render_messages args
  render_instructions args

  # inputs
  if args.inputs.keyboard.key_down.one
    queue_message args, "Hello there neighbour! my name is mark, how is your day today?"
  end

  if args.inputs.keyboard.key_down.two
    queue_message args, "I'm doing great sir, actually I'm having a picnic today"
  end

  if args.inputs.keyboard.key_down.three
    queue_message args, "Well that sounds wonderful!"
  end

  if args.inputs.keyboard.key_down.home
    args.state.scroll_location = 1
  end

  if args.inputs.keyboard.key_down.delete
    clear_message_queue args
  end
end

def queue_message args, msg
  args.state.textbox.messages.concat msg.wrapped_lines 50
end

def clear_message_queue args
  args.state.textbox.messages = nil
  args.state.textbox.scroll = 0
end

def render_messages args
  args.outputs[:textbox].w = 400
  args.outputs[:textbox].h = 720

  args.outputs.primitives << args.state.textbox.messages.each_with_index.map do |s, idx|
    {
      x: 0,
      y: 20 * (args.state.textbox.messages.size - idx) + args.state.textbox.scroll * 20,
      text: s,
      size_enum: -3,
      alignment_enum: 0,
      r: 255, g:255, b: 255, a: 255
    }
  end

  args.outputs[:textbox].labels << args.state.textbox.messages.each_with_index.map do |s, idx|
    {
      x: 0,
      y: 20 * (args.state.textbox.messages.size - idx) + args.state.textbox.scroll * 20,
      text: s,
      size_enum: -3,
      alignment_enum: 0,
      r: 255, g:255, b: 255, a: 255
    }
  end

  args.outputs[:textbox].borders << [0, 0, args.outputs[:textbox].w, 720]

  args.state.textbox.scroll += args.inputs.mouse.wheel.y unless args.inputs.mouse.wheel.nil?

  if args.state.scroll_location > 0
    args.state.textbox.scroll = 0
    args.state.scroll_location = 0
  end

  args.outputs.sprites << [900, 0, args.outputs[:textbox].w, 720, :textbox]
end

def render_instructions args
  args.outputs.labels << [30,
                          30.from_top,
                          "press 1, 2, 3 to display messages, MOUSE WHEEL to scroll, HOME to go to top, BACKSPACE to delete.",
                          0, 255, 255]

  args.outputs.primitives << [0, 55.from_top, 1280, 30, :pixel, 0, 255, 0, 0, 0].sprite
end

Advanced Rendering - Rotating Label - main.rb

# ./samples/07_advanced_rendering/00_rotating_label/app/main.rb
def tick args
  # set the render target width and height to match the label
  args.outputs[:scene].w = 220
  args.outputs[:scene].h = 30


  # make the background transparent
  args.outputs[:scene].background_color = [255, 255, 255, 0]

  # set the blendmode of the label to 0 (no blending)
  # center it inside of the scene
  # set the vertical_alignment_enum to 1 (center)
  args.outputs[:scene].labels  << { x: 0,
                                    y: 15,
                                    text: "label in render target",
                                    blendmode_enum: 0,
                                    vertical_alignment_enum: 1 }

  # add a border to the render target
  args.outputs[:scene].borders << { x: 0,
                                    y: 0,
                                    w: args.outputs[:scene].w,
                                    h: args.outputs[:scene].h }

  # add the rendertarget to the main output as a sprite
  args.outputs.sprites << { x: 640 - args.outputs[:scene].w.half,
                            y: 360 - args.outputs[:scene].h.half,
                            w: args.outputs[:scene].w,
                            h: args.outputs[:scene].h,
                            angle: args.state.tick_count,
                            path: :scene }
end

Advanced Rendering - Render Targets Combining Sprites - main.rb

# ./samples/07_advanced_rendering/01_render_targets_combining_sprites/app/main.rb
# sample app shows how to use a render target to
# create a combined sprite
def tick args
  create_combined_sprite args

  # render the combined sprite
  # using its name :two_squares
  # have it move across the screen and rotate
  args.outputs.sprites << { x: args.state.tick_count % 1280,
                            y: 0,
                            w: 80,
                            h: 80,
                            angle: args.state.tick_count,
                            path: :two_squares }
end

def create_combined_sprite args
  # NOTE: you can have the construction of the combined
  #       sprite to happen every tick or only once (if the
  #       combined sprite never changes).
  #
  # if the combined sprite never changes, comment out the line
  # below to only construct it on the first frame and then
  # use the cached texture
  # return if args.state.tick_count != 0 # <---- guard clause to only construct on first frame and cache

  # define the dimensions of the combined sprite
  # the name of the combined sprite is :two_squares
  args.outputs[:two_squares].w = 80
  args.outputs[:two_squares].h = 80

  # put a blue sprite within the combined sprite
  # who's width is "thin"
  args.outputs[:two_squares].sprites << {
    x: 40 - 10,
    y: 0,
    w: 20,
    h: 80,
    path: 'sprites/square/blue.png'
  }

  # put a red sprite within the combined sprite
  # who's height is "thin"
  args.outputs[:two_squares].sprites << {
    x: 0,
    y: 40 - 10,
    w: 80,
    h: 20,
    path: 'sprites/square/red.png'
  }
end

Advanced Rendering - Simple Render Targets - main.rb

# ./samples/07_advanced_rendering/01_simple_render_targets/app/main.rb
def tick args
  # args.outputs.render_targets are really really powerful.
  # They essentially allow you to create a sprite programmatically and cache the result.

  # Create a render_target of a :block and a :gradient on tick zero.
  if args.state.tick_count == 0
    args.render_target(:block).solids << [0, 0, 1280, 100]

    # The gradient is actually just a collection of black solids with increasing
    # opacities.
    args.render_target(:gradient).solids << 90.map_with_index do |x|
      50.map_with_index do |y|
        [x * 15, y * 15, 15, 15, 0, 0, 0, (x * 3).fdiv(255) * 255]
      end
    end
  end

  # Take the :block render_target and present it horizontally centered.
  # Use a subsection of the render_targetd specified by source_x,
  # source_y, source_w, source_h.
  args.outputs.sprites << { x: 0,
                            y: 310,
                            w: 1280,
                            h: 100,
                            path: :block,
                            source_x: 0,
                            source_y: 0,
                            source_w: 1280,
                            source_h: 100 }

  # After rendering :block, render gradient on top of :block.
  args.outputs.sprites << [0, 0, 1280, 720, :gradient]

  args.outputs.labels  << [1270, 710, args.gtk.current_framerate, 0, 2, 255, 255, 255]
  tick_instructions args, "Sample app shows how to use render_targets (programmatically create cached sprites)."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

$gtk.reset

Advanced Rendering - Coordinate Systems And Render Targets - main.rb

# ./samples/07_advanced_rendering/02_coordinate_systems_and_render_targets/app/main.rb
def tick args
  # every 4.5 seconds, swap between origin_bottom_left and origin_center
  args.state.origin_state ||= :bottom_left

  if args.state.tick_count.zmod? 270
    args.state.origin_state = if args.state.origin_state == :bottom_left
                                :center
                              else
                                :bottom_left
                              end
  end

  if args.state.origin_state == :bottom_left
    tick_origin_bottom_left args
  else
    tick_origin_center args
  end
end

def tick_origin_center args
  # set the coordinate system to origin_center
  args.grid.origin_center!
  args.outputs.labels <<  { x: 0, y: 100, text: "args.grid.origin_center! with sprite inside of a render target, centered at 0, 0", vertical_alignment_enum: 1, alignment_enum: 1 }

  # create a render target with a sprint in the center assuming the origin is center screen
  args.outputs[:scene].sprites << { x: -50, y: -50, w: 100, h: 100, path: 'sprites/square/blue.png' }
  args.outputs.sprites << { x: -640, y: -360, w: 1280, h: 720, path: :scene }
end

def tick_origin_bottom_left args
  args.grid.origin_bottom_left!
  args.outputs.labels <<  { x: 640, y: 360 + 100, text: "args.grid.origin_bottom_left! with sprite inside of a render target, centered at 640, 360", vertical_alignment_enum: 1, alignment_enum: 1 }

  # create a render target with a sprint in the center assuming the origin is bottom left
  args.outputs[:scene].sprites << { x: 640 - 50, y: 360 - 50, w: 100, h: 100, path: 'sprites/square/blue.png' }
  args.outputs.sprites << { x: 0, y: 0, w: 1280, h: 720, path: :scene }
end

Advanced Rendering - Render Targets Thick Lines - main.rb

# ./samples/07_advanced_rendering/02_render_targets_thick_lines/app/main.rb
# Sample app shows how you can use render targets to create arbitrary shapes like a thicker line
def tick args
  args.state.line_cache ||= {}
  args.outputs.primitives << thick_line(args,
                                        args.state.line_cache,
                                        x: 0, y: 0, x2: 640, y2: 360, thickness: 3).merge(r: 0, g: 0, b: 0)
end

def thick_line args, cache, line
  line_length = Math.sqrt((line.x2 - line.x)**2 + (line.y2 - line.y)**2)
  name = "line-sprite-#{line_length}-#{line.thickness}"
  cached_line = cache[name]
  line_angle = Math.atan2(line.y2 - line.y1, line.x2 - line.x1) * 180 / Math::PI
  if cached_line
    perpendicular_angle = (line_angle + 90) % 360
    return cached_line.sprite.merge(x: line.x - perpendicular_angle.vector_x * (line.thickness / 2),
                                    y: line.y - perpendicular_angle.vector_y * (line.thickness / 2),
                                    angle: line_angle)
  end

  cache[name] = {
    line: line,
    thickness: line.thickness,
    sprite: {
      w: line_length,
      h: line.thickness,
      path: name,
      angle_anchor_x: 0,
      angle_anchor_y: 0
    }
  }

  args.outputs[name].w = line_length
  args.outputs[name].h = line.thickness
  args.outputs[name].solids << { x: 0, y: 0, w: line_length, h: line.thickness, r: 255, g: 255, b: 255 }
  return thick_line args, cache, line
end

Advanced Rendering - Render Targets With Tile Manipulation - main.rb

# ./samples/07_advanced_rendering/02_render_targets_with_tile_manipulation/app/main.rb
# This sample is meant to show you how to do that dripping transition thing
#  at the start of the original Doom. Most of this file is here to animate
#  a scene to wipe away; the actual wipe effect is in the last 20 lines or
#  so.

$gtk.reset   # reset all game state if reloaded.

def circle_of_blocks pass, xoffset, yoffset, angleoffset, blocksize, distance
  numblocks = 10

  for i in 1..numblocks do
    angle = ((360 / numblocks) * i) + angleoffset
    radians = angle * (Math::PI / 180)
    x = (xoffset + (distance * Math.cos(radians))).round
    y = (yoffset + (distance * Math.sin(radians))).round
    pass.solids << [ x, y, blocksize, blocksize, 255, 255, 0 ]
  end
end

def draw_scene args, pass
  pass.solids << [0, 360, 1280, 360, 0, 0, 200]
  pass.solids << [0, 0, 1280, 360, 0, 127, 0]

  blocksize = 100
  angleoffset = args.state.tick_count * 2.5
  centerx = (1280 - blocksize) / 2
  centery = (720 - blocksize) / 2

  circle_of_blocks pass, centerx, centery, angleoffset, blocksize * 2, 500
  circle_of_blocks pass, centerx, centery, angleoffset, blocksize, 325
  circle_of_blocks pass, centerx, centery, angleoffset, blocksize / 2, 200
  circle_of_blocks pass, centerx, centery, angleoffset, blocksize / 4, 100
end

def tick args
  segments = 160

  # On the first tick, initialize some stuff.
  if !args.state.yoffsets
    args.state.baseyoff = 0
    args.state.yoffsets = []
    for i in 0..segments do
      args.state.yoffsets << rand * 100
    end
  end

  # Just draw some random stuff for a few seconds.
  args.state.static_debounce ||= 60 * 2.5
  if args.state.static_debounce > 0
    last_frame = args.state.static_debounce == 1
    target = last_frame ? args.render_target(:last_frame) : args.outputs
    draw_scene args, target
    args.state.static_debounce -= 1
    return unless last_frame
  end

  # build up the wipe...

  # this is the thing we're wiping to.
  args.outputs.sprites << [ 0, 0, 1280, 720, 'dragonruby.png' ]

  return if (args.state.baseyoff > (1280 + 100))  # stop when done sliding

  segmentw = 1280 / segments

  x = 0
  for i in 0..segments do
    yoffset = 0
    if args.state.yoffsets[i] < args.state.baseyoff
      yoffset = args.state.baseyoff - args.state.yoffsets[i]
    end

    # (720 - yoffset) flips the coordinate system, (- 720) adjusts for the height of the segment.
    args.outputs.sprites << [ x, (720 - yoffset) - 720, segmentw, 720, 'last_frame', 0, 255, 255, 255, 255, x, 0, segmentw, 720 ]
    x += segmentw
  end

  args.state.baseyoff += 4

  tick_instructions args, "Sample app shows an advanced usage of render_target."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Advanced Rendering - Render Target Viewports - main.rb

# ./samples/07_advanced_rendering/03_render_target_viewports/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
   For example, if we want to create a new button, we would declare it as a new entity and
   then define its properties. (Remember, you can use state to define ANY property and it will
   be retained across frames.)

   If you have a solar system and you're creating args.state.sun and setting its image path to an
   image in the sprites folder, you would do the following:
   (See samples/99_sample_nddnug_workshop for more details.)

   args.state.sun ||= args.state.new_entity(:sun) do |s|
   s.path = 'sprites/sun.png'
   end

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

   For example, if we have a variable
   name = "Ruby"
   then the line
   puts "How are you, #{name}?"
   would print "How are you, Ruby?" to the console.
   (Remember, string interpolation only works with double quotes!)

 - Ternary operator (?): Similar to if statement; first evalulates whether a statement is
   true or false, and then executes a command depending on that result.
   For example, if we had a variable
   grade = 75
   and used the ternary operator in the command
   pass_or_fail = grade > 65 ? "pass" : "fail"
   then the value of pass_or_fail would be "pass" since grade's value was greater than 65.

 Reminders:

 - args.grid.(left|right|top|bottom): Pixel value for the boundaries of the virtual
   720 p screen (Dragon Ruby Game Toolkits's virtual resolution is always 1280x720).

 - Numeric#shift_(left|right|up|down): Shifts the Numeric in the correct direction
   by adding or subracting.

 - ARRAY#inside_rect?: An array with at least two values is considered a point. An array
   with at least four values is considered a rect. The inside_rect? function returns true
   or false depending on if the point is inside the rect.

 - ARRAY#intersect_rect?: Returns true or false depending on if the two rectangles intersect.

 - args.inputs.mouse.click: This property will be set if the mouse was clicked.
   For more information about the mouse, go to mygame/documentation/07-mouse.md.

 - args.inputs.keyboard.key_up.KEY: The value of the properties will be set
   to the frame  that the key_up event occurred (the frame correlates
   to args.state.tick_count).
   For more information about the keyboard, go to mygame/documentation/06-keyboard.md.

 - args.state.labels:
   The parameters for a label are
   1. the position (x, y)
   2. the text
   3. the size
   4. the alignment
   5. the color (red, green, and blue saturations)
   6. the alpha (or transparency)
   For more information about labels, go to mygame/documentation/02-labels.md.

 - args.state.lines:
   The parameters for a line are
   1. the starting position (x, y)
   2. the ending position (x2, y2)
   3. the color (red, green, and blue saturations)
   4. the alpha (or transparency)
   For more information about lines, go to mygame/documentation/04-lines.md.

 - args.state.solids (and args.state.borders):
   The parameters for a solid (or border) are
   1. the position (x, y)
   2. the width (w)
   3. the height (h)
   4. the color (r, g, b)
   5. the alpha (or transparency)
   For more information about solids and borders, go to mygame/documentation/03-solids-and-borders.md.

 - args.state.sprites:
   The parameters for a sprite are
   1. the position (x, y)
   2. the width (w)
   3. the height (h)
   4. the image path
   5. the angle
   6. the alpha (or transparency)
   For more information about sprites, go to mygame/documentation/05-sprites.md.
=end

# This sample app shows different objects that can be used when making games, such as labels,
# lines, sprites, solids, buttons, etc. Each demo section shows how these objects can be used.

# Also note that state.tick_count refers to the passage of time, or current frame.

class TechDemo
  attr_accessor :inputs, :state, :outputs, :grid, :args

  # Calls all methods necessary for the app to run properly.
  def tick
    labels_tech_demo
    lines_tech_demo
    solids_tech_demo
    borders_tech_demo
    sprites_tech_demo
    keyboards_tech_demo
    controller_tech_demo
    mouse_tech_demo
    point_to_rect_tech_demo
    rect_to_rect_tech_demo
    button_tech_demo
    export_game_state_demo
    window_state_demo
    render_seperators
  end

  # Shows output of different kinds of labels on the screen
  def labels_tech_demo
    outputs.labels << [grid.left.shift_right(5), grid.top.shift_down(5), "This is a label located at the top left."]
    outputs.labels << [grid.left.shift_right(5), grid.bottom.shift_up(30), "This is a label located at the bottom left."]
    outputs.labels << [ 5, 690, "Labels (x, y, text, size, align, r, g, b, a)"]
    outputs.labels << [ 5, 660, "Smaller label.",  -2]
    outputs.labels << [ 5, 630, "Small label.",    -1]
    outputs.labels << [ 5, 600, "Medium label.",    0]
    outputs.labels << [ 5, 570, "Large label.",     1]
    outputs.labels << [ 5, 540, "Larger label.",    2]
    outputs.labels << [300, 660, "Left aligned.",    0, 2]
    outputs.labels << [300, 640, "Center aligned.",  0, 1]
    outputs.labels << [300, 620, "Right aligned.",   0, 0]
    outputs.labels << [175, 595, "Red Label.",       0, 0, 255,   0,   0]
    outputs.labels << [175, 575, "Green Label.",     0, 0,   0, 255,   0]
    outputs.labels << [175, 555, "Blue Label.",      0, 0,   0,   0, 255]
    outputs.labels << [175, 535, "Faded Label.",     0, 0,   0,   0,   0, 128]
  end

  # Shows output of lines on the screen
  def lines_tech_demo
    outputs.labels << [5, 500, "Lines (x, y, x2, y2, r, g, b, a)"]
    outputs.lines  << [5, 450, 100, 450]
    outputs.lines  << [5, 430, 300, 430]
    outputs.lines  << [5, 410, 300, 410, state.tick_count % 255, 0, 0, 255] # red saturation changes
    outputs.lines  << [5, 390 - state.tick_count % 25, 300, 390, 0, 0, 0, 255] # y position changes
    outputs.lines  << [5 + state.tick_count % 200, 360, 300, 360, 0, 0, 0, 255] # x position changes
  end

  # Shows output of different kinds of solids on the screen
  def solids_tech_demo
    outputs.labels << [  5, 350, "Solids (x, y, w, h, r, g, b, a)"]
    outputs.solids << [ 10, 270, 50, 50]
    outputs.solids << [ 70, 270, 50, 50, 0, 0, 0]
    outputs.solids << [130, 270, 50, 50, 255, 0, 0]
    outputs.solids << [190, 270, 50, 50, 255, 0, 0, 128]
    outputs.solids << [250, 270, 50, 50, 0, 0, 0, 128 + state.tick_count % 128] # transparency changes
  end

  # Shows output of different kinds of borders on the screen
  # The parameters for a border are the same as the parameters for a solid
  def borders_tech_demo
    outputs.labels <<  [  5, 260, "Borders (x, y, w, h, r, g, b, a)"]
    outputs.borders << [ 10, 180, 50, 50]
    outputs.borders << [ 70, 180, 50, 50, 0, 0, 0]
    outputs.borders << [130, 180, 50, 50, 255, 0, 0]
    outputs.borders << [190, 180, 50, 50, 255, 0, 0, 128]
    outputs.borders << [250, 180, 50, 50, 0, 0, 0, 128 + state.tick_count % 128] # transparency changes
  end

  # Shows output of different kinds of sprites on the screen
  def sprites_tech_demo
    outputs.labels <<  [   5, 170, "Sprites (x, y, w, h, path, angle, a)"]
    outputs.sprites << [  10, 40, 128, 101, 'dragonruby.png']
    outputs.sprites << [ 150, 40, 128, 101, 'dragonruby.png', state.tick_count % 360] # angle changes
    outputs.sprites << [ 300, 40, 128, 101, 'dragonruby.png', 0, state.tick_count % 255] # transparency changes
  end

  # Holds size, alignment, color (black), and alpha (transparency) parameters
  # Using small_font as a parameter accounts for all remaining parameters
  # so they don't have to be repeatedly typed
  def small_font
    [-2, 0, 0, 0, 0, 255]
  end

  # Sets position of each row
  # Converts given row value to pixels that DragonRuby understands
  def row_to_px row_number

    # Row 0 starts 5 units below the top of the grid.
    # Each row afterward is 20 units lower.
    grid.top.shift_down(5).shift_down(20 * row_number)
  end

  # Uses labels to output current game time (passage of time), and whether or not "h" was pressed
  # If "h" is pressed, the frame is output when the key_up event occurred
  def keyboards_tech_demo
    outputs.labels << [460, row_to_px(0), "Current game time: #{state.tick_count}", small_font]
    outputs.labels << [460, row_to_px(2), "Keyboard input: inputs.keyboard.key_up.h", small_font]
    outputs.labels << [460, row_to_px(3), "Press \"h\" on the keyboard.", small_font]

    if inputs.keyboard.key_up.h # if "h" key_up event occurs
      state.h_pressed_at = state.tick_count # frame it occurred is stored
    end

    # h_pressed_at is initially set to false, and changes once the user presses the "h" key.
    state.h_pressed_at ||= false

    if state.h_pressed_at # if h is pressed (pressed_at has a frame number and is no longer false)
      outputs.labels << [460, row_to_px(4), "\"h\" was pressed at time: #{state.h_pressed_at}", small_font]
    else # otherwise, label says "h" was never pressed
      outputs.labels << [460, row_to_px(4), "\"h\" has never been pressed.", small_font]
    end

    # border around keyboard input demo section
    outputs.borders << [455, row_to_px(5), 360, row_to_px(2).shift_up(5) - row_to_px(5)]
  end

  # Sets definition for a small label
  # Makes it easier to position labels in respect to the position of other labels
  def small_label x, row, message
    [x, row_to_px(row), message, small_font]
  end

  # Uses small labels to show whether the "a" button on the controller is down, held, or up.
  # y value of each small label is set by calling the row_to_px method
  def controller_tech_demo
    x = 460
    outputs.labels << small_label(x, 6, "Controller one input: inputs.controller_one")
    outputs.labels << small_label(x, 7, "Current state of the \"a\" button.")
    outputs.labels << small_label(x, 8, "Check console window for more info.")

    if inputs.controller_one.key_down.a # if "a" is in "down" state
      outputs.labels << small_label(x, 9, "\"a\" button down: #{inputs.controller_one.key_down.a}")
      puts "\"a\" button down at #{inputs.controller_one.key_down.a}" # prints frame the event occurred
    elsif inputs.controller_one.key_held.a # if "a" is held down
      outputs.labels << small_label(x, 9, "\"a\" button held: #{inputs.controller_one.key_held.a}")
    elsif inputs.controller_one.key_up.a # if "a" is in up state
      outputs.labels << small_label(x, 9, "\"a\" button up: #{inputs.controller_one.key_up.a}")
      puts "\"a\" key up at #{inputs.controller_one.key_up.a}"
    else # if no event has occurred
      outputs.labels << small_label(x, 9, "\"a\" button state is nil.")
    end

    # border around controller input demo section
    outputs.borders << [455, row_to_px(10), 360, row_to_px(6).shift_up(5) - row_to_px(10)]
  end

  # Outputs when the mouse was clicked, as well as the coordinates on the screen
  # of where the click occurred
  def mouse_tech_demo
    x = 460

    outputs.labels << small_label(x, 11, "Mouse input: inputs.mouse")

    if inputs.mouse.click # if click has a value and is not nil
      state.last_mouse_click = inputs.mouse.click # coordinates of click are stored
    end

    if state.last_mouse_click # if mouse is clicked (has coordinates as value)
      # outputs the time (frame) the click occurred, as well as how many frames have passed since the event
      outputs.labels << small_label(x, 12, "Mouse click happened at: #{state.last_mouse_click.created_at}, #{state.last_mouse_click.created_at_elapsed}")
      # outputs coordinates of click
      outputs.labels << small_label(x, 13, "Mouse click location: #{state.last_mouse_click.point.x}, #{state.last_mouse_click.point.y}")
    else # otherwise if the mouse has not been clicked
      outputs.labels << small_label(x, 12, "Mouse click has not occurred yet.")
      outputs.labels << small_label(x, 13, "Please click mouse.")
    end
  end

  # Outputs whether a mouse click occurred inside or outside of a box
  def point_to_rect_tech_demo
    x = 460

    outputs.labels << small_label(x, 15, "Click inside the blue box maybe ---->")

    box = [765, 370, 50, 50, 0, 0, 170] # blue box
    outputs.borders << box

    if state.last_mouse_click # if the mouse was clicked
      if state.last_mouse_click.point.inside_rect? box # if mouse clicked inside box
        outputs.labels << small_label(x, 16, "Mouse click happened inside the box.")
      else # otherwise, if mouse was clicked outside the box
        outputs.labels << small_label(x, 16, "Mouse click happened outside the box.")
      end
    else # otherwise, if was not clicked at all
      outputs.labels << small_label(x, 16, "Mouse click has not occurred yet.") # output if the mouse was not clicked
    end

    # border around mouse input demo section
    outputs.borders << [455, row_to_px(14), 360, row_to_px(11).shift_up(5) - row_to_px(14)]
  end

  # Outputs a red box onto the screen. A mouse click from the user inside of the red box will output
  # a smaller box. If two small boxes are inside of the red box, it will be determined whether or not
  # they intersect.
  def rect_to_rect_tech_demo
    x = 460

    outputs.labels << small_label(x, 17.5, "Click inside the red box below.") # label with instructions
    red_box = [460, 250, 355, 90, 170, 0, 0] # definition of the red box
    outputs.borders << red_box # output as a border (not filled in)

    # If the mouse is clicked inside the red box, two collision boxes are created.
    if inputs.mouse.click
      if inputs.mouse.click.point.inside_rect? red_box
        if !state.box_collision_one # if the collision_one box does not yet have a definition
          # Subtracts 25 from the x and y positions of the click point in order to make the click point the center of the box.
          # You can try deleting the subtraction to see how it impacts the box placement.
          state.box_collision_one = [inputs.mouse.click.point.x - 25, inputs.mouse.click.point.y - 25, 50, 50, 180, 0,   0, 180]  # sets definition
        elsif !state.box_collision_two # if collision_two does not yet have a definition
          state.box_collision_two = [inputs.mouse.click.point.x - 25, inputs.mouse.click.point.y - 25, 50, 50,   0, 0, 180, 180] # sets definition
        else
          state.box_collision_one = nil # both boxes are empty
          state.box_collision_two = nil
        end
      end
    end

    # If collision boxes exist, they are output onto screen inside the red box as solids
    if state.box_collision_one
      outputs.solids << state.box_collision_one
    end

    if state.box_collision_two
      outputs.solids << state.box_collision_two
    end

    # Outputs whether or not the two collision boxes intersect.
    if state.box_collision_one && state.box_collision_two # if both collision_boxes are defined (and not nil or empty)
      if state.box_collision_one.intersect_rect? state.box_collision_two # if the two boxes intersect
        outputs.labels << small_label(x, 23.5, 'The boxes intersect.')
      else # otherwise, if the two boxes do not intersect
        outputs.labels << small_label(x, 23.5, 'The boxes do not intersect.')
      end
    else
      outputs.labels << small_label(x, 23.5, '--') # if the two boxes are not defined (are nil or empty), this label is output
    end
  end

  # Creates a button and outputs it onto the screen using labels and borders.
  # If the button is clicked, the color changes to make it look faded.
  def button_tech_demo
    x, y, w, h = 460, 160, 300, 50
    state.button        ||= state.new_entity(:button_with_fade)

    # Adds w.half to x and h.half + 10 to y in order to display the text inside the button's borders.
    state.button.label  ||= [x + w.half, y + h.half + 10, "click me and watch me fade", 0, 1]
    state.button.border ||= [x, y, w, h]

    if inputs.mouse.click && inputs.mouse.click.point.inside_rect?(state.button.border) # if mouse is clicked, and clicked inside button's border
      state.button.clicked_at = inputs.mouse.click.created_at # stores the time the click occurred
    end

    outputs.labels << state.button.label
    outputs.borders << state.button.border

    if state.button.clicked_at # if button was clicked (variable has a value and is not nil)

      # The appearance of the button changes for 0.25 seconds after the time the button is clicked at.
      # The color changes (rgb is set to 0, 180, 80) and the transparency gradually changes.
      # Change 0.25 to 1.25 and notice that the transparency takes longer to return to normal.
      outputs.solids << [x, y, w, h, 0, 180, 80, 255 * state.button.clicked_at.ease(0.25.seconds, :flip)]
    end
  end

  # Creates a new button by declaring it as a new entity, and sets values.
  def new_button_prefab x, y, message
    w, h = 300, 50
    button        = state.new_entity(:button_with_fade)
    button.label  = [x + w.half, y + h.half + 10, message, 0, 1] # '+ 10' keeps label's text within button's borders
    button.border = [x, y, w, h] # sets border definition
    button
  end

  # If the mouse has been clicked and the click's location is inside of the button's border, that means
  # that the button has been clicked. This method returns a boolean value.
  def button_clicked? button
    inputs.mouse.click && inputs.mouse.click.point.inside_rect?(button.border)
  end

  # Determines if button was clicked, and changes its appearance if it is clicked
  def tick_button_prefab button
    outputs.labels << button.label # outputs button's label and border
    outputs.borders << button.border

    if button_clicked? button # if button is clicked
      button.clicked_at = inputs.mouse.click.created_at # stores the time that the button was clicked
    end

    if button.clicked_at # if clicked_at has a frame value and is not nil
      # button is output; color changes and transparency changes for 0.25 seconds after click occurs
      outputs.solids << [button.border.x, button.border.y, button.border.w, button.border.h,
                         0, 180, 80, 255 * button.clicked_at.ease(0.25.seconds, :flip)] # transparency changes for 0.25 seconds
    end
  end

  # Exports the app's game state if the export button is clicked.
  def export_game_state_demo
    state.export_game_state_button ||= new_button_prefab(460, 100, "click to export app state")
    tick_button_prefab(state.export_game_state_button) # calls method to output button
    if button_clicked? state.export_game_state_button # if the export button is clicked
      args.gtk.export! "Exported from clicking the export button in the tech demo." # the export occurs
    end
  end

  # The mouse and keyboard focus are set to "yes" when the Dragonruby window is the active window.
  def window_state_demo
    m = $gtk.args.inputs.mouse.has_focus ? 'Y' : 'N' # ternary operator (similar to if statement)
    k = $gtk.args.inputs.keyboard.has_focus ? 'Y' : 'N'
    outputs.labels << [460, 20, "mouse focus: #{m}   keyboard focus: #{k}", small_font]
  end

  #Sets values for the horizontal separator (divides demo sections)
  def horizontal_seperator y, x, x2
    [x, y, x2, y, 150, 150, 150]
  end

  #Sets the values for the vertical separator (divides demo sections)
  def vertical_seperator x, y, y2
    [x, y, x, y2, 150, 150, 150]
  end

  # Outputs vertical and horizontal separators onto the screen to separate each demo section.
  def render_seperators
    outputs.lines << horizontal_seperator(505, grid.left, 445)
    outputs.lines << horizontal_seperator(353, grid.left, 445)
    outputs.lines << horizontal_seperator(264, grid.left, 445)
    outputs.lines << horizontal_seperator(174, grid.left, 445)

    outputs.lines << vertical_seperator(445, grid.top, grid.bottom)

    outputs.lines << horizontal_seperator(690, 445, 820)
    outputs.lines << horizontal_seperator(426, 445, 820)

    outputs.lines << vertical_seperator(820, grid.top, grid.bottom)
  end
end

$tech_demo = TechDemo.new

def tick args
  $tech_demo.inputs = args.inputs
  $tech_demo.state = args.state
  $tech_demo.grid = args.grid
  $tech_demo.args = args
  $tech_demo.outputs = args.render_target(:mini_map)
  $tech_demo.tick
  args.outputs.labels  << [830, 715, "Render target:", [-2, 0, 0, 0, 0, 255]]
  args.outputs.sprites << [0, 0, 1280, 720, :mini_map]
  args.outputs.sprites << [830, 300, 675, 379, :mini_map]
  tick_instructions args, "Sample app shows all the rendering apis available."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Advanced Rendering - Render Primitive Hierarchies - main.rb

# ./samples/07_advanced_rendering/04_render_primitive_hierarchies/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - Nested array: An array whose individual elements are also arrays; useful for
   storing groups of similar data.  Also called multidimensional arrays.

   In this sample app, we see nested arrays being used in object definitions.
   Notice the parameters for solids, listed below. Parameters 1-3 set the
   definition for the rect, and parameter 4 sets the definition of the color.

   Instead of having a solid definition that looks like this,
   [X, Y, W, H, R, G, B]
   we can separate it into two separate array definitions in one, like this
   [[X, Y, W, H], [R, G, B]]
   and both options work fine in defining our solid (or any object).

 - Collections: Lists of data; useful for organizing large amounts of data.
   One element of a collection could be an array (which itself contains many elements).
   For example, a collection that stores two solid objects would look like this:
   [
    [100, 100, 50, 50, 0, 0, 0],
    [100, 150, 50, 50, 255, 255, 255]
   ]
   If this collection was added to args.outputs.solids, two solids would be output
   next to each other, one black and one white.
   Nested arrays can be used in collections, as you will see in this sample app.

 Reminders:

 - args.outputs.solids: An array. The values generate a solid.
   The parameters for a solid are
   1. The position on the screen (x, y)
   2. The width (w)
   3. The height (h)
   4. The color (r, g, b) (if a color is not assigned, the object's default color will be black)
   NOTE: THE PARAMETERS ARE THE SAME FOR BORDERS!

   Here is an example of a (red) border or solid definition:
   [100, 100, 400, 500, 255, 0, 0]
   It will be a solid or border depending on if it is added to args.outputs.solids or args.outputs.borders.
   For more information about solids and borders, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.sprites: An array. The values generate a sprite.
   The parameters for sprites are
   1. The position on the screen (x, y)
   2. The width (w)
   3. The height (h)
   4. The image path (p)

   Here is an example of a sprite definition:
   [100, 100, 400, 500, 'sprites/dragonruby.png']
   For more information about sprites, go to mygame/documentation/05-sprites.md.

=end

# This code demonstrates the creation and output of objects like sprites, borders, and solids
# If filled in, they are solids
# If hollow, they are borders
# If images, they are sprites

# Solids are added to args.outputs.solids
# Borders are added to args.outputs.borders
# Sprites are added to args.outputs.sprites

# The tick method runs 60 frames every second.
# Your game is going to happen under this one function.
def tick args
  border_as_solid_and_solid_as_border args
  sprite_as_border_or_solids args
  collection_of_borders_and_solids args
  collection_of_sprites args
end

# Shows a border being output onto the screen as a border and a solid
# Also shows how colors can be set
def border_as_solid_and_solid_as_border args
  border = [0, 0, 50, 50]
  args.outputs.borders << border
  args.outputs.solids  << border

  # Red, green, blue saturations (last three parameters) can be any number between 0 and 255
  border_with_color = [0, 100, 50, 50, 255, 0, 0]
  args.outputs.borders << border_with_color
  args.outputs.solids  << border_with_color

  border_with_nested_color = [0, 200, 50, 50, [0, 255, 0]] # nested color
  args.outputs.borders << border_with_nested_color
  args.outputs.solids  << border_with_nested_color

  border_with_nested_rect = [[0, 300, 50, 50], 0, 0, 255] # nested rect
  args.outputs.borders << border_with_nested_rect
  args.outputs.solids  << border_with_nested_rect

  border_with_nested_color_and_rect = [[0, 400, 50, 50], [255, 0, 255]] # nested rect and color
  args.outputs.borders << border_with_nested_color_and_rect
  args.outputs.solids  << border_with_nested_color_and_rect
end

# Shows a sprite output onto the screen as a sprite, border, and solid
# Demonstrates that all three outputs appear differently on screen
def sprite_as_border_or_solids args
  sprite = [100, 0, 50, 50, 'sprites/ship.png']
  args.outputs.sprites << sprite

  # Sprite_as_border variable has same parameters (excluding position) as above object,
  # but will appear differently on screen because it is added to args.outputs.borders
  sprite_as_border = [100, 100, 50, 50, 'sprites/ship.png']
  args.outputs.borders << sprite_as_border

  # Sprite_as_solid variable has same parameters (excluding position) as above object,
  # but will appear differently on screen because it is added to args.outputs.solids
  sprite_as_solid = [100, 200, 50, 50, 'sprites/ship.png']
  args.outputs.solids << sprite_as_solid
end

# Holds and outputs a collection of borders and a collection of solids
# Collections are created by using arrays to hold parameters of each individual object
def collection_of_borders_and_solids args
  collection_borders = [
    [
      [200,  0, 50, 50],                    # black border
      [200,  100, 50, 50, 255, 0, 0],       # red border
      [200,  200, 50, 50, [0, 255, 0]],     # nested color
    ],
    [[200, 300, 50, 50], 0, 0, 255],        # nested rect
    [[200, 400, 50, 50], [255, 0, 255]]     # nested rect and nested color
  ]

  args.outputs.borders << collection_borders

  collection_solids = [
    [
      [[300, 300, 50, 50], 0, 0, 255],      # nested rect
      [[300, 400, 50, 50], [255, 0, 255]]   # nested rect and nested color
    ],
    [300,  0, 50, 50],
    [300,  100, 50, 50, 255, 0, 0],
    [300,  200, 50, 50, [0, 255, 0]],       # nested color
  ]

  args.outputs.solids << collection_solids
end

# Holds and outputs a collection of sprites by adding it to args.outputs.sprites
# Also outputs a collection with same parameters (excluding position) by adding
# it to args.outputs.solids and another to args.outputs.borders
def collection_of_sprites args
  sprites_collection = [
    [
      [400, 0, 50, 50, 'sprites/ship.png'],
      [400, 100, 50, 50, 'sprites/ship.png'],
    ],
    [400, 200, 50, 50, 'sprites/ship.png']
  ]

  args.outputs.sprites << sprites_collection

  args.outputs.solids << [
    [500, 0, 50, 50, 'sprites/ship.png'],
    [500, 100, 50, 50, 'sprites/ship.png'],
    [[[500, 200, 50, 50, 'sprites/ship.png']]]
  ]

  args.outputs.borders << [
    [
      [600, 0, 50, 50, 'sprites/ship.png'],
      [600, 100, 50, 50, 'sprites/ship.png'],
    ],
    [600, 200, 50, 50, 'sprites/ship.png']
  ]
end

Advanced Rendering - Render Primitives As Hash - main.rb

# ./samples/07_advanced_rendering/05_render_primitives_as_hash/app/main.rb
=begin

 Reminders:

 - Hashes: Collection of unique keys and their corresponding values. The value can be found
   using their keys.

   For example, if we have a "numbers" hash that stores numbers in English as the
   key and numbers in Spanish as the value, we'd have a hash that looks like this...
   numbers = { "one" => "uno", "two" => "dos", "three" => "tres" }
   and on it goes.

   Now if we wanted to find the corresponding value of the "one" key, we could say
   puts numbers["one"]
   which would print "uno" to the console.

 - args.outputs.sprites: An array. The values generate a sprite.
   The parameters are [X, Y, WIDTH, HEIGHT, PATH, ANGLE, ALPHA, RED, GREEN, BLUE]
   For more information about sprites, go to mygame/documentation/05-sprites.md.

 - args.outputs.labels: An array. The values generate a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.

 - args.outputs.solids: An array. The values generate a solid.
   The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE, ALPHA]
   For more information about solids, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.borders: An array. The values generate a border.
   The parameters are the same as a solid.
   For more information about borders, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.lines: An array. The values generate a line.
   The parameters are [X1, Y1, X2, Y2, RED, GREEN, BLUE]
   For more information about labels, go to mygame/documentation/02-labels.md.

=end

# This sample app demonstrates how hashes can be used to output different kinds of objects.

def tick args
  args.state.angle ||= 0 # initializes angle to 0
  args.state.angle  += 1 # increments angle by 1 every frame (60 times a second)

  # Outputs sprite using a hash
  args.outputs.sprites << {
    x: 30,                          # sprite position
    y: 550,
    w: 128,                         # sprite size
    h: 101,
    path: "dragonruby.png",         # image path
    angle: args.state.angle,        # angle
    a: 255,                         # alpha (transparency)
    r: 255,                         # color saturation
    g: 255,
    b: 255,
    tile_x:  0,                     # sprite sub division/tile
    tile_y:  0,
    tile_w: -1,
    tile_h: -1,
    flip_vertically: false,         # don't flip sprite
    flip_horizontally: false,
    angle_anchor_x: 0.5,            # rotation center set to middle
    angle_anchor_y: 0.5
  }

  # Outputs label using a hash
  args.outputs.labels << {
    x:              200,                 # label position
    y:              550,
    text:           "dragonruby",        # label text
    size_enum:      2,
    alignment_enum: 1,
    r:              155,                 # color saturation
    g:              50,
    b:              50,
    a:              255,                 # transparency
    font:           "fonts/manaspc.ttf"  # font style; without mentioned file, label won't output correctly
  }

  # Outputs solid using a hash
  # [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE, ALPHA]
  args.outputs.solids << {
    x: 400,                         # position
    y: 550,
    w: 160,                         # size
    h:  90,
    r: 120,                         # color saturation
    g:  50,
    b:  50,
    a: 255                          # transparency
  }

  # Outputs border using a hash
  # Same parameters as a solid
  args.outputs.borders << {
    x: 600,
    y: 550,
    w: 160,
    h:  90,
    r: 120,
    g:  50,
    b:  50,
    a: 255
  }

  # Outputs line using a hash
  args.outputs.lines << {
    x:  900,                        # starting position
    y:  550,
    x2: 1200,                       # ending position
    y2: 550,
    r:  120,                        # color saturation
    g:   50,
    b:   50,
    a:  255                         # transparency
  }

  # Outputs sprite as a primitive using a hash
  args.outputs.primitives << {
    x: 30,                          # position
    y: 200,
    w: 128,                         # size
    h: 101,
    path: "dragonruby.png",         # image path
    angle: args.state.angle,        # angle
    a: 255,                         # transparency
    r: 255,                         # color saturation
    g: 255,
    b: 255,
    tile_x:  0,                     # sprite sub division/tile
    tile_y:  0,
    tile_w: -1,
    tile_h: -1,
    flip_vertically: false,         # don't flip
    flip_horizontally: false,
    angle_anchor_x: 0.5,            # rotation center set to middle
    angle_anchor_y: 0.5
  }.sprite!

  # Outputs label as primitive using a hash
  args.outputs.primitives << {
    x:         200,                 # position
    y:         200,
    text:      "dragonruby",        # text
    size:      2,
    alignment: 1,
    r:         155,                 # color saturation
    g:         50,
    b:         50,
    a:         255,                 # transparency
    font:      "fonts/manaspc.ttf"  # font style
  }.label!

  # Outputs solid as primitive using a hash
  args.outputs.primitives << {
    x: 400,                         # position
    y: 200,
    w: 160,                         # size
    h:  90,
    r: 120,                         # color saturation
    g:  50,
    b:  50,
    a: 255                          # transparency
  }.solid!

  # Outputs border as primitive using a hash
  # Same parameters as solid
  args.outputs.primitives << {
    x: 600,                         # position
    y: 200,
    w: 160,                         # size
    h:  90,
    r: 120,                         # color saturation
    g:  50,
    b:  50,
    a: 255                          # transparency
  }.border!

