• Docs and Samples
  • Docs
  • Samples
  • Table Of Contents

    Welcome link

    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.

    Tips for Learning DragonRuby Game Toolkit link

    The following tips will help you learn the DragonRuby quickly.

    Tip #1: Join the Community link

    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.

    Tip #2: Read the Book link

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

    Tip #3: Watch the Tutorial Video link

    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

    Tip #4: Go Through the Sample Apps in Order link

    The sample apps are located in the ./samples directory. The samples are ordered by increasing difficulty and cover all aspects of the game engine.

    Getting Started Tutorial link

    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 link

    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 link

    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 link

    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 link

    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 hash onto the list of them at
      # args.outputs.labels)
      args.outputs.labels << { x: 580, y: 400, text: '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 link

    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  << { x: 580, y: 400, text: 'Hello World!' }
      args.outputs.sprites << { x: 576, y: 100, w: 128, h: 101, path: '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 link

    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.state.rotation  -= 1
    
      args.outputs.labels  << { x: 580, y: 400, text: 'Hello World!' }
      args.outputs.sprites << { x: 576,
                                y: 100,
                                w: 128,
                                h: 101,
                                path: 'dragonruby.png',
                                angle: args.state.rotation }
    end
    

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

    Game State link

    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 link

    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 link

    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.x - 64
        args.state.y = args.inputs.mouse.y - 50
      end
    
      args.outputs.labels  << { x: 580, y: 400, text: 'Hello World!' }
      args.outputs.sprites << { x: args.state.x,
                                y: args.state.y,
                                w: 128,
                                h: 101,
                                path: 'dragonruby.png',
                                angle: 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 link

    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:

    sudo 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 link

    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 link

    The DragonRuby 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.

    The DragonRuby binary/package is designed to be committed in its entirety with your source code (it’s why we keep it small). This protects the “shelf life” for commercial games. 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 every game (and commit everything to source control).

    File access functions are sandoxed and assume that the dragonruby binary lives alongside the game you are building. Do not expect file access functions to return correct values if you are attempting to run the dragonruby binary from a shared location. It's recommended that the directory structure contained in the zip is not altered and games are built using that starting directory structure.

    Considerations For Public Git Repositories link

    You can open source your game's code given the following options.

    Option 1 (Recommended) link

    Your public repository needs only to contain the contents of ./mygame. This approach is the cleanest and doesn't require your .gitignore to be polluted with DragonRuby specific files.

    Option 2 (Restrictions Apply) link

    IMPORTANT: Do NOT commit dragonruby-publish(.exe), or dragonruby-bind(.exe).

    dragonruby
    dragonruby.exe
    dragonruby-publish
    dragonruby-publish.exe
    dragonruby-bind
    dragonruby-bind.exe
    /tmp/
    /builds/
    /logs/
    /samples/
    /docs/
    /.dragonruby/
    

    If you'd like people who do not own a DragonRuby license to run your game, you may include the dragonruby(.exe) binary within the repo. This permission is granted in good-faith and can be revoked if abused.

    Considerations For Private Git Repos link

    The following .gitignore should be used for private repositories (commercial games).

    /tmp/
    /logs/
    

    You'll notice that everything else is committed to source control (even the ./samples, ./docs, and ./builds directory).

    Deploying To Itch.io link

    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 link

    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 link

    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 link

    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 link

    For the HTML version of your game, the following configuration is required for your game to run correctly:

    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.

    Consider Adding Pause When Game is In Background link

    It's a good idea to pause the game if it doesn't have focus. Here's an example of how to do that

    def tick args
      # if the keyboard doesn't have focus, and the game is in production mode, and it isn't the first tick
      if !args.inputs.keyboard.has_focus && args.gtk.production && args.state.tick_count != 0
        args.outputs.background_color = [0, 0, 0]
        args.outputs.labels << { x: 640,
                                 y: 360,
                                 text: "Game Paused (click to resume).",
                                 alignment_enum: 1,
                                 r: 255, g: 255, b: 255 }
        # consider setting all audio volume to 0.0
      else
        # perform your regular tick function
      end
    end
    

    If you want your game to run at full speed even when it's in the background, add the following line to mygame/metadata/cvars.txt:

    renderer.background_sleep=0
    

    Consider Adding a Request to Review Your Game In-Game link

    Getting reviews of your game are extremely important and it's recommended that you put an option to review within the game itself. You can use args.gtk.open_url plus a review URL. Here's an example:

    def tick args
      # render the review button
      args.state.review_button ||= { x: 640 - 50,
                                     y: 360 - 25,
                                     w: 100,
                                     h: 50,
                                     path: :pixel,
                                     r: 0,
                                     g: 0,
                                     b: 0 }
      args.outputs.sprites << args.state.review_button
      args.outputs.labels << { x: 640, y: 360, anchor_x: 0.5, anchor_y: 0.5, text: "Review" }
    
      # check to see if the review button was clicked
      if args.inputs.mouse.intersect_rect? args.state.review_button
        # open platform specific review urls
        if args.gtk.platform? :ios
          # your app id is provided at Apple's Developer Portal (numeric value)
          args.gtk.openurl "itms-apps://itunes.apple.com/app/idYOURGAMEID?action=write-review"
        elsif args.gtk.platform? :android
          # your app id is the name of your android package
          args.gtk.openurl "https://play.google.com/store/apps/details?id=YOURGAMEID"
        elsif args.gtk.platform? :web
          # if they are playing the web version of the game, take them to the purchase page on itch
          args.gtk.openurl "https://amirrajan.itch.io/YOURGAMEID/purchase"
        else
          # if they are playing the desktop version of the game, take them to itch's rating page
          args.gtk.openurl "https://amirrajan.itch.io/YOURGAMEID/rate?source=game"
        end
      end
    end
    

    Deploying To Mobile Devices link

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

    Deploying to iOS link

    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.