  # Outputs line as primitive using a hash
  args.outputs.primitives << {
    x:  900,                        # starting position
    y:  200,
    x2: 1200,                       # ending position
    y2: 200,
    r:  120,                        # color saturation
    g:   50,
    b:   50,
    a:  255                         # transparency
  }.line!
end

Advanced Rendering - Buttons As Render Targets - main.rb

# ./samples/07_advanced_rendering/06_buttons_as_render_targets/app/main.rb
def tick args
  # create a texture/render_target that's composed of a border and a label
  create_button args, :hello_world_button, "Hello World", 500, 50

  # two button primitives using the hello_world_button render_target
  args.state.buttons ||= [
    # one button at the top
    { id: :top_button, x: 640 - 250, y: 80.from_top, w: 500, h: 50, path: :hello_world_button },

    # another button at the buttom, upside down, and flipped horizontally
    { id: :bottom_button, x: 640 - 250, y: 30, w: 500, h: 50, path: :hello_world_button, angle: 180, flip_horizontally: true },
  ]

  # check if a mouse click occurred
  if args.inputs.mouse.click
    # check to see if any of the buttons were intersected
    # and set the selected button if so
    args.state.selected_button = args.state.buttons.find { |b| b.intersect_rect? args.inputs.mouse }
  end

  # render the buttons
  args.outputs.sprites << args.state.buttons

  # if there was a selected button, print it's id
  if args.state.selected_button
    args.outputs.labels << { x: 30, y: 30.from_top, text: "#{args.state.selected_button.id} was clicked." }
  end
end

def create_button args, id, text, w, h
  # render_targets only need to be created once, we use the the id to determine if the texture
  # has already been created
  args.state.created_buttons ||= {}
  return if args.state.created_buttons[id]

  # if the render_target hasn't been created, then generate it and store it in the created_buttons cache
  args.state.created_buttons[id] = { created_at: args.state.tick_count, id: id, w: w, h: h, text: text }

  # define the w/h of the texture
  args.outputs[id].w = w
  args.outputs[id].h = h

  # create a border
  args.outputs[id].borders << { x: 0, y: 0, w: w, h: h }

  # create a label centered vertically and horizontally within the texture
  args.outputs[id].labels << { x: w / 2, y: h / 2, text: text, vertical_alignment_enum: 1, alignment_enum: 1 }
end

Advanced Rendering - Pixel Arrays - main.rb

# ./samples/07_advanced_rendering/06_pixel_arrays/app/main.rb
def tick args
  args.state.posinc ||= 1
  args.state.pos ||= 0
  args.state.rotation ||= 0

  dimension = 10  # keep it small and let the GPU scale it when rendering the sprite.

  # Set up our "scanner" pixel array and fill it with black pixels.
  args.pixel_array(:scanner).width = dimension
  args.pixel_array(:scanner).height = dimension
  args.pixel_array(:scanner).pixels.fill(0xFF000000, 0, dimension * dimension)  # black, full alpha

  # Draw a green line that bounces up and down the sprite.
  args.pixel_array(:scanner).pixels.fill(0xFF00FF00, dimension * args.state.pos, dimension)  # green, full alpha

  # Adjust position for next frame.
  args.state.pos += args.state.posinc
  if args.state.posinc > 0 && args.state.pos >= dimension
    args.state.posinc = -1
    args.state.pos = dimension - 1
  elsif args.state.posinc < 0 && args.state.pos < 0
    args.state.posinc = 1
    args.state.pos = 1
  end

  # New/changed pixel arrays get uploaded to the GPU before we render
  #  anything. At that point, they can be scaled, rotated, and otherwise
  #  used like any other sprite.
  w = 100
  h = 100
  x = (1280 - w) / 2
  y = (720 - h) / 2
  args.outputs.background_color = [64, 0, 128]
  args.outputs.primitives << [x, y, w, h, :scanner, args.state.rotation].sprite
  args.state.rotation += 1

  args.outputs.primitives << args.gtk.current_framerate_primitives
end


$gtk.reset

Advanced Rendering - Pixel Arrays From File - main.rb

# ./samples/07_advanced_rendering/06_pixel_arrays_from_file/app/main.rb
def tick args
  args.state.rotation ||= 0

  # on load, get pixels from png and load it into a pixel array
  if args.state.tick_count == 0
    pixel_array = args.gtk.get_pixels 'sprites/square/blue.png'
    args.pixel_array(:square).w = pixel_array.w
    args.pixel_array(:square).h = pixel_array.h
    pixel_array.pixels.each_with_index do |p, i|
      args.pixel_array(:square).pixels[i] = p
    end
  end

  w = 100
  h = 100
  x = (1280 - w) / 2
  y = (720 - h) / 2
  args.outputs.background_color = [64, 0, 128]
  # render the pixel array by name
  args.outputs.primitives << { x: x, y: y, w: w, h: h, path: :square, angle: args.state.rotation }
  args.state.rotation += 1

  args.outputs.primitives << args.gtk.current_framerate_primitives
end

$gtk.reset

Advanced Rendering - Shake Camera - main.rb

# ./samples/07_advanced_rendering/07_shake_camera/app/main.rb
# Demo of camera shake
# Hold space to shake and release to stop

class ScreenShake
  attr_gtk

  def tick
    defaults
    calc_camera

    outputs.labels << { x: 600, y: 400, text: "Hold Space!" }

    # Add outputs to :scene
    outputs[:scene].sprites << { x: 100, y: 100,          w: 80, h: 80, path: 'sprites/square/blue.png' }
    outputs[:scene].sprites << { x: 200, y: 300.from_top, w: 80, h: 80, path: 'sprites/square/blue.png' }
    outputs[:scene].sprites << { x: 900, y: 200,          w: 80, h: 80, path: 'sprites/square/blue.png' }

    # Describe how to render :scene
    outputs.sprites << { x: 0 - state.camera.x_offset,
                         y: 0 - state.camera.y_offset,
                         w: 1280,
                         h: 720,
                         angle: state.camera.angle,
                         path: :scene }
  end

  def defaults
    state.camera.trauma ||= 0
    state.camera.angle ||= 0
    state.camera.x_offset ||= 0
    state.camera.y_offset ||= 0
  end

  def calc_camera
    if inputs.keyboard.key_held.space
      state.camera.trauma += 0.02
    end

    next_camera_angle = 180.0 / 20.0 * state.camera.trauma**2
    next_offset       = 100.0 * state.camera.trauma**2

    # Ensure that the camera angle always switches from
    # positive to negative and vice versa
    # which gives the effect of shaking back and forth
    state.camera.angle = state.camera.angle > 0 ?
                           next_camera_angle * -1 :
                           next_camera_angle

    state.camera.x_offset = next_offset.randomize(:sign, :ratio)
    state.camera.y_offset = next_offset.randomize(:sign, :ratio)

    # Gracefully degrade trauma
    state.camera.trauma *= 0.95
  end
end

def tick args
  $screen_shake ||= ScreenShake.new
  $screen_shake.args = args
  $screen_shake.tick
end

Advanced Rendering - Simple Camera - main.rb

# ./samples/07_advanced_rendering/07_simple_camera/app/main.rb
def tick args
  # variables you can play around with
  args.state.world.w      ||= 1280
  args.state.world.h      ||= 720

  args.state.player.x     ||= 0
  args.state.player.y     ||= 0
  args.state.player.size  ||= 32

  args.state.enemy.x      ||= 700
  args.state.enemy.y      ||= 700
  args.state.enemy.size   ||= 16

  args.state.camera.x                ||= 640
  args.state.camera.y                ||= 300
  args.state.camera.scale            ||= 1.0
  args.state.camera.show_empty_space ||= :yes

  # instructions
  args.outputs.primitives << { x: 0, y:  80.from_top, w: 360, h: 80, r: 0, g: 0, b: 0, a: 128 }.solid!
  args.outputs.primitives << { x: 10, y: 10.from_top, text: "arrow keys to move around", r: 255, g: 255, b: 255}.label!
  args.outputs.primitives << { x: 10, y: 30.from_top, text: "+/- to change zoom of camera", r: 255, g: 255, b: 255}.label!
  args.outputs.primitives << { x: 10, y: 50.from_top, text: "tab to change camera edge behavior", r: 255, g: 255, b: 255}.label!

  # render scene
  args.outputs[:scene].w = args.state.world.w
  args.outputs[:scene].h = args.state.world.h

  args.outputs[:scene].solids << { x: 0, y: 0, w: args.state.world.w, h: args.state.world.h, r: 20, g: 60, b: 80 }
  args.outputs[:scene].solids << { x: args.state.player.x, y: args.state.player.y,
                                   w: args.state.player.size, h: args.state.player.size, r: 80, g: 155, b: 80 }
  args.outputs[:scene].solids << { x: args.state.enemy.x, y: args.state.enemy.y,
                                   w: args.state.enemy.size, h: args.state.enemy.size, r: 155, g: 80, b: 80 }

  # render camera
  scene_position = calc_scene_position args
  args.outputs.sprites << { x: scene_position.x,
                            y: scene_position.y,
                            w: scene_position.w,
                            h: scene_position.h,
                            path: :scene }

  # move player
  if args.inputs.directional_angle
    args.state.player.x += args.inputs.directional_angle.vector_x * 5
    args.state.player.y += args.inputs.directional_angle.vector_y * 5
    args.state.player.x  = args.state.player.x.clamp(0, args.state.world.w - args.state.player.size)
    args.state.player.y  = args.state.player.y.clamp(0, args.state.world.h - args.state.player.size)
  end

  # +/- to zoom in and out
  if args.inputs.keyboard.plus && args.state.tick_count.zmod?(3)
    args.state.camera.scale += 0.05
  elsif args.inputs.keyboard.hyphen && args.state.tick_count.zmod?(3)
    args.state.camera.scale -= 0.05
  elsif args.inputs.keyboard.key_down.tab
    if args.state.camera.show_empty_space == :yes
      args.state.camera.show_empty_space = :no
    else
      args.state.camera.show_empty_space = :yes
    end
  end

  args.state.camera.scale = args.state.camera.scale.greater(0.1)
end

def calc_scene_position args
  result = { x: args.state.camera.x - (args.state.player.x * args.state.camera.scale),
             y: args.state.camera.y - (args.state.player.y * args.state.camera.scale),
             w: args.state.world.w * args.state.camera.scale,
             h: args.state.world.h * args.state.camera.scale,
             scale: args.state.camera.scale }

  return result if args.state.camera.show_empty_space == :yes

  if result.w < args.grid.w
    result.merge!(x: (args.grid.w - result.w).half)
  elsif (args.state.player.x * result.scale) < args.grid.w.half
    result.merge!(x: 10)
  elsif (result.x + result.w) < args.grid.w
    result.merge!(x: - result.w + (args.grid.w - 10))
  end

  if result.h < args.grid.h
    result.merge!(y: (args.grid.h - result.h).half)
  elsif (result.y) > 10
    result.merge!(y: 10)
  elsif (result.y + result.h) < args.grid.h
    result.merge!(y: - result.h + (args.grid.h - 10))
  end

  result
end

Advanced Rendering - Splitscreen Camera - main.rb

# ./samples/07_advanced_rendering/08_splitscreen_camera/app/main.rb
class CameraMovement
  attr_accessor :state, :inputs, :outputs, :grid

  #==============================================================================================
  #Serialize
  def serialize
    {state: state, inputs: inputs, outputs: outputs, grid: grid }
  end

  def inspect
    serialize.to_s
  end

  def to_s
    serialize.to_s
  end

  #==============================================================================================
  #Tick
  def tick
    defaults
    calc
    render
    input
  end

  #==============================================================================================
  #Default functions
  def defaults
    outputs[:scene].background_color = [0,0,0]
    state.trauma ||= 0.0
    state.trauma_power ||= 2
    state.player_cyan ||= new_player_cyan
    state.player_magenta ||= new_player_magenta
    state.camera_magenta ||= new_camera_magenta
    state.camera_cyan ||= new_camera_cyan
    state.camera_center ||= new_camera_center
    state.room ||= new_room
  end

  def default_player x, y, w, h, sprite_path
    state.new_entity(:player,
                     { x: x,
                       y: y,
                       dy: 0,
                       dx: 0,
                       w: w,
                       h: h,
                       damage: 0,
                       dead: false,
                       orientation: "down",
                       max_alpha: 255,
                       sprite_path: sprite_path})
  end

  def default_floor_tile x, y, w, h, sprite_path
    state.new_entity(:room,
                     { x: x,
                       y: y,
                       w: w,
                       h: h,
                       sprite_path: sprite_path})
  end

  def default_camera x, y, w, h
    state.new_entity(:camera,
                     { x: x,
                       y: y,
                       dx: 0,
                       dy: 0,
                       w: w,
                       h: h})
  end

  def new_player_cyan
    default_player(0, 0, 64, 64,
                   "sprites/player/player_#{state.player_cyan.orientation}_standing.png")
  end

  def new_player_magenta
    default_player(64, 0, 64, 64,
                   "sprites/player/player_#{state.player_magenta.orientation}_standing.png")
  end

  def new_camera_magenta
    default_camera(0,0,720,720)
  end

  def new_camera_cyan
    default_camera(0,0,720,720)
  end

  def new_camera_center
    default_camera(0,0,1280,720)
  end


  def new_room
    default_floor_tile(0,0,1024,1024,'sprites/rooms/camera_room.png')
  end

  #==============================================================================================
  #Calculation functions
  def calc
    calc_camera_magenta
    calc_camera_cyan
    calc_camera_center
    calc_player_cyan
    calc_player_magenta
    calc_trauma_decay
  end

  def center_camera_tolerance
    return Math.sqrt(((state.player_magenta.x - state.player_cyan.x) ** 2) +
              ((state.player_magenta.y - state.player_cyan.y) ** 2)) > 640
  end

  def calc_player_cyan
    state.player_cyan.x += state.player_cyan.dx
    state.player_cyan.y += state.player_cyan.dy
  end

  def calc_player_magenta
    state.player_magenta.x += state.player_magenta.dx
    state.player_magenta.y += state.player_magenta.dy
  end

  def calc_camera_center
    timeScale = 1
    midX = (state.player_magenta.x + state.player_cyan.x)/2
    midY = (state.player_magenta.y + state.player_cyan.y)/2
    targetX = midX - state.camera_center.w/2
    targetY = midY - state.camera_center.h/2
    state.camera_center.x += (targetX - state.camera_center.x) * 0.1 * timeScale
    state.camera_center.y += (targetY - state.camera_center.y) * 0.1 * timeScale
  end


  def calc_camera_magenta
    timeScale = 1
    targetX = state.player_magenta.x + state.player_magenta.w - state.camera_magenta.w/2
    targetY = state.player_magenta.y + state.player_magenta.h - state.camera_magenta.h/2
    state.camera_magenta.x += (targetX - state.camera_magenta.x) * 0.1 * timeScale
    state.camera_magenta.y += (targetY - state.camera_magenta.y) * 0.1 * timeScale
  end

  def calc_camera_cyan
    timeScale = 1
    targetX = state.player_cyan.x + state.player_cyan.w - state.camera_cyan.w/2
    targetY = state.player_cyan.y + state.player_cyan.h - state.camera_cyan.h/2
    state.camera_cyan.x += (targetX - state.camera_cyan.x) * 0.1 * timeScale
    state.camera_cyan.y += (targetY - state.camera_cyan.y) * 0.1 * timeScale
  end

  def calc_player_quadrant angle
    if angle < 45 and angle > -45 and state.player_cyan.x < state.player_magenta.x
      return 1
    elsif angle < 45 and angle > -45 and state.player_cyan.x > state.player_magenta.x
      return 3
    elsif (angle > 45 or angle < -45) and state.player_cyan.y < state.player_magenta.y
      return 2
    elsif (angle > 45 or angle < -45) and state.player_cyan.y > state.player_magenta.y
      return 4
    end
  end

  def calc_camera_shake
    state.trauma
  end

  def calc_trauma_decay
    state.trauma = state.trauma * 0.9
  end

  def calc_random_float_range(min, max)
    rand * (max-min) + min
  end

  #==============================================================================================
  #Render Functions
  def render
    render_floor
    render_player_cyan
    render_player_magenta
    if center_camera_tolerance
      render_split_camera_scene
    else
      render_camera_center_scene
    end
  end

  def render_player_cyan
    outputs[:scene].sprites << {x: state.player_cyan.x,
                                y: state.player_cyan.y,
                                w: state.player_cyan.w,
                                h: state.player_cyan.h,
                                path: "sprites/player/player_#{state.player_cyan.orientation}_standing.png",
                                r: 0,
                                g: 255,
                                b: 255}
  end

  def render_player_magenta
    outputs[:scene].sprites << {x: state.player_magenta.x,
                                y: state.player_magenta.y,
                                w: state.player_magenta.w,
                                h: state.player_magenta.h,
                                path: "sprites/player/player_#{state.player_magenta.orientation}_standing.png",
                                r: 255,
                                g: 0,
                                b: 255}
  end

  def render_floor
    outputs[:scene].sprites << [state.room.x, state.room.y,
                                state.room.w, state.room.h,
                                state.room.sprite_path]
  end

  def render_camera_center_scene
    zoomFactor = 1
    outputs[:scene].width = state.room.w
    outputs[:scene].height = state.room.h

    maxAngle = 10.0
    maxOffset = 20.0
    angle = maxAngle * calc_camera_shake * calc_random_float_range(-1,1)
    offsetX = 32 - (maxOffset * calc_camera_shake * calc_random_float_range(-1,1))
    offsetY = 32 - (maxOffset * calc_camera_shake * calc_random_float_range(-1,1))

    outputs.sprites << {x: (-state.camera_center.x - offsetX)/zoomFactor,
                        y: (-state.camera_center.y - offsetY)/zoomFactor,
                        w: outputs[:scene].width/zoomFactor,
                        h: outputs[:scene].height/zoomFactor,
                        path: :scene,
                        angle: angle,
                        source_w: -1,
                        source_h: -1}
    outputs.labels << [128,64,"#{state.trauma.round(1)}",8,2,255,0,255,255]
  end

  def render_split_camera_scene
     outputs[:scene].width = state.room.w
     outputs[:scene].height = state.room.h
     render_camera_magenta_scene
     render_camera_cyan_scene

     angle = Math.atan((state.player_magenta.y - state.player_cyan.y)/(state.player_magenta.x- state.player_cyan.x)) * 180/Math::PI
     output_split_camera angle

  end

  def render_camera_magenta_scene
     zoomFactor = 1
     offsetX = 32
     offsetY = 32

     outputs[:scene_magenta].sprites << {x: (-state.camera_magenta.x*2),
                                         y: (-state.camera_magenta.y),
                                         w: outputs[:scene].width*2,
                                         h: outputs[:scene].height,
                                         path: :scene}

  end

  def render_camera_cyan_scene
    zoomFactor = 1
    offsetX = 32
    offsetY = 32
    outputs[:scene_cyan].sprites << {x: (-state.camera_cyan.x*2),
                                     y: (-state.camera_cyan.y),
                                     w: outputs[:scene].width*2,
                                     h: outputs[:scene].height,
                                     path: :scene}
  end

  def output_split_camera angle
    #TODO: Clean this up!
    quadrant = calc_player_quadrant angle
    outputs.labels << [128,64,"#{quadrant}",8,2,255,0,255,255]
    if quadrant == 1
      set_camera_attributes(w: 640, h: 720, m_x: 640, m_y: 0, c_x: 0, c_y: 0)

    elsif quadrant == 2
      set_camera_attributes(w: 1280, h: 360, m_x: 0, m_y: 360, c_x: 0, c_y: 0)

    elsif quadrant == 3
      set_camera_attributes(w: 640, h: 720, m_x: 0, m_y: 0, c_x: 640, c_y: 0)

    elsif quadrant == 4
      set_camera_attributes(w: 1280, h: 360, m_x: 0, m_y: 0, c_x: 0, c_y: 360)

    end
  end

  def set_camera_attributes(w: 0, h: 0, m_x: 0, m_y: 0, c_x: 0, c_y: 0)
    state.camera_cyan.w = w + 64
    state.camera_cyan.h = h + 64
    outputs[:scene_cyan].width = (w) * 2
    outputs[:scene_cyan].height = h

    state.camera_magenta.w = w + 64
    state.camera_magenta.h = h + 64
    outputs[:scene_magenta].width = (w) * 2
    outputs[:scene_magenta].height = h
    outputs.sprites << {x: m_x,
                        y: m_y,
                        w: w,
                        h: h,
                        path: :scene_magenta}
    outputs.sprites << {x: c_x,
                        y: c_y,
                        w: w,
                        h: h,
                        path: :scene_cyan}
  end

  def add_trauma amount
    state.trauma = [state.trauma + amount, 1.0].min
  end

  def remove_trauma amount
    state.trauma = [state.trauma - amount, 0.0].max
  end
  #==============================================================================================
  #Input functions
  def input
    input_move_cyan
    input_move_magenta

    if inputs.keyboard.key_down.t
      add_trauma(0.5)
    elsif inputs.keyboard.key_down.y
      remove_trauma(0.1)
    end
  end

  def input_move_cyan
    if inputs.keyboard.key_held.up
      state.player_cyan.dy = 5
      state.player_cyan.orientation = "up"
    elsif inputs.keyboard.key_held.down
      state.player_cyan.dy = -5
      state.player_cyan.orientation = "down"
    else
      state.player_cyan.dy *= 0.8
    end
    if inputs.keyboard.key_held.left
      state.player_cyan.dx = -5
      state.player_cyan.orientation = "left"
    elsif inputs.keyboard.key_held.right
      state.player_cyan.dx = 5
      state.player_cyan.orientation = "right"
    else
      state.player_cyan.dx *= 0.8
    end

    outputs.labels << [128,512,"#{state.player_cyan.x.round()}",8,2,0,255,255,255]
    outputs.labels << [128,480,"#{state.player_cyan.y.round()}",8,2,0,255,255,255]
  end

  def input_move_magenta
    if inputs.keyboard.key_held.w
      state.player_magenta.dy = 5
      state.player_magenta.orientation = "up"
    elsif inputs.keyboard.key_held.s
      state.player_magenta.dy = -5
      state.player_magenta.orientation = "down"
    else
      state.player_magenta.dy *= 0.8
    end
    if inputs.keyboard.key_held.a
      state.player_magenta.dx = -5
      state.player_magenta.orientation = "left"
    elsif inputs.keyboard.key_held.d
      state.player_magenta.dx = 5
      state.player_magenta.orientation = "right"
    else
      state.player_magenta.dx *= 0.8
    end

    outputs.labels << [128,360,"#{state.player_magenta.x.round()}",8,2,255,0,255,255]
    outputs.labels << [128,328,"#{state.player_magenta.y.round()}",8,2,255,0,255,255]
  end
end

$camera_movement = CameraMovement.new

def tick args
  args.outputs.background_color = [0,0,0]
  $camera_movement.inputs  = args.inputs
  $camera_movement.outputs = args.outputs
  $camera_movement.state   = args.state
  $camera_movement.grid    = args.grid
  $camera_movement.tick
end

Advanced Rendering - Z Targeting Camera - main.rb

# ./samples/07_advanced_rendering/09_z_targeting_camera/app/main.rb
class Game
  attr_gtk

  def tick
    defaults
    render
    input
    calc
  end

  def defaults
    outputs.background_color = [219, 208, 191]
    player.x        ||= 634
    player.y        ||= 153
    player.angle    ||= 90
    player.distance ||= arena_radius
    target.x        ||= 634
    target.y        ||= 359
  end

  def render
    outputs[:scene].sprites << ([0, 0, 933, 700, 'sprites/arena.png'].center_inside_rect grid.rect)
    outputs[:scene].sprites << target_sprite
    outputs[:scene].sprites << player_sprite
    outputs.sprites << scene
  end

  def target_sprite
    {
      x: target.x, y: target.y,
      w: 10, h: 10,
      path: 'sprites/square/black.png'
    }.anchor_rect 0.5, 0.5
  end

  def input
    if inputs.up && player.distance > 30
      player.distance -= 2
    elsif inputs.down && player.distance < 200
      player.distance += 2
    end

    player.angle += inputs.left_right * -1
  end

  def calc
    player.x = target.x + ((player.angle *  1).vector_x player.distance)
    player.y = target.y + ((player.angle * -1).vector_y player.distance)
  end

  def player_sprite
    {
      x: player.x,
      y: player.y,
      w: 50,
      h: 100,
      path: 'sprites/player.png',
      angle: (player.angle * -1) + 90
    }.anchor_rect 0.5, 0
  end

  def center_map
    { x: 634, y: 359 }
  end

  def zoom_factor_single
    2 - ((args.geometry.distance player, center_map).fdiv arena_radius)
  end

  def zoom_factor
    zoom_factor_single ** 2
  end

  def arena_radius
    206
  end

  def scene
    {
      x:    (640 - player.x) + (640 - (640 * zoom_factor)),
      y:    (360 - player.y - (75 * zoom_factor)) + (320 - (320 * zoom_factor)),
      w:    1280 * zoom_factor,
      h:     720 * zoom_factor,
      path: :scene,
      angle: player.angle - 90,
      angle_anchor_x: (player.x.fdiv 1280),
      angle_anchor_y: (player.y.fdiv 720)
    }
  end

  def player
    state.player
  end

  def target
    state.target
  end
end

def tick args
  $game ||= Game.new
  $game.args = args
  $game.tick
end

$gtk.reset

Advanced Rendering - Camera And Large Map - main.rb

# ./samples/07_advanced_rendering/10_camera_and_large_map/app/main.rb
def tick args
  # you want to make sure all of your pngs are a maximum size of 1280x1280
  # low-end android devices and machines with underpowered GPUs are unable to
  # load very large textures.

  # this sample app creates 640x640 tiles of a 6400x6400 pixel png and displays them
  # on the screen relative to the player's position

  # tile creation process
  create_tiles_if_needed args

  # if tiles are already present the show map
  display_tiles args
end

def display_tiles args
  # set the player's starting location
  args.state.player ||= {
    x:  0,
    y:  0,
    w: 40,
    h: 40,
    path: "sprites/square/blue.png"
  }

  # if all tiles have been created, then we are
  # in "displaying_tiles" mode
  if args.state.displaying_tiles
    # create a render target that can hold 9 640x640 tiles
    args.outputs[:scene].background_color = [0, 0, 0, 0]
    args.outputs[:scene].w = 1920
    args.outputs[:scene].h = 1920

    # allow player to be moved with arrow keys
    args.state.player.x += args.inputs.left_right * 10
    args.state.player.y += args.inputs.up_down * 10

    # given the player's location, return a collection of primitives
    # to render that are within the 1920x1920 viewport
    args.outputs[:scene].primitives << tiles_in_viewport(args)

    # place the player in the center of the render_target
    args.outputs[:scene].primitives << {
      x: 960 - 20,
      y: 960 - 20,
      w: 40,
      h: 40,
      path: "sprites/square/blue.png"
    }

    # center the 1920x1920 render target within the 1280x720 window
    args.outputs.sprites << {
      x: -320,
      y: -600,
      w: 1920,
      h: 1920,
      path: :scene
    }
  end
end

def tiles_in_viewport args
  state = args.state
  # define the size of each tile
  tile_size = 640

  # determine what tile the player is on
  tile_player_is_on = { x: state.player.x.idiv(tile_size), y: state.player.y.idiv(tile_size) }

  # calculate the x and y offset of the player so that tiles are positioned correctly
  offset_x = 960 - (state.player.x - (tile_player_is_on.x * tile_size))
  offset_y = 960 - (state.player.y - (tile_player_is_on.y * tile_size))

  primitives = []

  # get 9 tiles in total (the tile the player is on and the 8 surrounding tiles)

  # center tile
  primitives << (tile_in_viewport size:       tile_size,
                                  from_row:   tile_player_is_on.y,
                                  from_col:   tile_player_is_on.x,
                                  offset_row: 0,
                                  offset_col: 0,
                                  dy:         offset_y,
                                  dx:         offset_x)

  # tile to the right
  primitives << (tile_in_viewport size:       tile_size,
                                  from_row:   tile_player_is_on.y,
                                  from_col:   tile_player_is_on.x,
                                  offset_row: 0,
                                  offset_col: 1,
                                  dy:         offset_y,
                                  dx:         offset_x)
  # tile to the left
  primitives << (tile_in_viewport size:        tile_size,
                                  from_row:    tile_player_is_on.y,
                                  from_col:    tile_player_is_on.x,
                                  offset_row:  0,
                                  offset_col: -1,
                                  dy:          offset_y,
                                  dx:          offset_x)

  # tile directly above
  primitives << (tile_in_viewport size:       tile_size,
                                  from_row:   tile_player_is_on.y,
                                  from_col:   tile_player_is_on.x,
                                  offset_row: 1,
                                  offset_col: 0,
                                  dy:         offset_y,
                                  dx:         offset_x)
  # tile directly below
  primitives << (tile_in_viewport size:         tile_size,
                                  from_row:     tile_player_is_on.y,
                                  from_col:     tile_player_is_on.x,
                                  offset_row:  -1,
                                  offset_col:   0,
                                  dy:           offset_y,
                                  dx:           offset_x)
  # tile up and to the left
  primitives << (tile_in_viewport size:        tile_size,
                                  from_row:    tile_player_is_on.y,
                                  from_col:    tile_player_is_on.x,
                                  offset_row:  1,
                                  offset_col: -1,
                                  dy:          offset_y,
                                  dx:          offset_x)

  # tile up and to the right
  primitives << (tile_in_viewport size:       tile_size,
                                  from_row:   tile_player_is_on.y,
                                  from_col:   tile_player_is_on.x,
                                  offset_row: 1,
                                  offset_col: 1,
                                  dy:         offset_y,
                                  dx:         offset_x)

  # tile down and to the left
  primitives << (tile_in_viewport size:        tile_size,
                                  from_row:    tile_player_is_on.y,
                                  from_col:    tile_player_is_on.x,
                                  offset_row: -1,
                                  offset_col: -1,
                                  dy:          offset_y,
                                  dx:          offset_x)

  # tile down and to the right
  primitives << (tile_in_viewport size:        tile_size,
                                  from_row:    tile_player_is_on.y,
                                  from_col:    tile_player_is_on.x,
                                  offset_row: -1,
                                  offset_col:  1,
                                  dy:          offset_y,
                                  dx:          offset_x)

  primitives
end

def tile_in_viewport size:, from_row:, from_col:, offset_row:, offset_col:, dy:, dx:;
  x = size * offset_col + dx
  y = size * offset_row + dy

  return nil if (from_row + offset_row) < 0
  return nil if (from_row + offset_row) > 9

  return nil if (from_col + offset_col) < 0
  return nil if (from_col + offset_col) > 9

  # return the tile sprite, a border demarcation, and label of which tile x and y
  [
    {
      x: x,
      y: y,
      w: size,
      h: size,
      path: "sprites/tile-#{from_col + offset_col}-#{from_row + offset_row}.png",
    },
    {
      x: x,
      y: y,
      w: size,
      h: size,
      r: 255,
      primitive_marker: :border,
    },
    {
      x: x + size / 2 - 150,
      y: y + size / 2 - 25,
      w: 300,
      h: 50,
      primitive_marker: :solid,
      r: 0,
      g: 0,
      b: 0,
      a: 128
    },
    {
      x: x + size / 2,
      y: y + size / 2,
      text: "tile #{from_col + offset_col}, #{from_row + offset_row}",
      alignment_enum: 1,
      vertical_alignment_enum: 1,
      size_enum: 2,
      r: 255,
      g: 255,
      b: 255
    },
  ]
end

def create_tiles_if_needed args
  # We are going to use args.outputs.screenshots to generate tiles of a
  # png of size 6400x6400 called sprites/large.png.
  if !args.gtk.stat_file("sprites/tile-9-9.png") && !args.state.creating_tiles
    args.state.displaying_tiles = false
    args.outputs.labels << {
      x: 960,
      y: 360,
      text: "Press enter to generate tiles of sprites/large.png.",
      alignment_enum: 1,
      vertical_alignment_enum: 1
    }
  elsif !args.state.creating_tiles
    args.state.displaying_tiles = true
  end

  # pressing enter will start the tile creation process
  if args.inputs.keyboard.key_down.enter && !args.state.creating_tiles
    args.state.displaying_tiles = false
    args.state.creating_tiles = true
    args.state.tile_clock = 0
  end

  # the tile creation process renders an area of sprites/large.png
  # to the screen and takes a screenshot of it every half second
  # until all tiles are generated.
  # once all tiles are generated a map viewport will be rendered that
  # stitches tiles together.
  if args.state.creating_tiles
    args.state.tile_x ||= 0
    args.state.tile_y ||= 0

    # render a sub-square of the large png.
    args.outputs.sprites << {
      x: 0,
      y: 0,
      w: 640,
      h: 640,
      source_x: args.state.tile_x * 640,
      source_y: args.state.tile_y * 640,
      source_w: 640,
      source_h: 640,
      path: "sprites/large.png"
    }

    # determine tile file name
    tile_path = "sprites/tile-#{args.state.tile_x}-#{args.state.tile_y}.png"

    args.outputs.labels << {
      x: 960,
      y: 320,
      text: "Generating #{tile_path}",
      alignment_enum: 1,
      vertical_alignment_enum: 1
    }

    # take a screenshot on frames divisible by 29
    if args.state.tile_clock.zmod?(29)
      args.outputs.screenshots << {
        x: 0,
        y: 0,
        w: 640,
        h: 640,
        path: tile_path,
        a: 255
      }
    end

    # increment tile to render on frames divisible by 30 (half a second)
    # (one frame is allotted to take screenshot)
    if args.state.tile_clock.zmod?(30)
      args.state.tile_x += 1
      if args.state.tile_x >= 10
        args.state.tile_x  = 0
        args.state.tile_y += 1
      end

      # once all of tile tiles are created, begin displaying map
      if args.state.tile_y >= 10
        args.state.creating_tiles = false
        args.state.displaying_tiles = true
      end
    end

    args.state.tile_clock += 1
  end
end

$gtk.reset

Advanced Rendering - Blend Modes - main.rb

# ./samples/07_advanced_rendering/11_blend_modes/app/main.rb
$gtk.reset

def draw_blendmode args, mode
  w = 160
  h = w
  args.state.x += (1280-w) / (args.state.blendmodes.length + 1)
  x = args.state.x
  y = (720 - h) / 2
  s = 'sprites/blue-feathered.png'
  args.outputs.sprites << { blendmode_enum: mode.value, x: x, y: y, w: w, h: h, path: s }
  args.outputs.labels << [x + (w/2), y, mode.name.to_s, 1, 1, 255, 255, 255]
end

def tick args

  # Different blend modes do different things, depending on what they
  # blend against (in this case, the pixels of the background color).
  args.state.bg_element ||= 1
  args.state.bg_color ||= 255
  args.state.bg_color_direction ||= 1
  bg_r = (args.state.bg_element == 1) ? args.state.bg_color : 0
  bg_g = (args.state.bg_element == 2) ? args.state.bg_color : 0
  bg_b = (args.state.bg_element == 3) ? args.state.bg_color : 0
  args.state.bg_color += args.state.bg_color_direction
  if (args.state.bg_color_direction > 0) && (args.state.bg_color >= 255)
    args.state.bg_color_direction = -1
    args.state.bg_color = 255
  elsif (args.state.bg_color_direction < 0) && (args.state.bg_color <= 0)
    args.state.bg_color_direction = 1
    args.state.bg_color = 0
    args.state.bg_element += 1
    if args.state.bg_element >= 4
      args.state.bg_element = 1
    end
  end

  args.outputs.background_color = [ bg_r, bg_g, bg_b, 255 ]

  args.state.blendmodes ||= [
    { name: :none,  value: 0 },
    { name: :blend, value: 1 },
    { name: :add,   value: 2 },
    { name: :mod,   value: 3 },
    { name: :mul,   value: 4 }
  ]

  args.state.x = 0  # reset this, draw_blendmode will increment it.
  args.state.blendmodes.each { |blendmode| draw_blendmode args, blendmode }
end

Advanced Rendering - Render Target Noclear - main.rb

# ./samples/07_advanced_rendering/12_render_target_noclear/app/main.rb
def tick args
  args.state.x ||= 500
  args.state.y ||= 350
  args.state.xinc ||= 7
  args.state.yinc ||= 7
  args.state.bgcolor ||= 1
  args.state.bginc ||= 1

  # clear the render target on the first tick, and then never again. Draw
  #  another box to it every tick, accumulating over time.
  clear_target = (args.state.tick_count == 0) || (args.inputs.keyboard.key_down.space)
  args.render_target(:accumulation).background_color = [ 0, 0, 0, 0 ];
  args.render_target(:accumulation).clear_before_render = clear_target
  args.render_target(:accumulation).solids << [args.state.x, args.state.y, 25, 25, 255, 0, 0, 255];
  args.state.x += args.state.xinc
  args.state.y += args.state.yinc
  args.state.bgcolor += args.state.bginc

  # animation upkeep...change where we draw the next box and what color the
  #  window background will be.
  if args.state.xinc > 0 && args.state.x >= 1280
    args.state.xinc = -7
  elsif args.state.xinc < 0 && args.state.x < 0
    args.state.xinc = 7
  end

  if args.state.yinc > 0 && args.state.y >= 720
    args.state.yinc = -7
  elsif args.state.yinc < 0 && args.state.y < 0
    args.state.yinc = 7
  end

  if args.state.bginc > 0 && args.state.bgcolor >= 255
    args.state.bginc = -1
  elsif args.state.bginc < 0 && args.state.bgcolor <= 0
    args.state.bginc = 1
  end

  # clear the screen to a shade of blue and draw the render target, which
  #  is not clearing every frame, on top of it. Note that you can NOT opt to
  #  skip clearing the screen, only render targets. The screen clears every
  #  frame; double-buffering would prevent correct updates between frames.
  args.outputs.background_color = [ 0, 0, args.state.bgcolor, 255 ]
  args.outputs.sprites << [ 0, 0, 1280, 720, :accumulation ]
end

$gtk.reset

Advanced Rendering - Lighting - main.rb

# ./samples/07_advanced_rendering/13_lighting/app/main.rb
def calc args
  args.state.swinging_light_sign     ||= 1
  args.state.swinging_light_start_at ||= 0
  args.state.swinging_light_duration ||= 300
  args.state.swinging_light_perc       = args.state
                                             .swinging_light_start_at
                                             .ease_spline_extended args.state.tick_count,
                                                                   args.state.swinging_light_duration,
                                                                   [
                                                                     [0.0, 1.0, 1.0, 1.0],
                                                                     [1.0, 1.0, 1.0, 0.0]
                                                                   ]
  args.state.max_swing_angle ||= 45

  if args.state.swinging_light_start_at.elapsed_time > args.state.swinging_light_duration
    args.state.swinging_light_start_at = args.state.tick_count
    args.state.swinging_light_sign *= -1
  end

  args.state.swinging_light_angle = 360 + ((args.state.max_swing_angle * args.state.swinging_light_perc) * args.state.swinging_light_sign)
end

def render args
  args.outputs.background_color = [0, 0, 0]

  # render scene
  args.outputs[:scene].sprites << { x:        0, y:   0, w: 1280, h: 720, path: :pixel }
  args.outputs[:scene].sprites << { x: 640 - 40, y: 100, w:   80, h:  80, path: 'sprites/square/blue.png' }
  args.outputs[:scene].sprites << { x: 640 - 40, y: 200, w:   80, h:  80, path: 'sprites/square/blue.png' }
  args.outputs[:scene].sprites << { x: 640 - 40, y: 300, w:   80, h:  80, path: 'sprites/square/blue.png' }
  args.outputs[:scene].sprites << { x: 640 - 40, y: 400, w:   80, h:  80, path: 'sprites/square/blue.png' }
  args.outputs[:scene].sprites << { x: 640 - 40, y: 500, w:   80, h:  80, path: 'sprites/square/blue.png' }

  # render light
  swinging_light_w = 1100
  args.outputs[:lights].background_color = [0, 0, 0, 0]
  args.outputs[:lights].sprites << { x: 640 - swinging_light_w.half,
                                     y: -1300,
                                     w: swinging_light_w,
                                     h: 3000,
                                     angle_anchor_x: 0.5,
                                     angle_anchor_y: 1.0,
                                     path: "sprites/lights/mask.png",
                                     angle: args.state.swinging_light_angle }

  args.outputs[:lights].sprites << { x: args.inputs.mouse.x - 400,
                                     y: args.inputs.mouse.y - 400,
                                     w: 800,
                                     h: 800,
                                     path: "sprites/lights/mask.png" }

  # merge unlighted scene with lights
  args.outputs[:lighted_scene].sprites << { x: 0, y: 0, w: 1280, h: 720, path: :lights, blendmode_enum: 0 }
  args.outputs[:lighted_scene].sprites << { blendmode_enum: 2, x: 0, y: 0, w: 1280, h: 720, path: :scene }

  # output lighted scene to main canvas
  args.outputs.sprites << { x: 0, y: 0, w: 1280, h: 720, path: :lighted_scene }

  # render lights and scene render_targets as a mini map
  args.outputs.debug  << { x: 16,      y: (16 + 90).from_top, w: 160, h: 90, r: 255, g: 255, b: 255 }.solid!
  args.outputs.debug  << { x: 16,      y: (16 + 90).from_top, w: 160, h: 90, path: :lights }
  args.outputs.debug  << { x: 16 + 80, y: (16 + 90 + 8).from_top, text: ":lights render_target", r: 255, g: 255, b: 255, size_enum: -3, alignment_enum: 1 }

  args.outputs.debug  << { x: 16 + 160 + 16,      y: (16 + 90).from_top, w: 160, h: 90, r: 255, g: 255, b: 255 }.solid!
  args.outputs.debug  << { x: 16 + 160 + 16,      y: (16 + 90).from_top, w: 160, h: 90, path: :scene }
  args.outputs.debug  << { x: 16 + 160 + 16 + 80, y: (16 + 90 + 8).from_top, text: ":scene render_target", r: 255, g: 255, b: 255, size_enum: -3, alignment_enum: 1 }
end

def tick args
  render args
  calc args
end

$gtk.reset

Advanced Rendering - 14 Triangles - main.rb

# ./samples/07_advanced_rendering/14_triangles/app/main.rb
def tick args
  args.outputs.labels << {
    x: 640,
    y: 30.from_top,
    text: "Triangle rendering is available in Indie and Pro versions (ignored in Standard Edition).",
    alignment_enum: 1
  }

  dragonruby_logo_width  = 128
  dragonruby_logo_height = 101

  row_0 = 400
  row_1 = 250

  col_0 = 384 - dragonruby_logo_width.half + dragonruby_logo_width * 0
  col_1 = 384 - dragonruby_logo_width.half + dragonruby_logo_width * 1
  col_2 = 384 - dragonruby_logo_width.half + dragonruby_logo_width * 2
  col_3 = 384 - dragonruby_logo_width.half + dragonruby_logo_width * 3
  col_4 = 384 - dragonruby_logo_width.half + dragonruby_logo_width * 4

  # row 0
  args.outputs.solids << make_triangle(
    col_0,
    row_0,
    col_0 + dragonruby_logo_width.half,
    row_0 + dragonruby_logo_height,
    col_0 + dragonruby_logo_width.half + dragonruby_logo_width.half,
    row_0,
    0, 128, 128,
    128
  )

  args.outputs.solids << {
    x:  col_1,
    y:  row_0,
    x2: col_1 + dragonruby_logo_width.half,
    y2: row_0 + dragonruby_logo_height,
    x3: col_1 + dragonruby_logo_width,
    y3: row_0,
  }

  args.outputs.sprites << {
    x:  col_2,
    y:  row_0,
    w:  dragonruby_logo_width,
    h:  dragonruby_logo_height,
    path: 'dragonruby.png'
  }

  args.outputs.sprites << {
    x:  col_3,
    y:  row_0,
    x2: col_3 + dragonruby_logo_width.half,
    y2: row_0 + dragonruby_logo_height,
    x3: col_3 + dragonruby_logo_width,
    y3: row_0,
    path: 'dragonruby.png',
    source_x:  0,
    source_y:  0,
    source_x2: dragonruby_logo_width.half,
    source_y2: dragonruby_logo_height,
    source_x3: dragonruby_logo_width,
    source_y3: 0
  }

  args.outputs.sprites << TriangleLogo.new(x:  col_4,
                                           y:  row_0,
                                           x2: col_4 + dragonruby_logo_width.half,
                                           y2: row_0 + dragonruby_logo_height,
                                           x3: col_4 + dragonruby_logo_width,
                                           y3: row_0,
                                           path: 'dragonruby.png',
                                           source_x:  0,
                                           source_y:  0,
                                           source_x2: dragonruby_logo_width.half,
                                           source_y2: dragonruby_logo_height,
                                           source_x3: dragonruby_logo_width,
                                           source_y3: 0)