    Deploying to Android link

    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:

    # generating a keystore
    keytool -genkey -v -keystore APP.keystore -alias mygame -keyalg RSA -keysize 2048 -validity 10000
    
    # deploying to a local device/emulator
    apksigner sign --min-sdk-version 21 --ks ./profiles/mygame.keystore ./builds/APP-android.apk
    adb install ./builds/APP-android.apk
    # read logs of device
    adb logcat -e mygame
    
    # signing for Google Play
    apksigner sign --min-sdk-version 33 --ks ./profiles/APP.keystore ./builds/APP-googleplay.aab
    

    Deploying To Steam link

    If you have a Indie or Pro subscription, you also get streamlined deployment to Steam via dragonruby-publish. Please note that games developed using the Standard license can deploy to Steam using the Steamworks toolchain https://partner.steamgames.com/doc/store/releasing.

    Testing on Your Steam Deck link

    Easy Setup link

    1. Run dragonruby-publish --only-package.
    2. Find the Linux build of your game under the ./builds directory and load it onto an SD Card.
    3. Restart the Steam Deck in Desktop Mode.
    4. Copy your game binary onto an SD card.
    5. Find the game on the SD card and double click binary.

    Advanced Setup link

    1. Restart the Steam Deck in Desktop Mode.
    2. Open up Konsole and set an admin password via passwd.
    3. Disable readonly mode: sudo steamos-readonly disable.
    4. Update pacman sudo pacman-key --populate archlinux.
    5. Update sshd_config sudo vim /etc/ssh/sshd_config and uncomment the PubkeyAuthentication yes line.
    6. Enable ssh: sudo systemctl enable sshd.
    7. Start ssh: sudo systemctl start sshd.
    8. Run dragonruby-publish --only-package.
    9. Use scp to copy the game over from your dev machine without needing an SD Card: scp -R ./builds/SOURCE.bin deck@IP_ADDRESS:/home/deck/Downloads

    Note: Steps 2 through 7 need only be done once.

    Note: scp comes pre-installed on Mac and Linux. You can download the tool for Windows from https://winscp.net/eng/index.php

    Setting up the game on the Partner Site link

    Getting your App ID link

    You'll need to create a product on Steam. This is unfortunately manual and requires identity verification for taxation purposes. Valve offers pretty robust documentation on all this, though. Eventually, you'll have an App ID for your game.

    Go to https://partner.steamgames.com/apps/view/$APPID, where $APPID is your game's App ID.

    Specifing Supported Operating Systems for your game link

    Find the "Supported Operating Systems" section and make sure these things are checked:

    Click the "Save" button below it.

    Setting up SteamPipe Depots link

    Click the "SteamPipe" tab at the top of the page, click on "depots"

    Click the "Add a new depot" button. Give it a name like "My Game Name Linux Depot" and take whatever depot ID it offers you.

    You'll see this new depot is listed on the page now. Fix its settings:

    Do this again, make a "My Game Name Windows Depot", set it to the same things, except "Operating System," which should be "Windows," of course.

    Do this again, make a "My Game Name Mac Depot", set it to the same things, except "Operating System," which should be "macOS," of course.

    Push the big green "Save" button on the page. Now we have a place to upload platform-specific builds of your game.

    Setting up Launch Options link

    Click on the "Installation" tab near the top of the page, then "General Installation".

    Under "Launch Options," click the "Add new launch option" button, edit the new section that just popped up, and set it like this:

    (Whenever you see "mygamename" in here, this should be whatever your game_metadata's "gameid" value is set to. If you see "My Game Name", it's whatever your game_metadata's "gametitle" value is set to, but you'll have to check in case we mangled it to work as a filename.)

    Click the "Update" button on that section.

    Add another launch option, as before:

    Add another launch option, as before:

    Publish Changes link

    Go to the "Publish" tab at near the top of the page. Click the "View Diffs" button and make sure it looks sane (it should just be the things we've changed in here), then click "Prepare for Publishing", then "Publish to Steam" and follow the instructions to publish these changes.

    Go to https://partner.steamgames.com/apps/associated/$APPID For each package, make sure all three depots are included.

    Configuring dragonruby-publish link

    You only have to do this part once when first setting up your game. Note that this capability is only available for Indie and Pro license tiers. If you have a Standard DragonRuby License, you'll need to use the Steamworks toolchains directly.

    Go add a text file to your game's metadata directory called steam_metadata.txt ... note that this file will be filtered out dragonruby-publish packages the game and will not be distributed with the published game.

    steam.publish=true
    steam.branch=public
    steam.username=AAA
    steam.appid=BBB
    steam.linux_depotid=CCC
    steam.windows_depotid=DDD
    steam.mac_depotid=EEE
    

    If steam.publish is set to false then dragonruby-publish will not attempt to upload to Steam. false is the default if this file, or this setting, is missing.

    Where "AAA" is the login name on the Steamworks Partner Site to use for publishing builds, "BBB" is your game-specific AppID provided by Steam, "CCC", "DDD", and "EEE" are the DepotIDs you created for Linux, Windows, and macOS builds, respectively.

    Setting a branch live link

    Once your build is uploaded, you can assign it to a specific branch through the interface on the Partner site. You can make arbitrary branches here, like "beta" or "nightly" or "fixing-weird-bug" or whatever. The one that goes to the end users without them switching branches, is "default" and you should assume this is where paying customers live, so be careful before you set a build live there.

    You can have dragonruby-publish set the builds it publishes live on a branch immediately, if you prefer. Simply add...

    steam.branch=XXX
    

    ...to steam_metadata.txt, where "XXX" is the branch name from the partner website. If this is blank or unspecified, it will _not_ set the build live on _any_ branch. Setting the value to public will push to production.

    A reasonable strategy is to create a (possibly passworded) branch called "staging" and have dragonruby-publish always push to there automatically. Then you can test from a Steam install, pushing as often as you like, and when you are satisfied, manually set the latest build live on default for the general public to download.

    If you are feeling brave, you can always just set all published builds live on default, too. After all, if you break it, you can always just push a fix right away. :) (or use the Partner Site to roll back to a known-good build, you know.)

    Publishing Build link

    Run dragonuby-publish as you normally would. When it is time to publish to Steam, it will set up any tools it needs, attempt to log you into Steam, and upload the latest version of your game.

    Steam login is handled by Valve's steamcmd command line program, not dragonruby-publish. DragonRuby does not ever have access to your login credentials. You may need to take steps to get an authorization token in place if necessary, so you don't have to deal with Steam Guard in automated build processes (documentation on how to do this is forthcoming, or read Valve's SteamCMD manual for details).

    You (currently) have to set the new build live on the partner site before users will receive it. Optionally automating this step is coming soon!

    Questions/Need Help? link

    You probably have several. Please come visit the Discord and ask questions, and we'll do our best to help, and update this document.

    DragonRuby's Philosophy link

    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 link

    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 link

    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 link

    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 link

    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 link

    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 link

    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 link

    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 link

    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 link

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

    Frequently Asked Questions link

    What is DragonRuby LLP? link

    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? link

    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? link

    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 mygame --test tests/some_ruby_file.rb.
    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 link

    But Ruby is dead. link

    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. link

    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. link

    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 link

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

    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. link

    If you can afford to pay for DragonRuby, you should (and will). We don't tell authors 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. link

    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. link

    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. link

    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 continues.

    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: link

    How To Determine What Frame You Are On link

    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 link

    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 link

    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.

    NOTE: Rendering using an Array is "quick and dirty". It's generally recommended that you render using Hashes long term.

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

    Rendering a Sprite Using a Hash link

    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
    
        # sprites anchor/alignment (default is nil)
        anchor_x: 0.5,
        anchor_y: 0.5
      }
    end
    

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

    How To Render A Label link

    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.

    NOTE: Rendering using an Array is "quick and dirty". It's generally recommended that you render using Hashes long term.

    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 link

    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 link

    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 link

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

    If you use a Hash to render a label, you can set the label's size using either SIZE_ENUM or SIZE_PX. If both options are provided, SIZE_PX will be used.

    def tick args
      args.outputs.labels << {
        x:                       200,
        y:                       550,
        text:                    "dragonruby",
        # size specification can be either size_enum or size_px
        size_enum:               2,
        size_px:                 22,
        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
        anchor_x: 0.5,
        anchor_y: 0.5
        # 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 link

    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 link

    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 link

    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 link

    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 link

    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/

    IMPORTANT: File access functions are sandoxed and assume that the dragonruby binary lives alongside the game you are building. Do not expect file access functions to return correct values if you are attempting to run the dragonruby binary from a shared location. It's recommended that the directory structure contained in the zip is not altered and games are built using that starter template.

    Troubleshoot Performance link

    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
    
    args.state.fx_queue.each |fx|
      fx.count_down ||= 255
      fx.countdown -= 5
      if fx.countdown < 0
        args.state.fx_queue.delete fx
      end
    end
    

    Do:

    args.state.fx_queue.each |fx|
      fx.countdown ||= 255
      fx.countdown -= 5
    end
    
    args.state.fx_queue.reject! { |fx| fx.countdown < 0 }
    

    Outputs (args.outputs) link

    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     << { x: 0, y: 0, w: 100, h: 100 }
      args.outputs.sprites    << { x: 100, y: 100, w: 100, h: 100, path: "sprites/square/blue.png" }
      args.outputs.labels     << { x: 200, y: 200, text: "Hello World" }
      args.outputs.borders    << { x: 0, y: 0, w: 100, h: 100 }
      args.outputs.lines      << { x: 300, y: 300, x2: 400, y2: 400 }
    end
    

    Collection Render Orders link

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

    Primitives Collection (args.outputs.primitives) link

    args.outputs.primitives can take in any primitive and will render first in, first out.

    For example, you can render a solid above a sprite:

    def tick args
      args.outputs.primitives << { x: 100, y: 100,
                                   w: 100, h: 100,
                                   path: "sprites/square/blue.png" }
      args.outputs.primitives << { x: 0, y: 0, w: 100, h: 100, primitive_marker: :solid }
      args.outputs.primitives << { x: 0, y: 0, w: 100, h: 100, primitive_marker: :border }
    end
    

    Debug Collection (args.outputs.debug) link

    args.outputs.debug will not render in production mode and behaves like args.outputs.primitives. Objects in this collection are rendered above everything.

    Additionally, args.outputs.debug allows you to pass in a String as a primitive type. This is helpful for quickly showing the value of a variable on the screen. A label with black text and a white background will be created for each String sent in. The labels will be automatically stacked vertically for you.