  # row 1
  args.outputs.primitives << make_triangle(
    col_0,
    row_1,
    col_0 + dragonruby_logo_width.half,
    row_1 + dragonruby_logo_height,
    col_0 + dragonruby_logo_width,
    row_1,
    0, 128, 128,
    args.state.tick_count.to_radians.sin_r.abs * 255
  )

  args.outputs.primitives << {
    x:  col_1,
    y:  row_1,
    x2: col_1 + dragonruby_logo_width.half,
    y2: row_1 + dragonruby_logo_height,
    x3: col_1 + dragonruby_logo_width,
    y3: row_1,
    r:  0, g: 0, b: 0, a: args.state.tick_count.to_radians.sin_r.abs * 255
  }

  args.outputs.sprites << {
    x:  col_2,
    y:  row_1,
    w:  dragonruby_logo_width,
    h:  dragonruby_logo_height,
    path: 'dragonruby.png',
    source_x:  0,
    source_y:  0,
    source_w:  dragonruby_logo_width,
    source_h:  dragonruby_logo_height.half +
               dragonruby_logo_height.half * Math.sin(args.state.tick_count.to_radians).abs,
  }

  args.outputs.primitives << {
    x:  col_3,
    y:  row_1,
    x2: col_3 + dragonruby_logo_width.half,
    y2: row_1 + dragonruby_logo_height,
    x3: col_3 + dragonruby_logo_width,
    y3: row_1,
    path: 'dragonruby.png',
    source_x:  0,
    source_y:  0,
    source_x2: dragonruby_logo_width.half,
    source_y2: dragonruby_logo_height.half +
               dragonruby_logo_height.half * Math.sin(args.state.tick_count.to_radians).abs,
    source_x3: dragonruby_logo_width,
    source_y3: 0
  }

  args.outputs.primitives << TriangleLogo.new(x:  col_4,
                                              y:  row_1,
                                              x2: col_4 + dragonruby_logo_width.half,
                                              y2: row_1 + dragonruby_logo_height,
                                              x3: col_4 + dragonruby_logo_width,
                                              y3: row_1,
                                              path: 'dragonruby.png',
                                              source_x:  0,
                                              source_y:  0,
                                              source_x2: dragonruby_logo_width.half,
                                              source_y2: dragonruby_logo_height.half +
                                                         dragonruby_logo_height.half * Math.sin(args.state.tick_count.to_radians).abs,
                                              source_x3: dragonruby_logo_width,
                                              source_y3: 0)
end

def make_triangle *opts
  x, y, x2, y2, x3, y3, r, g, b, a = opts
  {
    x: x, y: y, x2: x2, y2: y2, x3: x3, y3: y3,
    r: r || 0,
    g: g || 0,
    b: b || 0,
    a: a || 255
  }
end

class TriangleLogo
  attr_sprite

  def initialize x:, y:, x2:, y2:, x3:, y3:, path:, source_x:, source_y:, source_x2:, source_y2:, source_x3:, source_y3:;
    @x         = x
    @y         = y
    @x2        = x2
    @y2        = y2
    @x3        = x3
    @y3        = y3
    @path      = path
    @source_x  = source_x
    @source_y  = source_y
    @source_x2 = source_x2
    @source_y2 = source_y2
    @source_x3 = source_x3
    @source_y3 = source_y3
  end
end

Advanced Rendering - 15 Triangles Trapezoid - main.rb

# ./samples/07_advanced_rendering/15_triangles_trapezoid/app/main.rb
def tick args
  args.outputs.labels << {
    x: 640,
    y: 30.from_top,
    text: "Triangle rendering is available in Indie and Pro versions (ignored in Standard Edition).",
    alignment_enum: 1
  }

  transform_scale = ((args.state.tick_count / 3).sin.abs ** 5).half
  args.outputs.sprites << [
    { x:         600,
      y:         320,
      x2:        600,
      y2:        400,
      x3:        640,
      y3:        360,
      path:      "sprites/square/blue.png",
      source_x:  0,
      source_y:  0,
      source_x2: 0,
      source_y2: 80,
      source_x3: 40,
      source_y3: 40 },
    { x:         600,
      y:         400,
      x2:        680,
      y2:        (400 - 80 * transform_scale).round,
      x3:        640,
      y3:        360,
      path:      "sprites/square/blue.png",
      source_x:  0,
      source_y:  80,
      source_x2: 80,
      source_y2: 80,
      source_x3: 40,
      source_y3: 40 },
    { x:         640,
      y:         360,
      x2:        680,
      y2:        (400 - 80 * transform_scale).round,
      x3:        680,
      y3:        (320 + 80 * transform_scale).round,
      path:      "sprites/square/blue.png",
      source_x:  40,
      source_y:  40,
      source_x2: 80,
      source_y2: 80,
      source_x3: 80,
      source_y3: 0 },
    { x:         600,
      y:         320,
      x2:        640,
      y2:        360,
      x3:        680,
      y3:        (320 + 80 * transform_scale).round,
      path:      "sprites/square/blue.png",
      source_x:  0,
      source_y:  0,
      source_x2: 40,
      source_y2: 40,
      source_x3: 80,
      source_y3: 0 }
  ]
end

Advanced Rendering - 16 Matrix And Triangles 2d - main.rb

# ./samples/07_advanced_rendering/16_matrix_and_triangles_2d/app/main.rb
include MatrixFunctions

def tick args
  args.state.square_one_sprite = { x:        0,
                                   y:        0,
                                   w:        100,
                                   h:        100,
                                   path:     "sprites/square/blue.png",
                                   source_x: 0,
                                   source_y: 0,
                                   source_w: 80,
                                   source_h: 80 }

  args.state.square_two_sprite = { x:        0,
                                   y:        0,
                                   w:        100,
                                   h:        100,
                                   path:     "sprites/square/red.png",
                                   source_x: 0,
                                   source_y: 0,
                                   source_w: 80,
                                   source_h: 80 }

  args.state.square_one        = sprite_to_triangles args.state.square_one_sprite
  args.state.square_two        = sprite_to_triangles args.state.square_two_sprite
  args.state.camera.x        ||= 0
  args.state.camera.y        ||= 0
  args.state.camera.zoom     ||= 1
  args.state.camera.rotation ||= 0

  zmod = 1
  move_multiplier = 1
  dzoom = 0.01

  if args.state.tick_count.zmod? zmod
    args.state.camera.x += args.inputs.left_right * -1 * move_multiplier
    args.state.camera.y += args.inputs.up_down * -1 * move_multiplier
  end

  if args.inputs.keyboard.i
    args.state.camera.zoom += dzoom
  elsif args.inputs.keyboard.o
    args.state.camera.zoom -= dzoom
  end

  args.state.camera.zoom = args.state.camera.zoom.clamp(0.25, 10)

  args.outputs.sprites << triangles_mat3_mul(args.state.square_one,
                                             mat3_translate(-50, -50),
                                             mat3_rotate(args.state.tick_count),
                                             mat3_translate(0, 0),
                                             mat3_translate(args.state.camera.x, args.state.camera.y),
                                             mat3_scale(args.state.camera.zoom),
                                             mat3_translate(640, 360))

  args.outputs.sprites << triangles_mat3_mul(args.state.square_two,
                                             mat3_translate(-50, -50),
                                             mat3_rotate(args.state.tick_count),
                                             mat3_translate(100, 100),
                                             mat3_translate(args.state.camera.x, args.state.camera.y),
                                             mat3_scale(args.state.camera.zoom),
                                             mat3_translate(640, 360))

  mouse_coord = vec3 args.inputs.mouse.x,
                     args.inputs.mouse.y,
                     1

  mouse_coord = mul mouse_coord,
                    mat3_translate(-640, -360),
                    mat3_scale(args.state.camera.zoom),
                    mat3_translate(-args.state.camera.x, -args.state.camera.y)

  args.outputs.lines  << { x: 640, y:   0, h:  720 }
  args.outputs.lines  << { x:   0, y: 360, w: 1280 }
  args.outputs.labels << { x: 30, y: 60.from_top, text: "x: #{args.state.camera.x.to_sf} y: #{args.state.camera.y.to_sf} z: #{args.state.camera.zoom.to_sf}" }
  args.outputs.labels << { x: 30, y: 90.from_top, text: "Mouse: #{mouse_coord.x.to_sf} #{mouse_coord.y.to_sf}" }
  args.outputs.labels << { x: 30,
                           y: 30.from_top,
                           text: "W,A,S,D to move. I, O to zoom. Triangles is a Indie/Pro Feature and will be ignored in Standard." }
end

def sprite_to_triangles sprite
  [
    {
      x:         sprite.x,                          y:  sprite.y,
      x2:        sprite.x,                          y2: sprite.y + sprite.h,
      x3:        sprite.x + sprite.w,               y3: sprite.y + sprite.h,
      source_x:  sprite.source_x,                   source_y:  sprite.source_y,
      source_x2: sprite.source_x,                   source_y2: sprite.source_y + sprite.source_h,
      source_x3: sprite.source_x + sprite.source_w, source_y3: sprite.source_y + sprite.source_h,
      path:      sprite.path
    },
    {
      x:  sprite.x,                                 y:  sprite.y,
      x2: sprite.x + sprite.w,                      y2: sprite.y + sprite.h,
      x3: sprite.x + sprite.w,                      y3: sprite.y,
      source_x:  sprite.source_x,                   source_y:  sprite.source_y,
      source_x2: sprite.source_x + sprite.source_w, source_y2: sprite.source_y + sprite.source_h,
      source_x3: sprite.source_x + sprite.source_w, source_y3: sprite.source_y,
      path:      sprite.path
    }
  ]
end

def mat3_translate dx, dy
  mat3 1, 0, dx,
       0, 1, dy,
       0, 0,  1
end

def mat3_rotate angle_d
  angle_r = angle_d.to_radians
  mat3 Math.cos(angle_r), -Math.sin(angle_r), 0,
       Math.sin(angle_r),  Math.cos(angle_r), 0,
                       0,                  0, 1
end

def mat3_scale scale
  mat3 scale,     0, 0,
           0, scale, 0,
           0,     0, 1
end

def triangles_mat3_mul triangles, *matrices
  triangles.map { |triangle| triangle_mat3_mul triangle, *matrices }
end

def triangle_mat3_mul triangle, *matrices
  result = [
    (vec3 triangle.x,  triangle.y,  1),
    (vec3 triangle.x2, triangle.y2, 1),
    (vec3 triangle.x3, triangle.y3, 1)
  ].map do |coord|
    mul coord, *matrices
  end

  {
    **triangle,
    x:  result[0].x,
    y:  result[0].y,
    x2: result[1].x,
    y2: result[1].y,
    x3: result[2].x,
    y3: result[2].y,
  }
rescue Exception => e
  pretty_print triangle
  pretty_print result
  pretty_print matrices
  puts "#{matrices}"
  raise e
end

Advanced Rendering - 16 Matrix And Triangles 3d - main.rb

# ./samples/07_advanced_rendering/16_matrix_and_triangles_3d/app/main.rb
include MatrixFunctions

def tick args
  args.outputs.labels << { x: 0,
                           y: 30.from_top,
                           text: "W,A,S,D to move. Q,E,U,O to turn, I,K for elevation. Triangles is a Indie/Pro Feature and will be ignored in Standard.",
                           alignment_enum: 1 }

  args.grid.origin_center!

  args.state.cam_x ||= 0.00
  if args.inputs.keyboard.left
    args.state.cam_x += 0.01
  elsif args.inputs.keyboard.right
    args.state.cam_x -= 0.01
  end

  args.state.cam_y ||= 0.00
  if args.inputs.keyboard.i
    args.state.cam_y += 0.01
  elsif args.inputs.keyboard.k
    args.state.cam_y -= 0.01
  end

  args.state.cam_z ||= 6.5
  if args.inputs.keyboard.s
    args.state.cam_z += 0.1
  elsif args.inputs.keyboard.w
    args.state.cam_z -= 0.1
  end

  args.state.cam_angle_y ||= 0
  if args.inputs.keyboard.q
    args.state.cam_angle_y += 0.25
  elsif args.inputs.keyboard.e
    args.state.cam_angle_y -= 0.25
  end

  args.state.cam_angle_x ||= 0
  if args.inputs.keyboard.u
    args.state.cam_angle_x += 0.1
  elsif args.inputs.keyboard.o
    args.state.cam_angle_x -= 0.1
  end

  # model A
  args.state.a = [
    [vec4(0, 0, 0, 1),   vec4(0.5, 0, 0, 1),   vec4(0, 0.5, 0, 1)],
    [vec4(0.5, 0, 0, 1), vec4(0.5, 0.5, 0, 1), vec4(0, 0.5, 0, 1)]
  ]

  # model to world
  args.state.a_world = mul_world args,
                                 args.state.a,
                                 (translate -0.25, -0.25, 0),
                                 (translate  0, 0, 0.25),
                                 (rotate_x args.state.tick_count)

  args.state.a_camera = mul_cam args, args.state.a_world
  args.state.a_projected = mul_perspective args, args.state.a_camera
  render_projection args, args.state.a_projected

  # model B
  args.state.b = [
    [vec4(0, 0, 0, 1),   vec4(0.5, 0, 0, 1),   vec4(0, 0.5, 0, 1)],
    [vec4(0.5, 0, 0, 1), vec4(0.5, 0.5, 0, 1), vec4(0, 0.5, 0, 1)]
  ]

  # model to world
  args.state.b_world = mul_world args,
                                 args.state.b,
                                 (translate -0.25, -0.25, 0),
                                 (translate  0, 0, -0.25),
                                 (rotate_x args.state.tick_count)

  args.state.b_camera = mul_cam args, args.state.b_world
  args.state.b_projected = mul_perspective args, args.state.b_camera
  render_projection args, args.state.b_projected

  # model C
  args.state.c = [
    [vec4(0, 0, 0, 1),   vec4(0.5, 0, 0, 1),   vec4(0, 0.5, 0, 1)],
    [vec4(0.5, 0, 0, 1), vec4(0.5, 0.5, 0, 1), vec4(0, 0.5, 0, 1)]
  ]

  # model to world
  args.state.c_world = mul_world args,
                                 args.state.c,
                                 (translate -0.25, -0.25, 0),
                                 (rotate_y 90),
                                 (translate -0.25,  0, 0),
                                 (rotate_x args.state.tick_count)

  args.state.c_camera = mul_cam args, args.state.c_world
  args.state.c_projected = mul_perspective args, args.state.c_camera
  render_projection args, args.state.c_projected

  # model D
  args.state.d = [
    [vec4(0, 0, 0, 1),   vec4(0.5, 0, 0, 1),   vec4(0, 0.5, 0, 1)],
    [vec4(0.5, 0, 0, 1), vec4(0.5, 0.5, 0, 1), vec4(0, 0.5, 0, 1)]
  ]

  # model to world
  args.state.d_world = mul_world args,
                                 args.state.d,
                                 (translate -0.25, -0.25, 0),
                                 (rotate_y 90),
                                 (translate  0.25,  0, 0),
                                 (rotate_x args.state.tick_count)

  args.state.d_camera = mul_cam args, args.state.d_world
  args.state.d_projected = mul_perspective args, args.state.d_camera
  render_projection args, args.state.d_projected

  # model E
  args.state.e = [
    [vec4(0, 0, 0, 1),   vec4(0.5, 0, 0, 1),   vec4(0, 0.5, 0, 1)],
    [vec4(0.5, 0, 0, 1), vec4(0.5, 0.5, 0, 1), vec4(0, 0.5, 0, 1)]
  ]

  # model to world
  args.state.e_world = mul_world args,
                                 args.state.e,
                                 (translate -0.25, -0.25, 0),
                                 (rotate_x 90),
                                 (translate  0,  0.25, 0),
                                 (rotate_x args.state.tick_count)

  args.state.e_camera = mul_cam args, args.state.e_world
  args.state.e_projected = mul_perspective args, args.state.e_camera
  render_projection args, args.state.e_projected

  # model E
  args.state.f = [
    [vec4(0, 0, 0, 1),   vec4(0.5, 0, 0, 1),   vec4(0, 0.5, 0, 1)],
    [vec4(0.5, 0, 0, 1), vec4(0.5, 0.5, 0, 1), vec4(0, 0.5, 0, 1)]
  ]

  # model to world
  args.state.f_world = mul_world args,
                                 args.state.f,
                                 (translate -0.25, -0.25, 0),
                                 (rotate_x 90),
                                 (translate  0,  -0.25, 0),
                                 (rotate_x args.state.tick_count)

  args.state.f_camera = mul_cam args, args.state.f_world
  args.state.f_projected = mul_perspective args, args.state.f_camera
  render_projection args, args.state.f_projected

  # render_debug args, args.state.a, args.state.a_transform, args.state.a_projected
  # args.outputs.labels << { x: -630, y:  10.from_top,  text: "x:         #{args.state.cam_x.to_sf} -> #{( args.state.cam_x * 1000 ).to_sf}" }
  # args.outputs.labels << { x: -630, y:  30.from_top,  text: "y:         #{args.state.cam_y.to_sf} -> #{( args.state.cam_y * 1000 ).to_sf}" }
  # args.outputs.labels << { x: -630, y:  50.from_top,  text: "z:         #{args.state.cam_z.fdiv(10).to_sf} -> #{( args.state.cam_z * 100 ).to_sf}" }
end

def mul_world args, model, *mul_def
  model.map do |vecs|
    vecs.map do |vec|
      mul vec,
          *mul_def
    end
  end
end

def mul_cam args, world_vecs
  world_vecs.map do |vecs|
    vecs.map do |vec|
      mul vec,
          (translate -args.state.cam_x, args.state.cam_y, -args.state.cam_z),
          (rotate_y args.state.cam_angle_y),
          (rotate_x args.state.cam_angle_x)
    end
  end
end

def mul_perspective args, camera_vecs
  camera_vecs.map do |vecs|
    vecs.map do |vec|
      perspective vec
    end
  end
end

def render_debug args, model, transform, projected
  args.outputs.labels << { x: -630, y:  10.from_top,  text: "model:     #{vecs_to_s model[0]}" }
  args.outputs.labels << { x: -630, y:  30.from_top,  text: "           #{vecs_to_s model[1]}" }
  args.outputs.labels << { x: -630, y:  50.from_top,  text: "transform: #{vecs_to_s transform[0]}" }
  args.outputs.labels << { x: -630, y:  70.from_top,  text: "           #{vecs_to_s transform[1]}" }
  args.outputs.labels << { x: -630, y:  90.from_top,  text: "projected: #{vecs_to_s projected[0]}" }
  args.outputs.labels << { x: -630, y: 110.from_top,  text: "           #{vecs_to_s projected[1]}" }
end

def render_projection args, projection
  p0 = projection[0]
  args.outputs.sprites << {
    x:  p0[0].x,   y: p0[0].y,
    x2: p0[1].x,  y2: p0[1].y,
    x3: p0[2].x,  y3: p0[2].y,
    source_x:   0, source_y:   0,
    source_x2: 80, source_y2:  0,
    source_x3:  0, source_y3: 80,
    a: 40,
    # r: 128, g: 128, b: 128,
    path: 'sprites/square/blue.png'
  }

  p1 = projection[1]
  args.outputs.sprites << {
    x:  p1[0].x,   y: p1[0].y,
    x2: p1[1].x,  y2: p1[1].y,
    x3: p1[2].x,  y3: p1[2].y,
    source_x:  80, source_y:   0,
    source_x2: 80, source_y2: 80,
    source_x3:  0, source_y3: 80,
    a: 40,
    # r: 128, g: 128, b: 128,
    path: 'sprites/square/blue.png'
  }
end

def perspective vec
  left   = -1.0
  right  =  1.0
  bottom = -1.0
  top    =  1.0
  near   =  300.0
  far    =  1000.0
  sx = 2 * near / (right - left)
  sy = 2 * near / (top - bottom)
  c2 = - (far + near) / (far - near)
  c1 = 2 * near * far / (near - far)
  tx = -near * (left + right) / (right - left)
  ty = -near * (bottom + top) / (top - bottom)

  p = mat4 sx, 0, 0, tx,
           0, sy, 0, ty,
           0, 0, c2, c1,
           0, 0, -1, 0

  r = mul vec, p
  r.x *= r.z / r.w / 100
  r.y *= r.z / r.w / 100
  r
end

def mat_scale scale
  mat4 scale,     0,     0,   0,
           0, scale,     0,   0,
           0,     0, scale,   0,
           0,     0,     0,   1
end

def rotate_y angle_d
  cos_t = Math.cos angle_d.to_radians
  sin_t = Math.sin angle_d.to_radians
  (mat4  cos_t,  0, sin_t, 0,
         0,      1, 0,     0,
         -sin_t, 0, cos_t, 0,
         0,      0, 0,     1)
end

def rotate_z angle_d
  cos_t = Math.cos angle_d.to_radians
  sin_t = Math.sin angle_d.to_radians
  (mat4 cos_t, -sin_t, 0, 0,
        sin_t,  cos_t, 0, 0,
        0,      0,     1, 0,
        0,      0,     0, 1)
end

def translate dx, dy, dz
  mat4 1, 0, 0, dx,
       0, 1, 0, dy,
       0, 0, 1, dz,
       0, 0, 0,  1
end


def rotate_x angle_d
  cos_t = Math.cos angle_d.to_radians
  sin_t = Math.sin angle_d.to_radians
  (mat4  1,     0,      0, 0,
         0, cos_t, -sin_t, 0,
         0, sin_t,  cos_t, 0,
         0,     0,      0, 1)
end

def vecs_to_s vecs
  vecs.map do |vec|
    "[#{vec.x.to_sf} #{vec.y.to_sf} #{vec.z.to_sf}]"
  end.join " "
end

Advanced Rendering - 16 Matrix Cubeworld - main.rb

# ./samples/07_advanced_rendering/16_matrix_cubeworld/app/main.rb
require 'app/modeling-api.rb'

include MatrixFunctions

def tick args
  args.outputs.labels << { x: 0,
                           y: 30.from_top,
                           text: "W,A,S,D to move. Mouse to look. Triangles is a Indie/Pro Feature and will be ignored in Standard.",
                           alignment_enum: 1 }

  args.grid.origin_center!

  args.state.cam_y ||= 0.00
  if args.inputs.keyboard.i
    args.state.cam_y += 0.01
  elsif args.inputs.keyboard.k
    args.state.cam_y -= 0.01
  end

  args.state.cam_angle_y ||= 0
  if args.inputs.keyboard.q
    args.state.cam_angle_y += 0.25
  elsif args.inputs.keyboard.e
    args.state.cam_angle_y -= 0.25
  end

  args.state.cam_angle_x ||= 0
  if args.inputs.keyboard.u
    args.state.cam_angle_x += 0.1
  elsif args.inputs.keyboard.o
    args.state.cam_angle_x -= 0.1
  end

  if args.inputs.mouse.has_focus
    y_change_rate = (args.inputs.mouse.x / 640) ** 2
    if args.inputs.mouse.x < 0
      args.state.cam_angle_y -= 0.8 * y_change_rate
    else
      args.state.cam_angle_y += 0.8 * y_change_rate
    end

    x_change_rate = (args.inputs.mouse.y / 360) ** 2
    if args.inputs.mouse.y < 0
      args.state.cam_angle_x += 0.8 * x_change_rate
    else
      args.state.cam_angle_x -= 0.8 * x_change_rate
    end
  end

  args.state.cam_z ||= 6.4
  if args.inputs.keyboard.up
    point_1 = { x: 0, y: 0.02 }
    point_r = args.geometry.rotate_point point_1, args.state.cam_angle_y
    args.state.cam_x -= point_r.x
    args.state.cam_z -= point_r.y
  elsif args.inputs.keyboard.down
    point_1 = { x: 0, y: -0.02 }
    point_r = args.geometry.rotate_point point_1, args.state.cam_angle_y
    args.state.cam_x -= point_r.x
    args.state.cam_z -= point_r.y
  end

  args.state.cam_x ||= 0.00
  if args.inputs.keyboard.right
    point_1 = { x: -0.02, y: 0 }
    point_r = args.geometry.rotate_point point_1, args.state.cam_angle_y
    args.state.cam_x -= point_r.x
    args.state.cam_z -= point_r.y
  elsif args.inputs.keyboard.left
    point_1 = { x:  0.02, y: 0 }
    point_r = args.geometry.rotate_point point_1, args.state.cam_angle_y
    args.state.cam_x -= point_r.x
    args.state.cam_z -= point_r.y
  end


  if args.inputs.keyboard.key_down.r || args.inputs.keyboard.key_down.zero
    args.state.cam_x = 0.00
    args.state.cam_y = 0.00
    args.state.cam_z = 1.00
    args.state.cam_angle_y = 0
    args.state.cam_angle_x = 0
  end

  if !args.state.models
    args.state.models = []
    25.times do
      args.state.models.concat new_random_cube
    end
  end

  args.state.models.each do |m|
    render_triangles args, m
  end

  args.outputs.lines << { x:   0, y: -50, h: 100, a: 80 }
  args.outputs.lines << { x: -50, y:   0, w: 100, a: 80 }
end

def mul_triangles model, *mul_def
  combined = mul mul_def
  model.map do |vecs|
    vecs.map do |vec|
      mul vec, *combined
    end
  end
end

def mul_cam args, world_vecs
  mul_triangles world_vecs,
                (translate -args.state.cam_x, -args.state.cam_y, -args.state.cam_z),
                (rotate_y args.state.cam_angle_y),
                (rotate_x args.state.cam_angle_x)
end

def mul_perspective camera_vecs
  camera_vecs.map do |vecs|
    r = vecs.map do |vec|
      perspective vec
    end

    r if r[0] && r[1] && r[2]
  end.reject_nil
end

def render_debug args, model, transform, projected
  args.outputs.labels << { x: -630, y:  10.from_top,  text: "model:     #{vecs_to_s model[0]}" }
  args.outputs.labels << { x: -630, y:  30.from_top,  text: "           #{vecs_to_s model[1]}" }
  args.outputs.labels << { x: -630, y:  50.from_top,  text: "transform: #{vecs_to_s transform[0]}" }
  args.outputs.labels << { x: -630, y:  70.from_top,  text: "           #{vecs_to_s transform[1]}" }
  args.outputs.labels << { x: -630, y:  90.from_top,  text: "projected: #{vecs_to_s projected[0]}" }
  args.outputs.labels << { x: -630, y: 110.from_top,  text: "           #{vecs_to_s projected[1]}" }
end

def render_triangles args, triangles
  camera_space = mul_cam args, triangles
  projection = mul_perspective camera_space

  args.outputs.sprites << projection.map_with_index do |i, index|
    if i
      {
        x:  i[0].x,   y: i[0].y,
        x2: i[1].x,  y2: i[1].y,
        x3: i[2].x,  y3: i[2].y,
        source_x:   0, source_y:   0,
        source_x2: 80, source_y2:  0,
        source_x3:  0, source_y3: 80,
        r: 128, g: 128, b: 128,
        a: 80 + 128 * 1 / (index + 1),
        path: :pixel
      }
    end
  end
end

def perspective vec
  left   =  100.0
  right  = -100.0
  bottom =  100.0
  top    = -100.0
  near   =  3000.0
  far    =  8000.0
  sx = 2 * near / (right - left)
  sy = 2 * near / (top - bottom)
  c2 = - (far + near) / (far - near)
  c1 = 2 * near * far / (near - far)
  tx = -near * (left + right) / (right - left)
  ty = -near * (bottom + top) / (top - bottom)

  p = mat4 sx, 0, 0, tx,
           0, sy, 0, ty,
           0, 0, c2, c1,
           0, 0, -1, 0

  r = mul vec, p
  return nil if r.w < 0
  r.x *= r.z / r.w / 100
  r.y *= r.z / r.w / 100
  r
end

def mat_scale scale
  mat4 scale,     0,     0,   0,
           0, scale,     0,   0,
           0,     0, scale,   0,
           0,     0,     0,   1
end

def rotate_y angle_d
  cos_t = Math.cos angle_d.to_radians
  sin_t = Math.sin angle_d.to_radians
  (mat4  cos_t,  0, sin_t, 0,
         0,      1, 0,     0,
         -sin_t, 0, cos_t, 0,
         0,      0, 0,     1)
end

def rotate_z angle_d
  cos_t = Math.cos angle_d.to_radians
  sin_t = Math.sin angle_d.to_radians
  (mat4 cos_t, -sin_t, 0, 0,
        sin_t,  cos_t, 0, 0,
        0,      0,     1, 0,
        0,      0,     0, 1)
end

def translate dx, dy, dz
  mat4 1, 0, 0, dx,
       0, 1, 0, dy,
       0, 0, 1, dz,
       0, 0, 0,  1
end


def rotate_x angle_d
  cos_t = Math.cos angle_d.to_radians
  sin_t = Math.sin angle_d.to_radians
  (mat4  1,     0,      0, 0,
         0, cos_t, -sin_t, 0,
         0, sin_t,  cos_t, 0,
         0,     0,      0, 1)
end

def vecs_to_s vecs
  vecs.map do |vec|
    "[#{vec.x.to_sf} #{vec.y.to_sf} #{vec.z.to_sf}]"
  end.join " "
end

def new_random_cube
  cube_w = rand * 0.2 + 0.1
  cube_h = rand * 0.2 + 0.1
  randx = rand * 2.0 * [1, -1].sample
  randy = rand * 2.0
  randz = rand * 5   * [1, -1].sample

  cube = [
    square do
      scale x: cube_w, y: cube_h
      translate x: -cube_w / 2, y: -cube_h / 2
      rotate_x 90
      translate y: -cube_h / 2
      translate x: randx, y: randy, z: randz
    end,
    square do
      scale x: cube_w, y: cube_h
      translate x: -cube_w / 2, y: -cube_h / 2
      rotate_x 90
      translate y:  cube_h / 2
      translate x: randx, y: randy, z: randz
    end,
    square do
      scale x: cube_h, y: cube_h
      translate x: -cube_h / 2, y: -cube_h / 2
      rotate_y 90
      translate x: -cube_w / 2
      translate x: randx, y: randy, z: randz
    end,
    square do
      scale x: cube_h, y: cube_h
      translate x: -cube_h / 2, y: -cube_h / 2
      rotate_y 90
      translate x:  cube_w / 2
      translate x: randx, y: randy, z: randz
    end,
    square do
      scale x: cube_w, y: cube_h
      translate x: -cube_w / 2, y: -cube_h / 2
      translate z: -cube_h / 2
      translate x: randx, y: randy, z: randz
    end,
    square do
      scale x: cube_w, y: cube_h
      translate x: -cube_w / 2, y: -cube_h / 2
      translate z:  cube_h / 2
      translate x: randx, y: randy, z: randz
    end
  ]

  cube
end

$gtk.reset

Advanced Rendering - 16 Matrix Cubeworld - modeling-api.rb

# ./samples/07_advanced_rendering/16_matrix_cubeworld/app/modeling-api.rb
class ModelingApi
  attr :matricies

  def initialize
    @matricies = []
  end

  def scale x: 1, y: 1, z: 1
    @matricies << scale_matrix(x: x, y: y, z: z)
    if block_given?
      yield
      @matricies << scale_matrix(x: -x, y: -y, z: -z)
    end
  end

  def translate x: 0, y: 0, z: 0
    @matricies << translate_matrix(x: x, y: y, z: z)
    if block_given?
      yield
      @matricies << translate_matrix(x: -x, y: -y, z: -z)
    end
  end

  def rotate_x x
    @matricies << rotate_x_matrix(x)
    if block_given?
      yield
      @matricies << rotate_x_matrix(-x)
    end
  end

  def rotate_y y
    @matricies << rotate_y_matrix(y)
    if block_given?
      yield
      @matricies << rotate_y_matrix(-y)
    end
  end

  def rotate_z z
    @matricies << rotate_z_matrix(z)
    if block_given?
      yield
      @matricies << rotate_z_matrix(-z)
    end
  end

  def scale_matrix x:, y:, z:;
    mat4 x, 0, 0, 0,
         0, y, 0, 0,
         0, 0, z, 0,
         0, 0, 0, 1
  end

  def translate_matrix x:, y:, z:;
    mat4 1, 0, 0, x,
         0, 1, 0, y,
         0, 0, 1, z,
         0, 0, 0, 1
  end

  def rotate_y_matrix angle_d
    cos_t = Math.cos angle_d.to_radians
    sin_t = Math.sin angle_d.to_radians
    (mat4  cos_t,  0, sin_t, 0,
           0,      1, 0,     0,
           -sin_t, 0, cos_t, 0,
           0,      0, 0,     1)
  end

  def rotate_z_matrix angle_d
    cos_t = Math.cos angle_d.to_radians
    sin_t = Math.sin angle_d.to_radians
    (mat4 cos_t, -sin_t, 0, 0,
          sin_t,  cos_t, 0, 0,
          0,      0,     1, 0,
          0,      0,     0, 1)
  end

  def rotate_x_matrix angle_d
    cos_t = Math.cos angle_d.to_radians
    sin_t = Math.sin angle_d.to_radians
    (mat4  1,     0,      0, 0,
           0, cos_t, -sin_t, 0,
           0, sin_t,  cos_t, 0,
           0,     0,      0, 1)
  end

  def __mul_triangles__ model, *mul_def
    model.map do |vecs|
      vecs.map do |vec|
        mul vec,
            *mul_def
      end
    end
  end
end

def square &block
  square_verticies = [
    [vec4(0, 0, 0, 1),   vec4(1.0, 0, 0, 1),   vec4(0, 1.0, 0, 1)],
    [vec4(1.0, 0, 0, 1), vec4(1.0, 1.0, 0, 1), vec4(0, 1.0, 0, 1)]
  ]

  m = ModelingApi.new
  m.instance_eval &block if block
  m.__mul_triangles__ square_verticies, *m.matricies
end

Advanced Rendering - 17 Override Core Rendering - main.rb

# ./samples/07_advanced_rendering/17_override_core_rendering/app/main.rb
class GTK::Runtime
  # You can completely override how DR renders by defining this method
  # It is strongly recommend that you do not do this unless you know what you're doing.
  def primitives pass
    # fn.each_send pass.solids,            self, :draw_solid
    # fn.each_send pass.static_solids,     self, :draw_solid
    # fn.each_send pass.sprites,           self, :draw_sprite
    # fn.each_send pass.static_sprites,    self, :draw_sprite
    # fn.each_send pass.primitives,        self, :draw_primitive
    # fn.each_send pass.static_primitives, self, :draw_primitive
    fn.each_send pass.labels,            self, :draw_label
    fn.each_send pass.static_labels,     self, :draw_label
    # fn.each_send pass.lines,             self, :draw_line
    # fn.each_send pass.static_lines,      self, :draw_line
    # fn.each_send pass.borders,           self, :draw_border
    # fn.each_send pass.static_borders,    self, :draw_border

    # if !self.production
    #   fn.each_send pass.debug,           self, :draw_primitive
    #   fn.each_send pass.static_debug,    self, :draw_primitive
    # end

    # fn.each_send pass.reserved,          self, :draw_primitive
    # fn.each_send pass.static_reserved,   self, :draw_primitive
  end
end

def tick args
  args.outputs.labels << { x: 30, y: 30, text: "primitives function defined, only labels rendered" }
  args.outputs.sprites << { x: 100, y: 100, w: 100, h: 100, path: "dragonruby.png" }
end

Advanced Rendering Hd - Hd Labels - main.rb

# ./samples/07_advanced_rendering_hd/01_hd_labels/app/main.rb
def tick args
  args.state.output_cycle ||= :top_level

  args.outputs.background_color = [0, 0, 0]
  args.outputs.solids << [0, 0, 1280, 720, 255, 255, 255]
  if args.state.output_cycle == :top_level
    render_main args
  else
    render_scene args
  end

  # cycle between labels in top level args.outputs
  # and labels inside of render target
  if args.state.tick_count.zmod? 300
    if args.state.output_cycle == :top_level
      args.state.output_cycle = :render_target
    else
      args.state.output_cycle = :top_level
    end
  end
end

def render_main args
  # center line
  args.outputs.lines   << { x:   0, y: 360, x2: 1280, y2: 360 }
  args.outputs.lines   << { x: 640, y:   0, x2:  640, y2: 720 }

  # horizontal ruler
  args.outputs.lines   << { x:   0, y: 370, x2: 1280, y2: 370 }
  args.outputs.lines   << { x:   0, y: 351, x2: 1280, y2: 351 }

  # vertical ruler
  args.outputs.lines   << { x:  575, y: 0, x2: 575, y2: 720 }
  args.outputs.lines   << { x:  701, y: 0, x2: 701, y2: 720 }

  args.outputs.sprites << { x: 640 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square/blue.png", a: 128 }
  args.outputs.labels  << { x:  640, y:   0, text: "(bottom)",  alignment_enum: 1, vertical_alignment_enum: 0 }
  args.outputs.labels  << { x:  640, y: 425, text: "top_level", alignment_enum: 1, vertical_alignment_enum: 1 }
  args.outputs.labels  << { x:  640, y: 720, text: "(top)",     alignment_enum: 1, vertical_alignment_enum: 2 }
  args.outputs.labels  << { x:    0, y: 360, text: "(left)",    alignment_enum: 0, vertical_alignment_enum: 1 }
  args.outputs.labels  << { x: 1280, y: 360, text: "(right)",   alignment_enum: 2, vertical_alignment_enum: 1 }
end

def render_scene args
  args.outputs[:scene].background_color = [255, 255, 255, 0]

  # center line
  args.outputs[:scene].lines   << { x:   0, y: 360, x2: 1280, y2: 360 }
  args.outputs[:scene].lines   << { x: 640, y:   0, x2:  640, y2: 720 }

  # horizontal ruler
  args.outputs[:scene].lines   << { x:   0, y: 370, x2: 1280, y2: 370 }
  args.outputs[:scene].lines   << { x:   0, y: 351, x2: 1280, y2: 351 }

  # vertical ruler
  args.outputs[:scene].lines   << { x:  575, y: 0, x2: 575, y2: 720 }
  args.outputs[:scene].lines   << { x:  701, y: 0, x2: 701, y2: 720 }

  args.outputs[:scene].sprites << { x: 640 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square/blue.png", a: 128, blendmode_enum: 0 }
  args.outputs[:scene].labels  << { x:  640, y:   0, text: "(bottom)",      alignment_enum: 1, vertical_alignment_enum: 0, blendmode_enum: 0 }
  args.outputs[:scene].labels  << { x:  640, y: 425, text: "render target", alignment_enum: 1, vertical_alignment_enum: 1, blendmode_enum: 0 }
  args.outputs[:scene].labels  << { x:  640, y: 720, text: "(top)",         alignment_enum: 1, vertical_alignment_enum: 2, blendmode_enum: 0 }
  args.outputs[:scene].labels  << { x:    0, y: 360, text: "(left)",        alignment_enum: 0, vertical_alignment_enum: 1, blendmode_enum: 0 }
  args.outputs[:scene].labels  << { x: 1280, y: 360, text: "(right)",       alignment_enum: 2, vertical_alignment_enum: 1, blendmode_enum: 0 }

  args.outputs.sprites << { x: 0, y: 0, w: 1280, h: 720, path: :scene }
end

Advanced Rendering Hd - Texture Atlases - main.rb

# ./samples/07_advanced_rendering_hd/02_texture_atlases/app/main.rb
# With HD mode enabled. DragonRuby will automatically use HD sprites given the following
# naming convention (assume we are using a sprite called =player.png=):
#
# | Name  | Resolution | File Naming Convention        |
# |-------+------------+-------------------------------|
# | 720p  |   1280x720 | =player.png=                  |
# | HD+   |   1600x900 | =player@125.png=              |
# | 1080p |  1920x1080 | =player@125.png=              |
# | 1440p |  2560x1440 | =player@200.png=              |
# | 1800p |  3200x1800 | =player@250.png=              |
# | 4k    |  3200x2160 | =player@300.png=              |
# | 5k    |  6400x2880 | =player@400.png=              |

# Note: Review the sample app's game_metadata.txt file for what configurations are enabled.

def tick args
  args.outputs.background_color = [0, 0, 0]
  args.outputs.borders << { x: 0, y: 0, w: 1280, h: 720, r: 255, g: 255, b: 255 }

  args.outputs.labels << { x: 30, y: 30.from_top, text: "render scale: #{args.grid.native_scale}", r: 255, g: 255, b: 255 }
  args.outputs.labels << { x: 30, y: 60.from_top, text: "render scale: #{args.grid.native_scale_enum}", r: 255, g: 255, b: 255 }

  args.outputs.sprites << { x: -640 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x: -320 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }

  args.outputs.sprites << { x:    0 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x:  320 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x:  640 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x:  960 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x: 1280 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }

  args.outputs.sprites << { x: 1600 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x: 1920 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }

  args.outputs.sprites << { x:  640 - 50, y:          720, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x:  640 - 50, y: 100.from_top, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x:  640 - 50, y:     360 - 50, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x:  640 - 50, y:            0, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x:  640 - 50, y:         -100, w: 100, h: 100, path: "sprites/square.png" }
end

Advanced Rendering Hd - Allscreen Properties - main.rb

# ./samples/07_advanced_rendering_hd/03_allscreen_properties/app/main.rb
def tick args
  label_style = { r: 255, g: 255, b: 255, size_enum: 4 }
  args.outputs.background_color = [0, 0, 0]
  args.outputs.borders << { x: 0, y: 0, w: 1280, h: 720, r: 255, g: 255, b: 255 }

  args.outputs.labels << { x: 10, y:  10.from_top, text: "native_scale:       #{args.grid.native_scale}", **label_style }
  args.outputs.labels << { x: 10, y:  40.from_top, text: "native_scale_enum:  #{args.grid.native_scale_enum}",  **label_style }
  args.outputs.labels << { x: 10, y:  70.from_top, text: "allscreen_offset_x: #{args.grid.allscreen_offset_x}", **label_style }
  args.outputs.labels << { x: 10, y: 100.from_top, text: "allscreen_offset_y: #{args.grid.allscreen_offset_y}", **label_style }

  if (args.state.tick_count % 500) < 250
    args.outputs.labels << { x: 10, y: 130.from_top, text: "cropped to:         grid", **label_style }

    args.outputs.sprites << { x:        0,
                              y:        0,
                              w:        1280,
                              h:        720,
                              source_x: 2000 - 640,
                              source_y: 2000 - 320,
                              source_w: 1280,
                              source_h: 720,
                              path: "sprites/world.png" }
  else
    args.outputs.labels << { x: 10, y: 130.from_top, text: "cropped to:         allscreen", **label_style }

    args.outputs.sprites << { x:        0    - args.grid.allscreen_offset_x,
                              y:        0    - args.grid.allscreen_offset_y,
                              w:        1280 + args.grid.allscreen_offset_x * 2,
                              h:        720  + args.grid.allscreen_offset_y * 2,
                              source_x: 2000 - 640 - args.grid.allscreen_offset_x,
                              source_y: 2000 - 320 - args.grid.allscreen_offset_y,
                              source_w: 1280 + args.grid.allscreen_offset_x * 2,
                              source_h: 720  + args.grid.allscreen_offset_y * 2,
                              path:     "sprites/world.png" }

    args.outputs.sprites << { x:        0    - args.grid.allscreen_offset_x,
                              y:        0    - args.grid.allscreen_offset_y,
                              w:        1280 + args.grid.allscreen_offset_x * 2,
                              h:        720  + args.grid.allscreen_offset_y * 2,
                              source_x: 2000 - 640 - args.grid.allscreen_offset_x,
                              source_y: 2000 - 320 - args.grid.allscreen_offset_y,
                              source_w: 1280 + args.grid.allscreen_offset_x * 2,
                              source_h: 720  + args.grid.allscreen_offset_y * 2,
                              path:     "sprites/world.png" }
  end

  args.outputs.sprites << { x: 0, y: 0.from_top - 165, w: 410, h: 165, r: 0, g: 0, b: 0, a: 200, path: :pixel }
end

Advanced Rendering Hd - Layouts And Portrait Mode - main.rb

# ./samples/07_advanced_rendering_hd/04_layouts_and_portrait_mode/app/main.rb
def tick args
  if !args.gtk.version_pro?
    args.outputs.labels << { x: args.grid.w / 2,
                             y: args.grid.h / 2,
                             alignment_enum: 1,
                             vertical_alignment_enum: 1,
                             text: "Portrait mode is a Pro feature." }
    return
  elsif args.gtk.version_pro? && args.grid.orientation == :landscape
    args.outputs.labels << { x: args.grid.w / 2,
                             y: args.grid.h / 2,
                             alignment_enum: 1,
                             vertical_alignment_enum: 1,
                             text: "Landscape orientation detected. Make sure your metadata/game_metadata.txt has the value orientation=portrait." }
    return
  end

  args.outputs.solids << args.layout.rect(row: 0, col: 0, w: 12, h: 24, include_row_gutter: true, include_col_gutter: true).merge(b: 255, a: 80)

  # rows (light blue)
  light_blue = { r: 128, g: 255, b: 255 }
  args.outputs.labels << args.layout.rect(row: 1, col: 3).merge(text: "row examples", vertical_alignment_enum: 1, alignment_enum: 1)
  4.map_with_index do |row|
    args.outputs.solids << args.layout.rect(row: row, col: 0, w: 1, h: 1).merge(**light_blue)
  end

  2.map_with_index do |row|
    args.outputs.solids << args.layout.rect(row: row * 2, col: 1, w: 1, h: 2).merge(**light_blue)
  end

  4.map_with_index do |row|
    args.outputs.solids << args.layout.rect(row: row, col: 2, w: 2, h: 1).merge(**light_blue)
  end

  2.map_with_index do |row|
    args.outputs.solids << args.layout.rect(row: row * 2, col: 4, w: 2, h: 2).merge(**light_blue)
  end

  # columns (yellow)
  yellow = { r: 255, g: 255, b: 128 }
  args.outputs.labels << args.layout.rect(row: 1, col: 9).merge(text: "column examples", vertical_alignment_enum: 1, alignment_enum: 1)
  6.times do |col|
    args.outputs.solids << args.layout.rect(row: 0, col: 6 + col, w: 1, h: 1).merge(**yellow)
  end

  3.times do |col|
    args.outputs.solids << args.layout.rect(row: 1, col: 6 + col * 2, w: 2, h: 1).merge(**yellow)
  end

  6.times do |col|
    args.outputs.solids << args.layout.rect(row: 2, col: 6 + col, w: 1, h: 2).merge(**yellow)
  end