    Example:

    def tick args
      args.state.player ||= { x: 100, y: 100 }
      args.state.player.x += 1
      args.state.player.x = 0 if args.state.player.x > 1280
    
      # the following string values will generate labels with backgrounds
      # and will auto stack vertically
      args.outputs.debug << "current tick: #{args.state.tick_count}"
      args.outputs.debug << "player x: #{args.state.player.x}"
    end
    

    solids link

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

    Rendering a solid using an Array link

    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 link

    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 link

    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,
        anchor_x: 0,
        anchor_y: 0,
        blendmode_enum: 1
      }
    end
    

    Rendering a solid using a Class link

    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, :anchor_x, :anchor_y, :blendmode_enum
    
      def primitive_marker
        :solid # or :border
      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 link

    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 link

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

    Rendering a sprite using an Array link

    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 a Hash link

    If you want a more readable (and faster) 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
    

    Here are all the properties that you can set on a sprite. The only required ones are x, y, w, h, and path.

    Required properties

    Anchors and Rotations

    Here's an example of rendering a 80x80 pixel sprite in the center of the screen:

    def tick args
      args.outputs.sprites << {
        x: 640 - 40, # the logical center of the screen horizontally is 640, minus half the width of the sprite
        y: 360 - 40, # the logical center of the screen vertically is 360, minus half the height of the sprite
        w: 80,
        h: 80,
        path: "sprites/square/blue.png"
     }
    end
    

    Instead of computing the offset, you can use anchor_x, and anchor_y to center the sprite. The following is equivalent to the code above:

    def tick args
      args.outputs.sprites << {
        x: 640,
        y: 360,
        w: 80,
        h: 80,
        path: "sprites/square/blue.png",
        anchor_x: 0.5, # position horizontally at 0.5 of the sprite's width
        anchor_y: 0.5  # position vertically at 0.5 of the sprite's height
     }
    end
    

    Cropping Properties

    See the sample apps under ./samples/03_rendering_sprites for examples of how to use this properties non-trivially.

    Blending Options

    The following sample apps show how blendmode_enum can be leveraged to create coloring and lighting effects:

    Triagles (Indie, Pro Feature)

    Sprites can be rendered as triangles at the Indie and Pro License Tiers. To rendering using triangles, instead of providing a w, h property, provide x2, y2, x3, y3. This applies for positioning and cropping.

    Here is an example:

    def tick args
      args.outputs.sprites << {
        x: 0,
        y: 0,
        x2: 80,
        y2: 0,
        x3: 0,
        y3: 80,
        source_x: 0,
        source_y: 0,
        source_x2: 80,
        source_y2: 0,
        source_x3: 0,
        source_y3: 80,
        path: "sprites/square/blue.png"
      }
    end
    

    For more example of rendering using triangles see:

    Rendering a sprite using a Class link

    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, :a, :r, :g, :b, :tile_x,
                    :tile_y, :tile_w, :tile_h, :flip_horizontally,
                    :flip_vertically, :angle_anchor_x, :angle_anchor_y, :id,
                    :angle_x, :angle_y, :z,
                    :source_x, :source_y, :source_w, :source_h, :blendmode_enum,
                    :source_x2, :source_y2, :source_x3, :source_y3, :x2, :y2, :x3, :y3,
                    :anchor_x, :anchor_y
    
      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 serialize
        {x:self.x, y:self.y, w:self.w, h:self.h, path:self.path}
      end
    
      def inspect
        serialize.to_s
      end
    
      def to_s
        serialize.to_s
      end
    end
    
    def tick args
      # render circle sprite
      args.outputs.sprites  << Circle.new(10, 10, 32,"sprites/circle/white.png")
    end
    

    attr_sprite link

    The attr_sprite class macro adds all properties needed to render a sprite to a class. This removes the need to manually define all sprites properties that DragonRuby offers for rendering.

    Instead of manually defining the properties, you can represent a sprite using the attr_sprite class macro:

    class BlueSquare
      # invoke the helper function at the class level for
      # anything you want to represent as a sprite
      attr_sprite
    
      def initialize(x: 0, y: 0, w: 0, h: 0k
        @x = x
        @y = y
        @w = w
        @h = 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
    

    labels link

    Add primitives to this collection to render a label.

    Rendering a label using an Array link

    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 link

    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 link

    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) link

    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.

    Inputs (args.inputs) link

    Access using input using args.inputs.

    last_active link

    This function returns the last active input which will be set to either :keyboard, :mouse, or :controller. The function is helpful when you need to present on screen instructions based on the input the player chose to play with.

    def tick args
      if args.inputs.last_active == :controller
        args.outputs.labels << { x: 60, y: 60, text: "Use the D-Pad to move around." }
      else
        args.outputs.labels << { x: 60, y: 60, text: "Use the arrow keys to move around." }
      end
    end
    

    :mouse, or :controller. The function is helpful when you need to present on screen instructions based on the input the player chose to play with.

    locale link

    Returns the ISO 639-1 two-letter langauge code based on OS preferences. Refer to the following link for locale strings: https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes).

    Defaults to "en" if locale can't be retrieved (args.inputs.locale_raw will be nil in this case).

    up link

    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.

    down link

    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.

    left link

    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.

    right link

    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.

    left_right link

    Returns -1 (left), 0 (neutral), or +1 (right). This method is aliased to args.inputs.left_right_with_wasd.

    The following inputs are inspected to determine the result:

    left_right_perc link

    Returns a floating point value between -1 and 1. This method is aliased to args.inputs.left_right_perc_with_wasd

    The following inputs are inspected to dermine the result:

    left_right_directional link

    Returns -1 (left), 0 (neutral), or +1 (right). This method is aliased to args.inputs.left_right_arrow.