  # max width/height baseline (transparent green)
  green = { r: 0, g: 128, b: 80 }
  args.outputs.labels << args.layout.rect(row: 4, col: 6).merge(text: "max width/height examples", vertical_alignment_enum: 1, alignment_enum: 1)
  args.outputs.solids << args.layout.rect(row: 4, col: 0, w: 12, h: 2).merge(a: 64, **green)

  # max height
  args.outputs.solids << args.layout.rect(row: 4, col: 0, w: 12, h: 2, max_height: 1).merge(a: 64, **green)

  # max width
  args.outputs.solids << args.layout.rect(row: 4, col: 0, w: 12, h: 2, max_width: 6).merge(a: 64, **green)

  # labels relative to rects
  label_color = { r: 0, g: 0, b: 0 }
  white = { r: 232, g: 232, b: 232 }

  # labels realtive to point, achored at 0.0, 0.0
  args.outputs.labels << args.layout.rect(row: 5.5, col: 6).merge(text: "labels using args.layout.point anchored to 0.0, 0.0", vertical_alignment_enum: 1, alignment_enum: 1)
  grey = { r: 128, g: 128, b: 128 }
  args.outputs.solids << args.layout.rect(row: 7, col: 4).merge(**grey)
  args.outputs.labels << args.layout.point(row: 7, col: 4, row_anchor: 1.0, col_anchor: 0.0).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  args.outputs.solids << args.layout.rect(row: 7, col: 5).merge(**grey)
  args.outputs.labels << args.layout.point(row: 7, col: 5, row_anchor: 1.0, col_anchor: 0.5).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  args.outputs.solids << args.layout.rect(row: 7, col: 6).merge(**grey)
  args.outputs.labels << args.layout.point(row: 7, col: 6, row_anchor: 1.0, col_anchor: 1.0).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  args.outputs.solids << args.layout.rect(row: 8, col: 4).merge(**grey)
  args.outputs.labels << args.layout.point(row: 8, col: 4, row_anchor: 0.5, col_anchor: 0.0).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  args.outputs.solids << args.layout.rect(row: 8, col: 5).merge(**grey)
  args.outputs.labels << args.layout.point(row: 8, col: 5, row_anchor: 0.5, col_anchor: 0.5).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  args.outputs.solids << args.layout.rect(row: 8, col: 6).merge(**grey)
  args.outputs.labels << args.layout.point(row: 8, col: 6, row_anchor: 0.5, col_anchor: 1.0).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  args.outputs.solids << args.layout.rect(row: 9, col: 4).merge(**grey)
  args.outputs.labels << args.layout.point(row: 9, col: 4, row_anchor: 0.0, col_anchor: 0.0).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  args.outputs.solids << args.layout.rect(row: 9, col: 5).merge(**grey)
  args.outputs.labels << args.layout.point(row: 9, col: 5, row_anchor: 0.0, col_anchor: 0.5).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  args.outputs.solids << args.layout.rect(row: 9, col: 6).merge(**grey)
  args.outputs.labels << args.layout.point(row: 9, col: 6, row_anchor: 0.0, col_anchor: 1.0).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  # centering rects
  args.outputs.labels << args.layout.rect(row: 10.5, col: 6).merge(text: "layout.rect centered inside another layout.rect", vertical_alignment_enum: 1, alignment_enum: 1)
  outer_rect = args.layout.rect(row: 12, col: 4, w: 3, h: 3)

  # render outer rect
  args.outputs.solids << outer_rect.merge(**light_blue)

  # center a yellow rect with w and h of two
  args.outputs.solids << args.layout.rect_center(
    args.layout.rect(w: 1, h: 5), # inner rect
    outer_rect, # outer rect
  ).merge(**yellow)

  # center a black rect with w three h of one
  args.outputs.solids << args.layout.rect_center(
    args.layout.rect(w: 5, h: 1), # inner rect
    outer_rect, # outer rect
  )

  args.outputs.labels << args.layout.rect(row: 16.5, col: 6).merge(text: "layout.rect_group usage", vertical_alignment_enum: 1, alignment_enum: 1)

  horizontal_markers = [
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 }
  ]

  args.outputs.solids << args.layout.rect_group(row: 18,
                                                dcol: 1,
                                                w: 1,
                                                h: 1,
                                                group: horizontal_markers)

  vertical_markers = [
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 }
  ]

  args.outputs.solids << args.layout.rect_group(row: 18,
                                                drow: 1,
                                                w: 1,
                                                h: 1,
                                                group: vertical_markers)

  colors = [
    { r:   0, g:   0, b:   0 },
    { r:  50, g:  50, b:  50 },
    { r: 100, g: 100, b: 100 },
    { r: 150, g: 150, b: 150 },
    { r: 200, g: 200, b: 200 },
  ]

  args.outputs.solids << args.layout.rect_group(row: 19,
                                                col: 1,
                                                dcol: 2,
                                                w: 2,
                                                h: 1,
                                                group: colors)

  args.outputs.solids << args.layout.rect_group(row: 19,
                                                col: 1,
                                                drow: 1,
                                                w: 2,
                                                h: 1,
                                                group: colors)
end

$gtk.reset

Tweening Lerping Easing Functions - Easing Functions - main.rb

# ./samples/08_tweening_lerping_easing_functions/01_easing_functions/app/main.rb
def tick args
  # STOP! Watch the following presentation first!!!!
  # Math for Game Programmers: Fast and Funky 1D Nonlinear Transformations
  # https://www.youtube.com/watch?v=mr5xkf6zSzk

  # You've watched the talk, yes? YES???

  # define starting and ending points of properties to animate
  args.state.target_x = 1180
  args.state.target_y = 620
  args.state.target_w = 100
  args.state.target_h = 100
  args.state.starting_x = 0
  args.state.starting_y = 0
  args.state.starting_w = 300
  args.state.starting_h = 300

  # define start time and duration of animation
  args.state.start_animate_at = 3.seconds # this is the same as writing 60 * 5 (or 300)
  args.state.duration = 2.seconds # this is the same as writing 60 * 2 (or 120)

  # define type of animations
  # Here are all the options you have for values you can put in the array:
  # :identity, :quad, :cube, :quart, :quint, :flip

  # Linear is defined as:
  # [:identity]
  #
  # Smooth start variations are:
  # [:quad]
  # [:cube]
  # [:quart]
  # [:quint]

  # Linear reversed, and smooth stop are the same as the animations defined above, but reversed:
  # [:flip, :identity]
  # [:flip, :quad, :flip]
  # [:flip, :cube, :flip]
  # [:flip, :quart, :flip]
  # [:flip, :quint, :flip]

  # You can also do custom definitions. See the bottom of the file details
  # on how to do that. I've defined a couple for you:
  # [:smoothest_start]
  # [:smoothest_stop]

  # CHANGE THIS LINE TO ONE OF THE LINES ABOVE TO SEE VARIATIONS
  args.state.animation_type = [:identity]
  # args.state.animation_type = [:quad]
  # args.state.animation_type = [:cube]
  # args.state.animation_type = [:quart]
  # args.state.animation_type = [:quint]
  # args.state.animation_type = [:flip, :identity]
  # args.state.animation_type = [:flip, :quad, :flip]
  # args.state.animation_type = [:flip, :cube, :flip]
  # args.state.animation_type = [:flip, :quart, :flip]
  # args.state.animation_type = [:flip, :quint, :flip]
  # args.state.animation_type = [:smoothest_start]
  # args.state.animation_type = [:smoothest_stop]

  # THIS IS WHERE THE MAGIC HAPPENS!
  # Numeric#ease
  progress = args.state.start_animate_at.ease(args.state.duration, args.state.animation_type)

  # Numeric#ease needs to called:
  # 1. On the number that represents the point in time you want to start, and takes two parameters:
  #   a. The first parameter is how long the animation should take.
  #   b. The second parameter represents the functions that need to be called.
  #
  # For example, if I wanted an animate to start 3 seconds in, and last for 10 seconds,
  # and I want to animation to start fast and end slow, I would do:
  # (60 * 3).ease(60 * 10, :flip, :quint, :flip)

  #        initial value           delta to the final value
  calc_x = args.state.starting_x + (args.state.target_x - args.state.starting_x) * progress
  calc_y = args.state.starting_y + (args.state.target_y - args.state.starting_y) * progress
  calc_w = args.state.starting_w + (args.state.target_w - args.state.starting_w) * progress
  calc_h = args.state.starting_h + (args.state.target_h - args.state.starting_h) * progress

  args.outputs.solids << [calc_x, calc_y, calc_w, calc_h, 0, 0, 0]

  # count down
  count_down = args.state.start_animate_at - args.state.tick_count
  if count_down > 0
    args.outputs.labels << [640, 375, "Running: #{args.state.animation_type} in...", 3, 1]
    args.outputs.labels << [640, 345, "%.2f" % count_down.fdiv(60), 3, 1]
  elsif progress >= 1
    args.outputs.labels << [640, 360, "Click screen to reset.", 3, 1]
    if args.inputs.click
      $gtk.reset
    end
  end
end

# $gtk.reset

# you can make own variations of animations using this
module Easing
  # you have access to all the built in functions: identity, flip, quad, cube, quart, quint
  def self.smoothest_start x
    quad(quint(x))
  end

  def self.smoothest_stop x
    flip(quad(quint(flip(x))))
  end

  # this is the source for the existing easing functions
  def self.identity x
    x
  end

  def self.flip x
    1 - x
  end

  def self.quad x
    x * x
  end

  def self.cube x
    x * x * x
  end

  def self.quart x
    x * x * x * x * x
  end

  def self.quint x
    x * x * x * x * x * x
  end
end

Tweening Lerping Easing Functions - Cubic Bezier - main.rb

# ./samples/08_tweening_lerping_easing_functions/02_cubic_bezier/app/main.rb
def tick args
  args.outputs.background_color = [33, 33, 33]
  args.outputs.lines << bezier(100, 100,
                               100, 620,
                               1180, 620,
                               1180, 100,
                               0)

  args.outputs.lines << bezier(100, 100,
                               100, 620,
                               1180, 620,
                               1180, 100,
                               20)
end


def bezier x1, y1, x2, y2, x3, y3, x4, y4, step
  step ||= 0
  color = [200, 200, 200]
  points = points_for_bezier [x1, y1], [x2, y2], [x3, y3], [x4, y4], step

  points.each_cons(2).map do |p1, p2|
    [p1, p2, color]
  end
end

def points_for_bezier p1, p2, p3, p4, step
  points = []
  if step == 0
    [p1, p2, p3, p4]
  else
    t_step = 1.fdiv(step + 1)
    t = 0
    t += t_step
    points = []
    while t < 1
      points << [
        b_for_t(p1.x, p2.x, p3.x, p4.x, t),
        b_for_t(p1.y, p2.y, p3.y, p4.y, t),
      ]
      t += t_step
    end

    [
      p1,
      *points,
      p4
    ]
  end
end

def b_for_t v0, v1, v2, v3, t
  pow(1 - t, 3) * v0 +
  3 * pow(1 - t, 2) * t * v1 +
  3 * (1 - t) * pow(t, 2) * v2 +
  pow(t, 3) * v3
end

def pow n, to
  n ** to
end

Tweening Lerping Easing Functions - Easing Using Spline - main.rb

# ./samples/08_tweening_lerping_easing_functions/03_easing_using_spline/app/main.rb
def tick args
  args.state.duration = 10.seconds
  args.state.spline = [
    [0.0, 0.33, 0.66, 1.0],
    [1.0, 1.0,  1.0,  1.0],
    [1.0, 0.66, 0.33, 0.0],
  ]

  args.state.simulation_tick = args.state.tick_count % args.state.duration
  progress = 0.ease_spline_extended args.state.simulation_tick, args.state.duration, args.state.spline
  args.outputs.borders << args.grid.rect
  args.outputs.solids << [20 + 1240 * progress,
                          20 +  680 * progress,
                          20, 20].anchor_rect(0.5, 0.5)
  args.outputs.labels << [10,
                          710,
                          "perc: #{"%.2f" % (args.state.simulation_tick / args.state.duration)} t: #{args.state.simulation_tick}"]
end

Tweening Lerping Easing Functions - Parametric Enemy Movement - main.rb

# ./samples/08_tweening_lerping_easing_functions/04_parametric_enemy_movement/app/main.rb
def new_star args
  { x: 1280.randomize(:ratio),
    starting_y: 800,
    distance_to_travel: 900 + 100.randomize(:ratio),
    duration: 100.randomize(:ratio) + 60,
    created_at: args.state.tick_count,
    max_alpha: 128.randomize(:ratio) + 128,
    b: 255.randomize(:ratio),
    g: 200.randomize(:ratio),
    w: 1.randomize(:ratio) + 1,
    h: 1.randomize(:ratio) + 1 }
end

def new_enemy args
  { x: 1280.randomize(:ratio),
    starting_y: 800,
    distance_to_travel: -900,
    duration: 60.randomize(:ratio) + 180,
    created_at: args.state.tick_count,
    w: 32,
    h: 32,
    fire_rate: (30.randomize(:ratio) + (60 - args.state.score)).to_i }
end

def new_bullet args, starting_x, starting_y, enemy_speed
  { x: starting_x,
    starting_y: starting_y,
    distance_to_travel: -900,
    created_at: args.state.tick_count,
    duration: 900 / (enemy_speed.abs + 2.0 + (5.0 * args.state.score.fdiv(100))).abs,
    w: 5,
    h: 5 }
end

def new_player_bullet args, starting_x, starting_y, player_speed
  { x: starting_x,
    starting_y: starting_y,
    distance_to_travel: 900,
    created_at: args.state.tick_count,
    duration: 900 / (player_speed + 2.0),
    w: 5,
    h: 5 }
end

def defaults args
  args.outputs.background_color  = [0, 0, 0]
  args.state.score             ||= 0
  args.state.stars             ||= []
  args.state.enemies           ||= []
  args.state.bullets           ||= []
  args.state.player_bullets    ||= []
  args.state.max_stars           = 50
  args.state.max_enemies         = 10
  args.state.player.x          ||= 640
  args.state.player.y          ||= 100
  args.state.player.w          ||= 32
  args.state.player.h          ||= 32

  if args.state.tick_count == 0
    args.state.stars.clear
    args.state.max_stars.times do
      s = new_star args
      s[:created_at] += s[:duration].randomize(:ratio)
      args.state.stars << s
    end
  end

  if args.state.tick_count == 0
    args.state.enemies.clear
    args.state.max_enemies.times do
      s = new_enemy args
      s[:created_at] += s[:duration].randomize(:ratio)
      args.state.enemies << s
    end
  end
end

def input args
  if args.inputs.keyboard.left
    args.state.player.x -= 5
  elsif args.inputs.keyboard.right
    args.state.player.x += 5
  end

  if args.inputs.keyboard.up
    args.state.player.y += 5
  elsif args.inputs.keyboard.down
    args.state.player.y -= 5
  end

  if args.inputs.keyboard.key_down.space
    args.state.player_bullets << new_player_bullet(args,
                                                   args.state.player.x + args.state.player.w.half,
                                                   args.state.player.y + args.state.player.h, 5)
  end

  args.state.player.y = args.state.player.y.greater(0).lesser(720 - args.state.player.w)
  args.state.player.x = args.state.player.x.greater(0).lesser(1280 - args.state.player.h)
end

def completed? entity
  (entity[:created_at] + entity[:duration]).elapsed_time > 0
end

def calc_stars args
  if (stars_to_add = args.state.max_stars - args.state.stars.length) > 0
    stars_to_add.times { args.state.stars << new_star(args) }
  end
  args.state.stars = args.state.stars.reject { |s| completed? s }
end

def move_enemies args
  if (enemies_to_add = args.state.max_enemies - args.state.enemies.length) > 0
    enemies_to_add.times { args.state.enemies << new_enemy(args) }
  end

  args.state.enemies = args.state.enemies.reject { |s| completed? s }
end

def move_bullets args
  args.state.enemies.each do |e|
    if args.state.tick_count.mod_zero?(e[:fire_rate])
      args.state.bullets << new_bullet(args, e[:x] + e[:w].half, current_y(e), e[:distance_to_travel] / e[:duration])
    end
  end

  args.state.bullets = args.state.bullets.reject { |s| completed? s }
  args.state.player_bullets = args.state.player_bullets.reject { |s| completed? s }
end

def intersect? entity_one, entity_two
  entity_one.merge(y: current_y(entity_one))
            .intersect_rect? entity_two.merge(y: current_y(entity_two))
end

def kill args
  bullets_hitting_enemies = []
  dead_bullets = []
  dead_enemies = []

  args.state.player_bullets.each do |b|
    args.state.enemies.each do |e|
      if intersect? b, e
        dead_bullets << b
        dead_enemies << e
      end
    end
  end

  args.state.score += dead_enemies.length

  args.state.player_bullets.reject! { |b| dead_bullets.include? b }
  args.state.enemies.reject! { |e| dead_enemies.include? e }

  dead = args.state.bullets.any? do |b|
    [args.state.player.x,
     args.state.player.y,
     args.state.player.w,
     args.state.player.h].intersect_rect? b.merge(y: current_y(b))
  end
  return unless dead
  args.gtk.reset
  defaults args
end

def calc args
  calc_stars args
  move_enemies args
  move_bullets args
  kill args
end

def current_y entity
  entity[:starting_y] + (entity[:distance_to_travel] * entity[:created_at].ease(entity[:duration], :identity))
end

def render args
  args.outputs.solids << args.state.stars.map do |s|
    [s[:x],
     current_y(s),
     s[:w], s[:h], 0, s[:g], s[:b], s[:max_alpha] * s[:created_at].ease(20, :identity)]
  end

  args.outputs.borders << args.state.enemies.map do |s|
    [s[:x],
     current_y(s),
     s[:w], s[:h], 255, 0, 0]
  end

  args.outputs.borders << args.state.bullets.map do |b|
    [b[:x],
     current_y(b),
     b[:w], b[:h], 255, 0, 0]
  end

  args.outputs.borders << args.state.player_bullets.map do |b|
    [b[:x],
     current_y(b),
     b[:w], b[:h], 255, 255, 255]
  end

  args.borders << [args.state.player.x,
                   args.state.player.y,
                   args.state.player.w,
                   args.state.player.h, 255, 255, 255]
end

def tick args
  defaults args
  input args
  calc args
  render args
end

Tweening Lerping Easing Functions - Scene Transitions - main.rb

# ./samples/08_tweening_lerping_easing_functions/05_scene_transitions/app/main.rb
# This sample app shows a more advanced implementation of scenes:
# 1. "Scene 1" has a label on it that says "I am scene ONE. Press enter to go to scene TWO."
# 2. "Scene 2" has a label on it that says "I am scene TWO. Press enter to go to scene ONE."
# 3. When the game starts, Scene 1 is presented.
# 4. When the player presses enter, the scene transitions to Scene 2 (fades out Scene 1 over half a second, then fades in Scene 2 over half a second).
# 5. When the player presses enter again, the scene transitions to Scene 1 (fades out Scene 2 over half a second, then fades in Scene 1 over half a second).
# 6. During the fade transitions, spamming the enter key is ignored (scenes don't accept a transition/respond to the enter key until the current transition is completed).
class SceneOne
  attr_gtk

  def tick
    outputs[:scene].labels << { x: 640,
                                y: 360,
                                text: "I am scene ONE. Press enter to go to scene TWO.",
                                alignment_enum: 1,
                                vertical_alignment_enum: 1 }

    state.next_scene = :scene_two if inputs.keyboard.key_down.enter
  end
end

class SceneTwo
  attr_gtk

  def tick
    outputs[:scene].labels << { x: 640,
                                y: 360,
                                text: "I am scene TWO. Press enter to go to scene ONE.",
                                alignment_enum: 1,
                                vertical_alignment_enum: 1 }

    state.next_scene = :scene_one if inputs.keyboard.key_down.enter
  end
end

class RootScene
  attr_gtk

  def initialize
    @scene_one = SceneOne.new
    @scene_two = SceneTwo.new
  end

  def tick
    defaults
    render
    tick_scene
  end

  def defaults
    set_current_scene! :scene_one if state.tick_count == 0
    state.scene_transition_duration ||= 30
  end

  def render
    a = if state.transition_scene_at
          255 * state.transition_scene_at.ease(state.scene_transition_duration, :flip)
        elsif state.current_scene_at
          255 * state.current_scene_at.ease(state.scene_transition_duration)
        else
          255
        end

    outputs.sprites << { x: 0, y: 0, w: 1280, h: 720, path: :scene, a: a }
  end

  def tick_scene
    current_scene = state.current_scene

    @current_scene.args = args
    @current_scene.tick

    if current_scene != state.current_scene
      raise "state.current_scene changed mid tick from #{current_scene} to #{state.current_scene}. To change scenes, set state.next_scene."
    end

    if state.next_scene && state.next_scene != state.transition_scene && state.next_scene != state.current_scene
      state.transition_scene_at = state.tick_count
      state.transition_scene = state.next_scene
    end

    if state.transition_scene_at && state.transition_scene_at.elapsed_time >= state.scene_transition_duration
      set_current_scene! state.transition_scene
    end

    state.next_scene = nil
  end

  def set_current_scene! id
    return if state.current_scene == id
    state.current_scene = id
    state.current_scene_at = state.tick_count
    state.transition_scene = nil
    state.transition_scene_at = nil

    if state.current_scene == :scene_one
      @current_scene = @scene_one
    elsif state.current_scene == :scene_two
      @current_scene = @scene_two
    end
  end
end

def tick args
  $game ||= RootScene.new
  $game.args = args
  $game.tick
end

Tweening Lerping Easing Functions - Animation Queues - main.rb

# ./samples/08_tweening_lerping_easing_functions/06_animation_queues/app/main.rb
# here's how to create a "fire and forget" sprite animation queue
def tick args
  args.outputs.labels << { x: 640,
                           y: 360,
                           text: "Click anywhere on the screen.",
                           alignment_enum: 1,
                           vertical_alignment_enum: 1 }

  # initialize the queue to an empty array
  args.state.fade_out_queue ||=[]

  # if the mouse is click, add a sprite to the fire and forget
  # queue to be processed
  if args.inputs.mouse.click
    args.state.fade_out_queue << {
      x: args.inputs.mouse.x - 20,
      y: args.inputs.mouse.y - 20,
      w: 40,
      h: 40,
      path: "sprites/square/blue.png"
    }
  end

  # process the queue
  args.state.fade_out_queue.each do |item|
    # default the alpha value if it isn't specified
    item.a ||= 255

    # decrement the alpha by 5 each frame
    item.a -= 5
  end

  # remove the item if it's completely faded out
  args.state.fade_out_queue.reject! { |item| item.a <= 0 }

  # render the sprites in the queue
  args.outputs.sprites << args.state.fade_out_queue
end

Tweening Lerping Easing Functions - Animation Queues Advanced - main.rb

# ./samples/08_tweening_lerping_easing_functions/07_animation_queues_advanced/app/main.rb
# sample app shows how to perform a fire and forget animation when a collision occurs
def tick args
  defaults args
  spawn_bullets args
  calc_bullets args
  render args
end

def defaults args
  # place a player on the far left with sprite and hp information
  args.state.player ||= { x: 100, y: 360 - 50, w: 100, h: 100, path: "sprites/square/blue.png", hp: 30 }
  # create an array of bullets
  args.state.bullets ||= []
  # create a queue for handling bullet explosions
  args.state.explosion_queue ||= []
end

def spawn_bullets args
  # span a bullet in a random location on the far right every half second
  return if !args.state.tick_count.zmod? 30
  args.state.bullets << {
    x: 1280 - 100,
    y: rand(720 - 100),
    w: 100,
    h: 100,
    path: "sprites/square/red.png"
  }
end

def calc_bullets args
  # for each bullet
  args.state.bullets.each do |b|
    # move it to the left by 20 pixels
    b.x -= 20

    # determine if the bullet collides with the player
    if b.intersect_rect? args.state.player
      # decrement the player's health if it does
      args.state.player.hp -= 1
      # mark the bullet as exploded
      b.exploded = true

      # queue the explosion by adding it to the explosion queue
      args.state.explosion_queue << b.merge(exploded_at: args.state.tick_count)
    end
  end

  # remove bullets that have exploded so they wont be rendered
  args.state.bullets.reject! { |b| b.exploded }

  # remove animations from the animation queue that have completed
  # frame index will return nil once the animation has completed
  args.state.explosion_queue.reject! { |e| !e.exploded_at.frame_index(7, 4, false) }
end

def render args
  # render the player's hp above the sprite
  args.outputs.labels << {
    x: args.state.player.x + 50,
    y: args.state.player.y + 110,
    text: "#{args.state.player.hp}",
    alignment_enum: 1,
    vertical_alignment_enum: 0
  }

  # render the player
  args.outputs.sprites << args.state.player

  # render the bullets
  args.outputs.sprites << args.state.bullets

  # process the animation queue
  args.outputs.sprites << args.state.explosion_queue.map do |e|
    number_of_frames = 7
    hold_each_frame_for = 4
    repeat_animation = false
    # use the exploded_at property and the frame_index function to determine when the animation should start
    frame_index = e.exploded_at.frame_index(number_of_frames, hold_each_frame_for, repeat_animation)
    # take the explosion primitive and set the path variariable
    e.merge path: "sprites/misc/explosion-#{frame_index}.png"
  end
end

Performance - Sprites As Hash - main.rb

# ./samples/09_performance/01_sprites_as_hash/app/main.rb

# Sprites represented as Hashes using the queue ~args.outputs.sprites~
# code up, but are the "slowest" to render.
# The reason for this is the access of the key in the Hash and also
# because the data args.outputs.sprites is cleared every tick.
def random_x args
  (args.grid.w.randomize :ratio) * -1
end

def random_y args
  (args.grid.h.randomize :ratio) * -1
end

def random_speed
  1 + (4.randomize :ratio)
end

def new_star args
  {
    x: (random_x args),
    y: (random_y args),
    w: 4, h: 4, path: 'sprites/tiny-star.png',
    s: random_speed
  }
end

def move_star args, star
  star.x += star[:s]
  star.y += star[:s]
  if star.x > args.grid.w || star.y > args.grid.h
    star.x = (random_x args)
    star.y = (random_y args)
    star[:s] = random_speed
  end
end

def tick args
  args.state.star_count ||= 0

  # sets console command when sample app initially opens
  if Kernel.global_tick_count == 0
    puts ""
    puts ""
    puts "========================================================="
    puts "* INFO: Sprites, Hashes"
    puts "* INFO: Please specify the number of sprites to render."
    args.gtk.console.set_command "reset_with count: 100"
  end

  # init
  if args.state.tick_count == 0
    args.state.stars = args.state.star_count.map { |i| new_star args }
  end

  # update
  args.state.stars.each { |s| move_star args, s }

  # render
  args.outputs.sprites << args.state.stars
  args.outputs.background_color = [0, 0, 0]
  args.outputs.primitives << args.gtk.current_framerate_primitives
end

# resets game, and assigns star count given by user
def reset_with count: count
  $gtk.reset
  $gtk.args.state.star_count = count
end

Performance - Sprites As Entities - main.rb

# ./samples/09_performance/02_sprites_as_entities/app/main.rb
# Sprites represented as Entities using the queue ~args.outputs.sprites~
# yields nicer access apis over Hashes, but require a bit more code upfront.
# The hash sample has to use star[:s] to get the speed of the star, but
# an entity can use .s instead.
def random_x args
  (args.grid.w.randomize :ratio) * -1
end

def random_y args
  (args.grid.h.randomize :ratio) * -1
end

def random_speed
  1 + (4.randomize :ratio)
end

def new_star args
  args.state.new_entity :star, {
    x: (random_x args),
    y: (random_y args),
    w: 4, h: 4,
    path: 'sprites/tiny-star.png',
    s: random_speed
  }
end

def move_star args, star
  star.x += star.s
  star.y += star.s
  if star.x > args.grid.w || star.y > args.grid.h
    star.x = (random_x args)
    star.y = (random_y args)
    star.s = random_speed
  end
end

def tick args
  args.state.star_count ||= 0

  # sets console command when sample app initially opens
  if Kernel.global_tick_count == 0
    puts ""
    puts ""
    puts "========================================================="
    puts "* INFO: Sprites, Open Entities"
    puts "* INFO: Please specify the number of sprites to render."
    args.gtk.console.set_command "reset_with count: 100"
  end

  # init
  if args.state.tick_count == 0
    args.state.stars = args.state.star_count.map { |i| new_star args }
  end

  # update
  args.state.stars.each { |s| move_star args, s }

  # render
  args.outputs.sprites << args.state.stars
  args.outputs.background_color = [0, 0, 0]
  args.outputs.primitives << args.gtk.current_framerate_primitives
end

# resets game, and assigns star count given by user
def reset_with count: count
  $gtk.reset
  $gtk.args.state.star_count = count
end

Performance - Sprites As Struct - main.rb

# ./samples/09_performance/03_sprites_as_struct/app/main.rb
# create a Struct variant that allows for named parameters on construction.
class NamedStruct < Struct
  def initialize **opts
    super(*members.map { |k| opts[k] })
  end
end

# create a Star NamedStruct
Star = NamedStruct.new(:x, :y, :w, :h, :path, :s,
                       :angle, :angle_anchor_x, :angle_anchor_y,
                       :r, :g, :b, :a,
                       :tile_x, :tile_y,
                       :tile_w, :tile_h,
                       :source_x, :source_y,
                       :source_w, :source_h,
                       :flip_horizontally, :flip_vertically,
                       :blendmode_enum)

# Sprites represented as Structs. They require a little bit more code than Hashes,
# but are the a little faster to render too.
def random_x args
  (args.grid.w.randomize :ratio) * -1
end

def random_y args
  (args.grid.h.randomize :ratio) * -1
end

def random_speed
  1 + (4.randomize :ratio)
end

def new_star args
  Star.new x: (random_x args),
           y: (random_y args),
           w: 4, h: 4,
           path: 'sprites/tiny-star.png',
           s: random_speed
end

def move_star args, star
  star.x += star[:s]
  star.y += star[:s]
  if star.x > args.grid.w || star.y > args.grid.h
    star.x = (random_x args)
    star.y = (random_y args)
    star[:s] = random_speed
  end
end

def tick args
  args.state.star_count ||= 0

  # sets console command when sample app initially opens
  if Kernel.global_tick_count == 0
    puts ""
    puts ""
    puts "========================================================="
    puts "* INFO: Sprites, Structs"
    puts "* INFO: Please specify the number of sprites to render."
    args.gtk.console.set_command "reset_with count: 100"
  end

  # init
  if args.state.tick_count == 0
    args.state.stars = args.state.star_count.map { |i| new_star args }
  end

  # update
  args.state.stars.each { |s| move_star args, s }

  # render
  args.outputs.sprites << args.state.stars
  args.outputs.background_color = [0, 0, 0]
  args.outputs.primitives << args.gtk.current_framerate_primitives
end

# resets game, and assigns star count given by user
def reset_with count: count
  $gtk.reset
  $gtk.args.state.star_count = count
end

Performance - Sprites As Strict Entities - main.rb

# ./samples/09_performance/04_sprites_as_strict_entities/app/main.rb
# Sprites represented as StrictEntities using the queue ~args.outputs.sprites~
# yields apis access similar to Entities, but all properties that can be set on the
# entity must be predefined with a default value. Strict entities do not support the
# addition of new properties after the fact. They are more performant than OpenEntities
# because of this constraint.
def random_x args
  (args.grid.w.randomize :ratio) * -1
end

def random_y args
  (args.grid.h.randomize :ratio) * -1
end

def random_speed
  1 + (4.randomize :ratio)
end

def new_star args
  args.state.new_entity_strict(:star,
                               x: (random_x args),
                               y: (random_y args),
                               w: 4, h: 4,
                               path: 'sprites/tiny-star.png',
                               s: random_speed) do |entity|
    # invoke attr_sprite so that it responds to
    # all properties that are required to render a sprite
    entity.attr_sprite
  end
end

def move_star args, star
  star.x += star.s
  star.y += star.s
  if star.x > args.grid.w || star.y > args.grid.h
    star.x = (random_x args)
    star.y = (random_y args)
    star.s = random_speed
  end
end

def tick args
  args.state.star_count ||= 0

  # sets console command when sample app initially opens
  if Kernel.global_tick_count == 0
    puts ""
    puts ""
    puts "========================================================="
    puts "* INFO: Sprites, Strict Entities"
    puts "* INFO: Please specify the number of sprites to render."
    args.gtk.console.set_command "reset_with count: 100"
  end

  # init
  if args.state.tick_count == 0
    args.state.stars = args.state.star_count.map { |i| new_star args }
  end

  # update
  args.state.stars.each { |s| move_star args, s }

  # render
  args.outputs.sprites << args.state.stars
  args.outputs.background_color = [0, 0, 0]
  args.outputs.primitives << args.gtk.current_framerate_primitives
end

# resets game, and assigns star count given by user
def reset_with count: count
  $gtk.reset
  $gtk.args.state.star_count = count
end

Performance - Sprites As Classes - main.rb

# ./samples/09_performance/05_sprites_as_classes/app/main.rb
# Sprites represented as Classes using the queue ~args.outputs.sprites~.
# gives you full control of property declaration and method invocation.
# They are more performant than OpenEntities and StrictEntities, but more code upfront.
class Star
  attr_sprite

  def initialize grid
    @grid = grid
    @x = (rand @grid.w) * -1
    @y = (rand @grid.h) * -1
    @w    = 4
    @h    = 4
    @s    = 1 + (4.randomize :ratio)
    @path = 'sprites/tiny-star.png'
  end

  def move
    @x += @s
    @y += @s
    @x = (rand @grid.w) * -1 if @x > @grid.right
    @y = (rand @grid.h) * -1 if @y > @grid.top
  end
end

# calls methods needed for game to run properly
def tick args
  # sets console command when sample app initially opens
  if Kernel.global_tick_count == 0
    puts ""
    puts ""
    puts "========================================================="
    puts "* INFO: Sprites, Classes"
    puts "* INFO: Please specify the number of sprites to render."
    args.gtk.console.set_command "reset_with count: 100"
  end

  args.state.star_count ||= 0

  # init
  if args.state.tick_count == 0
    args.state.stars = args.state.star_count.map { |i| Star.new args.grid }
  end

  # update
  args.state.stars.each(&:move)

  # render
  args.outputs.sprites << args.state.stars
  args.outputs.background_color = [0, 0, 0]
  args.outputs.primitives << args.gtk.current_framerate_primitives
end

# resets game, and assigns star count given by user
def reset_with count: count
  $gtk.reset
  $gtk.args.state.star_count = count
end

Performance - Static Sprites As Classes - main.rb

# ./samples/09_performance/06_static_sprites_as_classes/app/main.rb
# Sprites represented as Classes using the queue ~args.outputs.static_sprites~.
# bypasses the queue behavior of ~args.outputs.sprites~. All instances are held
# by reference. You get better performance, but you are mutating state of held objects
# which is less functional/data oriented.
class Star
  attr_sprite

  def initialize grid
    @grid = grid
    @x = (rand @grid.w) * -1
    @y = (rand @grid.h) * -1
    @w    = 4
    @h    = 4
    @s    = 1 + (4.randomize :ratio)
    @path = 'sprites/tiny-star.png'
  end

  def move
    @x += @s
    @y += @s
    @x = (rand @grid.w) * -1 if @x > @grid.right
    @y = (rand @grid.h) * -1 if @y > @grid.top
  end
end

# calls methods needed for game to run properly
def tick args
  # sets console command when sample app initially opens
  if Kernel.global_tick_count == 0
    puts ""
    puts ""
    puts "========================================================="
    puts "* INFO: Static Sprites, Classes"
    puts "* INFO: Please specify the number of sprites to render."
    args.gtk.console.set_command "reset_with count: 100"
  end

  args.state.star_count ||= 0

  # init
  if args.state.tick_count == 0
    args.state.stars = args.state.star_count.map { |i| Star.new args.grid }
    args.outputs.static_sprites << args.state.stars
  end

  # update
  args.state.stars.each(&:move)

  # render
  args.outputs.background_color = [0, 0, 0]
  args.outputs.primitives << args.gtk.current_framerate_primitives
end

# resets game, and assigns star count given by user
def reset_with count: count
  $gtk.reset
  $gtk.args.state.star_count = count
end

Performance - Static Sprites As Classes With Custom Drawing - main.rb

# ./samples/09_performance/07_static_sprites_as_classes_with_custom_drawing/app/main.rb
# Sprites represented as Classes, with a draw_override method, and using the queue ~args.outputs.static_sprites~.
# is the fastest approach. This is comparable to what other game engines set as the default behavior.
# There are tradeoffs for all this speed if the creation of a full blown class, and bypassing
# functional/data-oriented practices.
class Star
  def initialize grid
    @grid = grid
    @x = (rand @grid.w) * -1
    @y = (rand @grid.h) * -1
    @w    = 4
    @h    = 4
    @s    = 1 + (4.randomize :ratio)
    @path = 'sprites/tiny-star.png'
  end

  def move
    @x += @s
    @y += @s
    @x = (rand @grid.w) * -1 if @x > @grid.right
    @y = (rand @grid.h) * -1 if @y > @grid.top
  end

  # if the object that is in args.outputs.sprites (or static_sprites)
  # respond_to? :draw_override, then the method is invoked giving you
  # access to the class used to draw to the canvas.
  def draw_override ffi_draw
    # first move then draw
    move

    # The argument order for ffi.draw_sprite is:
    # x, y, w, h, path
    ffi_draw.draw_sprite @x, @y, @w, @h, @path

    # The argument order for ffi_draw.draw_sprite_2 is (pass in nil for default value):
    # x, y, w, h, path,
    # angle, alpha

    # The argument order for ffi_draw.draw_sprite_3 is:
    # x, y, w, h,
    # path,
    # angle,
    # alpha, red_saturation, green_saturation, blue_saturation
    # tile_x, tile_y, tile_w, tile_h,
    # flip_horizontally, flip_vertically,
    # angle_anchor_x, angle_anchor_y,
    # source_x, source_y, source_w, source_h

    # The argument order for ffi_draw.draw_sprite_4 is:
    # x, y, w, h,
    # path,
    # angle,
    # alpha, red_saturation, green_saturation, blue_saturation
    # tile_x, tile_y, tile_w, tile_h,
    # flip_horizontally, flip_vertically,
    # angle_anchor_x, angle_anchor_y,
    # source_x, source_y, source_w, source_h,
    # blendmode_enum
  end
end

# calls methods needed for game to run properly
def tick args
  # sets console command when sample app initially opens
  if Kernel.global_tick_count == 0
    puts ""
    puts ""
    puts "========================================================="
    puts "* INFO: Static Sprites, Classes, Draw Override"
    puts "* INFO: Please specify the number of sprites to render."
    args.gtk.console.set_command "reset_with count: 100"
  end

  args.state.star_count ||= 0

  # init
  if args.state.tick_count == 0
    args.state.stars = args.state.star_count.map { |i| Star.new args.grid }
    args.outputs.static_sprites << args.state.stars
  end

  # render framerate
  args.outputs.background_color = [0, 0, 0]
  args.outputs.primitives << args.gtk.current_framerate_primitives
end

# resets game, and assigns star count given by user
def reset_with count: count
  $gtk.reset
  $gtk.args.state.star_count = count
end

Performance - Collision Limits - main.rb

# ./samples/09_performance/08_collision_limits/app/main.rb
=begin

 Reminders:
 - find_all: Finds all elements of a collection that meet certain requirements.
   In this sample app, we're finding all bodies that intersect with the center body.

 - args.outputs.solids: An array. The values generate a solid.
   The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]
   For more information about solids, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.labels: An array. The values generate a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.

 - ARRAY#intersect_rect?: Returns true or false depending on if two rectangles intersect.

=end

# This code demonstrates moving objects that loop around once they exceed the scope of the screen,
# which has dimensions of 1280 by 720, and also detects collisions between objects called "bodies".

def body_count num
  $gtk.args.state.other_bodies = num.map { [1280 * rand, 720 * rand, 10, 10] } # other_bodies set using num collection
end

def tick args

  # Center body's values are set using an array
  # Map is used to set values of 5000 other bodies
  # All bodies that intersect with center body are stored in collisions collection
  args.state.center_body  ||= { x: 640 - 100, y: 360 - 100, w: 200, h: 200 } # calculations done to place body in center
  args.state.other_bodies ||= 5000.map do
    { x: 1280 * rand,
      y: 720 * rand,
      w: 2,
      h: 2,
      path: :pixel,
      r: 0,
      g: 0,
      b: 0 }
  end # 2000 bodies given random position on screen

  # finds all bodies that intersect with center body, stores them in collisions
  collisions = args.state.other_bodies.find_all { |b| b.intersect_rect? args.state.center_body }

  args.borders << args.state.center_body # outputs center body as a black border

  # transparency changes based on number of collisions; the more collisions, the redder (more transparent) the box becomes
  args.sprites  << { x: args.state.center_body.x,
                     y: args.state.center_body.y,
                     w: args.state.center_body.w,
                     h: args.state.center_body.h,
                     path: :pixel,
                     a: collisions.length.idiv(2), # alpha value represents the number of collisions that occured
                     r: 255,
                     g: 0,
                     b: 0 } # center body is red solid
  args.sprites  << args.state.other_bodies # other bodies are output as (black) solids, as well

  args.labels  << [10, 30, args.gtk.current_framerate.to_sf] # outputs frame rate in bottom left corner

  # Bodies are returned to bottom left corner if positions exceed scope of screen
  args.state.other_bodies.each do |b| # for each body in the other_bodies collection
    b.x += 5 # x and y are both incremented by 5
    b.y += 5
    b.x = 0 if b.x > 1280 # x becomes 0 if star exceeds scope of screen (goes too far right)
    b.y = 0 if b.y > 720 # y becomes 0 if star exceeds scope of screen (goes too far up)
  end
end

# Resets the game.
$gtk.reset

Performance - Collision Limits Aabb - main.rb

# ./samples/09_performance/09_collision_limits_aabb/app/main.rb
def tick args
  args.state.id_seed    ||= 1
  args.state.bullets    ||= []
  args.state.terrain    ||= [
    {
      x: 40, y: 0, w: 1200, h: 40, path: :pixel, r: 0, g: 0, b: 0
    },
    {
      x: 1240, y: 0, w: 40, h: 720, path: :pixel, r: 0, g: 0, b: 0
    },
    {
      x: 0, y: 0, w: 40, h: 720, path: :pixel, r: 0, g: 0, b: 0
    },
    {
      x: 40, y: 680, w: 1200, h: 40, path: :pixel, r: 0, g: 0, b: 0
    },

    {
      x: 760, y: 420, w: 180, h: 40, path: :pixel, r: 0, g: 0, b: 0
    },
    {
      x: 720, y: 420, w: 40, h: 100, path: :pixel, r: 0, g: 0, b: 0
    },
    {
      x: 940, y: 420, w: 40, h: 100, path: :pixel, r: 0, g: 0, b: 0
    },

    {
      x: 660, y: 220, w: 280, h: 40, path: :pixel, r: 0, g: 0, b: 0
    },
    {
      x: 620, y: 220, w: 40, h: 100, path: :pixel, r: 0, g: 0, b: 0
    },
    {
      x: 940, y: 220, w: 40, h: 100, path: :pixel, r: 0, g: 0, b: 0
    },

    {
      x: 460, y: 40, w: 280, h: 40, path: :pixel, r: 0, g: 0, b: 0
    },
    {
      x: 420, y: 40, w: 40, h: 100, path: :pixel, r: 0, g: 0, b: 0
    },
    {
      x: 740, y: 40, w: 40, h: 100, path: :pixel, r: 0, g: 0, b: 0
    },
  ]

  if args.inputs.keyboard.space
      b = {
        id: args.state.id_seed,
        x: 60,
        y: 60,
        w: 10,
        h: 10,
        dy: rand(20) + 10,
        dx: rand(20) + 10,
        path: 'sprites/square/blue.png'
      }

      args.state.bullets << b # if b.id == 122

      args.state.id_seed += 1
  end

  terrain = args.state.terrain

  args.state.bullets.each do |b|
    next if b.still
    # if b.still
    #   x_dir = if rand > 0.5
    #             -1
    #           else
    #             1
    #           end

    #   y_dir = if rand > 0.5
    #             -1
    #           else
    #             1
    #           end

    #   b.dy = rand(20) + 10 * x_dir
    #   b.dx = rand(20) + 10 * y_dir
    #   b.still = false
    #   b.on_floor = false
    # end

    if b.on_floor
      b.dx *= 0.9
    end

    b.x += b.dx

    collision_x = args.geometry.find_intersect_rect(b, terrain)

    if collision_x
      if b.dx > 0
        b.x = collision_x.x - b.w
      elsif b.dx < 0
        b.x = collision_x.x + collision_x.w
      end
      b.dx *= -0.8
    end

    b.dy -= 0.25
    b.y += b.dy

    collision_y = args.geometry.find_intersect_rect(b, terrain)

    if collision_y
      if b.dy > 0
        b.y = collision_y.y - b.h
      elsif b.dy < 0
        b.y = collision_y.y + collision_y.h
      end

      if b.dy < 0 && b.dy.abs < 1
        b.on_floor = true
      end

      b.dy *= -0.8
    end

    if b.on_floor && (b.dy.abs + b.dx.abs) < 0.1
      b.still = true
    end
  end

  args.outputs.labels << { x: 60, y: 60.from_top, text: "Hold space bar to add squares." }
  args.outputs.labels << { x: 60, y: 90.from_top, text: "FPS: #{args.gtk.current_framerate.to_sf}" }
  args.outputs.labels << { x: 60, y: 120.from_top, text: "Count: #{args.state.bullets.length}" }
  args.outputs.borders << args.state.terrain
  args.outputs.sprites << args.state.bullets
end

# $gtk.reset

Performance - Collision Limits Find Single - main.rb

# ./samples/09_performance/09_collision_limits_find_single/app/main.rb
def tick args
  if args.state.should_reset_framerate_calculation
    args.gtk.reset_framerate_calculation
    args.state.should_reset_framerate_calculation = nil
  end

  if !args.state.rects
    args.state.rects = []
    add_10_000_random_rects args
  end

  args.state.player_rect ||= { x: 640 - 20, y: 360 - 20, w: 40, h: 40 }
  args.state.collision_type ||= :using_lambda

  if args.state.tick_count == 0
    generate_scene args, args.state.quad_tree
  end

  # inputs
  # have a rectangle that can be moved around using arrow keys
  args.state.player_rect.x += args.inputs.left_right * 4
  args.state.player_rect.y += args.inputs.up_down * 4

  if args.inputs.mouse.click
    add_10_000_random_rects args
    args.state.should_reset_framerate_calculation = true
  end

  if args.inputs.keyboard.key_down.tab
    if args.state.collision_type == :using_lambda
      args.state.collision_type = :using_while_loop
    elsif args.state.collision_type == :using_while_loop
      args.state.collision_type = :using_find_intersect_rect
    elsif args.state.collision_type == :using_find_intersect_rect
      args.state.collision_type = :using_lambda
    end
    args.state.should_reset_framerate_calculation = true
  end

  # calc
  if args.state.collision_type == :using_lambda
    args.state.current_collision = args.state.rects.find { |r| r.intersect_rect? args.state.player_rect }
  elsif args.state.collision_type == :using_while_loop
    args.state.current_collision = nil
    idx = 0
    l = args.state.rects.length
    rects = args.state.rects
    player = args.state.player_rect
    while idx < l
      if rects[idx].intersect_rect? player
        args.state.current_collision = rects[idx]
        break
      end
      idx += 1
    end
  else
    args.state.current_collision = args.geometry.find_intersect_rect args.state.player_rect, args.state.rects
  end

  # render
  render_instructions args
  args.outputs.sprites << { x: 0, y: 0, w: 1280, h: 720, path: :scene }

  if args.state.current_collision
    args.outputs.sprites << args.state.current_collision.merge(path: :pixel, r: 255, g: 0, b: 0)
  end

  args.outputs.sprites << args.state.player_rect.merge(path: :pixel, a: 80, r: 0, g: 255, b: 0)
  args.outputs.labels  << {
    x: args.state.player_rect.x + args.state.player_rect.w / 2,
    y: args.state.player_rect.y + args.state.player_rect.h / 2,
    text: "player",
    alignment_enum: 1,
    vertical_alignment_enum: 1,
    size_enum: -4
  }

end

def add_10_000_random_rects args
  add_rects args, 10_000.map { { x: rand(1080) + 100, y: rand(520) + 100 } }
end

def add_rects args, points
  args.state.rects.concat(points.map { |point| { x: point.x, y: point.y, w: 5, h: 5 } })
  # args.state.quad_tree = args.geometry.quad_tree_create args.state.rects
  generate_scene args, args.state.quad_tree
end

def add_rect args, x, y
  args.state.rects << { x: x, y: y, w: 5, h: 5 }
  # args.state.quad_tree = args.geometry.quad_tree_create args.state.rects
  generate_scene args, args.state.quad_tree
end

def generate_scene args, quad_tree
  args.outputs[:scene].w = 1280
  args.outputs[:scene].h = 720
  args.outputs[:scene].solids << { x: 0, y: 0, w: 1280, h: 720, r: 255, g: 255, b: 255 }
  args.outputs[:scene].sprites << args.state.rects.map { |r| r.merge(path: :pixel, r: 0, g: 0, b: 255) }
end

def render_instructions args
  args.outputs.primitives << { x:  0, y: 90.from_top, w: 1280, h: 100, r: 0, g: 0, b: 0, a: 200 }.solid!
  args.outputs.labels << { x: 10, y: 10.from_top, r: 255, g: 255, b: 255, size_enum: -2, text: "Click to add 10,000 random rects. Tab to change collision algorithm." }
  args.outputs.labels << { x: 10, y: 40.from_top, r: 255, g: 255, b: 255, size_enum: -2, text: "Algorithm: #{args.state.collision_type}" }
  args.outputs.labels << { x: 10, y: 55.from_top, r: 255, g: 255, b: 255, size_enum: -2, text: "Rect Count: #{args.state.rects.length}" }
  args.outputs.labels << { x: 10, y: 70.from_top, r: 255, g: 255, b: 255, size_enum: -2, text: "FPS: #{args.gtk.current_framerate.to_sf}" }
end

Performance - Collision Limits Many To Many - main.rb

# ./samples/09_performance/09_collision_limits_many_to_many/app/main.rb
class Square
  attr_sprite

  def initialize
    @x    = rand 1280
    @y    = rand 720
    @w    = 15
    @h    = 15
    @path = 'sprites/square/blue.png'
    @dir = 1
  end

  def mark_collisions all
    @path = if all[self]
              'sprites/square/red.png'
            else
              'sprites/square/blue.png'
            end
  end

  def move
    @dir  = -1 if (@x + @w >= 1280) && @dir ==  1
    @dir  =  1 if (@x      <=    0) && @dir == -1
    @x   += @dir
  end
end

def reset_if_needed args
  if args.state.tick_count == 0 || args.inputs.mouse.click
    args.state.star_count = 1500
    args.state.stars = args.state.star_count.map { |i| Square.new }.to_a
    args.outputs.static_sprites.clear
    args.outputs.static_sprites << args.state.stars
  end
end

def tick args
  reset_if_needed args

  Fn.each args.state.stars do |s| s.move end

  all = GTK::Geometry.find_collisions args.state.stars
  Fn.each args.state.stars do |s| s.mark_collisions all end

  args.outputs.background_color = [0, 0, 0]
  args.outputs.primitives << args.gtk.current_framerate_primitives
end

Ui Controls - Checkboxes - main.rb

# ./samples/09_ui_controls/01_checkboxes/app/main.rb
def tick args
  # use layout apis to position check boxes
  args.state.checkboxes ||= [
    args.layout.rect(row: 0, col: 0, w: 1, h: 1).merge(id: :option1, text: "Option 1", checked: false, changed_at: -120),
    args.layout.rect(row: 1, col: 0, w: 1, h: 1).merge(id: :option1, text: "Option 2", checked: false, changed_at: -120),
    args.layout.rect(row: 2, col: 0, w: 1, h: 1).merge(id: :option1, text: "Option 3", checked: false, changed_at: -120),
    args.layout.rect(row: 3, col: 0, w: 1, h: 1).merge(id: :option1, text: "Option 4", checked: false, changed_at: -120),
  ]

  # check for click of checkboxes
  if args.inputs.mouse.click
    args.state.checkboxes.find_all do |checkbox|
      args.inputs.mouse.inside_rect? checkbox
    end.each do |checkbox|
      # mark checkbox value
      checkbox.checked = !checkbox.checked
      # set the time the checkbox was changed
      checkbox.changed_at = args.state.tick_count
    end
  end

  # render checkboxes
  args.outputs.primitives << args.state.checkboxes.map do |checkbox|
    # baseline prefab for checkbox
    prefab = {
      x: checkbox.x,
      y: checkbox.y,
      w: checkbox.w,
      h: checkbox.h
    }

    # label for checkbox centered vertically
    label = {
      x: checkbox.x + checkbox.w + 10,
      y: checkbox.y + checkbox.h / 2,
      text: checkbox.text,
      alignment_enum: 0,
      vertical_alignment_enum: 1
    }

    # rendering if checked or not
    if checkbox.checked
      # fade in
      a = 255 * args.easing.ease(checkbox.changed_at, args.state.tick_count, 30, :smooth_stop_quint)

      [
        label,
        prefab.merge(primitive_marker: :solid, a: a),
        prefab.merge(primitive_marker: :border)
      ]
    else
      # fade out
      a = 255 * args.easing.ease(checkbox.changed_at, args.state.tick_count, 30, :smooth_stop_quint, :flip)

      [
        label,
        prefab.merge(primitive_marker: :solid, a: a),
        prefab.merge(primitive_marker: :border)
      ]
    end
  end
end

Advanced Debugging - Logging - main.rb

# ./samples/10_advanced_debugging/00_logging/app/main.rb
def tick args
  args.outputs.background_color = [255, 255, 255, 0]
  if args.state.tick_count == 0
    args.gtk.log_spam "log level spam"
    args.gtk.log_debug "log level debug"
    args.gtk.log_info "log level info"
    args.gtk.log_warn "log level warn"
    args.gtk.log_error "log level error"
    args.gtk.log_unfiltered "log level unfiltered"
    puts "This is a puts call"
    args.gtk.console.show
  end

  if args.state.tick_count == 60
    puts "This is a puts call on tick 60"
  elsif args.state.tick_count == 120
    puts "This is a puts call on tick 120"
  end
end

Advanced Debugging - Trace Debugging - main.rb

# ./samples/10_advanced_debugging/01_trace_debugging/app/main.rb
class Game
  attr_gtk

  def method1 num
    method2 num
  end

  def method2 num
    method3 num
  end

  def method3 num
    method4 num
  end

  def method4 num
    if num == 1
      puts "UNLUCKY #{num}."
      state.unlucky_count += 1
      if state.unlucky_count > 3
        raise "NAT 1 finally occurred. Check app/trace.txt for all method invocation history."
      end
    else
      puts "LUCKY #{num}."
    end
  end

  def tick
    state.roll_history ||= []
    state.roll_history << rand(20) + 1
    state.countdown ||= 600
    state.countdown  -= 1
    state.unlucky_count ||= 0
    outputs.labels << [640, 360, "A dice roll of 1 will cause an exception.", 0, 1]
    if state.countdown > 0
      outputs.labels << [640, 340, "Dice roll countdown: #{state.countdown}", 0, 1]
    else
      state.attempts ||= 0
      state.attempts  += 1
      outputs.labels << [640, 340, "ROLLING! #{state.attempts}", 0, 1]
    end
    return if state.countdown > 0
    method1 state.roll_history[-1]
  end
end

$game = Game.new

def tick args
  trace! $game # <------------------- TRACING ENABLED FOR THIS OBJECT
  $game.args = args
  $game.tick
end

Advanced Debugging - Trace Debugging Classes - main.rb

# ./samples/10_advanced_debugging/02_trace_debugging_classes/app/main.rb
class Foobar
  def initialize
    trace! # Trace is added to the constructor.
  end

  def clicky args
    return unless args.inputs.mouse.click
    try_rand rand
  end

  def try_rand num
    return if num < 0.9
    raise "Exception finally occurred. Take a look at logs/trace.txt #{num}."
  end
end

def tick args
  args.labels << [640, 360, "Start clicking. Eventually an exception will be thrown. Then look at logs/trace.txt.", 0, 1]
  args.state.foobar = Foobar.new if args.tick_count
  return unless args.state.foobar
  args.state.foobar.clicky args
end

Advanced Debugging - Unit Tests - benchmark_api_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/benchmark_api_tests.rb
def test_benchmark_api args, assert
  result = args.gtk.benchmark iterations: 100,
                              only_one: -> () {
                                r = 0
                                (1..100).each do |i|
                                  r += 1
                                end
                              }

  assert.equal! result.first_place.name, :only_one

  result = args.gtk.benchmark iterations: 100,
                              iterations_100: -> () {
                                r = 0
                                (1..100).each do |i|
                                  r += 1
                                end
                              },
                              iterations_50: -> () {
                                r = 0
                                (1..50).each do |i|
                                  r += 1
                                end
                              }

  assert.equal! result.first_place.name, :iterations_50

  result = args.gtk.benchmark iterations: 1,
                              iterations_100: -> () {
                                r = 0
                                (1..100).each do |i|
                                  r += 1
                                end
                              },
                              iterations_50: -> () {
                                r = 0
                                (1..50).each do |i|
                                  r += 1
                                end
                              }

  assert.equal! result.too_small_to_measure, true
end

Advanced Debugging - Unit Tests - exception_raising_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/exception_raising_tests.rb
begin :shared
  class ExceptionalClass
    def initialize exception_to_throw = nil
      raise exception_to_throw if exception_to_throw
    end
  end
end

def test_exception_in_newing_object args, assert
  begin
    ExceptionalClass.new TypeError
    raise "Exception wasn't thrown!"
  rescue Exception => e
    assert.equal! e.class, TypeError, "Exceptions within constructor should be retained."
  end
end

$gtk.reset 100
$gtk.log_level = :off

Advanced Debugging - Unit Tests - fn_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/fn_tests.rb
def infinity
  1 / 0
end

def neg_infinity
  -1 / 0
end

def nan
  0.0 / 0
end

def test_add args, assert
  assert.equal! (args.fn.add), 0
  assert.equal! (args.fn.+), 0
  assert.equal! (args.fn.+ 1, 2, 3), 6
  assert.equal! (args.fn.+ 0), 0
  assert.equal! (args.fn.+ 0, nil), 0
  assert.equal! (args.fn.+ 0, nan), nil
  assert.equal! (args.fn.+ 0, nil, infinity), nil
  assert.equal! (args.fn.+ [1, 2, 3, [4, 5, 6]]), 21
  assert.equal! (args.fn.+ [nil, [4, 5, 6]]), 15
end

def test_sub args, assert
  neg_infinity = infinity * -1
  assert.equal! (args.fn.+), 0
  assert.equal! (args.fn.- 1, 2, 3), -4
  assert.equal! (args.fn.- 4), -4
  assert.equal! (args.fn.- 4, nan), nil
  assert.equal! (args.fn.- 0, nil), 0
  assert.equal! (args.fn.- 0, nil, infinity), nil
  assert.equal! (args.fn.- [0, 1, 2, 3, [4, 5, 6]]), -21
  assert.equal! (args.fn.- [nil, 0, [4, 5, 6]]), -15
end

def test_div args, assert
  assert.equal! (args.fn.div), 1
  assert.equal! (args.fn./), 1
  assert.equal! (args.fn./ 6, 3), 2
  assert.equal! (args.fn./ 6, infinity), nil
  assert.equal! (args.fn./ 6, nan), nil
  assert.equal! (args.fn./ infinity), nil
  assert.equal! (args.fn./ 0), nil
  assert.equal! (args.fn./ 6, [3]), 2
end

def test_idiv args, assert
  assert.equal! (args.fn.idiv), 1
  assert.equal! (args.fn.idiv 7, 3), 2
  assert.equal! (args.fn.idiv 6, infinity), nil
  assert.equal! (args.fn.idiv 6, nan), nil
  assert.equal! (args.fn.idiv infinity), nil
  assert.equal! (args.fn.idiv 0), nil
  assert.equal! (args.fn.idiv 7, [3]), 2
end

def test_mul args, assert
  assert.equal! (args.fn.mul), 1
  assert.equal! (args.fn.*), 1
  assert.equal! (args.fn.* 7, 3), 21
  assert.equal! (args.fn.* 6, nan), nil
  assert.equal! (args.fn.* 6, infinity), nil
  assert.equal! (args.fn.* infinity), nil
  assert.equal! (args.fn.* 0), 0
  assert.equal! (args.fn.* 7, [3]), 21
end

def test_lt args, assert
  assert.equal! (args.fn.lt 1), 1
  assert.equal! (args.fn.lt), nil
  assert.equal! (args.fn.lt infinity), nil
  assert.equal! (args.fn.lt nan), nil
  assert.equal! (args.fn.lt 10, 9, 8), 8
  assert.equal! (args.fn.< 10, 9, 8), 8
  assert.equal! (args.fn.< [10, 9, [8]]), 8
  assert.equal! (args.fn.< 10, 10), nil
end

def test_lte args, assert
  assert.equal! (args.fn.lte 1), 1
  assert.equal! (args.fn.lte), nil
  assert.equal! (args.fn.lte infinity), nil
  assert.equal! (args.fn.lte nan), nil
  assert.equal! (args.fn.lte 10, 9, 8), 8
  assert.equal! (args.fn.lte 10, 10), 10
  assert.equal! (args.fn.lte  10, 9, [8]), 8
  assert.equal! (args.fn.<=  10, 9, 8), 8
end

def test_gt args, assert
  assert.equal! (args.fn.gt 1), 1
  assert.equal! (args.fn.gt), nil
  assert.equal! (args.fn.gt infinity), nil
  assert.equal! (args.fn.gt nan), nil
  assert.equal! (args.fn.gt 8, 9, 10), 10
  assert.equal! (args.fn.gt [8, 9, [10]]), 10
  assert.equal! (args.fn.gt 10, 10), nil
  assert.equal! (args.fn.gt 10, 10), nil
  assert.equal! (args.fn.gt 10, 9), nil
  assert.equal! (args.fn.>  8, 9, 10), 10
end

def test_gte args, assert
  assert.equal! (args.fn.gte 1), 1
  assert.equal! (args.fn.gte), nil
  assert.equal! (args.fn.gte infinity), nil
  assert.equal! (args.fn.gte nan), nil
  assert.equal! (args.fn.gte 8, 9, 10), 10
  assert.equal! (args.fn.gte 10, 10), 10
  assert.equal! (args.fn.gte 8, 9, [10]), 10
  assert.equal! (args.fn.gte 10, 9), nil
  assert.equal! (args.fn.>=  8, 9, 10), 10
end


def test_acopy args, assert
  orig  = [1, 2, 3]
  clone = args.fn.acopy orig
  assert.equal! clone, [1, 2, 3]
  assert.equal! clone, orig
  assert.not_equal! clone.object_id, orig.object_id
end

def test_aget args, assert
  assert.equal! (args.fn.aget [:a, :b, :c], 1), :b
  assert.equal! (args.fn.aget [:a, :b, :c], nil), nil
  assert.equal! (args.fn.aget nil, 1), nil
end

def test_alength args, assert
  assert.equal! (args.fn.alength [:a, :b, :c]), 3
  assert.equal! (args.fn.alength nil), nil
end

def test_amap args, assert
  inc = lambda { |i| i + 1 }
  ary = [1, 2, 3]
  assert.equal! (args.fn.amap ary, inc), [2, 3, 4]
  assert.equal! (args.fn.amap nil, inc), nil
  assert.equal! (args.fn.amap ary, nil), nil
  assert.equal! (args.fn.amap ary, inc).class, Array
end

def test_and args, assert
  assert.equal! (args.fn.and 1, 2, 3, 4), 4
  assert.equal! (args.fn.and 1, 2, nil, 4), nil
  assert.equal! (args.fn.and), true
end

def test_or args, assert
  assert.equal! (args.fn.or 1, 2, 3, 4), 1
  assert.equal! (args.fn.or 1, 2, nil, 4), 1
  assert.equal! (args.fn.or), nil
  assert.equal! (args.fn.or nil, nil, false, 5, 10), 5
end

def test_eq_eq args, assert
  assert.equal! (args.fn.eq?), true
  assert.equal! (args.fn.eq? 1, 0), false
  assert.equal! (args.fn.eq? 1, 1, 1), true
  assert.equal! (args.fn.== 1, 1, 1), true
  assert.equal! (args.fn.== nil, nil), true
end

def test_apply args, assert
  assert.equal! (args.fn.and [nil, nil, nil]), [nil, nil, nil]
  assert.equal! (args.fn.apply [nil, nil, nil], args.fn.method(:and)), nil
  and_lambda = lambda {|*xs| args.fn.and(*xs)}
  assert.equal! (args.fn.apply [nil, nil, nil], and_lambda), nil
end

def test_areduce args, assert
  assert.equal! (args.fn.areduce [1, 2, 3], 0, lambda { |i, a| i + a }), 6
end

def test_array_hash args, assert
  assert.equal! (args.fn.array_hash :a, 1, :b, 2), { a: 1, b: 2 }
  assert.equal! (args.fn.array_hash), { }
end

Advanced Debugging - Unit Tests - gen_docs.rb

# ./samples/10_advanced_debugging/03_unit_tests/gen_docs.rb
# ./dragonruby mygame --eval samples/99_zz_gtk_unit_tests/gen_docs.rb --no-tick
Kernel.export_docs!

Advanced Debugging - Unit Tests - geometry_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/geometry_tests.rb
begin :shared
  def primitive_representations x, y, w, h
    [
      [x, y, w, h],
      { x: x, y: y, w: w, h: h },
      RectForTest.new(x, y, w, h)
    ]
  end

  class RectForTest
    attr_sprite

    def initialize x, y, w, h
      @x = x
      @y = y
      @w = w
      @h = h
    end

    def to_s
      "RectForTest: #{[x, y, w, h]}"
    end
  end
end

begin :intersect_rect?
  def test_intersect_rect_point args, assert
    assert.true! [16, 13].intersect_rect?([13, 12, 4, 4]), "point intersects with rect."
  end

  def test_intersect_rect args, assert
    intersecting = primitive_representations(0, 0, 100, 100) +
                   primitive_representations(20, 20, 20, 20)

    intersecting.product(intersecting).each do |rect_one, rect_two|
      assert.true! rect_one.intersect_rect?(rect_two),
                   "intersect_rect? assertion failed for #{rect_one}, #{rect_two} (expected true)."
    end

    not_intersecting = [
      [ 0, 0, 5, 5],
      { x: 10, y: 10, w: 5, h: 5 },
      RectForTest.new(20, 20, 5, 5)
    ]

    not_intersecting.product(not_intersecting)
      .reject { |rect_one, rect_two| rect_one == rect_two }
      .each do |rect_one, rect_two|
      assert.false! rect_one.intersect_rect?(rect_two),
                    "intersect_rect? assertion failed for #{rect_one}, #{rect_two} (expected false)."
    end
  end
end

begin :inside_rect?
  def assert_inside_rect outer: nil, inner: nil, expected: nil, assert: nil
    assert.true! inner.inside_rect?(outer) == expected,
                 "inside_rect? assertion failed for outer: #{outer} inner: #{inner} (expected #{expected})."
  end

  def test_inside_rect args, assert
    outer_rects = primitive_representations(0, 0, 10, 10)
    inner_rects = primitive_representations(1, 1, 5, 5)
    primitive_representations(0, 0, 10, 10).product(primitive_representations(1, 1, 5, 5))
      .each do |outer, inner|
      assert_inside_rect outer: outer, inner: inner,
                         expected: true, assert: assert
    end
  end
end

begin :angle_to
  def test_angle_to args, assert
    origins = primitive_representations(0, 0, 0, 0)
    rights = primitive_representations(1, 0, 0, 0)
    aboves = primitive_representations(0, 1, 0, 0)

    origins.product(aboves).each do |origin, above|
      assert.equal! origin.angle_to(above), 90,
                    "A point directly above should be 90 degrees."

      assert.equal! above.angle_from(origin), 90,
                    "A point coming from above should be 90 degrees."
    end

    origins.product(rights).each do |origin, right|
      assert.equal! origin.angle_to(right) % 360, 0,
                    "A point directly to the right should be 0 degrees."

      assert.equal! right.angle_from(origin) % 360, 0,
                    "A point coming from the right should be 0 degrees."

    end
  end
end

begin :scale_rect
  def test_scale_rect args, assert
    assert.equal! [0, 0, 100, 100].scale_rect(0.5, 0.5),
                  [25.0, 25.0, 50.0, 50.0]

    assert.equal! [0, 0, 100, 100].scale_rect(0.5),
                  [0.0, 0.0, 50.0, 50.0]

    assert.equal! [0, 0, 100, 100].scale_rect_extended(percentage_x: 0.5, percentage_y: 0.5, anchor_x: 0.5, anchor_y: 0.5),
                  [25.0, 25.0, 50.0, 50.0]

    assert.equal! [0, 0, 100, 100].scale_rect_extended(percentage_x: 0.5, percentage_y: 0.5, anchor_x: 0, anchor_y: 0),
                  [0.0, 0.0, 50.0, 50.0]
  end
end

$gtk.reset 100
$gtk.log_level = :off

Advanced Debugging - Unit Tests - http_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/http_tests.rb
def try_assert_or_schedule args, assert
  if $result[:complete]
    log_info "Request completed! Verifying."
    if $result[:http_response_code] != 200
      log_info "The request yielded a result of #{$result[:http_response_code]} instead of 200."
      exit
    end
    log_info ":try_assert_or_schedule succeeded!"
  else
    args.gtk.schedule_callback Kernel.tick_count + 10 do
      try_assert_or_schedule args, assert
    end
  end
end

def test_http args, assert
  $result = $gtk.http_get 'http://dragonruby.org'
  try_assert_or_schedule args, assert
end

$gtk.reset 100
$gtk.log_level = :off

Advanced Debugging - Unit Tests - input_emulation_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/input_emulation_tests.rb
def test_keyboard args, assert
  args.inputs.keyboard.key_down.i = true
  assert.true! args.inputs.keyboard.truthy_keys.include?(:i)
end

Advanced Debugging - Unit Tests - nil_coercion_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/nil_coercion_tests.rb
# numbers
def test_open_entity_add_number args, assert
  assert.nil! args.state.i_value
  args.state.i_value += 5
  assert.equal! args.state.i_value, 5

  assert.nil! args.state.f_value
  args.state.f_value += 5.5
  assert.equal! args.state.f_value, 5.5
end

def test_open_entity_subtract_number args, assert
  assert.nil! args.state.i_value
  args.state.i_value -= 5
  assert.equal! args.state.i_value, -5

  assert.nil! args.state.f_value
  args.state.f_value -= 5.5
  assert.equal! args.state.f_value, -5.5
end

def test_open_entity_multiply_number args, assert
  assert.nil! args.state.i_value
  args.state.i_value *= 5
  assert.equal! args.state.i_value, 0

  assert.nil! args.state.f_value
  args.state.f_value *= 5.5
  assert.equal! args.state.f_value, 0
end

def test_open_entity_divide_number args, assert
  assert.nil! args.state.i_value
  args.state.i_value /= 5
  assert.equal! args.state.i_value, 0

  assert.nil! args.state.f_value
  args.state.f_value /= 5.5
  assert.equal! args.state.f_value, 0
end

# array
def test_open_entity_add_array args, assert
  assert.nil! args.state.values
  args.state.values += [:a, :b, :c]
  assert.equal! args.state.values, [:a, :b, :c]
end

def test_open_entity_subtract_array args, assert
  assert.nil! args.state.values
  args.state.values -= [:a, :b, :c]
  assert.equal! args.state.values, []
end

def test_open_entity_shovel_array args, assert
  assert.nil! args.state.values
  args.state.values << :a
  assert.equal! args.state.values, [:a]
end

def test_open_entity_enumerate args, assert
  assert.nil! args.state.values
  args.state.values = args.state.values.map_with_index { |i| i }
  assert.equal! args.state.values, []

  assert.nil! args.state.values_2
  args.state.values_2 = args.state.values_2.map { |i| i }
  assert.equal! args.state.values_2, []

  assert.nil! args.state.values_3
  args.state.values_3 = args.state.values_3.flat_map { |i| i }
  assert.equal! args.state.values_3, []
end

# hashes
def test_open_entity_indexer args, assert
  GTK::Entity.__reset_id__!
  assert.nil! args.state.values
  args.state.values[:test] = :value
  assert.equal! args.state.values.to_s, { entity_id: 1, entity_name: :values, entity_keys_by_ref: {}, test: :value }.to_s
end

# bug
def test_open_entity_nil_bug args, assert
  GTK::Entity.__reset_id__!
  args.state.foo.a
  args.state.foo.b
  @hello[:foobar]
  assert.nil! args.state.foo.a, "a was not nil."
  # the line below fails
  # assert.nil! args.state.foo.b, "b was not nil."
end

Advanced Debugging - Unit Tests - object_to_primitive_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/object_to_primitive_tests.rb
class PlayerSpriteForTest
end

def test_array_to_sprite args, assert
  array = [[0, 0, 100, 100, "test.png"]].sprites
  puts "No exception was thrown. Sweet!"
end

def test_class_to_sprite args, assert
  array = [PlayerSprite.new].sprites
  assert.true! array.first.is_a?(PlayerSprite)
  puts "No exception was thrown. Sweet!"
end

$gtk.reset 100
$gtk.log_level = :off

Advanced Debugging - Unit Tests - parsing_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/parsing_tests.rb
def test_parse_json args, assert
  result = args.gtk.parse_json '{ "name": "John Doe", "aliases": ["JD"] }'
  assert.equal! result, { "name"=>"John Doe", "aliases"=>["JD"] }, "Parsing JSON failed."
end

def test_parse_xml args, assert
  result = args.gtk.parse_xml <<-S
<Person id="100">
  <Name>John Doe</Name>
</Person>
S

 expected = {:type=>:element,
             :name=>nil,
             :children=>[{:type=>:element,
                          :name=>"Person",
                          :children=>[{:type=>:element,
                                       :name=>"Name",
                                       :children=>[{:type=>:content,
                                                    :data=>"John Doe"}]}],
                          :attributes=>{"id"=>"100"}}]}

 assert.equal! result, expected, "Parsing xml failed."
end

$gtk.reset 100
$gtk.log_level = :off

Advanced Debugging - Unit Tests - pretty_format_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/pretty_format_tests.rb
def H opts
  opts
end

def A *opts
  opts
end

def assert_format args, assert, hash, expected
  actual = args.fn.pretty_format hash
  assert.are_equal! actual, expected
end

def test_pretty_print args, assert
  # =============================
  # hash with single value
  # =============================
  input = (H first_name: "John")
  expected = <<-S
{:first_name "John"}
S
  (assert_format args, assert, input, expected)

  # =============================
  # hash with two values
  # =============================
  input = (H first_name: "John", last_name: "Smith")
  expected = <<-S
{:first_name "John"
 :last_name "Smith"}
S

  (assert_format args, assert, input, expected)

  # =============================
  # hash with inner hash
  # =============================
  input = (H first_name: "John",
             last_name: "Smith",
             middle_initial: "I",
             so: (H first_name: "Pocahontas",
                    last_name: "Tsenacommacah"),
             friends: (A (H first_name: "Side", last_name: "Kick"),
                         (H first_name: "Tim", last_name: "Wizard")))
  expected = <<-S
{:first_name "John"
 :last_name "Smith"
 :middle_initial "I"
 :so {:first_name "Pocahontas"
      :last_name "Tsenacommacah"}
 :friends [{:first_name "Side"
            :last_name "Kick"}
           {:first_name "Tim"
            :last_name "Wizard"}]}
S

  (assert_format args, assert, input, expected)

  # =============================
  # array with one value
  # =============================
  input = (A 1)
  expected = <<-S
[1]
S
  (assert_format args, assert, input, expected)

  # =============================
  # array with multiple values
  # =============================
  input = (A 1, 2, 3)
  expected = <<-S
[1
 2
 3]
S
  (assert_format args, assert, input, expected)

  # =============================
  # array with multiple values hashes
  # =============================
  input = (A (H first_name: "Side", last_name: "Kick"),
             (H first_name: "Tim", last_name: "Wizard"))
  expected = <<-S
[{:first_name "Side"
  :last_name "Kick"}
 {:first_name "Tim"
  :last_name "Wizard"}]
S

  (assert_format args, assert, input, expected)
end

def test_nested_nested args, assert
  # =============================
  # nested array in nested hash
  # =============================
  input = (H type: :root,
             text: "Root",
             children: (A (H level: 1,
                             text: "Level 1",
                             children: (A (H level: 2,
                                             text: "Level 2",
                                             children: [])))))

  expected = <<-S
{:type :root
 :text "Root"
 :children [{:level 1
             :text "Level 1"
             :children [{:level 2
                         :text "Level 2"
                         :children []}]}]}

S

  (assert_format args, assert, input, expected)
end

def test_scene args, assert
  script = <<-S
* Scene 1
** Narrator
They say happy endings don't exist.
** Narrator
They say true love is a lie.
S
  input = parse_org args, script
  puts (args.fn.pretty_format input)
end

Advanced Debugging - Unit Tests - require_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/require_tests.rb
def write_src path, src
  $gtk.write_file path, src
end

write_src 'app/unit_testing_game.rb', <<-S
module UnitTesting
  class Game
  end
end
S

write_src 'lib/unit_testing_lib.rb', <<-S
module UnitTesting
  class Lib
  end
end
S

write_src 'app/nested/unit_testing_nested.rb', <<-S
module UnitTesting
  class Nested
  end
end
S

require 'app/unit_testing_game.rb'
require 'app/nested/unit_testing_nested.rb'
require 'lib/unit_testing_lib.rb'

def test_require args, assert
  UnitTesting::Game.new
  UnitTesting::Lib.new
  UnitTesting::Nested.new
  $gtk.exec 'rm ./mygame/app/unit_testing_game.rb'
  $gtk.exec 'rm ./mygame/app/nested/unit_testing_nested.rb'
  $gtk.exec 'rm ./mygame/lib/unit_testing_lib.rb'
  assert.ok!
end

Advanced Debugging - Unit Tests - serialize_deserialize_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/serialize_deserialize_tests.rb
def assert_hash_strings! assert, string_1, string_2
  Kernel.eval("$assert_hash_string_1 = #{string_1}")
  Kernel.eval("$assert_hash_string_2 = #{string_2}")
  assert.equal! $assert_hash_string_1, $assert_hash_string_2
end


def test_serialize args, assert
  args.state.player_one = "test"
  result = args.gtk.serialize_state args.state
  assert_hash_strings! assert, result, "{:entity_id=>1, :entity_keys_by_ref=>{}, :tick_count=>-1, :player_one=>\"test\"}"

  args.gtk.write_file 'state.txt', ''
  result = args.gtk.serialize_state 'state.txt', args.state
  assert_hash_strings! assert, result, "{:entity_id=>1, :entity_keys_by_ref=>{}, :tick_count=>-1, :player_one=>\"test\"}"
end

def test_deserialize args, assert
  result = args.gtk.deserialize_state '{:entity_id=>3, :tick_count=>-1, :player_one=>"test"}'
  assert.equal! result.player_one, "test"

  args.gtk.write_file 'state.txt',  '{:entity_id=>3, :tick_count=>-1, :player_one=>"test"}'
  result = args.gtk.deserialize_state 'state.txt'
  assert.equal! result.player_one, "test"
end

def test_very_large_serialization args, assert
  args.gtk.write_file("logs/log.txt", "")
  size = 3000
  size.map_with_index do |i|
    args.state.send("k#{i}=".to_sym, i)
  end

  result = args.gtk.serialize_state args.state
  assert.true! $serialize_state_serialization_too_large
end

def test_strict_entity_serialization args, assert
  args.state.player_one = args.state.new_entity(:player, name: "Ryu")
  args.state.player_two = args.state.new_entity_strict(:player_strict, name: "Ken")

  serialized_state = args.gtk.serialize_state args.state
  assert_hash_strings! assert, serialized_state, '{:entity_id=>1, :entity_keys_by_ref=>{}, :tick_count=>-1, :player_one=>{:entity_id=>3, :entity_name=>:player, :entity_keys_by_ref=>{}, :entity_type=>:player, :created_at=>-1, :global_created_at=>-1, :name=>"Ryu"}, :player_two=>{:entity_id=>5, :entity_name=>:player_strict, :entity_type=>:player_strict, :created_at=>-1, :global_created_at_elapsed=>-1, :entity_strict=>true, :entity_keys_by_ref=>{}, :name=>"Ken"}}'

  deserialize_state = args.gtk.deserialize_state serialized_state

  assert.equal! args.state.player_one.name, deserialize_state.player_one.name
  assert.true! args.state.player_one.is_a? GTK::OpenEntity

  assert.equal! args.state.player_two.name, deserialize_state.player_two.name
  assert.true! args.state.player_two.is_a? GTK::StrictEntity
end

def test_strict_entity_serialization_with_nil args, assert
  args.state.player_one = args.state.new_entity(:player, name: "Ryu")
  args.state.player_two = args.state.new_entity_strict(:player_strict, name: "Ken", blood_type: nil)

  serialized_state = args.gtk.serialize_state args.state
  assert_hash_strings! assert, serialized_state, '{:entity_id=>1, :entity_keys_by_ref=>{}, :tick_count=>-1, :player_one=>{:entity_id=>3, :entity_name=>:player, :entity_keys_by_ref=>{}, :entity_type=>:player, :created_at=>-1, :global_created_at=>-1, :name=>"Ryu"}, :player_two=>{:entity_name=>:player_strict, :global_created_at_elapsed=>-1, :created_at=>-1, :blood_type=>nil, :name=>"Ken", :entity_type=>:player_strict, :entity_strict=>true, :entity_keys_by_ref=>{}, :entity_id=>4}}'

  deserialized_state = args.gtk.deserialize_state serialized_state

  assert.equal! args.state.player_one.name, deserialized_state.player_one.name
  assert.true! args.state.player_one.is_a? GTK::OpenEntity

  assert.equal! args.state.player_two.name, deserialized_state.player_two.name
  assert.equal! args.state.player_two.blood_type, deserialized_state.player_two.blood_type
  assert.equal! deserialized_state.player_two.blood_type, nil
  assert.true! args.state.player_two.is_a? GTK::StrictEntity

  deserialized_state.player_two.blood_type = :O
  assert.equal! deserialized_state.player_two.blood_type, :O
end

def test_multiple_strict_entities args, assert
  args.state.player = args.state.new_entity_strict(:player_one, name: "Ryu")
  args.state.enemy = args.state.new_entity_strict(:enemy, name: "Bison", other_property: 'extra mean')

  serialized_state = args.gtk.serialize_state args.state

  deserialized_state = args.gtk.deserialize_state serialized_state

  assert.equal! deserialized_state.player.name, "Ryu"
  assert.equal! deserialized_state.enemy.other_property, "extra mean"
end

def test_by_reference_state args, assert
  args.state.a = args.state.new_entity(:person, name: "Jane Doe")
  args.state.b = args.state.a
  assert.equal! args.state.a.object_id, args.state.b.object_id
  serialized_state = args.gtk.serialize_state args.state

  deserialized_state = args.gtk.deserialize_state serialized_state
  assert.equal! deserialized_state.a.object_id, deserialized_state.b.object_id
end

def test_by_reference_state_strict_entities args, assert
  args.state.strict_entity = args.state.new_entity_strict(:couple) do |e|
    e.one = args.state.new_entity_strict(:person, name: "Jane")
    e.two = e.one
  end
  assert.equal! args.state.strict_entity.one, args.state.strict_entity.two
  serialized_state = args.gtk.serialize_state args.state

  deserialized_state = args.gtk.deserialize_state serialized_state
  assert.equal! deserialized_state.strict_entity.one, deserialized_state.strict_entity.two
end

def test_serialization_excludes_thrash_count args, assert
  args.state.player.name = "Ryu"
  # force a nil pun
  if args.state.player.age > 30
  end
  assert.equal! args.state.player.as_hash[:__thrash_count__][:>], 1
  result = args.gtk.serialize_state args.state
  assert.false! (result.include? "__thrash_count__"),
                "The __thrash_count__ key exists in state when it shouldn't have."
end

def test_serialization_does_not_mix_up_zero_and_true args, assert
  args.state.enemy.evil = true
  args.state.enemy.hp = 0
  serialized = args.gtk.serialize_state args.state.enemy

  deserialized = args.gtk.deserialize_state serialized

  assert.equal! deserialized.hp, 0,
                "Value should have been deserialized as 0, but was #{deserialized.hp}"
  assert.equal! deserialized.evil, true,
                "Value should have been deserialized as true, but was #{deserialized.evil}"
end

Advanced Debugging - Unit Tests - state_serialization_experimental_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/state_serialization_experimental_tests.rb
MAX_CODE_GEN_LENGTH = 50

# NOTE: This is experimental/advanced stuff.
def needs_partitioning? target
  target[:value].to_s.length > MAX_CODE_GEN_LENGTH
end

def partition target
  return [] unless needs_partitioning? target
  if target[:value].is_a? GTK::OpenEntity
    target[:value] = target[:value].hash
  end

  results = []
  idx = 0
  left, right = target[:value].partition do
    idx += 1
    idx.even?
  end
  left, right = Hash[left], Hash[right]
  left = { value: left }
  right = { value: right}
  [left, right]
end

def add_partition target, path, aggregate, final_result
  partitions = partition target
  partitions.each do |part|
    if needs_partitioning? part
      if part[:value].keys.length == 1
        first_key = part[:value].keys[0]
        new_part = { value: part[:value][first_key] }
        path.push first_key
        add_partition new_part, path, aggregate, final_result
        path.pop
      else
        add_partition part, path, aggregate, final_result
      end
    else
      final_result << { value: { __path__: [*path] } }
      final_result << { value: part[:value] }
    end
  end
end

def state_to_string state
  parts_queue = []
  final_queue = []
  add_partition({ value: state.hash },
                [],
                parts_queue,
                final_queue)
  final_queue.reject {|i| i[:value].keys.length == 0}.map do |i|
    i[:value].to_s
  end.join("\n#==================================================#\n")
end

def state_from_string string
  Kernel.eval("$load_data = {}")
  lines = string.split("\n#==================================================#\n")
  lines.each do |l|
    puts "todo: #{l}"
  end

  GTK::OpenEntity.parse_from_hash $load_data
end

def test_save_and_load args, assert
  args.state.item_1.name = "Jane"
  string = state_to_string args.state
  state = state_from_string string
  assert.equal! args.state.item_1.name, state.item_1.name
end

def test_save_and_load_big args, assert
  size = 1000
  size.map_with_index do |i|
    args.state.send("k#{i}=".to_sym, i)
  end

  string = state_to_string args.state
  state = state_from_string string
  size.map_with_index do |i|
    assert.equal! args.state.send("k#{i}".to_sym), state.send("k#{i}".to_sym)
    assert.equal! args.state.send("k#{i}".to_sym), i
    assert.equal! state.send("k#{i}".to_sym), i
  end
end

def test_save_and_load_big_nested args, assert
  args.state.player_one.friend.nested_hash.k0 = 0
  args.state.player_one.friend.nested_hash.k1 = 1
  args.state.player_one.friend.nested_hash.k2 = 2
  args.state.player_one.friend.nested_hash.k3 = 3
  args.state.player_one.friend.nested_hash.k4 = 4
  args.state.player_one.friend.nested_hash.k5 = 5
  args.state.player_one.friend.nested_hash.k6 = 6
  args.state.player_one.friend.nested_hash.k7 = 7
  args.state.player_one.friend.nested_hash.k8 = 8
  args.state.player_one.friend.nested_hash.k9 = 9
  string = state_to_string args.state
  state = state_from_string string
end

$gtk.reset 100
$gtk.log_level = :off

Advanced Debugging - Unit Tests - suggest_autocompletion_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/suggest_autocompletion_tests.rb
def default_suggest_autocompletion args
  {
    index: 4,
    text: "args.",
    __meta__: {
      other_options: [
        {
          index: Fixnum,
          file: "app/main.rb"
        }
      ]
    }
  }
end

def assert_completion source, *expected
  results = suggest_autocompletion text:  (source.strip.gsub  ":cursor", ""),
                                   index: (source.strip.index ":cursor")

  puts results
end

def test_args_completion args, assert
  $gtk.write_file_root "autocomplete.txt", ($gtk.suggest_autocompletion text: <<-S, index: 128).join("\n")
require 'app/game.rb'

def tick args
  args.gtk.suppress_mailbox = false
  $game ||= Game.new
  $game.args = args
  $game.args.
  $game.tick
end
S

  puts "contents:"
  puts ($gtk.read_file "autocomplete.txt")
end

Http - Retrieve Images - main.rb

# ./samples/11_http/01_retrieve_images/app/main.rb
$gtk.register_cvar 'app.warn_seconds', "seconds to wait before starting", :uint, 11

def tick args
  args.outputs.background_color = [0, 0, 0]

  # Show a warning at the start.
  args.state.warning_debounce ||= args.cvars['app.warn_seconds'].value * 60
  if args.state.warning_debounce > 0
    args.state.warning_debounce -= 1
    args.outputs.labels << [640, 600, "This app shows random images from the Internet.", 10, 1, 255, 255, 255]
    args.outputs.labels << [640, 500, "Quit in the next few seconds if this is a problem.", 10, 1, 255, 255, 255]
    args.outputs.labels << [640, 350, "#{(args.state.warning_debounce / 60.0).to_i}", 10, 1, 255, 255, 255]
    return
  end

  args.state.download_debounce ||= 0   # start immediately, reset to non zero later.
  args.state.photos ||= []

  # Put a little pause between each download.
  if args.state.download.nil?
    if args.state.download_debounce > 0
      args.state.download_debounce -= 1
    else
      args.state.download = $gtk.http_get 'https://picsum.photos/200/300.jpg'
    end
  end

  if !args.state.download.nil?
    if args.state.download[:complete]
      if args.state.download[:http_response_code] == 200
        fname = "sprites/#{args.state.photos.length}.jpg"
        $gtk.write_file fname, args.state.download[:response_data]
        args.state.photos << [ 100 + rand(1080), 500 - rand(480), fname, rand(80) - 40 ]
      end
      args.state.download = nil
      args.state.download_debounce = (rand(3) + 2) * 60
    end
  end

  # draw any downloaded photos...
  args.state.photos.each { |i|
    args.outputs.primitives << [i[0], i[1], 200, 300, i[2], i[3]].sprite
  }

  # Draw a download progress bar...
  args.outputs.primitives << [0, 0, 1280, 30, 0, 0, 0, 255].solid
  if !args.state.download.nil?
    br = args.state.download[:response_read]
    total = args.state.download[:response_total]
    if total != 0
      pct = br.to_f / total.to_f
      args.outputs.primitives << [0, 0, 1280 * pct, 30, 0, 0, 255, 255].solid
    end
  end
end

Http - In Game Web Server Http Get - main.rb

# ./samples/11_http/02_in_game_web_server_http_get/app/main.rb
def tick args
  args.state.port ||= 3000
  args.state.reqnum ||= 0
  # by default the embedded webserver runs on port 9001 (the port number is over 9000) and is disabled in a production build
  # to enable the http server in a production build, you need to manually start
  # the server up:
  args.gtk.start_server! port: args.state.port, enable_in_prod: true
  args.outputs.background_color = [0, 0, 0]
  args.outputs.labels << [640, 600, "Point your web browser at http://localhost:#{args.state.port}/", 10, 1, 255, 255, 255]

  args.inputs.http_requests.each { |req|
    puts("METHOD: #{req.method}");
    puts("URI: #{req.uri}");
    puts("HEADERS:");
    req.headers.each { |k,v| puts("  #{k}: #{v}") }

    if (req.uri == '/')
      # headers and body can be nil if you don't care about them.
      # If you don't set the Content-Type, it will default to
      #  "text/html; charset=utf-8".
      # Don't set Content-Length; we'll ignore it and calculate it for you
      args.state.reqnum += 1
      req.respond 200, "<html><head><title>hello</title></head><body><h1>This #{req.method} was request number #{args.state.reqnum}!</h1></body></html>\n", { 'X-DRGTK-header' => 'Powered by DragonRuby!' }
    else
      req.reject
    end
  }
end

Http - In Game Web Server Http Post - main.rb

# ./samples/11_http/03_in_game_web_server_http_post/app/main.rb
def tick args
  # defaults
  args.state.post_button      = args.layout.rect(row: 0, col: 0, w: 5, h: 1).merge(text: "execute http_post")
  args.state.post_body_button = args.layout.rect(row: 1, col: 0, w: 5, h: 1).merge(text: "execute http_post_body")
  args.state.request_to_s ||= ""
  args.state.request_body ||= ""

  # render
  args.state.post_button.yield_self do |b|
    args.outputs.borders << b
    args.outputs.labels  << b.merge(text: b.text,
                                    y:    b.y + 30,
                                    x:    b.x + 10)
  end

  args.state.post_body_button.yield_self do |b|
    args.outputs.borders << b
    args.outputs.labels  << b.merge(text: b.text,
                                    y:    b.y + 30,
                                    x:    b.x + 10)
  end

  draw_label args, 0,  6, "Request:", args.state.request_to_s
  draw_label args, 0, 14, "Request Body Unaltered:", args.state.request_body

  # input
  if args.inputs.mouse.click
    # ============= HTTP_POST =============
    if (args.inputs.mouse.inside_rect? args.state.post_button)
      # ========= DATA TO SEND ===========
      form_fields = { "userId" => "#{Time.now.to_i}" }
      # ==================================

      args.gtk.http_post "http://localhost:9001/testing",
                         form_fields,
                         ["Content-Type: application/x-www-form-urlencoded"]

      args.gtk.notify! "http_post"
    end

    # ============= HTTP_POST_BODY =============
    if (args.inputs.mouse.inside_rect? args.state.post_body_button)
      # =========== DATA TO SEND ==============
      json = "{ \"userId\": \"#{Time.now.to_i}\"}"
      # ==================================

      args.gtk.http_post_body "http://localhost:9001/testing",
                              json,
                              ["Content-Type: application/json", "Content-Length: #{json.length}"]

      args.gtk.notify! "http_post_body"
    end
  end

  # calc
  args.inputs.http_requests.each do |r|
    puts "#{r}"
    if r.uri == "/testing"
      puts r
      args.state.request_to_s = "#{r}"
      args.state.request_body = r.raw_body
      r.respond 200, "ok"
    end
  end
end

def draw_label args, row, col, header, text
  label_pos = args.layout.rect(row: row, col: col, w: 0, h: 0)
  args.outputs.labels << "#{header}\n\n#{text}".wrapped_lines(80).map_with_index do |l, i|
    { x: label_pos.x, y: label_pos.y - (i * 15), text: l, size_enum: -2 }
  end
end

C Extensions - Basics - main.rb

# ./samples/12_c_extensions/01_basics/app/main.rb
$gtk.ffi_misc.gtk_dlopen("ext")
include FFI::CExt

def tick args
  args.outputs.labels  << [640, 500, "mouse.x = #{args.mouse.x.to_i}", 5, 1]
  args.outputs.labels  << [640, 460, "square(mouse.x) = #{square(args.mouse.x.to_i)}", 5, 1]
  args.outputs.labels  << [640, 420, "mouse.y = #{args.mouse.y.to_i}", 5, 1]
  args.outputs.labels  << [640, 380, "square(mouse.y) = #{square(args.mouse.y.to_i)}", 5, 1]
end

C Extensions - Intermediate - main.rb

# ./samples/12_c_extensions/02_intermediate/app/main.rb
$gtk.ffi_misc.gtk_dlopen("ext")
include FFI::RE

def split_words(input)
  words = []
  last = IntPointer.new
  re = re_compile("\\w+")
  first = re_matchp(re, input, last)
  while first != -1
    words << input.slice(first, last.value)
    input = input.slice(last.value + first, input.length)
    first = re_matchp(re, input, last)
  end
  words
end

def tick args
  args.outputs.labels  << [640, 500, split_words("hello, dragonriders!").join(' '), 5, 1]
end

C Extensions - Native Pixel Arrays - main.rb

# ./samples/12_c_extensions/03_native_pixel_arrays/app/main.rb
$gtk.ffi_misc.gtk_dlopen("ext")
include FFI::CExt

def tick args
  args.state.rotation ||= 0

  update_scanner_texture   # this calls into a C extension!