    The following inputs are inspected to determine the result:

    left_right_directional_perc link

    Returns a floating point value between -1 and 1. The following inputs are inspected to dermine the result:

    Here is some sample code to help visualize the left_right functions.

    def tick args
      args.outputs.debug << "* Variations of args.inputs.left_right"
      args.outputs.debug << "  args.inputs.left_right(_with_wasd) #{args.inputs.left_right}"
      args.outputs.debug << "  args.inputs.left_right_perc(_with_wasd) #{args.inputs.left_right_perc}"
      args.outputs.debug << "  args.inputs.left_right_directional #{args.inputs.left_right_directional}"
      args.outputs.debug << "  args.inputs.left_right_directional_perc #{args.inputs.left_right_directional_perc}"
      args.outputs.debug << "** Keyboard"
      args.outputs.debug << "   args.inputs.keyboard.a #{args.inputs.keyboard.a}"
      args.outputs.debug << "   args.inputs.keyboard.d #{args.inputs.keyboard.d}"
      args.outputs.debug << "   args.inputs.keyboard.left_arrow #{args.inputs.keyboard.left_arrow}"
      args.outputs.debug << "   args.inputs.keyboard.right_arrow #{args.inputs.keyboard.right_arrow}"
      args.outputs.debug << "** Controller"
      args.outputs.debug << "   args.inputs.controller_one.dpad_left #{args.inputs.controller_one.dpad_left}"
      args.outputs.debug << "   args.inputs.controller_one.dpad_right #{args.inputs.controller_one.dpad_right}"
      args.outputs.debug << "   args.inputs.controller_one.left_analog_x_perc #{args.inputs.controller_one.left_analog_x_perc}"
    end
    

    up_down link

    Returns -1 (down), 0 (neutral), or +1 (up). This method is aliased to args.inputs.up_down_with_wasd.

    The following inputs are inspected to determine the result:

    up_down_directional link

    Returns -1 (down), 0 (neutral), or +1 (up). This method is aliased to args.inputs.up_down_arrow.

    The following inputs are inspected to determine the result:

    up_down_perc link

    Returns a floating point value between -1 and 1. The following inputs are inspected to dermine the result:

    Here is some sample code to help visualize the up_down functions.

    def tick args
      args.outputs.debug << "* Variations of args.inputs.up_down"
      args.outputs.debug << "  args.inputs.up_down #{args.inputs.up_down}"
      args.outputs.debug << "  args.inputs.up_down_directional #{args.inputs.up_down_directional}"
      args.outputs.debug << "  args.inputs.up_down_perc #{args.inputs.up_down_perc}"
      args.outputs.debug << "** Keyboard"
      args.outputs.debug << "   args.inputs.keyboard.a #{args.inputs.keyboard.a}"
      args.outputs.debug << "   args.inputs.keyboard.d #{args.inputs.keyboard.d}"
      args.outputs.debug << "   args.inputs.keyboard.up_arrow #{args.inputs.keyboard.up_arrow}"
      args.outputs.debug << "   args.inputs.keyboard.down_arrow #{args.inputs.keyboard.down_arrow}"
      args.outputs.debug << "** Controller"
      args.outputs.debug << "   args.inputs.controller_one.dpad_up #{args.inputs.controller_one.dpad_up}"
      args.outputs.debug << "   args.inputs.controller_one.dpad_down #{args.inputs.controller_one.dpad_down}"
      args.outputs.debug << "   args.inputs.controller_one.up_analog_x_perc #{args.inputs.controller_one.up_analog_x_perc}"
    end
    

    text link

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

    Mouse (args.inputs.mouse) link

    Represents the user's mouse.

    has_focus link

    Return's true if the game has mouse focus.

    x link

    Returns the current x location of the mouse.

    y link

    Returns the current y location of the mouse.

    inside_rect? rect link

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

    inside_circle? center_point, radius link

    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:

    moved link

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

    button_left link

    Returns true if the left mouse button is down.

    button_middle link

    Returns true if the middle mouse button is down.

    button_right link

    Returns true if the right mouse button is down.

    button_bits link

    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.

    wheel link

    Represents the mouse wheel. Returns nil if no mouse wheel actions occurred. Otherwise args.inputs.mouse.wheel will return a Hash with x, and y (representing movement on each axis).

    click OR down, previous_click, up link

    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. This value will be true if any of the mouse's buttons caused these events. To scope to a specific button use .button_left, .button_middle, .button_right, or .button_bits.

    Touch link

    The following touch apis are available on touch devices (iOS, Android, Mobile Web, Surface).

    args.inputs.touch link

    Returns a Hash representing all touch points on a touch device.

    args.inputs.finger_left link

    Returns a Hash with x and y denoting a touch point that is on the left side of the screen.

    args.inputs.finger_right link

    Returns a Hash with x and y denoting a touch point that is on the right side of the screen.

    Controller (args.inputs.controller_(one-four)) link

    Represents controllers connected to the usb ports.

    active link

    Returns true if any of the controller's buttons were used.

    up link

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

    down link

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

    left link

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

    right link

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

    left_right link

    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.

    up_down link

    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.

    (left|right)_analog_x_raw link

    Returns the raw integer value for the analog's horizontal movement (-32,767 to +32,767).

    (left|right)_analog_y_raw link

    Returns the raw integer value for the analog's vertical movement (-32,767 to +32,767).