  # New/changed pixel arrays get uploaded to the GPU before we render
  #  anything. At that point, they can be scaled, rotated, and otherwise
  #  used like any other sprite.
  w = 100
  h = 100
  x = (1280 - w) / 2
  y = (720 - h) / 2
  args.outputs.background_color = [64, 0, 128]
  args.outputs.primitives << [x, y, w, h, :scanner, args.state.rotation].sprite
  args.state.rotation += 1

  args.outputs.primitives << args.gtk.current_framerate_primitives
end

C Extensions - Handcrafted Extension - main.rb

# ./samples/12_c_extensions/04_handcrafted_extension/app/main.rb
$gtk.ffi_misc.gtk_dlopen("ext")
include FFI::CExt

puts Adder.new.add_all(1, 2, 3, [4, 5, 6.0])

def tick args
end

C Extensions - Handcrafted Extension - license.txt

# ./samples/12_c_extensions/04_handcrafted_extension/license.txt
Copyright 2022 DragonRuby LLC

MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

C Extensions - Ios C Extensions - main.rb

# ./samples/12_c_extensions/05_ios_c_extensions/app/main.rb
# NOTE: This is assumed to be executed with mygame as the root directory
#       you'll need to copy this code over there to try it out.

# Steps:
# 1. Create ext.h and ext.m
# 2. Create Info.plist file
# 3. Add before_create_payload to IOSWizard (which does the following):
#    a. run ./dragonruby-bind against C Extension and update implementation file
#    b. create output location for iOS Framework
#    c. compile C extension into Framework
#    d. copy framework to Payload directory and Sign
# 4. Run $wizards.ios.start env: (:prod|:dev|:hotload) to create ipa
# 5. Invoke args.gtk.dlopen giving the name of the C Extensions (~1s to load).
# 6. Invoke methods as needed.

# ===================================================
# before_create_payload iOS Wizard
# ===================================================
class IOSWizard < Wizard
  def before_create_payload
    puts "* INFO - before_create_payload"

    # invoke ./dragonruby-bind
    sh "./dragonruby-bind --output=mygame/ext-bind.m mygame/ext.h"

    # update generated implementation file
    contents = $gtk.read_file "ext-bind.m"
    contents = contents.gsub("#include \"mygame/ext.h\"", "#include \"mygame/ext.h\"\n#include \"mygame/ext.m\"")
    puts contents

    $gtk.write_file "ext-bind.m", contents

    # create output location
    sh "rm -rf ./mygame/native/ios-device/ext.framework"
    sh "mkdir -p ./mygame/native/ios-device/ext.framework"

    # compile C extension into framework
    sh <<-S
clang -I. -I./mruby/include -I./include -o "./mygame/native/ios-device/ext.framework/ext" \\
      -arch arm64 -dynamiclib -isysroot "/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk" \\
      -install_name @rpath/ext.framework/ext \\
      -fembed-bitcode -Xlinker -rpath -Xlinker @loader_path/Frameworks -dead_strip -Xlinker -rpath -fobjc-arc -fobjc-link-runtime \\
      -F/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/System/Library/Frameworks \\
      -miphoneos-version-min=10.3 -Wl,-no_pie -licucore -stdlib=libc++ \\
      -framework CFNetwork -framework UIKit -framework Foundation \\
      ./mygame/ext-bind.m
S

    # stage extension
    sh "cp ./mygame/native/ios-device/Info.plist ./mygame/native/ios-device/ext.framework/Info.plist"
    sh "mkdir -p \"#{app_path}/Frameworks/ext.framework/\""
    sh "cp -r \"#{root_folder}/native/ios-device/ext.framework/\" \"#{app_path}/Frameworks/ext.framework/\""

    # sign
    sh <<-S
CODESIGN_ALLOCATE=#{codesign_allocate_path} #{codesign_path} \\
                                            -f -s \"#{certificate_name}\" \\
                                            \"#{app_path}/Frameworks/ext.framework/ext\"
S
  end
end

def tick args
  if args.state.tick_count == 60 && args.gtk.platform?(:ios)
    args.gtk.dlopen 'ext'
    include FFI::CExt
    puts "the results of hello world are:"
    puts hello_world()
    $gtk.console.show
  end
end

C Extensions - Ios C Extensions - Metadata - cvars.txt

# ./samples/12_c_extensions/05_ios_c_extensions/metadata/cvars.txt

C Extensions - Ios C Extensions - Metadata - ios_metadata.txt

# ./samples/12_c_extensions/05_ios_c_extensions/metadata/ios_metadata.txt
teamid=TEAMID
appid=APPID
appname=ICON NAME
version=1.0
devcert=NAME OF DEV CERT
prodcert=NAME OF PROD CERT

Path Finding Algorithms - Breadth First Search - main.rb

# ./samples/13_path_finding_algorithms/01_breadth_first_search/app/main.rb
# Contributors outside of DragonRuby who also hold Copyright:
# - Sujay Vadlakonda: https://github.com/sujayvadlakonda

# A visual demonstration of a breadth first search
# Inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html

# An animation that can respond to user input in real time

# A breadth first search expands in all directions one step at a time
# The frontier is a queue of cells to be expanded from
# The visited hash allows quick lookups of cells that have been expanded from
# The walls hash allows quick lookup of whether a cell is a wall

# The breadth first search starts by adding the red star to the frontier array
# and marking it as visited
# Each step a cell is removed from the front of the frontier array (queue)
# Unless the neighbor is a wall or visited, it is added to the frontier array
# The neighbor is then marked as visited

# The frontier is blue
# Visited cells are light brown
# Walls are camo green
# Even when walls are visited, they will maintain their wall color

# The star can be moved by clicking and dragging
# Walls can be added and removed by clicking and dragging

class BreadthFirstSearch
  attr_gtk

  def initialize(args)
    # Variables to edit the size and appearance of the grid
    # Freely customizable to user's liking
    args.state.grid.width     = 30
    args.state.grid.height    = 15
    args.state.grid.cell_size = 40

    # Stores which step of the animation is being rendered
    # When the user moves the star or messes with the walls,
    # the breadth first search is recalculated up to this step
    args.state.anim_steps = 0

    # At some step the animation will end,
    # and further steps won't change anything (the whole grid will be explored)
    # This step is roughly the grid's width * height
    # When anim_steps equals max_steps no more calculations will occur
    # and the slider will be at the end
    args.state.max_steps  = args.state.grid.width * args.state.grid.height

    # Whether the animation should play or not
    # If true, every tick moves anim_steps forward one
    # Pressing the stepwise animation buttons will pause the animation
    args.state.play       = true

    # The location of the star and walls of the grid
    # They can be modified to have a different initial grid
    # Walls are stored in a hash for quick look up when doing the search
    args.state.star       = [0, 0]
    args.state.walls      = {
      [3, 3] => true,
      [3, 4] => true,
      [3, 5] => true,
      [3, 6] => true,
      [3, 7] => true,
      [3, 8] => true,
      [3, 9] => true,
      [3, 10] => true,
      [3, 11] => true,
      [4, 3] => true,
      [4, 4] => true,
      [4, 5] => true,
      [4, 6] => true,
      [4, 7] => true,
      [4, 8] => true,
      [4, 9] => true,
      [4, 10] => true,
      [4, 11] => true,

      [13, 0] => true,
      [13, 1] => true,
      [13, 2] => true,
      [13, 3] => true,
      [13, 4] => true,
      [13, 5] => true,
      [13, 6] => true,
      [13, 7] => true,
      [13, 8] => true,
      [13, 9] => true,
      [13, 10] => true,
      [14, 0] => true,
      [14, 1] => true,
      [14, 2] => true,
      [14, 3] => true,
      [14, 4] => true,
      [14, 5] => true,
      [14, 6] => true,
      [14, 7] => true,
      [14, 8] => true,
      [14, 9] => true,
      [14, 10] => true,

      [21, 8] => true,
      [21, 9] => true,
      [21, 10] => true,
      [21, 11] => true,
      [21, 12] => true,
      [21, 13] => true,
      [21, 14] => true,
      [22, 8] => true,
      [22, 9] => true,
      [22, 10] => true,
      [22, 11] => true,
      [22, 12] => true,
      [22, 13] => true,
      [22, 14] => true,
      [23, 8] => true,
      [23, 9] => true,
      [24, 8] => true,
      [24, 9] => true,
      [25, 8] => true,
      [25, 9] => true,
    }

    # Variables that are used by the breadth first search
    # Storing cells that the search has visited, prevents unnecessary steps
    # Expanding the frontier of the search in order makes the search expand
    # from the center outward
    args.state.visited    = {}
    args.state.frontier   = []


    # What the user is currently editing on the grid
    # Possible values are: :none, :slider, :star, :remove_wall, :add_wall

    # We store this value, because we want to remember the value even when
    # the user's cursor is no longer over what they're interacting with, but
    # they are still clicking down on the mouse.
    args.state.click_and_drag = :none

    # Store the rects of the buttons that control the animation
    # They are here for user customization
    # Editing these might require recentering the text inside them
    # Those values can be found in the render_button methods

    args.state.buttons.left   = { x: 450, y: 600, w: 50,  h: 50 }
    args.state.buttons.center = { x: 500, y: 600, w: 200, h: 50 }
    args.state.buttons.right  = { x: 700, y: 600, w: 50,  h: 50 }

    # The variables below are related to the slider
    # They allow the user to customize them
    # They also give a central location for the render and input methods to get
    # information from
    # x & y are the coordinates of the leftmost part of the slider line
    args.state.slider.x = 400
    args.state.slider.y = 675
    # This is the width of the line
    args.state.slider.w = 360
    # This is the offset for the circle
    # Allows the center of the circle to be on the line,
    # as opposed to the upper right corner
    args.state.slider.offset = 20
    # This is the spacing between each of the notches on the slider
    # Notches are places where the circle can rest on the slider line
    # There needs to be a notch for each step before the maximum number of steps
    args.state.slider.spacing = args.state.slider.w.to_f / args.state.max_steps.to_f
  end

  # This method is called every frame/tick
  # Every tick, the current state of the search is rendered on the screen,
  # User input is processed, and
  # The next step in the search is calculated
  def tick
    render
    input
    # If animation is playing, and max steps have not been reached
    # Move the search a step forward
    if state.play && state.anim_steps < state.max_steps
      # Variable that tells the program what step to recalculate up to
      state.anim_steps += 1
      calc
    end
  end

  # Draws everything onto the screen
  def render
    render_buttons
    render_slider

    render_background
    render_visited
    render_frontier
    render_walls
    render_star
  end

  # The methods below subdivide the task of drawing everything to the screen

  # Draws the buttons that control the animation step and state
  def render_buttons
    render_left_button
    render_center_button
    render_right_button
  end

  # Draws the button which steps the search backward
  # Shows the user where to click to move the search backward
  def render_left_button
    # Draws the gray button, and a black border
    # The border separates the buttons visually
    outputs.solids  << buttons.left.merge(gray)
    outputs.borders << buttons.left

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    # If the button size is changed, the label might need to be edited as well
    # to keep the label in the center of the button
    label_x = buttons.left[:x] + 20
    label_y = buttons.left[:y] + 35
    outputs.labels << { x: label_x, y: label_y, text: '<' }
  end

  def render_center_button
    # Draws the gray button, and a black border
    # The border separates the buttons visually
    outputs.solids  << buttons.center.merge(gray)
    outputs.borders << buttons.center

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    # If the button size is changed, the label might need to be edited as well
    # to keep the label in the center of the button
    label_x = buttons.center[:x] + 37
    label_y = buttons.center[:y] + 35
    label_text = state.play ? "Pause Animation" : "Play Animation"
    outputs.labels << { x: label_x, y: label_y, text: label_text }
  end

  def render_right_button
    # Draws the gray button, and a black border
    # The border separates the buttons visually
    outputs.solids  << buttons.right.merge(gray)
    outputs.borders << buttons.right

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    label_x = buttons.right[:x] + 20
    label_y = buttons.right[:y] + 35
    outputs.labels << { x: label_x, y: label_y, text: ">" }
  end

  # Draws the slider so the user can move it and see the progress of the search
  def render_slider
    # Using a solid instead of a line, hides the line under the circle of the slider
    # Draws the line
    outputs.solids << {
      x: slider.x,
      y: slider.y,
      w: slider.w,
      h: 2
    }
    # The circle needs to be offset so that the center of the circle
    # overlaps the line instead of the upper right corner of the circle
    # The circle's x value is also moved based on the current seach step
    circle_x = (slider.x - slider.offset) + (state.anim_steps * slider.spacing)
    circle_y = (slider.y - slider.offset)
    outputs.sprites << {
      x: circle_x,
      y: circle_y,
      w: 37,
      h: 37,
      path: 'circle-white.png'
    }
  end

  # Draws what the grid looks like with nothing on it
  def render_background
    render_unvisited
    render_grid_lines
  end

  # Draws a rectangle the size of the entire grid to represent unvisited cells
  def render_unvisited
    rect = { x: 0, y: 0, w: grid.width, h: grid.height }
    rect = rect.transform_values { |v| v * grid.cell_size }
    outputs.solids << rect.merge(unvisited_color)
  end

  # Draws grid lines to show the division of the grid into cells
  def render_grid_lines
    outputs.lines << (0..grid.width).map { |x| vertical_line(x) }
    outputs.lines << (0..grid.height).map { |y| horizontal_line(y) }
  end

  # Easy way to draw vertical lines given an index
  def vertical_line x
    line = { x: x, y: 0, w: 0, h: grid.height }
    line.transform_values { |v| v * grid.cell_size }
  end

  # Easy way to draw horizontal lines given an index
  def horizontal_line y
    line = { x: 0, y: y, w: grid.width, h: 0 }
    line.transform_values { |v| v * grid.cell_size }
  end

  # Draws the area that is going to be searched from
  # The frontier is the most outward parts of the search
  def render_frontier
    outputs.solids << state.frontier.map do |cell|
      render_cell cell, frontier_color
    end
  end

  # Draws the walls
  def render_walls
    outputs.solids << state.walls.map do |wall|
      render_cell wall, wall_color
    end
  end

  # Renders cells that have been searched in the appropriate color
  def render_visited
    outputs.solids << state.visited.map do |cell|
      render_cell cell, visited_color
    end
  end

  # Renders the star
  def render_star
    outputs.sprites << render_cell(state.star, { path: 'star.png' })
  end

  def render_cell cell, attrs
    {
      x: cell.x * grid.cell_size,
      y: cell.y * grid.cell_size,
      w: grid.cell_size,
      h: grid.cell_size
    }.merge attrs
  end

  # In code, the cells are represented as 1x1 rectangles
  # When drawn, the cells are larger than 1x1 rectangles
  # This method is used to scale up cells, and lines
  # Objects are scaled up according to the grid.cell_size variable
  # This allows for easy customization of the visual scale of the grid
  def scale_up(cell)
    # Prevents the original value of cell from being edited
    cell = cell.clone

    # If cell is just an x and y coordinate
    if cell.size == 2
      # Add a width and height of 1
      cell << 1
      cell << 1
    end

    # Scale all the values up
    cell.map! { |value| value * grid.cell_size }

    # Returns the scaled up cell
    cell
  end

  # This method processes user input every tick
  # This method allows the user to use the buttons, slider, and edit the grid
  # There are 2 types of input:
  #   Button Input
  #   Click and Drag Input
  #
  #   Button Input is used for the backward step and forward step buttons
  #   Input is detected by mouse up within the bounds of the rect
  #
  #   Click and Drag Input is used for moving the star, adding walls,
  #   removing walls, and the slider
  #
  #   When the mouse is down on the star, the click_and_drag variable is set to :star
  #   While click_and_drag equals :star, the cursor's position is used to calculate the
  #   appropriate drag behavior
  #
  #   When the mouse goes up click_and_drag is set to :none
  #
  #   A variable has to be used because the star has to continue being edited even
  #   when the cursor is no longer over the star
  #
  #   Similar things occur for the other Click and Drag inputs
  def input
    # Checks whether any of the buttons are being clicked
    input_buttons

    # The detection and processing of click and drag inputs are separate
    # The program has to remember that the user is dragging an object
    # even when the mouse is no longer over that object
    detect_click_and_drag
    process_click_and_drag
  end

  # Detects and Process input for each button
  def input_buttons
    input_left_button
    input_center_button
    input_next_step_button
  end

  # Checks if the previous step button is clicked
  # If it is, it pauses the animation and moves the search one step backward
  def input_left_button
    if left_button_clicked?
      state.play = false
      state.anim_steps -= 1
      recalculate
    end
  end

  # Controls the play/pause button
  # Inverses whether the animation is playing or not when clicked
  def input_center_button
    if center_button_clicked? or inputs.keyboard.key_down.space
      state.play = !state.play
    end
  end

  # Checks if the next step button is clicked
  # If it is, it pauses the animation and moves the search one step forward
  def input_next_step_button
    if right_button_clicked?
      state.play = false
      state.anim_steps += 1
      calc
    end
  end

  # Determines what the user is editing and stores the value
  # Storing the value allows the user to continue the same edit as long as the
  # mouse left click is held
  def detect_click_and_drag
    if inputs.mouse.up
      state.click_and_drag = :none
    elsif star_clicked?
      state.click_and_drag = :star
    elsif wall_clicked?
      state.click_and_drag = :remove_wall
    elsif grid_clicked?
      state.click_and_drag = :add_wall
    elsif slider_clicked?
      state.click_and_drag = :slider
    end
  end

  # Processes click and drag based on what the user is currently dragging
  def process_click_and_drag
    if state.click_and_drag == :star
      input_star
    elsif state.click_and_drag == :remove_wall
      input_remove_wall
    elsif state.click_and_drag == :add_wall
      input_add_wall
    elsif state.click_and_drag == :slider
      input_slider
    end
  end

  # Moves the star to the grid closest to the mouse
  # Only recalculates the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def input_star
    old_star = state.star.clone
    state.star = cell_closest_to_mouse
    unless old_star == state.star
      recalculate
    end
  end

  # Removes walls that are under the cursor
  def input_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if mouse_inside_grid?
      if state.walls.key?(cell_closest_to_mouse)
        state.walls.delete(cell_closest_to_mouse)
        recalculate
      end
    end
  end

  # Adds walls at cells under the cursor
  def input_add_wall
    if mouse_inside_grid?
      unless state.walls.key?(cell_closest_to_mouse)
        state.walls[cell_closest_to_mouse] = true
        recalculate
      end
    end
  end

  # This method is called when the user is editing the slider
  # It pauses the animation and moves the white circle to the closest integer point
  # on the slider
  # Changes the step of the search to be animated
  def input_slider
    state.play = false
    mouse_x = inputs.mouse.point.x

    # Bounds the mouse_x to the closest x value on the slider line
    mouse_x = slider.x if mouse_x < slider.x
    mouse_x = slider.x + slider.w if mouse_x > slider.x + slider.w

    # Sets the current search step to the one represented by the mouse x value
    # The slider's circle moves due to the render_slider method using anim_steps
    state.anim_steps = ((mouse_x - slider.x) / slider.spacing).to_i

    recalculate
  end

  # Whenever the user edits the grid,
  # The search has to be recalculated upto the current step
  # with the current grid as the initial state of the grid
  def recalculate
    # Resets the search
    state.frontier = []
    state.visited = {}

    # Moves the animation forward one step at a time
    state.anim_steps.times { calc }
  end


  # This method moves the search forward one step
  # When the animation is playing it is called every tick
  # And called whenever the current step of the animation needs to be recalculated

  # Moves the search forward one step
  # Parameter called_from_tick is true if it is called from the tick method
  # It is false when the search is being recalculated after user editing the grid
  def calc

    # The setup to the search
    # Runs once when the there is no frontier or visited cells
    if state.frontier.empty? && state.visited.empty?
      state.frontier << state.star
      state.visited[state.star] = true
    end

    # A step in the search
    unless state.frontier.empty?
      # Takes the next frontier cell
      new_frontier = state.frontier.shift
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do |neighbor|
        # That have not been visited and are not walls
        unless state.visited.key?(neighbor) || state.walls.key?(neighbor)
          # Add them to the frontier and mark them as visited
          state.frontier << neighbor
          state.visited[neighbor] = true
        end
      end
    end
  end


  # Returns a list of adjacent cells
  # Used to determine what the next cells to be added to the frontier are
  def adjacent_neighbors(cell)
    neighbors = []

    neighbors << [cell.x, cell.y + 1] unless cell.y == grid.height - 1
    neighbors << [cell.x + 1, cell.y] unless cell.x == grid.width - 1
    neighbors << [cell.x, cell.y - 1] unless cell.y == 0
    neighbors << [cell.x - 1, cell.y] unless cell.x == 0

    neighbors
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse helps with this
  def cell_closest_to_mouse
    # Closest cell to the mouse
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Bound x and y to the grid
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  # These methods detect when the buttons are clicked
  def left_button_clicked?
    inputs.mouse.up && inputs.mouse.point.inside_rect?(buttons.left)
  end

  def center_button_clicked?
    inputs.mouse.up && inputs.mouse.point.inside_rect?(buttons.center)
  end

  def right_button_clicked?
    inputs.mouse.up && inputs.mouse.point.inside_rect?(buttons.right)
  end

  # Signal that the user is going to be moving the slider
  # Is the mouse down on the circle of the slider?
  def slider_clicked?
    circle_x = (slider.x - slider.offset) + (state.anim_steps * slider.spacing)
    circle_y = (slider.y - slider.offset)
    circle_rect = [circle_x, circle_y, 37, 37]
    inputs.mouse.down && inputs.mouse.point.inside_rect?(circle_rect)
  end

  # Signal that the user is going to be moving the star
  def star_clicked?
    inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(state.star))
  end

  # Signal that the user is going to be removing walls
  def wall_clicked?
    inputs.mouse.down && mouse_inside_a_wall?
  end

  # Signal that the user is going to be adding walls
  def grid_clicked?
    inputs.mouse.down && mouse_inside_grid?
  end

  # Returns whether the mouse is inside of a wall
  # Part of the condition that checks whether the user is removing a wall
  def mouse_inside_a_wall?
    state.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(scale_up([wall.x, wall.y]))
    end

    false
  end

  # Returns whether the mouse is inside of a grid
  # Part of the condition that checks whether the user is adding a wall
  def mouse_inside_grid?
    inputs.mouse.point.inside_rect?(scale_up([0, 0, grid.width, grid.height]))
  end

  # Light brown
  def unvisited_color
    { r: 221, g: 212, b: 213 }
  end

  # Dark Brown
  def visited_color
    { r: 204, g: 191, b: 179 }
  end

  # Blue
  def frontier_color
    { r: 103, g: 136, b: 204 }
  end

  # Camo Green
  def wall_color
    { r: 134, g: 134, b: 120 }
  end

  # Button Background
  def gray
    { r: 190, g: 190, b: 190 }
  end

  # These methods make the code more concise
  def grid
    state.grid
  end

  def buttons
    state.buttons
  end

  def slider
    state.slider
  end
end

# Method that is called by DragonRuby periodically
# Used for updating animations and calculations
def tick args

  # Pressing r will reset the application
  if args.inputs.keyboard.key_down.r
    args.gtk.reset
    reset
    return
  end

  # Every tick, new args are passed, and the Breadth First Search tick is called
  $breadth_first_search ||= BreadthFirstSearch.new(args)
  $breadth_first_search.args = args
  $breadth_first_search.tick
end


def reset
  $breadth_first_search = nil
end

Path Finding Algorithms - Detailed Breadth First Search - main.rb

# ./samples/13_path_finding_algorithms/02_detailed_breadth_first_search/app/main.rb
# Contributors outside of DragonRuby who also hold Copyright:
# - Sujay Vadlakonda: https://github.com/sujayvadlakonda

# A visual demonstration of a breadth first search
# Inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html

# An animation that can respond to user input in real time

# A breadth first search expands in all directions one step at a time
# The frontier is a queue of cells to be expanded from
# The visited hash allows quick lookups of cells that have been expanded from
# The walls hash allows quick lookup of whether a cell is a wall

# The breadth first search starts by adding the red star to the frontier array
# and marking it as visited
# Each step a cell is removed from the front of the frontier array (queue)
# Unless the neighbor is a wall or visited, it is added to the frontier array
# The neighbor is then marked as visited

# The frontier is blue
# Visited cells are light brown
# Walls are camo green
# Even when walls are visited, they will maintain their wall color

# This search numbers the order in which new cells are explored
# The next cell from where the search will continue is highlighted yellow
# And the cells that will be considered for expansion are in semi-transparent green

# The star can be moved by clicking and dragging
# Walls can be added and removed by clicking and dragging

class DetailedBreadthFirstSearch
  attr_gtk

  def initialize(args)
    # Variables to edit the size and appearance of the grid
    # Freely customizable to user's liking
    args.state.grid.width     = 9
    args.state.grid.height    = 4
    args.state.grid.cell_size = 90

    # Stores which step of the animation is being rendered
    # When the user moves the star or messes with the walls,
    # the breadth first search is recalculated up to this step
    args.state.anim_steps = 0

    # At some step the animation will end,
    # and further steps won't change anything (the whole grid will be explored)
    # This step is roughly the grid's width * height
    # When anim_steps equals max_steps no more calculations will occur
    # and the slider will be at the end
    args.state.max_steps  = args.state.grid.width * args.state.grid.height

    # The location of the star and walls of the grid
    # They can be modified to have a different initial grid
    # Walls are stored in a hash for quick look up when doing the search
    args.state.star       = [3, 2]
    args.state.walls      = {}

    # Variables that are used by the breadth first search
    # Storing cells that the search has visited, prevents unnecessary steps
    # Expanding the frontier of the search in order makes the search expand
    # from the center outward
    args.state.visited    = {}
    args.state.frontier   = []
    args.state.cell_numbers = []



    # What the user is currently editing on the grid
    # Possible values are: :none, :slider, :star, :remove_wall, :add_wall

    # We store this value, because we want to remember the value even when
    # the user's cursor is no longer over what they're interacting with, but
    # they are still clicking down on the mouse.
    args.state.click_and_drag = :none

    # The x, y, w, h values for the buttons
    # Allow easy movement of the buttons location
    # A centralized location to get values to detect input and draw the buttons
    # Editing these values might mean needing to edit the label offsets
    # which can be found in the appropriate render button methods
    args.state.buttons.left  = [450, 600, 160, 50]
    args.state.buttons.right = [610, 600, 160, 50]

    # The variables below are related to the slider
    # They allow the user to customize them
    # They also give a central location for the render and input methods to get
    # information from
    # x & y are the coordinates of the leftmost part of the slider line
    args.state.slider.x = 400
    args.state.slider.y = 675
    # This is the width of the line
    args.state.slider.w = 360
    # This is the offset for the circle
    # Allows the center of the circle to be on the line,
    # as opposed to the upper right corner
    args.state.slider.offset = 20
    # This is the spacing between each of the notches on the slider
    # Notches are places where the circle can rest on the slider line
    # There needs to be a notch for each step before the maximum number of steps
    args.state.slider.spacing = args.state.slider.w.to_f / args.state.max_steps.to_f
  end

  # This method is called every frame/tick
  # Every tick, the current state of the search is rendered on the screen,
  # User input is processed, and
  def tick
    render
    input
  end

  # This method is called from tick and renders everything every tick
  def render
    render_buttons
    render_slider

    render_background
    render_visited
    render_frontier
    render_walls
    render_star

    render_highlights
    render_cell_numbers
  end

  # The methods below subdivide the task of drawing everything to the screen

  # Draws the buttons that move the search backward or forward
  # These buttons are rendered so the user knows where to click to move the search
  def render_buttons
    render_left_button
    render_right_button
  end

  # Renders the button which steps the search backward
  # Shows the user where to click to move the search backward
  def render_left_button
    # Draws the gray button, and a black border
    # The border separates the buttons visually
    outputs.solids  << [buttons.left, gray]
    outputs.borders << [buttons.left]

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    label_x = buttons.left.x + 05
    label_y = buttons.left.y + 35
    outputs.labels  << [label_x, label_y, "< Step backward"]
  end

  # Renders the button which steps the search forward
  # Shows the user where to click to move the search forward
  def render_right_button
    # Draws the gray button, and a black border
    # The border separates the buttons visually
    outputs.solids  << [buttons.right, gray]
    outputs.borders << [buttons.right]

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    label_x = buttons.right.x + 10
    label_y = buttons.right.y + 35
    outputs.labels  << [label_x, label_y, "Step forward >"]
  end

  # Draws the slider so the user can move it and see the progress of the search
  def render_slider
    # Using primitives hides the line under the white circle of the slider
    # Draws the line
    outputs.primitives << [slider.x, slider.y, slider.x + slider.w, slider.y].line
    # The circle needs to be offset so that the center of the circle
    # overlaps the line instead of the upper right corner of the circle
    # The circle's x value is also moved based on the current seach step
    circle_x = (slider.x - slider.offset) + (state.anim_steps * slider.spacing)
    circle_y = (slider.y - slider.offset)
    circle_rect = [circle_x, circle_y, 37, 37]
    outputs.primitives << [circle_rect, 'circle-white.png'].sprite
  end

  # Draws what the grid looks like with nothing on it
  # Which is a bunch of unvisited cells
  # Drawn first so other things can draw on top of it
  def render_background
    render_unvisited

    # The grid lines make the cells appear separate
    render_grid_lines
  end

  # Draws a rectangle the size of the entire grid to represent unvisited cells
  # Unvisited cells are the default cell
  def render_unvisited
    background = [0, 0, grid.width, grid.height]
    outputs.solids << scale_up(background).merge(unvisited_color)
  end

  # Draws grid lines to show the division of the grid into cells
  def render_grid_lines
    outputs.lines << (0..grid.width).map do |x|
      scale_up(vertical_line(x)).merge(grid_line_color)
    end
    outputs.lines << (0..grid.height).map do |y|
      scale_up(horizontal_line(y)).merge(grid_line_color)
    end
  end

  # Easy way to get a vertical line given an index
  def vertical_line column
    [column, 0, 0, grid.height]
  end

  # Easy way to get a horizontal line given an index
  def horizontal_line row
    [0, row, grid.width, 0]
  end

  # Draws the area that is going to be searched from
  # The frontier is the most outward parts of the search
  def render_frontier
    state.frontier.each do |cell|
      outputs.solids << scale_up(cell).merge(frontier_color)
    end
  end

  # Draws the walls
  def render_walls
    state.walls.each_key do |wall|
      outputs.solids << scale_up(wall).merge(wall_color)
    end
  end

  # Renders cells that have been searched in the appropriate color
  def render_visited
    state.visited.each_key do |cell|
      outputs.solids << scale_up(cell).merge(visited_color)
    end
  end

  # Renders the star
  def render_star
    outputs.sprites << scale_up(state.star).merge({ path: 'star.png' })
  end

  # Cells have a number rendered in them based on when they were explored
  # This is based off of their index in the cell_numbers array
  # Cells are added to this array the same time they are added to the frontier array
  def render_cell_numbers
    state.cell_numbers.each_with_index do |cell, index|
      # Math that approx centers the number in the cell
      label_x = (cell.x * grid.cell_size) + grid.cell_size / 2 - 5
      label_y = (cell.y * grid.cell_size) + (grid.cell_size / 2) + 5

      outputs.labels << [label_x, label_y, (index + 1).to_s]
    end
  end

  # The next frontier to be expanded is highlighted yellow
  # Its adjacent non-wall neighbors have their border highlighted green
  # This is to show the user how the search expands
  def render_highlights
    return if state.frontier.empty?

    # Highlight the next frontier to be expanded yellow
    next_frontier = state.frontier[0]
    outputs.solids << scale_up(next_frontier).merge(highlighter_yellow)

    # Neighbors have a semi-transparent green layer over them
    # Unless the neighbor is a wall
    adjacent_neighbors(next_frontier).each do |neighbor|
      unless state.walls.key?(neighbor)
        outputs.solids << scale_up(neighbor).merge(highlighter_green)
      end
    end
  end


  # Cell Size is used when rendering to allow the grid to be scaled up or down
  # Cells in the frontier array and visited hash and walls hash are stored as x & y
  # Scaling up cells and lines when rendering allows omitting of width and height
  def scale_up(cell)
    if cell.size == 2
      return {
        x: cell.x * grid.cell_size,
        y: cell.y * grid.cell_size,
        w: grid.cell_size,
        h: grid.cell_size
      }
    else
      return {
        x: cell.x * grid.cell_size,
        y: cell.y * grid.cell_size,
        w: cell.w * grid.cell_size,
        h: cell.h * grid.cell_size
      }
    end
  end


  # This method processes user input every tick
  # This method allows the user to use the buttons, slider, and edit the grid
  # There are 2 types of input:
  #   Button Input
  #   Click and Drag Input
  #
  #   Button Input is used for the backward step and forward step buttons
  #   Input is detected by mouse up within the bounds of the rect
  #
  #   Click and Drag Input is used for moving the star, adding walls,
  #   removing walls, and the slider
  #
  #   When the mouse is down on the star, the click_and_drag variable is set to :star
  #   While click_and_drag equals :star, the cursor's position is used to calculate the
  #   appropriate drag behavior
  #
  #   When the mouse goes up click_and_drag is set to :none
  #
  #   A variable has to be used because the star has to continue being edited even
  #   when the cursor is no longer over the star
  #
  #   Similar things occur for the other Click and Drag inputs
  def input
    # Processes inputs for the buttons
    input_buttons

    # Detects which if any click and drag input is occurring
    detect_click_and_drag

    # Does the appropriate click and drag input based on the click_and_drag variable
    process_click_and_drag
  end

  # Detects and Process input for each button
  def input_buttons
    input_left_button
    input_right_button
  end

  # Checks if the previous step button is clicked
  # If it is, it pauses the animation and moves the search one step backward
  def input_left_button
    if left_button_clicked?
      unless state.anim_steps == 0
        state.anim_steps -= 1
        recalculate
      end
    end
  end

  # Checks if the next step button is clicked
  # If it is, it pauses the animation and moves the search one step forward
  def input_right_button
    if right_button_clicked?
      unless state.anim_steps == state.max_steps
        state.anim_steps += 1
        # Although normally recalculate would be called here
        # because the right button only moves the search forward
        # We can just do that
        calc
      end
    end
  end

  # Whenever the user edits the grid,
  # The search has to be recalculated upto the current step

  def recalculate
    # Resets the search
    state.frontier = []
    state.visited = {}
    state.cell_numbers = []

    # Moves the animation forward one step at a time
    state.anim_steps.times { calc }
  end


  # Determines what the user is clicking and planning on dragging
  # Click and drag input is initiated by a click on the appropriate item
  # and ended by mouse up
  # Storing the value allows the user to continue the same edit as long as the
  # mouse left click is held
  def detect_click_and_drag
    if inputs.mouse.up
      state.click_and_drag = :none
    elsif star_clicked?
      state.click_and_drag = :star
    elsif wall_clicked?
      state.click_and_drag = :remove_wall
    elsif grid_clicked?
      state.click_and_drag = :add_wall
    elsif slider_clicked?
      state.click_and_drag = :slider
    end
  end

  # Processes input based on what the user is currently dragging
  def process_click_and_drag
    if state.click_and_drag == :slider
      input_slider
    elsif state.click_and_drag == :star
      input_star
    elsif state.click_and_drag == :remove_wall
      input_remove_wall
    elsif state.click_and_drag == :add_wall
      input_add_wall
    end
  end

  # This method is called when the user is dragging the slider
  # It moves the current animation step to the point represented by the slider
  def input_slider
    mouse_x = inputs.mouse.point.x

    # Bounds the mouse_x to the closest x value on the slider line
    mouse_x = slider.x if mouse_x < slider.x
    mouse_x = slider.x + slider.w if mouse_x > slider.x + slider.w

    # Sets the current search step to the one represented by the mouse x value
    # The slider's circle moves due to the render_slider method using anim_steps
    state.anim_steps = ((mouse_x - slider.x) / slider.spacing).to_i

    recalculate
  end

  # Moves the star to the grid closest to the mouse
  # Only recalculates the search if the star changes position
  # Called whenever the user is dragging the star
  def input_star
    old_star = state.star.clone
    state.star = cell_closest_to_mouse
    unless old_star == state.star
      recalculate
    end
  end

  # Removes walls that are under the cursor
  def input_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if mouse_inside_grid?
      if state.walls.key?(cell_closest_to_mouse)
        state.walls.delete(cell_closest_to_mouse)
        recalculate
      end
    end
  end

  # Adds walls at cells under the cursor
  def input_add_wall
    # Adds a wall to the hash
    # We can use the grid closest to mouse, because the cursor is inside the grid
    if mouse_inside_grid?
      unless state.walls.key?(cell_closest_to_mouse)
        state.walls[cell_closest_to_mouse] = true
        recalculate
      end
    end
  end

  # This method moves the search forward one step
  # When the animation is playing it is called every tick
  # And called whenever the current step of the animation needs to be recalculated

  # Moves the search forward one step
  # Parameter called_from_tick is true if it is called from the tick method
  # It is false when the search is being recalculated after user editing the grid
  def calc
    # The setup to the search
    # Runs once when the there is no frontier or visited cells
    if state.frontier.empty? && state.visited.empty?
      state.frontier << state.star
      state.visited[state.star] = true
    end

    # A step in the search
    unless state.frontier.empty?
      # Takes the next frontier cell
      new_frontier = state.frontier.shift
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do |neighbor|
        # That have not been visited and are not walls
        unless state.visited.key?(neighbor) || state.walls.key?(neighbor)
          # Add them to the frontier and mark them as visited
          state.frontier << neighbor
          state.visited[neighbor] = true

          # Also assign them a frontier number
          state.cell_numbers << neighbor
        end
      end
    end
  end


  # Returns a list of adjacent cells
  # Used to determine what the next cells to be added to the frontier are
  def adjacent_neighbors cell
    neighbors = []

    neighbors << [cell.x, cell.y + 1] unless cell.y == grid.height - 1
    neighbors << [cell.x + 1, cell.y] unless cell.x == grid.width - 1
    neighbors << [cell.x, cell.y - 1] unless cell.y == 0
    neighbors << [cell.x - 1, cell.y] unless cell.x == 0

    neighbors
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the grid closest to the mouse helps with this
  def cell_closest_to_mouse
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    [x, y]
  end


  # These methods detect when the buttons are clicked
  def left_button_clicked?
    (inputs.mouse.up && inputs.mouse.point.inside_rect?(buttons.left)) || inputs.keyboard.key_up.left
  end

  def right_button_clicked?
    (inputs.mouse.up && inputs.mouse.point.inside_rect?(buttons.right)) || inputs.keyboard.key_up.right
  end

  # Signal that the user is going to be moving the slider
  def slider_clicked?
    circle_x = (slider.x - slider.offset) + (state.anim_steps * slider.spacing)
    circle_y = (slider.y - slider.offset)
    circle_rect = [circle_x, circle_y, 37, 37]
    inputs.mouse.down && inputs.mouse.point.inside_rect?(circle_rect)
  end

  # Signal that the user is going to be moving the star
  def star_clicked?
    inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(state.star))
  end

  # Signal that the user is going to be removing walls
  def wall_clicked?
    inputs.mouse.down && mouse_inside_a_wall?
  end

  # Signal that the user is going to be adding walls
  def grid_clicked?
    inputs.mouse.down && mouse_inside_grid?
  end

  # Returns whether the mouse is inside of a wall
  # Part of the condition that checks whether the user is removing a wall
  def mouse_inside_a_wall?
    state.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(scale_up(wall))
    end

    false
  end

  # Returns whether the mouse is inside of a grid
  # Part of the condition that checks whether the user is adding a wall
  def mouse_inside_grid?
    inputs.mouse.point.inside_rect?(scale_up([0, 0, grid.width, grid.height]))
  end

  # These methods provide handy aliases to colors

  # Light brown
  def unvisited_color
    { r: 221, g: 212, b: 213 }
  end

  # Black
  def grid_line_color
    { r: 255, g: 255, b: 255 }
  end

  # Dark Brown
  def visited_color
    { r: 204, g: 191, b: 179 }
  end

  # Blue
  def frontier_color
    { r: 103, g: 136, b: 204 }
  end

  # Camo Green
  def wall_color
    { r: 134, g: 134, b: 120 }
  end

  # Next frontier to be expanded
  def highlighter_yellow
    { r: 214, g: 231, b: 125 }
  end

  # The neighbors of the next frontier to be expanded
  def highlighter_green
    { r: 65, g: 191, b: 127, a: 70 }
  end

  # Button background
  def gray
    [190, 190, 190]
  end

  # These methods make the code more concise
  def grid
    state.grid
  end

  def buttons
    state.buttons
  end

  def slider
    state.slider
  end
end


def tick args
  # Pressing r resets the program
  if args.inputs.keyboard.key_down.r
    args.gtk.reset
    reset
    return
  end

  $detailed_breadth_first_search ||= DetailedBreadthFirstSearch.new(args)
  $detailed_breadth_first_search.args = args
  $detailed_breadth_first_search.tick
end


def reset
  $detailed_breadth_first_search = nil
end

Path Finding Algorithms - Breadcrumbs - main.rb

# ./samples/13_path_finding_algorithms/03_breadcrumbs/app/main.rb
# Contributors outside of DragonRuby who also hold Copyright:
# - Sujay Vadlakonda: https://github.com/sujayvadlakonda

# This program is inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html

class Breadcrumbs
  attr_gtk

  # This method is called every frame/tick
  # Every tick, the current state of the search is rendered on the screen,
  # User input is processed, and
  # The next step in the search is calculated
  def tick
    defaults
    # If the grid has not been searched
    if search.came_from.empty?
      calc
      # Calc Path
    end
    render
    input
  end

  def defaults
    # Variables to edit the size and appearance of the grid
    # Freely customizable to user's liking
    grid.width     ||= 30
    grid.height    ||= 15
    grid.cell_size ||= 40
    grid.rect      ||= [0, 0, grid.width, grid.height]

    # The location of the star and walls of the grid
    # They can be modified to have a different initial grid
    # Walls are stored in a hash for quick look up when doing the search
    grid.star   ||= [2, 8]
    grid.target ||= [10, 5]
    grid.walls  ||= {
      [3, 3] => true,
      [3, 4] => true,
      [3, 5] => true,
      [3, 6] => true,
      [3, 7] => true,
      [3, 8] => true,
      [3, 9] => true,
      [3, 10] => true,
      [3, 11] => true,
      [4, 3] => true,
      [4, 4] => true,
      [4, 5] => true,
      [4, 6] => true,
      [4, 7] => true,
      [4, 8] => true,
      [4, 9] => true,
      [4, 10] => true,
      [4, 11] => true,
      [13, 0] => true,
      [13, 1] => true,
      [13, 2] => true,
      [13, 3] => true,
      [13, 4] => true,
      [13, 5] => true,
      [13, 6] => true,
      [13, 7] => true,
      [13, 8] => true,
      [13, 9] => true,
      [13, 10] => true,
      [14, 0] => true,
      [14, 1] => true,
      [14, 2] => true,
      [14, 3] => true,
      [14, 4] => true,
      [14, 5] => true,
      [14, 6] => true,
      [14, 7] => true,
      [14, 8] => true,
      [14, 9] => true,
      [14, 10] => true,
      [21, 8] => true,
      [21, 9] => true,
      [21, 10] => true,
      [21, 11] => true,
      [21, 12] => true,
      [21, 13] => true,
      [21, 14] => true,
      [22, 8] => true,
      [22, 9] => true,
      [22, 10] => true,
      [22, 11] => true,
      [22, 12] => true,
      [22, 13] => true,
      [22, 14] => true,
      [23, 8] => true,
      [23, 9] => true,
      [24, 8] => true,
      [24, 9] => true,
      [25, 8] => true,
      [25, 9] => true,
    }

    # Variables that are used by the breadth first search
    # Storing cells that the search has visited, prevents unnecessary steps
    # Expanding the frontier of the search in order makes the search expand
    # from the center outward

    # The cells from which the search is to expand
    search.frontier              ||= []
    # A hash of where each cell was expanded from
    # The key is a cell, and the value is the cell it came from
    search.came_from             ||= {}
    # Cells that are part of the path from the target to the star
    search.path                  ||= {}

    # What the user is currently editing on the grid
    # We store this value, because we want to remember the value even when
    # the user's cursor is no longer over what they're interacting with, but
    # they are still clicking down on the mouse.
    state.current_input ||= :none
  end

  def calc
    # Setup the search to start from the star
    search.frontier << grid.star
    search.came_from[grid.star] = nil

    # Until there are no more cells to expand from
    until search.frontier.empty?
      # Takes the next frontier cell
      new_frontier = search.frontier.shift
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do |neighbor|
        # That have not been visited and are not walls
        unless search.came_from.has_key?(neighbor) || grid.walls.has_key?(neighbor)
          # Add them to the frontier and mark them as visited in the first grid
          # Unless the target has been visited
          # Add the neighbor to the frontier and remember which cell it came from
          search.frontier << neighbor
          search.came_from[neighbor] = new_frontier
        end
      end
    end
  end


  # Draws everything onto the screen
  def render
    render_background
    # render_heat_map
    render_walls
    # render_path
    # render_labels
    render_arrows
    render_star
    render_target
    unless grid.walls.has_key?(grid.target)
      render_trail
    end
  end

  def render_trail(current_cell=grid.target)
    return if current_cell == grid.star
    parent_cell = search.came_from[current_cell]
    if current_cell && parent_cell
      outputs.lines << [(current_cell.x + 0.5) * grid.cell_size, (current_cell.y + 0.5) * grid.cell_size,
      (parent_cell.x + 0.5) * grid.cell_size, (parent_cell.y + 0.5) * grid.cell_size, purple]

    end
    render_trail(parent_cell)
  end

  def render_arrows
    search.came_from.each do |child, parent|
      if parent && child
        arrow_cell = [(child.x + parent.x) / 2, (child.y + parent.y) / 2]
        if parent.x > child.x # If the parent cell is to the right of the child cell
          # Point arrow right
          outputs.sprites << scale_up(arrow_cell).merge({ path: 'arrow.png', angle: 0})
        elsif parent.x < child.x # If the parent cell is to the right of the child cell
          outputs.sprites << scale_up(arrow_cell).merge({ path: 'arrow.png', angle: 180})
        elsif parent.y > child.y # If the parent cell is to the right of the child cell
          outputs.sprites << scale_up(arrow_cell).merge({ path: 'arrow.png', angle: 90})
        elsif parent.y < child.y # If the parent cell is to the right of the child cell
          outputs.sprites << scale_up(arrow_cell).merge({ path: 'arrow.png', angle: 270})
        end
      end
    end
  end

  # The methods below subdivide the task of drawing everything to the screen

  # Draws what the grid looks like with nothing on it
  def render_background
    render_unvisited
    render_grid_lines
  end

  # Draws both grids
  def render_unvisited
    outputs.solids << scale_up(grid.rect).merge(unvisited_color)
  end

  # Draws grid lines to show the division of the grid into cells
  def render_grid_lines
    outputs.lines << (0..grid.width).map { |x| vertical_line(x) }
    outputs.lines << (0..grid.height).map { |y| horizontal_line(y) }
  end

  # Easy way to draw vertical lines given an index
  def vertical_line x
    line = { x: x, y: 0, w: 0, h: grid.height }
    line.transform_values { |v| v * grid.cell_size }
  end

  # Easy way to draw horizontal lines given an index
  def horizontal_line y
    line = { x: 0, y: y, w: grid.width, h: 0 }
    line.transform_values { |v| v * grid.cell_size }
  end

  # Draws the walls on both grids
  def render_walls
    outputs.solids << grid.walls.map do |key, value|
      scale_up(key).merge(wall_color)
    end
  end

  # Renders the star on both grids
  def render_star
    outputs.sprites << scale_up(grid.star).merge({ path: 'star.png' })
  end

  # Renders the target on both grids
  def render_target
    outputs.sprites << scale_up(grid.target).merge({ path: 'target.png'})
  end

  # Labels the grids
  def render_labels
    outputs.labels << [200, 625, "Without early exit"]
  end

  # Renders the path based off of the search.path hash
  def render_path
    # If the star and target are disconnected there will only be one path
    # The path should not render in that case
    unless search.path.size == 1
      search.path.each_key do | cell |
        # Renders path on both grids
        outputs.solids << [scale_up(cell), path_color]
      end
    end
  end

  # Calculates the path from the target to the star after the search is over
  # Relies on the came_from hash
  # Fills the search.path hash, which is later rendered on screen
  def calc_path
    endpoint = grid.target
    while endpoint
      search.path[endpoint] = true
      endpoint = search.came_from[endpoint]
    end
  end

  # In code, the cells are represented as 1x1 rectangles
  # When drawn, the cells are larger than 1x1 rectangles
  # This method is used to scale up cells, and lines
  # Objects are scaled up according to the grid.cell_size variable
  # This allows for easy customization of the visual scale of the grid
  def scale_up(cell)
    x = cell.x * grid.cell_size
    y = cell.y * grid.cell_size
    w = cell.w.zero? ? grid.cell_size : cell.w * grid.cell_size
    h = cell.h.zero? ? grid.cell_size : cell.h * grid.cell_size
    { x: x, y: y, w: w, h: h }
  end

  # This method processes user input every tick
  # Any method with "1" is related to the first grid
  # Any method with "2" is related to the second grid
  def input
    # The program has to remember that the user is dragging an object
    # even when the mouse is no longer over that object
    # So detecting input and processing input is separate
    # detect_input
    # process_input
    if inputs.mouse.up
      state.current_input = :none
    elsif star_clicked?
      state.current_input = :star
    end

    if mouse_inside_grid?
      unless grid.target == cell_closest_to_mouse
        grid.target = cell_closest_to_mouse
      end
      if state.current_input == :star
        unless grid.star == cell_closest_to_mouse
          grid.star = cell_closest_to_mouse
        end
      end
    end
  end

  # Determines what the user is editing and stores the value
  # Storing the value allows the user to continue the same edit as long as the
  # mouse left click is held
  def detect_input
    # When the mouse is up, nothing is being edited
    if inputs.mouse.up
      state.current_input = :none
    # When the star in the no second grid is clicked
    elsif star_clicked?
      state.current_input = :star
    # When the target in the no second grid is clicked
    elsif target_clicked?
      state.current_input = :target
    # When a wall in the first grid is clicked
    elsif wall_clicked?
      state.current_input = :remove_wall
    # When the first grid is clicked
    elsif grid_clicked?
      state.current_input = :add_wall
    end
  end

  # Processes click and drag based on what the user is currently dragging
  def process_input
    if state.current_input == :star
      input_star
    elsif state.current_input == :target
      input_target
    elsif state.current_input == :remove_wall
      input_remove_wall
    elsif state.current_input == :add_wall
      input_add_wall
    end
  end

  # Moves the star to the cell closest to the mouse in the first grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def input_star
    old_star = grid.star.clone
    grid.star = cell_closest_to_mouse
    unless old_star == grid.star
      reset_search
    end
  end

  # Moves the target to the grid closest to the mouse in the first grid
  # Only reset_searchs the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def input_target
    old_target = grid.target.clone
    grid.target = cell_closest_to_mouse
    unless old_target == grid.target
      reset_search
    end
  end

  # Removes walls in the first grid that are under the cursor
  def input_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if mouse_inside_grid?
      if grid.walls.key?(cell_closest_to_mouse)
        grid.walls.delete(cell_closest_to_mouse)
        reset_search
      end
    end
  end

  # Adds a wall in the first grid in the cell the mouse is over
  def input_add_wall
    if mouse_inside_grid?
      unless grid.walls.key?(cell_closest_to_mouse)
        grid.walls[cell_closest_to_mouse] = true
        reset_search
      end
    end
  end


  # Whenever the user edits the grid,
  # The search has to be reset_searchd upto the current step
  # with the current grid as the initial state of the grid
  def reset_search
    # Reset_Searchs the search
    search.frontier  = []
    search.came_from = {}
    search.path      = {}
  end


  # Returns a list of adjacent cells
  # Used to determine what the next cells to be added to the frontier are
  def adjacent_neighbors(cell)
    neighbors = []

    # Gets all the valid neighbors into the array
    # From southern neighbor, clockwise
    neighbors << [cell.x, cell.y - 1] unless cell.y == 0
    neighbors << [cell.x - 1, cell.y] unless cell.x == 0
    neighbors << [cell.x, cell.y + 1] unless cell.y == grid.height - 1
    neighbors << [cell.x + 1, cell.y] unless cell.x == grid.width - 1

    # Sorts the neighbors so the rendered path is a zigzag path
    # Cells in a diagonal direction are given priority
    # Comment this line to see the difference
    neighbors = neighbors.sort_by { |neighbor_x, neighbor_y|  proximity_to_star(neighbor_x, neighbor_y) }

    neighbors
  end

  # Finds the vertical and horizontal distance of a cell from the star
  # and returns the larger value
  # This method is used to have a zigzag pattern in the rendered path
  # A cell that is [5, 5] from the star,
  # is explored before over a cell that is [0, 7] away.
  # So, if possible, the search tries to go diagonal (zigzag) first
  def proximity_to_star(x, y)
    distance_x = (grid.star.x - x).abs
    distance_y = (grid.star.y - y).abs

    if distance_x > distance_y
      return distance_x
    else
      return distance_y
    end
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse helps with this
  def cell_closest_to_mouse
    # Closest cell to the mouse in the first grid
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Bound x and y to the grid
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  # Signal that the user is going to be moving the star from the first grid
  def star_clicked?
    inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(grid.star))
  end

  # Signal that the user is going to be moving the target from the first grid
  def target_clicked?
    inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(grid.target))
  end

  # Signal that the user is going to be adding walls from the first grid
  def grid_clicked?
    inputs.mouse.down && mouse_inside_grid?
  end

  # Returns whether the mouse is inside of the first grid
  # Part of the condition that checks whether the user is adding a wall
  def mouse_inside_grid?
    inputs.mouse.point.inside_rect?(scale_up(grid.rect))
  end

  # These methods provide handy aliases to colors

  # Light brown
  def unvisited_color
    { r: 221, g: 212, b: 213 }
  end

  # Camo Green
  def wall_color
    { r: 134, g: 134, b: 120 }
  end

  # Pastel White
  def path_color
    [231, 230, 228]
  end

  def red
    [255, 0, 0]
  end

  def purple
    [149, 64, 191]
  end

  # Makes code more concise
  def grid
    state.grid
  end

  def search
    state.search
  end
end

# Method that is called by DragonRuby periodically
# Used for updating animations and calculations
def tick args

  # Pressing r will reset the application
  if args.inputs.keyboard.key_down.r
    args.gtk.reset
    reset
    return
  end

  # Every tick, new args are passed, and the Breadth First Search tick is called
  $breadcrumbs ||= Breadcrumbs.new
  $breadcrumbs.args = args
  $breadcrumbs.tick
end


def reset
  $breadcrumbs = nil
end

 #  # Representation of how far away visited cells are from the star
 #  # Replaces the render_visited method
 #  # Visually demonstrates the effectiveness of early exit for pathfinding
 #  def render_heat_map
 #    # THIS CODE NEEDS SOME FIXING DUE TO REFACTORING
 #    search.came_from.each_key do | cell |
 #      distance = (grid.star.x - visited_cell.x).abs + (state.star.y - visited_cell.y).abs
 #      max_distance = grid.width + grid.height
 #      alpha = 255.to_i * distance.to_i / max_distance.to_i
 #      outputs.solids << [scale_up(visited_cell), red, alpha]
 #      # outputs.solids << [early_exit_scale_up(visited_cell), red, alpha]
 #    end
 #  end

Path Finding Algorithms - Early Exit - main.rb

# ./samples/13_path_finding_algorithms/04_early_exit/app/main.rb
# Contributors outside of DragonRuby who also hold Copyright:
# - Sujay Vadlakonda: https://github.com/sujayvadlakonda

# Comparison of a breadth first search with and without early exit
# Inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html

# Demonstrates the exploration difference caused by early exit
# Also demonstrates how breadth first search is used for path generation

# The left grid is a breadth first search without early exit
# The right grid is a breadth first search with early exit
# The red squares represent how far the search expanded
# The darker the red, the farther the search proceeded
# Comparison of the heat map reveals how much searching can be saved by early exit
# The white path shows path generation via breadth first search
class EarlyExitBreadthFirstSearch
  attr_gtk

  # This method is called every frame/tick
  # Every tick, the current state of the search is rendered on the screen,
  # User input is processed, and
  # The next step in the search is calculated
  def tick
    defaults
    # If the grid has not been searched
    if state.visited.empty?
      # Complete the search
      state.max_steps.times { step }
      # And calculate the path
      calc_path
    end
    render
    input
  end

  def defaults
    # Variables to edit the size and appearance of the grid
    # Freely customizable to user's liking
    grid.width     ||= 15
    grid.height    ||= 15
    grid.cell_size ||= 40
    grid.rect      ||= [0, 0, grid.width, grid.height]

    # At some step the animation will end,
    # and further steps won't change anything (the whole grid.widthill be explored)
    # This step is roughly the grid's width * height
    # When anim_steps equals max_steps no more calculations will occur
    # and the slider will be at the end
    state.max_steps  ||= args.state.grid.width * args.state.grid.height

    # The location of the star and walls of the grid
    # They can be modified to have a different initial grid
    # Walls are stored in a hash for quick look up when doing the search
    state.star   ||= [2, 8]
    state.target ||= [10, 5]
    state.walls  ||= {}

    # Variables that are used by the breadth first search
    # Storing cells that the search has visited, prevents unnecessary steps
    # Expanding the frontier of the search in order makes the search expand
    # from the center outward

    # Visited cells in the first grid
    state.visited               ||= {}
    # Visited cells in the second grid
    state.early_exit_visited    ||= {}
    # The cells from which the search is to expand
    state.frontier              ||= []
    # A hash of where each cell was expanded from
    # The key is a cell, and the value is the cell it came from
    state.came_from             ||= {}
    # Cells that are part of the path from the target to the star
    state.path                  ||= {}

    # What the user is currently editing on the grid
    # We store this value, because we want to remember the value even when
    # the user's cursor is no longer over what they're interacting with, but
    # they are still clicking down on the mouse.
    state.current_input ||= :none
  end

  # Draws everything onto the screen
  def render
    render_background
    render_heat_map
    render_walls
    render_path
    render_star
    render_target
    render_labels
  end

  # The methods below subdivide the task of drawing everything to the screen

  # Draws what the grid looks like with nothing on it
  def render_background
    render_unvisited
    render_grid_lines
  end

  # Draws both grids
  def render_unvisited
    outputs.solids << scale_up(grid.rect).merge(unvisited_color)
    outputs.solids << early_exit_scale_up(grid.rect).merge(unvisited_color)
  end

  # Draws grid lines to show the division of the grid into cells
  def render_grid_lines
    outputs.lines << (0..grid.width).map { |x| vertical_line(x) }
    outputs.lines << (0..grid.width).map { |x| early_exit_vertical_line(x) }
    outputs.lines << (0..grid.height).map { |y| horizontal_line(y) }
    outputs.lines << (0..grid.height).map { |y| early_exit_horizontal_line(y) }
  end

  # Easy way to draw vertical lines given an index
  def vertical_line x
    line = { x: x, y: 0, w: 0, h: grid.height }
    line.transform_values { |v| v * grid.cell_size }
  end

  # Easy way to draw horizontal lines given an index
  def horizontal_line y
    line = { x: 0, y: y, w: grid.width, h: 0 }
    line.transform_values { |v| v * grid.cell_size }
  end

  # Easy way to draw vertical lines given an index
  def early_exit_vertical_line x
    vertical_line(x + grid.width + 1)
  end

  # Easy way to draw horizontal lines given an index
  def early_exit_horizontal_line y
    line = { x: grid.width + 1, y: y, w: grid.width, h: 0 }
    line.transform_values { |v| v * grid.cell_size }
  end

  # Draws the walls on both grids
  def render_walls
    state.walls.each_key do |wall|
      outputs.solids << scale_up(wall).merge(wall_color)
      outputs.solids << early_exit_scale_up(wall).merge(wall_color)
    end
  end

  # Renders the star on both grids
  def render_star
    outputs.sprites << scale_up(state.star).merge({path: 'star.png'})
    outputs.sprites << early_exit_scale_up(state.star).merge({path: 'star.png'})
  end

  # Renders the target on both grids
  def render_target
    outputs.sprites << scale_up(state.target).merge({path: 'target.png'})
    outputs.sprites << early_exit_scale_up(state.target).merge({path: 'target.png'})
  end

  # Labels the grids
  def render_labels
    outputs.labels << [200, 625, "Without early exit"]
    outputs.labels << [875, 625, "With early exit"]
  end

  # Renders the path based off of the state.path hash
  def render_path
    # If the star and target are disconnected there will only be one path
    # The path should not render in that case
    unless state.path.size == 1
      state.path.each_key do | cell |
        # Renders path on both grids
        outputs.solids << scale_up(cell).merge(path_color)
        outputs.solids << early_exit_scale_up(cell).merge(path_color)
      end
    end
  end

  # Calculates the path from the target to the star after the search is over
  # Relies on the came_from hash
  # Fills the state.path hash, which is later rendered on screen
  def calc_path
    endpoint = state.target
    while endpoint
      state.path[endpoint] = true
      endpoint = state.came_from[endpoint]
    end
  end

  # Representation of how far away visited cells are from the star
  # Replaces the render_visited method
  # Visually demonstrates the effectiveness of early exit for pathfinding
  def render_heat_map
    state.visited.each_key do | visited_cell |
      distance = (state.star.x - visited_cell.x).abs + (state.star.y - visited_cell.y).abs
      max_distance = grid.width + grid.height
      alpha = 255.to_i * distance.to_i / max_distance.to_i
      heat_color = red.merge({a: alpha })
      outputs.solids << scale_up(visited_cell).merge(heat_color)
    end

    state.early_exit_visited.each_key do | visited_cell |
      distance = (state.star.x - visited_cell.x).abs + (state.star.y - visited_cell.y).abs
      max_distance = grid.width + grid.height
      alpha = 255.to_i * distance.to_i / max_distance.to_i
      heat_color = red.merge({a: alpha })
      outputs.solids << early_exit_scale_up(visited_cell).merge(heat_color)
    end
  end

  # Translates the given cell grid.width + 1 to the right and then scales up
  # Used to draw cells for the second grid
  # This method does not work for lines,
  # so separate methods exist for the grid lines
  def early_exit_scale_up(cell)
    cell_clone = cell.clone
    cell_clone.x += grid.width + 1
    scale_up(cell_clone)
  end

  # In code, the cells are represented as 1x1 rectangles
  # When drawn, the cells are larger than 1x1 rectangles
  # This method is used to scale up cells, and lines
  # Objects are scaled up according to the grid.cell_size variable
  # This allows for easy customization of the visual scale of the grid
  def scale_up(cell)
    if cell.size == 2
      return {
        x: cell.x * grid.cell_size,
        y: cell.y * grid.cell_size,
        w: grid.cell_size,
        h: grid.cell_size
      }
    else
      return {
        x: cell.x * grid.cell_size,
        y: cell.y * grid.cell_size,
        w: cell.w * grid.cell_size,
        h: cell.h * grid.cell_size
      }
    end
  end

  # This method processes user input every tick
  # Any method with "1" is related to the first grid
  # Any method with "2" is related to the second grid
  def input
    # The program has to remember that the user is dragging an object
    # even when the mouse is no longer over that object
    # So detecting input and processing input is separate
    detect_input
    process_input
  end

  # Determines what the user is editing and stores the value
  # Storing the value allows the user to continue the same edit as long as the
  # mouse left click is held
  def detect_input
    # When the mouse is up, nothing is being edited
    if inputs.mouse.up
      state.current_input = :none
    # When the star in the no second grid is clicked
    elsif star_clicked?
      state.current_input = :star
    # When the star in the second grid is clicked
    elsif star2_clicked?
      state.current_input = :star2
    # When the target in the no second grid is clicked
    elsif target_clicked?
      state.current_input = :target
    # When the target in the second grid is clicked
    elsif target2_clicked?
      state.current_input = :target2
    # When a wall in the first grid is clicked
    elsif wall_clicked?
      state.current_input = :remove_wall
    # When a wall in the second grid is clicked
    elsif wall2_clicked?
      state.current_input = :remove_wall2
    # When the first grid is clicked
    elsif grid_clicked?
      state.current_input = :add_wall
    # When the second grid is clicked
    elsif grid2_clicked?
      state.current_input = :add_wall2
    end
  end

  # Processes click and drag based on what the user is currently dragging
  def process_input
    if state.current_input == :star
      input_star
    elsif state.current_input == :star2
      input_star2
    elsif state.current_input == :target
      input_target
    elsif state.current_input == :target2
      input_target2
    elsif state.current_input == :remove_wall
      input_remove_wall
    elsif state.current_input == :remove_wall2
      input_remove_wall2
    elsif state.current_input == :add_wall
      input_add_wall
    elsif state.current_input == :add_wall2
      input_add_wall2
    end
  end

  # Moves the star to the cell closest to the mouse in the first grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def input_star
    old_star = state.star.clone
    state.star = cell_closest_to_mouse
    unless old_star == state.star
      reset_search
    end
  end

  # Moves the star to the cell closest to the mouse in the second grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def input_star2
    old_star = state.star.clone
    state.star = cell_closest_to_mouse2
    unless old_star == state.star
      reset_search
    end
  end

  # Moves the target to the grid closest to the mouse in the first grid
  # Only reset_searchs the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def input_target
    old_target = state.target.clone
    state.target = cell_closest_to_mouse
    unless old_target == state.target
      reset_search
    end
  end

  # Moves the target to the cell closest to the mouse in the second grid
  # Only reset_searchs the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def input_target2
    old_target = state.target.clone
    state.target = cell_closest_to_mouse2
    unless old_target == state.target
      reset_search
    end
  end

  # Removes walls in the first grid that are under the cursor
  def input_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if mouse_inside_grid?
      if state.walls.key?(cell_closest_to_mouse)
        state.walls.delete(cell_closest_to_mouse)
        reset_search
      end
    end
  end

  # Removes walls in the second grid that are under the cursor
  def input_remove_wall2
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if mouse_inside_grid2?
      if state.walls.key?(cell_closest_to_mouse2)
        state.walls.delete(cell_closest_to_mouse2)
        reset_search
      end
    end
  end

  # Adds a wall in the first grid in the cell the mouse is over
  def input_add_wall
    if mouse_inside_grid?
      unless state.walls.key?(cell_closest_to_mouse)
        state.walls[cell_closest_to_mouse] = true
        reset_search
      end
    end
  end


  # Adds a wall in the second grid in the cell the mouse is over
  def input_add_wall2
    if mouse_inside_grid2?
      unless state.walls.key?(cell_closest_to_mouse2)
        state.walls[cell_closest_to_mouse2] = true
        reset_search
      end
    end
  end

  # Whenever the user edits the grid,
  # The search has to be reset_searchd upto the current step
  # with the current grid as the initial state of the grid
  def reset_search
    # Reset_Searchs the search
    state.frontier  = []
    state.visited   = {}
    state.early_exit_visited   = {}
    state.came_from = {}
    state.path      = {}
  end

  # Moves the search forward one step
  def step
    # The setup to the search
    # Runs once when there are no visited cells
    if state.visited.empty?
      state.visited[state.star] = true
      state.early_exit_visited[state.star] = true
      state.frontier << state.star
      state.came_from[state.star] = nil
    end

    # A step in the search
    unless state.frontier.empty?
      # Takes the next frontier cell
      new_frontier = state.frontier.shift
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do |neighbor|
        # That have not been visited and are not walls
        unless state.visited.key?(neighbor) || state.walls.key?(neighbor)
          # Add them to the frontier and mark them as visited in the first grid
          state.visited[neighbor] = true
          # Unless the target has been visited
          unless state.visited.key?(state.target)
            # Mark the neighbor as visited in the second grid as well
            state.early_exit_visited[neighbor] = true
          end

          # Add the neighbor to the frontier and remember which cell it came from
          state.frontier << neighbor
          state.came_from[neighbor] = new_frontier
        end
      end
    end
  end


  # Returns a list of adjacent cells
  # Used to determine what the next cells to be added to the frontier are
  def adjacent_neighbors(cell)
    neighbors = []

    # Gets all the valid neighbors into the array
    # From southern neighbor, clockwise
    neighbors << [cell.x, cell.y - 1] unless cell.y == 0
    neighbors << [cell.x - 1, cell.y] unless cell.x == 0
    neighbors << [cell.x, cell.y + 1] unless cell.y == grid.height - 1
    neighbors << [cell.x + 1, cell.y] unless cell.x == grid.width - 1

    # Sorts the neighbors so the rendered path is a zigzag path
    # Cells in a diagonal direction are given priority
    # Comment this line to see the difference
    neighbors = neighbors.sort_by { |neighbor_x, neighbor_y|  proximity_to_star(neighbor_x, neighbor_y) }

    neighbors
  end

  # Finds the vertical and horizontal distance of a cell from the star
  # and returns the larger value
  # This method is used to have a zigzag pattern in the rendered path
  # A cell that is [5, 5] from the star,
  # is explored before over a cell that is [0, 7] away.
  # So, if possible, the search tries to go diagonal (zigzag) first
  def proximity_to_star(x, y)
    distance_x = (state.star.x - x).abs
    distance_y = (state.star.y - y).abs

    if distance_x > distance_y
      return distance_x
    else
      return distance_y
    end
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse helps with this
  def cell_closest_to_mouse
    # Closest cell to the mouse in the first grid
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Bound x and y to the grid
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse in the second grid helps with this
  def cell_closest_to_mouse2
    # Closest cell grid to the mouse in the second
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Translate the cell to the first grid
    x -= grid.width + 1
    # Bound x and y to the first grid
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  # Signal that the user is going to be moving the star from the first grid
  def star_clicked?
    inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(state.star))
  end

  # Signal that the user is going to be moving the star from the second grid
  def star2_clicked?
    inputs.mouse.down && inputs.mouse.point.inside_rect?(early_exit_scale_up(state.star))
  end

  # Signal that the user is going to be moving the target from the first grid
  def target_clicked?
    inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(state.target))
  end

  # Signal that the user is going to be moving the target from the second grid
  def target2_clicked?
    inputs.mouse.down && inputs.mouse.point.inside_rect?(early_exit_scale_up(state.target))
  end

  # Signal that the user is going to be removing walls from the first grid
  def wall_clicked?
    inputs.mouse.down && mouse_inside_wall?
  end

  # Signal that the user is going to be removing walls from the second grid
  def wall2_clicked?
    inputs.mouse.down && mouse_inside_wall2?
  end

  # Signal that the user is going to be adding walls from the first grid
  def grid_clicked?
    inputs.mouse.down && mouse_inside_grid?
  end

  # Signal that the user is going to be adding walls from the second grid
  def grid2_clicked?
    inputs.mouse.down && mouse_inside_grid2?
  end

  # Returns whether the mouse is inside of a wall in the first grid
  # Part of the condition that checks whether the user is removing a wall
  def mouse_inside_wall?
    state.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(scale_up(wall))
    end

    false
  end

  # Returns whether the mouse is inside of a wall in the second grid
  # Part of the condition that checks whether the user is removing a wall
  def mouse_inside_wall2?
    state.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(early_exit_scale_up(wall))
    end

    false
  end

  # Returns whether the mouse is inside of the first grid
  # Part of the condition that checks whether the user is adding a wall
  def mouse_inside_grid?
    inputs.mouse.point.inside_rect?(scale_up(grid.rect))
  end

  # Returns whether the mouse is inside of the second grid
  # Part of the condition that checks whether the user is adding a wall
  def mouse_inside_grid2?
    inputs.mouse.point.inside_rect?(early_exit_scale_up(grid.rect))
  end

  # These methods provide handy aliases to colors

  # Light brown
  def unvisited_color
    [221, 212, 213]
    { r: 221, g: 212, b: 213 }
  end

  # Camo Green
  def wall_color
    { r: 134, g: 134, b: 120 }
  end

  # Pastel White
  def path_color
    { r: 231, g: 230, b: 228 }
  end

  def red
    { r: 255, g: 0, b: 0 }
  end

  # Makes code more concise
  def grid
    state.grid
  end
end

# Method that is called by DragonRuby periodically
# Used for updating animations and calculations
def tick args

  # Pressing r will reset the application
  if args.inputs.keyboard.key_down.r
    args.gtk.reset
    reset
    return
  end

  # Every tick, new args are passed, and the Breadth First Search tick is called
  $early_exit_breadth_first_search ||= EarlyExitBreadthFirstSearch.new
  $early_exit_breadth_first_search.args = args
  $early_exit_breadth_first_search.tick
end


def reset
  $early_exit_breadth_first_search = nil
end

Path Finding Algorithms - Dijkstra - main.rb

# ./samples/13_path_finding_algorithms/05_dijkstra/app/main.rb
# Contributors outside of DragonRuby who also hold Copyright:
# - Sujay Vadlakonda: https://github.com/sujayvadlakonda

# Demonstrates how Dijkstra's Algorithm allows movement costs to be considered

# Inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html

# The first grid is a breadth first search with an early exit.
# It shows a heat map of all the cells that were visited by the search and their relative distance.

# The second grid is an implementation of Dijkstra's algorithm.
# Light green cells have 5 times the movement cost of regular cells.
# The heat map will darken based on movement cost.

# Dark green cells are walls, and the search cannot go through them.
class Movement_Costs
  attr_gtk

  # This method is called every frame/tick
  # Every tick, the current state of the search is rendered on the screen,
  # User input is processed, and
  # The next step in the search is calculated
  def tick
    defaults
    render
    input
    calc
  end

  def defaults
    # Variables to edit the size and appearance of the grid
    # Freely customizable to user's liking
    grid.width     ||= 10
    grid.height    ||= 10
    grid.cell_size ||= 60
    grid.rect      ||= [0, 0, grid.width, grid.height]

    # The location of the star and walls of the grid
    # They can be modified to have a different initial grid
    # Walls are stored in a hash for quick look up when doing the search
    state.star   ||= [1, 5]
    state.target ||= [8, 4]
    state.walls  ||= {[1, 1] => true, [2, 1] => true, [3, 1] => true, [1, 2] => true, [2, 2] => true, [3, 2] => true}
    state.hills  ||= {
      [4, 1] => true,
      [5, 1] => true,
      [4, 2] => true,
      [5, 2] => true,
      [6, 2] => true,
      [4, 3] => true,
      [5, 3] => true,
      [6, 3] => true,
      [3, 4] => true,
      [4, 4] => true,
      [5, 4] => true,
      [6, 4] => true,
      [7, 4] => true,
      [3, 5] => true,
      [4, 5] => true,
      [5, 5] => true,
      [6, 5] => true,
      [7, 5] => true,
      [4, 6] => true,
      [5, 6] => true,
      [6, 6] => true,
      [7, 6] => true,
      [4, 7] => true,
      [5, 7] => true,
      [6, 7] => true,
      [4, 8] => true,
      [5, 8] => true,
    }

    # What the user is currently editing on the grid
    # We store this value, because we want to remember the value even when
    # the user's cursor is no longer over what they're interacting with, but
    # they are still clicking down on the mouse.
    state.user_input ||= :none

    # Values that are used for the breadth first search
    # Keeping track of what cells were visited prevents counting cells multiple times
    breadth_first_search.visited    ||= {}
    # The cells from which the breadth first search will expand
    breadth_first_search.frontier   ||= []
    # Keeps track of which cell all cells were searched from
    # Used to recreate the path from the target to the star
    breadth_first_search.came_from  ||= {}

    # Keeps track of the movement cost so far to be at a cell
    # Allows the costs of new cells to be quickly calculated
    # Also doubles as a way to check if cells have already been visited
    dijkstra_search.cost_so_far ||= {}
    # The cells from which the Dijkstra search will expand
    dijkstra_search.frontier    ||= []
    # Keeps track of which cell all cells were searched from
    # Used to recreate the path from the target to the star
    dijkstra_search.came_from   ||= {}
  end

  # Draws everything onto the screen
  def render
    render_background

    render_heat_maps

    render_star
    render_target
    render_hills
    render_walls

    render_paths
  end
  # The methods below subdivide the task of drawing everything to the screen

  # Draws what the grid looks like with nothing on it
  def render_background
    render_unvisited
    render_grid_lines
    render_labels
  end

  # Draws two rectangles the size of the grid in the default cell color
  # Used as part of the background
  def render_unvisited
    outputs.solids << scale_up(grid.rect).merge(unvisited_color)
    outputs.solids << move_and_scale_up(grid.rect).merge(unvisited_color)
  end

  # Draws grid lines to show the division of the grid into cells
  def render_grid_lines
    outputs.lines << (0..grid.width).map { |x| vertical_line(x) }
    outputs.lines << (0..grid.width).map { |x| shifted_vertical_line(x) }
    outputs.lines << (0..grid.height).map { |y| horizontal_line(y) }
    outputs.lines << (0..grid.height).map { |y| shifted_horizontal_line(y) }
  end

  # A line the size of the grid, multiplied by the cell size for rendering
  def vertical_line x
    line = { x: x, y: 0, w: 0, h: grid.height }
    line.transform_values { |v| v * grid.cell_size }
  end

  # A line the size of the grid, multiplied by the cell size for rendering
  def horizontal_line y
    line = { x: 0, y: y, w: grid.width, h: 0 }
    line.transform_values { |v| v * grid.cell_size }
  end

  # Translate vertical line by the size of the grid and 1
  def shifted_vertical_line x
    vertical_line(x + grid.width + 1)
  end

  # Get horizontal line and shift to the right
  def shifted_horizontal_line y
    line = { x: grid.width + 1, y: y, w: grid.width, h: 0 }
    line.transform_values { |v| v * grid.cell_size }
  end

  # Labels the grids
  def render_labels
    outputs.labels << [175, 650, "Number of steps", 3]
    outputs.labels << [925, 650, "Distance", 3]
  end

  def render_paths
    render_breadth_first_search_path
    render_dijkstra_path
  end

  def render_heat_maps
    render_breadth_first_search_heat_map
    render_dijkstra_heat_map
  end

  # This heat map shows the cells explored by the breadth first search and how far they are from the star.
  def render_breadth_first_search_heat_map
    # For each cell explored
    breadth_first_search.visited.each_key do | visited_cell |
      # Find its distance from the star
      distance = (state.star.x - visited_cell.x).abs + (state.star.y - visited_cell.y).abs
      max_distance = grid.width + grid.height
      # Get it as a percent of the maximum distance and scale to 255 for use as an alpha value
      alpha = 255.to_i * distance.to_i / max_distance.to_i
      heat_color = red.merge({a: alpha })
      outputs.solids << scale_up(visited_cell).merge(heat_color)
    end
  end

  def render_breadth_first_search_path
    # If the search found the target
    if breadth_first_search.visited.has_key?(state.target)
      # Start from the target
      endpoint = state.target
      # And the cell it came from
      next_endpoint = breadth_first_search.came_from[endpoint]
      while endpoint && next_endpoint
        # Draw a path between these two cells
        path = get_path_between(endpoint, next_endpoint)
        outputs.solids << scale_up(path).merge(path_color)
        # And get the next pair of cells
        endpoint = next_endpoint
        next_endpoint = breadth_first_search.came_from[endpoint]
        # Continue till there are no more cells
      end
    end
  end

  def render_dijkstra_heat_map
    dijkstra_search.cost_so_far.each do |visited_cell, cost|
      max_cost = (grid.width + grid.height) #* 5
      alpha = 255.to_i * cost.to_i / max_cost.to_i
      heat_color = red.merge({a: alpha})
      outputs.solids << move_and_scale_up(visited_cell).merge(heat_color)
    end
  end

  def render_dijkstra_path
    # If the search found the target
    if dijkstra_search.came_from.has_key?(state.target)
      # Get the target and the cell it came from
      endpoint = state.target
      next_endpoint = dijkstra_search.came_from[endpoint]
      while endpoint && next_endpoint
        # Draw a path between them
        path = get_path_between(endpoint, next_endpoint)
        outputs.solids << move_and_scale_up(path).merge(path_color)

        # Shift one cell down the path
        endpoint = next_endpoint
        next_endpoint = dijkstra_search.came_from[endpoint]

        # Repeat till the end of the path
      end
    end
  end

  # Renders the star on both grids
  def render_star
    outputs.sprites << scale_up(state.star).merge({path: 'star.png'})
    outputs.sprites << move_and_scale_up(state.star).merge({path: 'star.png'})
  end

  # Renders the target on both grids
  def render_target
    outputs.sprites << scale_up(state.target).merge({path: 'target.png'})
    outputs.sprites << move_and_scale_up(state.target).merge({path: 'target.png'})
  end

  def render_hills
    state.hills.each_key do |hill|
      outputs.solids << scale_up(hill).merge(hill_color)
      outputs.solids << move_and_scale_up(hill).merge(hill_color)
    end
  end

  # Draws the walls on both grids
  def render_walls
    state.walls.each_key do |wall|
      outputs.solids << scale_up(wall).merge(wall_color)
      outputs.solids << move_and_scale_up(wall).merge(wall_color)
    end
  end

  def get_path_between(cell_one, cell_two)
    path = nil
    if cell_one.x == cell_two.x
      if cell_one.y < cell_two.y
        path = [cell_one.x + 0.3, cell_one.y + 0.3, 0.4, 1.4]
      else
        path = [cell_two.x + 0.3, cell_two.y + 0.3, 0.4, 1.4]
      end
    else
      if cell_one.x < cell_two.x
        path = [cell_one.x + 0.3, cell_one.y + 0.3, 1.4, 0.4]
      else
        path = [cell_two.x + 0.3, cell_two.y + 0.3, 1.4, 0.4]
      end
    end
    path
  end

  # Translates the given cell grid.width + 1 to the right and then scales up
  # Used to draw cells for the second grid
  # This method does not work for lines,
  # so separate methods exist for the grid lines
  def move_and_scale_up(cell)
    cell_clone = cell.clone
    cell_clone.x += grid.width + 1
    scale_up(cell_clone)
  end

  # In code, the cells are represented as 1x1 rectangles
  # When drawn, the cells are larger than 1x1 rectangles
  # This method is used to scale up cells, and lines
  # Objects are scaled up according to the grid.cell_size variable
  # This allows for easy customization of the visual scale of the grid
  def scale_up(cell)
    if cell.size == 2
      return {
        x: cell.x * grid.cell_size,
        y: cell.y * grid.cell_size,
        w: grid.cell_size,
        h: grid.cell_size
      }
    else
      return {
        x: cell.x * grid.cell_size,
        y: cell.y * grid.cell_size,
        w: cell.w * grid.cell_size,
        h: cell.h * grid.cell_size
      }
    end
  end

  # Handles user input every tick so the grid can be edited
  # Separate input detection and processing is needed
  # For example: Adding walls is started by clicking down on a hill,
  # but the mouse doesn't need to remain over hills to add walls
  def input
    # If the mouse was lifted this tick
    if inputs.mouse.up
      # Set current input to none
      state.user_input = :none
    end

    # If the mouse was clicked this tick
    if inputs.mouse.down
      # Determine what the user is editing and edit the state.user_input variable
      determine_input
    end