    (left|right)_analog_x_perc link

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

    (left|right)_analog_y_perc link

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

    dpad_up, directional_up link

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

    dpad_down, directional_down link

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

    dpad_left, directional_left link

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

    dpad_right, directional_right link

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

    (a|b|x|y|l1|r1|l2|r2|l3|r3|start|select) link

    Returns true if the specific button is pressed or held. Note: For PS4 and PS5 controllers a maps to Cross, b maps to Circle, x maps to Square, and y maps to Triangle.

    truthy_keys link

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

    key_down link

    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.

    key_held link

    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).

    key_up link

    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.

    Keyboard (args.inputs.keyboard) link

    Represents the user's keyboard.

    active link

    Returns Kernel.tick_count (args.state.tick_count) if any keys on the keyboard were pressed.

    has_focus link

    Returns true if the game has keyboard focus.

    up link

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

    down link

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

    left link

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

    right link

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

    left_right link

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

    up_down link

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

    keyboard properties link

    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:

    char link

    Method is available under inputs.key_down, inputs.key_held, and inputs.key_up. Take note that

    args.inputs.keyboard.key_held.char will only return the ascii value of the last key that was held. Use args.inputs.keyboard.key_held.truthy_keys to get an Array of Symbols representing all keys being held.

    To get a picture of all key states args.inputs.keyboard.keys returns a Hash with the following keys: :down, :held, :down_or_held, :up.

    NOTE: args.inputs.keyboard.key_down.char will be set in line with key repeat behavior of your OS.

    This is a demonstration of the behavior (see ./samples/02_input_basics/01_keyboard for a more detailed example):

    def tick args
      # uncomment the line below to see the value changes at a slower rate
      # $gtk.slowmo! 30
    
      keyboard = args.inputs.keyboard
    
      args.outputs.labels << { x: 30,
                               y: 720,
                               text: "use the J key to test" }
    
      args.outputs.labels << { x: 30,
                               y: 720 - 30,
                               text: "key_down.char: #{keyboard.key_down.char.inspect}" }
    
      args.outputs.labels << { x: 30,
                               y: 720 - 60,
                               text: "key_down.j:    #{keyboard.key_down.j}" }
    
      args.outputs.labels << { x: 30,
                               y: 720 - 30,
                               text: "key_held.char: #{keyboard.key_held.char.inspect}" }
    
      args.outputs.labels << { x: 30,
                               y: 720 - 60,
                               text: "key_held.j:    #{keyboard.key_held.j}" }
    
      args.outputs.labels << { x: 30,
                               y: 720 - 30,
                               text: "key_up.char:   #{keyboard.key_up.char.inspect}" }
    
      args.outputs.labels << { x: 30,
                               y: 720 - 60,
                               text: "key_up.j:      #{keyboard.key_up.j}" }
    end
    

    keys link

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

    Runtime (args.gtk) link

    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
    

    Class Macros link

    The following class macros are available within DragonRuby.

    attr link

    The attr class macro is an alias to attr_accessor.

    Instead of:

    class Player
      attr_accessor :hp, :armor
    end
    

    You can do:

    class Player
      attr :hp, :armor
    end
    

    attr_gtk link

    As the size/complexity of your game increases. You may want to create classes to organize everything. The attr_gtk class macro adds DragonRuby's environment methods (such as args.state, args.inputs, args.outputs, args.audio, etc) to your class so you don't have to pass args around everwhere.

    Instead of:

    class Game
      def tick args
        defaults args
        calc args
        render args
      end
    
      def defaults args
        args.state.space_pressed_at ||= 0
      end
    
      def calc args
        if args.inputs.keyboard.key_down.space
          args.state.space_pressed_at = args.state.tick_count
        end
      end
    
      def render args
        if args.state.space_pressed_at == 0
          args.outputs.labels << { x: 100, y: 100,
                                   text: "press space" }
        else
          args.outputs.labels << { x: 100, y: 100,
                                   text: "space was pressed at: #{args.state.space_pressed_at}" }
        end
      end
    end
    
    def tick args
      $game ||= Game.new
      $game.tick args
    end
    

    You can do:

    class Game
      attr_gtk # attr_gtk class macro
    
      def tick
        defaults
        calc
        render
      end
    
      def defaults
        state.space_pressed_at ||= 0
      end
    
      def calc
        if inputs.keyboard.key_down.space
          state.space_pressed_at = state.tick_count
        end
      end
    
      def render
        if state.space_pressed_at == 0
          outputs.labels << { x: 100, y: 100,
                              text: "press space" }
        else
          outputs.labels << { x: 100, y: 100,
                              text: "space was pressed at: #{state.space_pressed_at}" }
        end
      end
    end
    
    def tick args
      $game ||= Game.new
      $game.args = args # set args property on game
      $game.tick        # call tick without passing in args
    end
    
    $game = nil
    

    Indie and Pro Functions link

    The following functions are only available at the Indie and Pro License tiers.

    get_pixels link

    Given a file_path to a sprite, this function returns a Hash with w, h, and pixels. The pixels key contains an array of hexadecimal values representing the ABGR of each pixel in a sprite with item 0 representing the top left corner of the png.