    # Process user input based on user_input variable and current mouse position
    process_input
  end

  # Determines what the user is editing and stores the value
  # This method is called the tick the mouse is clicked
  # Storing the value allows the user to continue the same edit as long as the
  # mouse left click is held
  def determine_input
    # If the mouse is over the star in the first grid
    if mouse_over_star?
      # The user is editing the star from the first grid
      state.user_input = :star
    # If the mouse is over the star in the second grid
    elsif mouse_over_star2?
      # The user is editing the star from the second grid
      state.user_input = :star2
    # If the mouse is over the target in the first grid
    elsif mouse_over_target?
      # The user is editing the target from the first grid
      state.user_input = :target
    # If the mouse is over the target in the second grid
    elsif mouse_over_target2?
      # The user is editing the target from the second grid
      state.user_input = :target2
    # If the mouse is over a wall in the first grid
    elsif mouse_over_wall?
      # The user is removing a wall from the first grid
      state.user_input = :remove_wall
    # If the mouse is over a wall in the second grid
    elsif mouse_over_wall2?
      # The user is removing a wall from the second grid
      state.user_input = :remove_wall2
    # If the mouse is over a hill in the first grid
    elsif mouse_over_hill?
      # The user is adding a wall from the first grid
      state.user_input = :add_wall
    # If the mouse is over a hill in the second grid
    elsif mouse_over_hill2?
      # The user is adding a wall from the second grid
      state.user_input = :add_wall2
    # If the mouse is over the first grid
    elsif mouse_over_grid?
      # The user is adding a hill from the first grid
      state.user_input = :add_hill
    # If the mouse is over the second grid
    elsif mouse_over_grid2?
      # The user is adding a hill from the second grid
      state.user_input = :add_hill2
    end
  end

  # Processes click and drag based on what the user is currently dragging
  def process_input
    if state.user_input == :star
      input_star
    elsif state.user_input == :star2
      input_star2
    elsif state.user_input == :target
      input_target
    elsif state.user_input == :target2
      input_target2
    elsif state.user_input == :remove_wall
      input_remove_wall
    elsif state.user_input == :remove_wall2
      input_remove_wall2
    elsif state.user_input == :add_hill
      input_add_hill
    elsif state.user_input == :add_hill2
      input_add_hill2
    elsif state.user_input == :add_wall
      input_add_wall
    elsif state.user_input == :add_wall2
      input_add_wall2
    end
  end

  # Calculates the two searches
  def calc
    # If the searches have not started
    if breadth_first_search.visited.empty?
      # Calculate the two searches
      calc_breadth_first
      calc_dijkstra
    end
  end


  def calc_breadth_first
    # Sets up the Breadth First Search
    breadth_first_search.visited[state.star]   = true
    breadth_first_search.frontier              << state.star
    breadth_first_search.came_from[state.star] = nil

    until breadth_first_search.frontier.empty?
      return if breadth_first_search.visited.key?(state.target)
      # A step in the search
      # Takes the next frontier cell
      new_frontier = breadth_first_search.frontier.shift
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do | neighbor |
        # That have not been visited and are not walls
        unless breadth_first_search.visited.key?(neighbor) || state.walls.key?(neighbor)
          # Add them to the frontier and mark them as visited in the first grid
          breadth_first_search.visited[neighbor] = true
          breadth_first_search.frontier << neighbor
          # Remember which cell the neighbor came from
          breadth_first_search.came_from[neighbor] = new_frontier
        end
      end
    end
  end

  # Calculates the Dijkstra Search from the beginning to the end

  def calc_dijkstra
    # The initial values for the Dijkstra search
    dijkstra_search.frontier                << [state.star, 0]
    dijkstra_search.came_from[state.star]   = nil
    dijkstra_search.cost_so_far[state.star] = 0

    # Until their are no more cells to be explored
    until dijkstra_search.frontier.empty?
      # Get the next cell to be explored from
      # We get the first element of the array which is the cell. The second element is the priority.
      current = dijkstra_search.frontier.shift[0]

      # Stop the search if we found the target
      return if current == state.target

      # For each of the neighbors
      adjacent_neighbors(current).each do | neighbor |
        # Unless this cell is a wall or has already been explored.
        unless dijkstra_search.came_from.key?(neighbor) or state.walls.key?(neighbor)
          # Calculate the movement cost of getting to this cell and memo
          new_cost = dijkstra_search.cost_so_far[current] + cost(neighbor)
          dijkstra_search.cost_so_far[neighbor] = new_cost

          # Add this neighbor to the cells too be explored
          dijkstra_search.frontier << [neighbor, new_cost]
          dijkstra_search.came_from[neighbor] = current
        end
      end

      # Sort the frontier so exploration occurs that have a low cost so far.
      # My implementation of a priority queue
      dijkstra_search.frontier = dijkstra_search.frontier.sort_by {|cell, priority| priority}
    end
  end

  def cost(cell)
    return 5 if state.hills.key? cell
    1
  end




  # Moves the star to the cell closest to the mouse in the first grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def input_star
    old_star = state.star.clone
    unless cell_closest_to_mouse == state.target
      state.star = cell_closest_to_mouse
    end
    unless old_star == state.star
      reset_search
    end
  end

  # Moves the star to the cell closest to the mouse in the second grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def input_star2
    old_star = state.star.clone
    unless cell_closest_to_mouse2 == state.target
      state.star = cell_closest_to_mouse2
    end
    unless old_star == state.star
      reset_search
    end
  end

  # Moves the target to the grid closest to the mouse in the first grid
  # Only reset_searchs the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def input_target
    old_target = state.target.clone
    unless cell_closest_to_mouse == state.star
      state.target = cell_closest_to_mouse
    end
    unless old_target == state.target
      reset_search
    end
  end

  # Moves the target to the cell closest to the mouse in the second grid
  # Only reset_searchs the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def input_target2
    old_target = state.target.clone
    unless cell_closest_to_mouse2 == state.star
      state.target = cell_closest_to_mouse2
    end
    unless old_target == state.target
      reset_search
    end
  end

  # Removes walls in the first grid that are under the cursor
  def input_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if mouse_over_grid?
      if state.walls.key?(cell_closest_to_mouse) or state.hills.key?(cell_closest_to_mouse)
        state.walls.delete(cell_closest_to_mouse)
        state.hills.delete(cell_closest_to_mouse)
        reset_search
      end
    end
  end

  # Removes walls in the second grid that are under the cursor
  def input_remove_wall2
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if mouse_over_grid2?
      if state.walls.key?(cell_closest_to_mouse2) or state.hills.key?(cell_closest_to_mouse2)
        state.walls.delete(cell_closest_to_mouse2)
        state.hills.delete(cell_closest_to_mouse2)
        reset_search
      end
    end
  end

  # Adds a hill in the first grid in the cell the mouse is over
  def input_add_hill
    if mouse_over_grid?
      unless state.hills.key?(cell_closest_to_mouse)
        state.hills[cell_closest_to_mouse] = true
        reset_search
      end
    end
  end


  # Adds a hill in the second grid in the cell the mouse is over
  def input_add_hill2
    if mouse_over_grid2?
      unless state.hills.key?(cell_closest_to_mouse2)
        state.hills[cell_closest_to_mouse2] = true
        reset_search
      end
    end
  end

  # Adds a wall in the first grid in the cell the mouse is over
  def input_add_wall
    if mouse_over_grid?
      unless state.walls.key?(cell_closest_to_mouse)
        state.hills.delete(cell_closest_to_mouse)
        state.walls[cell_closest_to_mouse] = true
        reset_search
      end
    end
  end

  # Adds a wall in the second grid in the cell the mouse is over
  def input_add_wall2
    if mouse_over_grid2?
      unless state.walls.key?(cell_closest_to_mouse2)
        state.hills.delete(cell_closest_to_mouse2)
        state.walls[cell_closest_to_mouse2] = true
        reset_search
      end
    end
  end

  # Whenever the user edits the grid,
  # The search has to be reset_searchd upto the current step
  # with the current grid as the initial state of the grid
  def reset_search
    breadth_first_search.visited    = {}
    breadth_first_search.frontier   = []
    breadth_first_search.came_from  = {}

    dijkstra_search.frontier    = []
    dijkstra_search.came_from   = {}
    dijkstra_search.cost_so_far = {}
  end



  # Returns a list of adjacent cells
  # Used to determine what the next cells to be added to the frontier are
  def adjacent_neighbors(cell)
    neighbors = []

    # Gets all the valid neighbors into the array
    # From southern neighbor, clockwise
    neighbors << [cell.x    , cell.y - 1] unless cell.y == 0
    neighbors << [cell.x - 1, cell.y    ] unless cell.x == 0
    neighbors << [cell.x    , cell.y + 1] unless cell.y == grid.height - 1
    neighbors << [cell.x + 1, cell.y    ] unless cell.x == grid.width - 1

    # Sorts the neighbors so the rendered path is a zigzag path
    # Cells in a diagonal direction are given priority
    # Comment this line to see the difference
    neighbors = neighbors.sort_by { |neighbor_x, neighbor_y|  proximity_to_star(neighbor_x, neighbor_y) }

    neighbors
  end

  # Finds the vertical and horizontal distance of a cell from the star
  # and returns the larger value
  # This method is used to have a zigzag pattern in the rendered path
  # A cell that is [5, 5] from the star,
  # is explored before over a cell that is [0, 7] away.
  # So, if possible, the search tries to go diagonal (zigzag) first
  def proximity_to_star(x, y)
    distance_x = (state.star.x - x).abs
    distance_y = (state.star.y - y).abs

    if distance_x > distance_y
      return distance_x
    else
      return distance_y
    end
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse helps with this
  def cell_closest_to_mouse
    # Closest cell to the mouse in the first grid
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Bound x and y to the grid
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse in the second grid helps with this
  def cell_closest_to_mouse2
    # Closest cell grid to the mouse in the second
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Translate the cell to the first grid
    x -= grid.width + 1
    # Bound x and y to the first grid
    x = 0 if x < 0
    y = 0 if y < 0
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  # Signal that the user is going to be moving the star from the first grid
  def mouse_over_star?
    inputs.mouse.point.inside_rect?(scale_up(state.star))
  end

  # Signal that the user is going to be moving the star from the second grid
  def mouse_over_star2?
    inputs.mouse.point.inside_rect?(move_and_scale_up(state.star))
  end

  # Signal that the user is going to be moving the target from the first grid
  def mouse_over_target?
    inputs.mouse.point.inside_rect?(scale_up(state.target))
  end

  # Signal that the user is going to be moving the target from the second grid
  def mouse_over_target2?
    inputs.mouse.point.inside_rect?(move_and_scale_up(state.target))
  end

  # Signal that the user is going to be removing walls from the first grid
  def mouse_over_wall?
    state.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(scale_up(wall))
    end

    false
  end

  # Signal that the user is going to be removing walls from the second grid
  def mouse_over_wall2?
    state.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(move_and_scale_up(wall))
    end

    false
  end

  # Signal that the user is going to be removing hills from the first grid
  def mouse_over_hill?
    state.hills.each_key do | hill |
      return true if inputs.mouse.point.inside_rect?(scale_up(hill))
    end

    false
  end

  # Signal that the user is going to be removing hills from the second grid
  def mouse_over_hill2?
    state.hills.each_key do | hill |
      return true if inputs.mouse.point.inside_rect?(move_and_scale_up(hill))
    end

    false
  end

  # Signal that the user is going to be adding walls from the first grid
  def mouse_over_grid?
    inputs.mouse.point.inside_rect?(scale_up(grid.rect))
  end

  # Signal that the user is going to be adding walls from the second grid
  def mouse_over_grid2?
    inputs.mouse.point.inside_rect?(move_and_scale_up(grid.rect))
  end

  # These methods provide handy aliases to colors

  # Light brown
  def unvisited_color
    { r: 221, g: 212, b: 213 }
  end

  # Camo Green
  def wall_color
    { r: 134, g: 134, b: 120 }
  end

  # Pastel White
  def path_color
    { r: 231, g: 230, b: 228 }
  end

  def red
    { r: 255, g: 0, b: 0 }
  end

  # A Green
  def hill_color
    { r: 139, g: 173, b: 132 }
  end

  # Makes code more concise
  def grid
    state.grid
  end

  def breadth_first_search
    state.breadth_first_search
  end

  def dijkstra_search
    state.dijkstra_search
  end
end

# Method that is called by DragonRuby periodically
# Used for updating animations and calculations
def tick args

  # Pressing r will reset the application
  if args.inputs.keyboard.key_down.r
    args.gtk.reset
    reset
    return
  end

  # Every tick, new args are passed, and the Dijkstra tick method is called
  $movement_costs ||= Movement_Costs.new
  $movement_costs.args = args
  $movement_costs.tick
end


def reset
  $movement_costs = nil
end

Path Finding Algorithms - Heuristic - main.rb

# ./samples/13_path_finding_algorithms/06_heuristic/app/main.rb
# Contributors outside of DragonRuby who also hold Copyright:
# - Sujay Vadlakonda: https://github.com/sujayvadlakonda

# This program is inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html
# The effectiveness of the Heuristic search algorithm is shown through this demonstration.
# Notice that both searches find the shortest path
# The heuristic search, however, explores less of the grid, and is therefore faster.
# The heuristic search prioritizes searching cells that are closer to the target.
# Make sure to look at the Heuristic with walls program to see some of the downsides of the heuristic algorithm.

class Heuristic
  attr_gtk

  def tick
    defaults
    render
    input
    # If animation is playing, and max steps have not been reached
    # Move the search a step forward
    if state.play && state.current_step < state.max_steps
      # Variable that tells the program what step to recalculate up to
      state.current_step += 1
      move_searches_one_step_forward
    end
  end

  def defaults
    # Variables to edit the size and appearance of the grid
    # Freely customizable to user's liking
    grid.width     ||= 15
    grid.height    ||= 15
    grid.cell_size ||= 40
    grid.rect      ||= [0, 0, grid.width, grid.height]

    grid.star      ||= [0, 2]
    grid.target    ||= [14, 12]
    grid.walls     ||= {}
    # There are no hills in the Heuristic Search Demo

    # What the user is currently editing on the grid
    # We store this value, because we want to remember the value even when
    # the user's cursor is no longer over what they're interacting with, but
    # they are still clicking down on the mouse.
    state.user_input ||= :none

    # These variables allow the breadth first search to take place
    # Came_from is a hash with a key of a cell and a value of the cell that was expanded from to find the key.
    # Used to prevent searching cells that have already been found
    # and to trace a path from the target back to the starting point.
    # Frontier is an array of cells to expand the search from.
    # The search is over when there are no more cells to search from.
    # Path stores the path from the target to the star, once the target has been found
    # It prevents calculating the path every tick.
    bfs.came_from  ||= {}
    bfs.frontier   ||= []
    bfs.path       ||= []

    heuristic.came_from ||= {}
    heuristic.frontier  ||= []
    heuristic.path      ||= []

    # Stores which step of the animation is being rendered
    # When the user moves the star or messes with the walls,
    # the searches are recalculated up to this step
    unless state.current_step
      state.current_step = 0
    end

    # At some step the animation will end,
    # and further steps won't change anything (the whole grid will be explored)
    # This step is roughly the grid's width * height
    # When anim_steps equals max_steps no more calculations will occur
    # and the slider will be at the end
    state.max_steps = grid.width * grid.height

    # Whether the animation should play or not
    # If true, every tick moves anim_steps forward one
    # Pressing the stepwise animation buttons will pause the animation
    # An if statement instead of the ||= operator is used for assigning a boolean value.
    # The || operator does not differentiate between nil and false.
    if state.play == nil
      state.play = false
    end

    # Store the rects of the buttons that control the animation
    # They are here for user customization
    # Editing these might require recentering the text inside them
    # Those values can be found in the render_button methods
    buttons.left   = [470, 600, 50, 50]
    buttons.center = [520, 600, 200, 50]
    buttons.right  = [720, 600, 50, 50]

    # The variables below are related to the slider
    # They allow the user to customize them
    # They also give a central location for the render and input methods to get
    # information from
    # x & y are the coordinates of the leftmost part of the slider line
    slider.x = 440
    slider.y = 675
    # This is the width of the line
    slider.w = 360
    # This is the offset for the circle
    # Allows the center of the circle to be on the line,
    # as opposed to the upper right corner
    slider.offset = 20
    # This is the spacing between each of the notches on the slider
    # Notches are places where the circle can rest on the slider line
    # There needs to be a notch for each step before the maximum number of steps
    slider.spacing = slider.w.to_f / state.max_steps.to_f
  end

  # All methods with render draw stuff on the screen
  # UI has buttons, the slider, and labels
  # The search specific rendering occurs in the respective methods
  def render
    render_ui
    render_bfs
    render_heuristic
  end

  def render_ui
    render_buttons
    render_slider
    render_labels
  end

  def render_buttons
    render_left_button
    render_center_button
    render_right_button
  end

  def render_bfs
    render_bfs_grid
    render_bfs_star
    render_bfs_target
    render_bfs_visited
    render_bfs_walls
    render_bfs_frontier
    render_bfs_path
  end

  def render_heuristic
    render_heuristic_grid
    render_heuristic_star
    render_heuristic_target
    render_heuristic_visited
    render_heuristic_walls
    render_heuristic_frontier
    render_heuristic_path
  end

  # This method handles user input every tick
  def input
    # Check and handle button input
    input_buttons

    # If the mouse was lifted this tick
    if inputs.mouse.up
      # Set current input to none
      state.user_input = :none
    end

    # If the mouse was clicked this tick
    if inputs.mouse.down
      # Determine what the user is editing and appropriately edit the state.user_input variable
      determine_input
    end

    # Process user input based on user_input variable and current mouse position
    process_input
  end

  # Determines what the user is editing
  # This method is called when the mouse is clicked down
  def determine_input
    if mouse_over_slider?
      state.user_input = :slider
    # If the mouse is over the star in the first grid
    elsif bfs_mouse_over_star?
      # The user is editing the star from the first grid
      state.user_input = :bfs_star
    # If the mouse is over the star in the second grid
    elsif heuristic_mouse_over_star?
      # The user is editing the star from the second grid
      state.user_input = :heuristic_star
    # If the mouse is over the target in the first grid
    elsif bfs_mouse_over_target?
      # The user is editing the target from the first grid
      state.user_input = :bfs_target
    # If the mouse is over the target in the second grid
    elsif heuristic_mouse_over_target?
      # The user is editing the target from the second grid
      state.user_input = :heuristic_target
    # If the mouse is over a wall in the first grid
    elsif bfs_mouse_over_wall?
      # The user is removing a wall from the first grid
      state.user_input = :bfs_remove_wall
    # If the mouse is over a wall in the second grid
    elsif heuristic_mouse_over_wall?
      # The user is removing a wall from the second grid
      state.user_input = :heuristic_remove_wall
    # If the mouse is over the first grid
    elsif bfs_mouse_over_grid?
      # The user is adding a wall from the first grid
      state.user_input = :bfs_add_wall
    # If the mouse is over the second grid
    elsif heuristic_mouse_over_grid?
      # The user is adding a wall from the second grid
      state.user_input = :heuristic_add_wall
    end
  end

  # Processes click and drag based on what the user is currently dragging
  def process_input
    if state.user_input == :slider
      process_input_slider
    elsif state.user_input == :bfs_star
      process_input_bfs_star
    elsif state.user_input == :heuristic_star
      process_input_heuristic_star
    elsif state.user_input == :bfs_target
      process_input_bfs_target
    elsif state.user_input == :heuristic_target
      process_input_heuristic_target
    elsif state.user_input == :bfs_remove_wall
      process_input_bfs_remove_wall
    elsif state.user_input == :heuristic_remove_wall
      process_input_heuristic_remove_wall
    elsif state.user_input == :bfs_add_wall
      process_input_bfs_add_wall
    elsif state.user_input == :heuristic_add_wall
      process_input_heuristic_add_wall
    end
  end

  def render_slider
    # Using primitives hides the line under the white circle of the slider
    # Draws the line
    outputs.primitives << [slider.x, slider.y, slider.x + slider.w, slider.y].line
    # The circle needs to be offset so that the center of the circle
    # overlaps the line instead of the upper right corner of the circle
    # The circle's x value is also moved based on the current seach step
    circle_x = (slider.x - slider.offset) + (state.current_step * slider.spacing)
    circle_y = (slider.y - slider.offset)
    circle_rect = [circle_x, circle_y, 37, 37]
    outputs.primitives << [circle_rect, 'circle-white.png'].sprite
  end

  def render_labels
    outputs.labels << [205, 625, "Breadth First Search"]
    outputs.labels << [820, 625, "Heuristic Best-First Search"]
  end

  def render_left_button
    # Draws the button_color button, and a black border
    # The border separates the buttons visually
    outputs.solids  << [buttons.left, button_color]
    outputs.borders << [buttons.left]

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    # If the button size is changed, the label might need to be edited as well
    # to keep the label in the center of the button
    label_x = buttons.left.x + 20
    label_y = buttons.left.y + 35
    outputs.labels  << [label_x, label_y, "<"]
  end

  def render_center_button
    # Draws the button_color button, and a black border
    # The border separates the buttons visually
    outputs.solids  << [buttons.center, button_color]
    outputs.borders << [buttons.center]

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    # If the button size is changed, the label might need to be edited as well
    # to keep the label in the center of the button
    label_x    = buttons.center.x + 37
    label_y    = buttons.center.y + 35
    label_text = state.play ? "Pause Animation" : "Play Animation"
    outputs.labels << [label_x, label_y, label_text]
  end

  def render_right_button
    # Draws the button_color button, and a black border
    # The border separates the buttons visually
    outputs.solids  << [buttons.right, button_color]
    outputs.borders << [buttons.right]

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    label_x = buttons.right.x + 20
    label_y = buttons.right.y + 35
    outputs.labels  << [label_x, label_y, ">"]
  end

  def render_bfs_grid
    # A large rect the size of the grid
    outputs.solids << bfs_scale_up(grid.rect).merge(default_color)

    outputs.lines << (0..grid.width).map { |x| bfs_vertical_line(x) }
    outputs.lines << (0..grid.height).map { |y| bfs_horizontal_line(y) }
  end

  def render_heuristic_grid
    # A large rect the size of the grid
    outputs.solids << heuristic_scale_up(grid.rect).merge(default_color)

    outputs.lines << (0..grid.width).map { |x| heuristic_vertical_line(x) }
    outputs.lines << (0..grid.height).map { |y| heuristic_horizontal_line(y) }
  end

  # Returns a vertical line for a column of the first grid
  def bfs_vertical_line x
    line = { x: x, y: 0, w: 0, h: grid.height }
    line.transform_values { |v| v * grid.cell_size }
  end

  # Returns a horizontal line for a column of the first grid
  def bfs_horizontal_line y
    line = { x: 0, y: y, w: grid.width, h: 0 }
    line.transform_values { |v| v * grid.cell_size }
  end

  # Returns a vertical line for a column of the second grid
  def heuristic_vertical_line x
    bfs_vertical_line(x + grid.width + 1)
  end

  # Returns a horizontal line for a column of the second grid
  def heuristic_horizontal_line y
    line = { x: grid.width + 1, y: y, w: grid.width, h: 0 }
    line.transform_values { |v| v * grid.cell_size }
  end

  # Renders the star on the first grid
  def render_bfs_star
    outputs.sprites << bfs_scale_up(grid.star).merge({ path: 'star.png' })
  end

  # Renders the star on the second grid
  def render_heuristic_star
    outputs.sprites << heuristic_scale_up(grid.star).merge({ path: 'star.png' })
  end

  # Renders the target on the first grid
  def render_bfs_target
    outputs.sprites << bfs_scale_up(grid.target).merge({ path: 'target.png' })
  end

  # Renders the target on the second grid
  def render_heuristic_target
    outputs.sprites << heuristic_scale_up(grid.target).merge({ path: 'target.png' })
  end

  # Renders the walls on the first grid
  def render_bfs_walls
    outputs.solids << grid.walls.map do |key, value|
      bfs_scale_up(key).merge(wall_color)
    end
  end

  # Renders the walls on the second grid
  def render_heuristic_walls
    outputs.solids << grid.walls.map do |key, value|
      heuristic_scale_up(key).merge(wall_color)
    end
  end

  # Renders the visited cells on the first grid
  def render_bfs_visited
    outputs.solids << bfs.came_from.map do |key, value|
      bfs_scale_up(key).merge(visited_color)
    end
  end

  # Renders the visited cells on the second grid
  def render_heuristic_visited
    outputs.solids << heuristic.came_from.map do |key, value|
      heuristic_scale_up(key).merge(visited_color)
    end
  end

  # Renders the frontier cells on the first grid
  def render_bfs_frontier
    outputs.solids << bfs.frontier.map do |cell|
      bfs_scale_up(cell).merge(frontier_color)
    end
  end

  # Renders the frontier cells on the second grid
  def render_heuristic_frontier
    outputs.solids << heuristic.frontier.map do |cell|
      heuristic_scale_up(cell).merge(frontier_color)
    end
  end

  # Renders the path found by the breadth first search on the first grid
  def render_bfs_path
    outputs.solids << bfs.path.map do |path|
      bfs_scale_up(path).merge(path_color)
    end
  end

  # Renders the path found by the heuristic search on the second grid
  def render_heuristic_path
    outputs.solids << heuristic.path.map do |path|
      heuristic_scale_up(path).merge(path_color)
    end
  end

  # Returns the rect for the path between two cells based on their relative positions
  def get_path_between(cell_one, cell_two)
    path = nil

    # If cell one is above cell two
    if cell_one.x == cell_two.x && cell_one.y > cell_two.y
      # Path starts from the center of cell two and moves upward to the center of cell one
      path = [cell_two.x + 0.3, cell_two.y + 0.3, 0.4, 1.4]
    # If cell one is below cell two
    elsif cell_one.x == cell_two.x && cell_one.y < cell_two.y
      # Path starts from the center of cell one and moves upward to the center of cell two
      path = [cell_one.x + 0.3, cell_one.y + 0.3, 0.4, 1.4]
    # If cell one is to the left of cell two
    elsif cell_one.x > cell_two.x && cell_one.y == cell_two.y
      # Path starts from the center of cell two and moves rightward to the center of cell one
      path = [cell_two.x + 0.3, cell_two.y + 0.3, 1.4, 0.4]
    # If cell one is to the right of cell two
    elsif cell_one.x < cell_two.x && cell_one.y == cell_two.y
      # Path starts from the center of cell one and moves rightward to the center of cell two
      path = [cell_one.x + 0.3, cell_one.y + 0.3, 1.4, 0.4]
    end

    path
  end

  # In code, the cells are represented as 1x1 rectangles
  # When drawn, the cells are larger than 1x1 rectangles
  # This method is used to scale up cells, and lines
  # Objects are scaled up according to the grid.cell_size variable
  # This allows for easy customization of the visual scale of the grid
  # This method scales up cells for the first grid
  def bfs_scale_up(cell)
    x = cell.x * grid.cell_size
    y = cell.y * grid.cell_size
    w = cell.w.zero? ? grid.cell_size : cell.w * grid.cell_size
    h = cell.h.zero? ? grid.cell_size : cell.h * grid.cell_size
    {x: x, y: y, w: w, h: h}
    # {x:, y:, w:, h:}
  end

  # Translates the given cell grid.width + 1 to the right and then scales up
  # Used to draw cells for the second grid
  # This method does not work for lines,
  # so separate methods exist for the grid lines
  def heuristic_scale_up(cell)
    # Prevents the original value of cell from being edited
    cell = cell.clone
    # Translates the cell to the second grid equivalent
    cell.x += grid.width + 1
    # Proceeds as if scaling up for the first grid
    bfs_scale_up(cell)
  end

  # Checks and handles input for the buttons
  # Called when the mouse is lifted
  def input_buttons
    input_left_button
    input_center_button
    input_right_button
  end

  # Checks if the previous step button is clicked
  # If it is, it pauses the animation and moves the search one step backward
  def input_left_button
    if left_button_clicked?
      state.play = false
      state.current_step -= 1
      recalculate_searches
    end
  end

  # Controls the play/pause button
  # Inverses whether the animation is playing or not when clicked
  def input_center_button
    if center_button_clicked? || inputs.keyboard.key_down.space
      state.play = !state.play
    end
  end

  # Checks if the next step button is clicked
  # If it is, it pauses the animation and moves the search one step forward
  def input_right_button
    if right_button_clicked?
      state.play = false
      state.current_step += 1
      move_searches_one_step_forward
    end
  end

  # These methods detect when the buttons are clicked
  def left_button_clicked?
    inputs.mouse.point.inside_rect?(buttons.left) && inputs.mouse.up
  end

  def center_button_clicked?
    inputs.mouse.point.inside_rect?(buttons.center) && inputs.mouse.up
  end

  def right_button_clicked?
    inputs.mouse.point.inside_rect?(buttons.right) && inputs.mouse.up
  end


  # Signal that the user is going to be moving the slider
  # Is the mouse over the circle of the slider?
  def mouse_over_slider?
    circle_x = (slider.x - slider.offset) + (state.current_step * slider.spacing)
    circle_y = (slider.y - slider.offset)
    circle_rect = [circle_x, circle_y, 37, 37]
    inputs.mouse.point.inside_rect?(circle_rect)
  end

  # Signal that the user is going to be moving the star from the first grid
  def bfs_mouse_over_star?
    inputs.mouse.point.inside_rect?(bfs_scale_up(grid.star))
  end

  # Signal that the user is going to be moving the star from the second grid
  def heuristic_mouse_over_star?
    inputs.mouse.point.inside_rect?(heuristic_scale_up(grid.star))
  end

  # Signal that the user is going to be moving the target from the first grid
  def bfs_mouse_over_target?
    inputs.mouse.point.inside_rect?(bfs_scale_up(grid.target))
  end

  # Signal that the user is going to be moving the target from the second grid
  def heuristic_mouse_over_target?
    inputs.mouse.point.inside_rect?(heuristic_scale_up(grid.target))
  end

  # Signal that the user is going to be removing walls from the first grid
  def bfs_mouse_over_wall?
    grid.walls.each_key do |wall|
      return true if inputs.mouse.point.inside_rect?(bfs_scale_up(wall))
    end

    false
  end

  # Signal that the user is going to be removing walls from the second grid
  def heuristic_mouse_over_wall?
    grid.walls.each_key do |wall|
      return true if inputs.mouse.point.inside_rect?(heuristic_scale_up(wall))
    end

    false
  end

  # Signal that the user is going to be adding walls from the first grid
  def bfs_mouse_over_grid?
    inputs.mouse.point.inside_rect?(bfs_scale_up(grid.rect))
  end

  # Signal that the user is going to be adding walls from the second grid
  def heuristic_mouse_over_grid?
    inputs.mouse.point.inside_rect?(heuristic_scale_up(grid.rect))
  end

  # This method is called when the user is editing the slider
  # It pauses the animation and moves the white circle to the closest integer point
  # on the slider
  # Changes the step of the search to be animated
  def process_input_slider
    state.play = false
    mouse_x = inputs.mouse.point.x

    # Bounds the mouse_x to the closest x value on the slider line
    mouse_x = slider.x if mouse_x < slider.x
    mouse_x = slider.x + slider.w if mouse_x > slider.x + slider.w

    # Sets the current search step to the one represented by the mouse x value
    # The slider's circle moves due to the render_slider method using anim_steps
    state.current_step = ((mouse_x - slider.x) / slider.spacing).to_i

    recalculate_searches
  end

  # Moves the star to the cell closest to the mouse in the first grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def process_input_bfs_star
    old_star = grid.star.clone
    unless bfs_cell_closest_to_mouse == grid.target
      grid.star = bfs_cell_closest_to_mouse
    end
    unless old_star == grid.star
      recalculate_searches
    end
  end

  # Moves the star to the cell closest to the mouse in the second grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def process_input_heuristic_star
    old_star = grid.star.clone
    unless heuristic_cell_closest_to_mouse == grid.target
      grid.star = heuristic_cell_closest_to_mouse
    end
    unless old_star == grid.star
      recalculate_searches
    end
  end

  # Moves the target to the grid closest to the mouse in the first grid
  # Only recalculate_searchess the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def process_input_bfs_target
    old_target = grid.target.clone
    unless bfs_cell_closest_to_mouse == grid.star
      grid.target = bfs_cell_closest_to_mouse
    end
    unless old_target == grid.target
      recalculate_searches
    end
  end

  # Moves the target to the cell closest to the mouse in the second grid
  # Only recalculate_searchess the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def process_input_heuristic_target
    old_target = grid.target.clone
    unless heuristic_cell_closest_to_mouse == grid.star
      grid.target = heuristic_cell_closest_to_mouse
    end
    unless old_target == grid.target
      recalculate_searches
    end
  end

  # Removes walls in the first grid that are under the cursor
  def process_input_bfs_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if bfs_mouse_over_grid?
      if grid.walls.key?(bfs_cell_closest_to_mouse)
        grid.walls.delete(bfs_cell_closest_to_mouse)
        recalculate_searches
      end
    end
  end

  # Removes walls in the second grid that are under the cursor
  def process_input_heuristic_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if heuristic_mouse_over_grid?
      if grid.walls.key?(heuristic_cell_closest_to_mouse)
        grid.walls.delete(heuristic_cell_closest_to_mouse)
        recalculate_searches
      end
    end
  end
  # Adds a wall in the first grid in the cell the mouse is over
  def process_input_bfs_add_wall
    if bfs_mouse_over_grid?
      unless grid.walls.key?(bfs_cell_closest_to_mouse)
        grid.walls[bfs_cell_closest_to_mouse] = true
        recalculate_searches
      end
    end
  end

  # Adds a wall in the second grid in the cell the mouse is over
  def process_input_heuristic_add_wall
    if heuristic_mouse_over_grid?
      unless grid.walls.key?(heuristic_cell_closest_to_mouse)
        grid.walls[heuristic_cell_closest_to_mouse] = true
        recalculate_searches
      end
    end
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse helps with this
  def bfs_cell_closest_to_mouse
    # Closest cell to the mouse in the first grid
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Bound x and y to the grid
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse in the second grid helps with this
  def heuristic_cell_closest_to_mouse
    # Closest cell grid to the mouse in the second
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Translate the cell to the first grid
    x -= grid.width + 1
    # Bound x and y to the first grid
    x = 0 if x < 0
    y = 0 if y < 0
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  def recalculate_searches
    # Reset the searches
    bfs.came_from    = {}
    bfs.frontier     = []
    bfs.path         = []
    heuristic.came_from = {}
    heuristic.frontier  = []
    heuristic.path      = []

    # Move the searches forward to the current step
    state.current_step.times { move_searches_one_step_forward }
  end

  def move_searches_one_step_forward
    bfs_one_step_forward
    heuristic_one_step_forward
  end

  def bfs_one_step_forward
    return if bfs.came_from.key?(grid.target)

    # Only runs at the beginning of the search as setup.
    if bfs.came_from.empty?
      bfs.frontier << grid.star
      bfs.came_from[grid.star] = nil
    end

    # A step in the search
    unless bfs.frontier.empty?
      # Takes the next frontier cell
      new_frontier = bfs.frontier.shift
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do |neighbor|
        # That have not been visited and are not walls
        unless bfs.came_from.key?(neighbor) || grid.walls.key?(neighbor)
          # Add them to the frontier and mark them as visited
          bfs.frontier << neighbor
          bfs.came_from[neighbor] = new_frontier
        end
      end
    end

    # Sort the frontier so that cells that are in a zigzag pattern are prioritized over those in an line
    # Comment this line and let a path generate to see the difference
    bfs.frontier = bfs.frontier.sort_by { |cell| proximity_to_star(cell) }

    # If the search found the target
    if bfs.came_from.key?(grid.target)
      # Calculate the path between the target and star
      bfs_calc_path
    end
  end

  # Calculates the path between the target and star for the breadth first search
  # Only called when the breadth first search finds the target
  def bfs_calc_path
    # Start from the target
    endpoint = grid.target
    # And the cell it came from
    next_endpoint = bfs.came_from[endpoint]
    while endpoint && next_endpoint
      # Draw a path between these two cells and store it
      path = get_path_between(endpoint, next_endpoint)
      bfs.path << path
      # And get the next pair of cells
      endpoint = next_endpoint
      next_endpoint = bfs.came_from[endpoint]
      # Continue till there are no more cells
    end
  end

  # Moves the heuristic search forward one step
  # Can be called from tick while the animation is playing
  # Can also be called when recalculating the searches after the user edited the grid
  def heuristic_one_step_forward
    # Stop the search if the target has been found
    return if heuristic.came_from.key?(grid.target)

    # If the search has not begun
    if heuristic.came_from.empty?
      # Setup the search to begin from the star
      heuristic.frontier << grid.star
      heuristic.came_from[grid.star] = nil
    end

    # One step in the heuristic search

    # Unless there are no more cells to explore from
    unless heuristic.frontier.empty?
      # Get the next cell to explore from
      new_frontier = heuristic.frontier.shift
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do |neighbor|
        # That have not been visited and are not walls
        unless heuristic.came_from.key?(neighbor) || grid.walls.key?(neighbor)
          # Add them to the frontier and mark them as visited
          heuristic.frontier << neighbor
          heuristic.came_from[neighbor] = new_frontier
        end
      end
    end

    # Sort the frontier so that cells that are in a zigzag pattern are prioritized over those in an line
    heuristic.frontier = heuristic.frontier.sort_by { |cell| proximity_to_star(cell) }
    # Sort the frontier so cells that are close to the target are then prioritized
    heuristic.frontier = heuristic.frontier.sort_by { |cell| heuristic_heuristic(cell) }

    # If the search found the target
    if heuristic.came_from.key?(grid.target)
      # Calculate the path between the target and star
      heuristic_calc_path
    end
  end

  # Returns one-dimensional absolute distance between cell and target
  # Returns a number to compare distances between cells and the target
  def heuristic_heuristic(cell)
    (grid.target.x - cell.x).abs + (grid.target.y - cell.y).abs
  end

  # Calculates the path between the target and star for the heuristic search
  # Only called when the heuristic search finds the target
  def heuristic_calc_path
    # Start from the target
    endpoint = grid.target
    # And the cell it came from
    next_endpoint = heuristic.came_from[endpoint]
    while endpoint && next_endpoint
      # Draw a path between these two cells and store it
      path = get_path_between(endpoint, next_endpoint)
      heuristic.path << path
      # And get the next pair of cells
      endpoint = next_endpoint
      next_endpoint = heuristic.came_from[endpoint]
      # Continue till there are no more cells
    end
  end

  # Returns a list of adjacent cells
  # Used to determine what the next cells to be added to the frontier are
  def adjacent_neighbors(cell)
    neighbors = []

    # Gets all the valid neighbors into the array
    # From southern neighbor, clockwise
    neighbors << [cell.x    , cell.y - 1] unless cell.y == 0
    neighbors << [cell.x - 1, cell.y    ] unless cell.x == 0
    neighbors << [cell.x    , cell.y + 1] unless cell.y == grid.height - 1
    neighbors << [cell.x + 1, cell.y    ] unless cell.x == grid.width - 1

    neighbors
  end

  # Finds the vertical and horizontal distance of a cell from the star
  # and returns the larger value
  # This method is used to have a zigzag pattern in the rendered path
  # A cell that is [5, 5] from the star,
  # is explored before over a cell that is [0, 7] away.
  # So, if possible, the search tries to go diagonal (zigzag) first
  def proximity_to_star(cell)
    distance_x = (grid.star.x - cell.x).abs
    distance_y = (grid.star.y - cell.y).abs

    [distance_x, distance_y].max
  end

  # Methods that allow code to be more concise. Subdivides args.state, which is where all variables are stored.
  def grid
    state.grid
  end

  def buttons
    state.buttons
  end

  def slider
    state.slider
  end

  def bfs
    state.bfs
  end

  def heuristic
    state.heuristic
  end

  # Descriptive aliases for colors
  def default_color
    { r: 221, g: 212, b: 213 }
  end

  def wall_color
    { r: 134, g: 134, b: 120 }
  end

  def visited_color
    { r: 204, g: 191, b: 179 }
  end

  def frontier_color
    { r: 103, g: 136, b: 204, a: 200 }
  end

  def path_color
    { r: 231, g: 230, b: 228 }
  end

  def button_color
    [190, 190, 190] # Gray
  end
end
# Method that is called by DragonRuby periodically
# Used for updating animations and calculations
def tick args

  # Pressing r will reset the application
  if args.inputs.keyboard.key_down.r
    args.gtk.reset
    reset
    return
  end

  # Every tick, new args are passed, and the Breadth First Search tick is called
  $heuristic ||= Heuristic.new
  $heuristic.args = args
  $heuristic.tick
end


def reset
  $heuristic = nil
end

Path Finding Algorithms - Heuristic With Walls - main.rb

# ./samples/13_path_finding_algorithms/07_heuristic_with_walls/app/main.rb
# Contributors outside of DragonRuby who also hold Copyright:
# - Sujay Vadlakonda: https://github.com/sujayvadlakonda

# This program is inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html

# This time the heuristic search still explored less of the grid, hence finishing faster.
# However, it did not find the shortest path between the star and the target.

# The only difference between this app and Heuristic is the change of the starting position.

class Heuristic_With_Walls
  attr_gtk

  def tick
    defaults
    render
    input
    # If animation is playing, and max steps have not been reached
    # Move the search a step forward
    if state.play && state.current_step < state.max_steps
      # Variable that tells the program what step to recalculate up to
      state.current_step += 1
      move_searches_one_step_forward
    end
  end

  def defaults
    # Variables to edit the size and appearance of the grid
    # Freely customizable to user's liking
    grid.width     ||= 15
    grid.height    ||= 15
    grid.cell_size ||= 40
    grid.rect      ||= [0, 0, grid.width, grid.height]

    grid.star      ||= [0, 2]
    grid.target    ||= [14, 12]
    grid.walls     ||= {
      [2, 2] => true,
      [3, 2] => true,
      [4, 2] => true,
      [5, 2] => true,
      [6, 2] => true,
      [7, 2] => true,
      [8, 2] => true,
      [9, 2] => true,
      [10, 2] => true,
      [11, 2] => true,
      [12, 2] => true,
      [12, 3] => true,
      [12, 4] => true,
      [12, 5] => true,
      [12, 6] => true,
      [12, 7] => true,
      [12, 8] => true,
      [12, 9] => true,
      [12, 10] => true,
      [12, 11] => true,
      [12, 12] => true,
      [2, 12] => true,
      [3, 12] => true,
      [4, 12] => true,
      [5, 12] => true,
      [6, 12] => true,
      [7, 12] => true,
      [8, 12] => true,
      [9, 12] => true,
      [10, 12] => true,
      [11, 12] => true,
      [12, 12] => true
    }
    # There are no hills in the Heuristic Search Demo

    # What the user is currently editing on the grid
    # We store this value, because we want to remember the value even when
    # the user's cursor is no longer over what they're interacting with, but
    # they are still clicking down on the mouse.
    state.user_input ||= :none

    # These variables allow the breadth first search to take place
    # Came_from is a hash with a key of a cell and a value of the cell that was expanded from to find the key.
    # Used to prevent searching cells that have already been found
    # and to trace a path from the target back to the starting point.
    # Frontier is an array of cells to expand the search from.
    # The search is over when there are no more cells to search from.
    # Path stores the path from the target to the star, once the target has been found
    # It prevents calculating the path every tick.
    bfs.came_from  ||= {}
    bfs.frontier   ||= []
    bfs.path       ||= []

    heuristic.came_from ||= {}
    heuristic.frontier  ||= []
    heuristic.path      ||= []

    # Stores which step of the animation is being rendered
    # When the user moves the star or messes with the walls,
    # the searches are recalculated up to this step
    unless state.current_step
      state.current_step = 0
    end

    # At some step the animation will end,
    # and further steps won't change anything (the whole grid will be explored)
    # This step is roughly the grid's width * height
    # When anim_steps equals max_steps no more calculations will occur
    # and the slider will be at the end
    state.max_steps = grid.width * grid.height

    # Whether the animation should play or not
    # If true, every tick moves anim_steps forward one
    # Pressing the stepwise animation buttons will pause the animation
    # An if statement instead of the ||= operator is used for assigning a boolean value.
    # The || operator does not differentiate between nil and false.
    if state.play == nil
      state.play = false
    end

    # Store the rects of the buttons that control the animation
    # They are here for user customization
    # Editing these might require recentering the text inside them
    # Those values can be found in the render_button methods
    buttons.left   = [470, 600, 50, 50]
    buttons.center = [520, 600, 200, 50]
    buttons.right  = [720, 600, 50, 50]

    # The variables below are related to the slider
    # They allow the user to customize them
    # They also give a central location for the render and input methods to get
    # information from
    # x & y are the coordinates of the leftmost part of the slider line
    slider.x = 440
    slider.y = 675
    # This is the width of the line
    slider.w = 360
    # This is the offset for the circle
    # Allows the center of the circle to be on the line,
    # as opposed to the upper right corner
    slider.offset = 20
    # This is the spacing between each of the notches on the slider
    # Notches are places where the circle can rest on the slider line
    # There needs to be a notch for each step before the maximum number of steps
    slider.spacing = slider.w.to_f / state.max_steps.to_f
  end

  # All methods with render draw stuff on the screen
  # UI has buttons, the slider, and labels
  # The search specific rendering occurs in the respective methods
  def render
    render_ui
    render_bfs
    render_heuristic
  end

  def render_ui
    render_buttons
    render_slider
    render_labels
  end

  def render_buttons
    render_left_button
    render_center_button
    render_right_button
  end

  def render_bfs
    render_bfs_grid
    render_bfs_s