    Here's an example of how to get the color data for a pixel:

    def tick args
      # load the pixels from the image
      args.state.image ||= args.gtk.get_pixels "sprites/square/blue.png"
    
      # initialize state variables for the pixel coordinates
      args.state.x_px ||= 0
      args.state.y_px ||= 0
    
      sprite_pixels = args.state.image.pixels
      sprite_h = args.state.image.h
      sprite_w = args.state.image.w
    
      # move the pixel coordinates using keyboard
      args.state.x_px += args.inputs.left_right
      args.state.y_px += args.inputs.up_down
    
      # get pixel at the current coordinates
      args.state.x_px = args.state.x_px.clamp(0, sprite_w - 1)
      args.state.y_px = args.state.y_px.clamp(0, sprite_h - 1)
      row = sprite_h - args.state.y_px - 1
      col = args.state.x_px
      abgr = sprite_pixels[sprite_h * row + col]
      a = (abgr >> 24) & 0xff
      b = (abgr >> 16) & 0xff
      g = (abgr >> 8) & 0xff
      r = (abgr >> 0) & 0xff
    
      # render debug information
      args.outputs.debug << "row: #{row} col: #{col}"
      args.outputs.debug << "pixel entry 0: rgba #{r} #{g} #{b} #{a}"
    
      # render the sprite plus crosshairs
      args.outputs.sprites << { x: 0, y: 0, w: 80, h: 80, path: "sprites/square/blue.png" }
      args.outputs.lines << { x: args.state.x_px, y: 0, h: 720 }
      args.outputs.lines << { x: 0, y: args.state.y_px, w: 1280 }
    end
    

    See the following sample apps for how to use pixel arrays:

    dlopen link

    Loads a precompiled C Extension into your game.

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

    Environment and Utility Functions link

    The following functions will help in interacting with the OS and rendering pipeline.

    calcstringbox link

    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 link

    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? link

    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 link

    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? link

    Returns true if the window is currently in fullscreen mode.

    set_window_scale link

    This function takes in a float value and uses that to resize the game window to a percentage of 1280x720 (or 720x1280 in portrait mode). The valid scale options are 0.1, 0.25, 0.5, 0.75, 1.25, 1.5, 2.0, 2.5, 3.0, and 4.0. The float value you pass in will be floored to the nearest valid scale option.

    platform? link

    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
      label_style = { x: 640, y: 360, anchor_x: 0.5, anchor_y: 0.5 }
      if    args.gtk.platform? :macos
        args.outputs.labels << { text: "I am running on MacOS.", **label_style }
      elsif args.gtk.platform? :win
        args.outputs.labels << { text: "I am running on Windows.", **label_style }
      elsif args.gtk.platform? :linux
        args.outputs.labels << { text: "I am running on Linux.", **label_style }
      elsif args.gtk.platform? :web
        args.outputs.labels << { text: "I am running on a web page.", **label_style }
      elsif args.gtk.platform? :android
        args.outputs.labels << { text: "I am running on Android.", **label_style }
      elsif args.gtk.platform? :ios
        args.outputs.labels << { text: "I am running on iOS.", **label_style }
      elsif args.gtk.platform? :touch
        args.outputs.labels << { text: "I am running on a device that supports touch (either iOS/Android native or mobile web).", **label_style }
      elsif args.gtk.platform? :steam
        args.outputs.labels << { text: "I am running via steam (covers both desktop and steamdeck).", **label_style }
      elsif args.gtk.platform? :steam_deck
        args.outputs.labels << { text: "I am running via steam on the Steam Deck (not steam desktop).", **label_style }
      elsif args.gtk.platform? :steam_desktop
        args.outputs.labels << { text: "I am running via steam on desktop (not steam deck).", **label_style }
      end
    end
    

    production? link

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

    If you want to simulate a production build. Add an empty file called dragonruby_production_build inside of the metadata folder. This will turn of all logging and all creation of temp files used for development purposes.

    platform_mappings link

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

    {
      "Mac OS X"   => [:desktop, :macos, :osx, :mac, :macosx], # may also include :steam and :steam_desktop run via steam
      "Windows"    => [:desktop, :windows, :win],              # may also include :steam and :steam_desktop run via steam
      "Linux"      => [:desktop, :linux, :nix],                # may also include :steam and :steam_desktop run via steam
      "Emscripten" => [:web, :wasm, :html, :emscripten],       # may also include :touch if running in the web browser on mobile
      "iOS"        => [:mobile, :ios, :touch],
      "Android"    => [:mobile, :android, :touch],
      "Steam Deck" => [:steamdeck, :steam_deck, :steam],
    }
    

    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 link

    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 link

    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 link

    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 link

    Shows the mouse cursor.

    hide_cursor link

    Hides the mouse cursor.

    cursor_shown? link

    Returns true if the mouse cursor is visible.

    set_mouse_grab link

    Takes in a numeric parameter representing the mouse grab mode.

    set_system_cursor link

    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 link

    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
    

    File IO Functions link

    The following functions give you the ability to interact with the file system.

    IMPORTANT: File access functions are sandoxed and assume that the dragonruby binary lives alongside the game you are building. Do not expect these functions to return correct values if you are attempting to run the dragonruby binary from a shared location. It's recommended that the directory structure contained in the zip is not altered and games are built using that starter template.

    list_files link

    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 link

    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 link

    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 link

    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 link

    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 link

    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 link

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

    XML and JSON link

    The following functions help with parsing xml and json.

    parse_json link

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

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

    parse_json_file link

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

    parse_xml link

    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 link

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

    Network IO Functions link

    The following functions help with interacting with the network.

    http_get link

    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 link

    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" => "1707021218" }
      args.state.result ||= args.gtk.http_post "http://httpbin.org/post",
                                               args.state.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 link

    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! link

    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
    

    Developer Support Functions link

    The following functions help support the development process. It is not recommended to use this functions in "production" game logic.

    version link

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

    version_pro? link

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

    reset link

    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
    

    Resetting iVars (advanced)

    NOTE: args.gtk.reset does not reset global variables or instance of classes you have have constructed. If you want to also reset global variables or instances of classes when $gtk.reset is called. Define a reset method. Here's an example:

    class Game
      def initialize
        puts "Game initialize called"
      end
    end
    
    def tick args
      $game ||= Game.new
    
      if args.state.tick_count == 0
        puts "tick_count is 0"
      end
    
      # if r is pressed on the keyboard, reset the game
      if args.inputs.keyboard.key_down.r
        args.gtk.reset
      end
    end
    
    # custom reset function
    def reset
      puts "Custom reset function was called."
      $game = nil
    end
    

    seed and RNG (advanced)

    Optionally, $gtk.reset (args.gtk.reset) can take in a named parameter for RNG called seed:. Passing in seed: will reset RNG so that rand returns a repeatable set of random numbers. This seed value is initialized with the start time of your game ($gtk.started_at). Having this option is is helpful for replays and unit tests.

    Don't worry about this capability if you aren't using DragonRuby's unit testing, or replay capabilities.

    Here is the behavior of $gtk.reset when given a seed:

    def tick args
      if args.state.tick_count == 0
        puts rand
        puts rand
        puts rand
        puts rand
      end
    end
    
    puts "Started at (RNG seed inital value)"
    puts $gtk.started_at # Time as an integer that your game was started at
    
    puts "Seed value that will be used on reset"
    puts $gtk.seed # current value that RNG was seeded with
    
    # reset the game and use the last seed to reset RNG
    $gtk.reset
    
    # === OR ===
    # sets the seed value to predefined value
    # subsequent resets will use the new predefined value
    # $gtk.reset seed: 100
    # (or shorthand)
    # $gtk.reset 100
    
    # sets the seed back to its original value
    # $gtk.reset seed: $gtk.started_at
    

    If you want to set RNG without resetting your game state, you can use $gtk.set_rng VALUE.

    reset_next_tick link

    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 link

    Sprites when loaded are cached. Given a string parameter, this method invalidates the cache record of a sprite so that updates on from the disk can be loaded.

    reset_sprites link

    Sprites when loaded are cached. This method invalidates the cache record of all sprites so that updates on from the disk can be loaded. This function is automatically called when args.gtk.reset ($gtk.reset) is invoked.

    calcspritebox link

    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 link

    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 link

    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! link

    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 link

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

    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! link

    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! link

    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! link

    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 link

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

    hide_console link

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

    enable_console link

    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 link

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

    disable_reset_via_ctrl_r link

    By default, pressing CTRL+R invokes $gtk.reset_next_tick (safely resetting your game with a convenient key combo).

    If you want to disable this behavior, add the following to the main.rb:

    def tick args
      ...
    end
    
    $gtk.disable_reset_via_ctrl_r
    

    NOTE: $gtk.disable_console will also disable the CTRL+R reset behavior.

    start_recording link

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

    stop_recording link

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

    cancel_recording link

    Function cancels a gameplay recording session and discards the replay.

    start_replay link

    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 link

    Function stops a replay that is currently executing.

    get_base_dir link

    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 link

    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 link

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

    open_game_dir link

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

    write_file_root link

    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 link

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

    argv link

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

    cli_arguments link

    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.

    download_stb_rb(_raw) link

    These two functions can help facilitate the integration of external code files. OSS contributors are encouraged to create libraries that all fit in one file (lowering the barrier to entry for adoption).

    Examples:

    def tick args
    end
    
    # option 1:
    # source code will be downloaded from the specified GitHub url, and saved locally with a
    # predefined folder convension.
    $gtk.download_stb_rb "https://github.com/xenobrain/ruby_vectormath/blob/main/vectormath_2d.rb"
    
    # option 2:
    # source code will be downloaded from the specified GitHub username, repository, and file.
    # code will be saved locally with a predefined folder convension.
    $gtk.download_stb_rb "xenobrain", "ruby_vectormath", "vectormath_2d.rb"
    
    # option 3:
    # source code will be downloaded from a direct/raw url and saved to a direct/raw local path.
    $gtk.download_stb_rb_raw "https://raw.githubusercontent.com/xenobrain/ruby_vectormath/main/vectormath_2d.rb",
                             "lib/xenobrain/ruby_vectionmath/vectormath_2d.rb"
    

    reload_history link

    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 link

    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 link

    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.

    State (args.state) link

    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
    

    entity_id link

    Entities automatically receive an entity_id of type Fixnum.

    entity_type link

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

    created_at link

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

    created_at_elapsed link

    Returns the elapsed number of ticks since creation.

    global_created_at link

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

    global_created_at_elapsed link

    Returns the elapsed number of global ticks since creation.

    as_hash link

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

    new_entity link

    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
    

    new_entity_strict link

    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_strict 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 link

    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.

    add_caller_to_puts! link

    If you need to hund down rogue puts statements in your code do:

    def tick args
      # adding the following line to the TOP of your tick method
      # will print ~caller~ along side each ~puts~ statement
      $gtk.add_caller_to_puts!
    end
    

    Geometry (args.geometry) link

    The Geometry module contains methods for calculations that are frequently used in game development.

    The following functions of Geometry are mixed into Hash, Array, and DragonRuby's Entity class:

    You can invoke the functions above using either the mixin variant or the module variant. Example:

    def tick args
      # define to rectangles
      rect_1 = { x: 0, y: 0, w: 100, h: 100 }
      rect_2 = { x: 50, y: 50, w: 100, h: 100 }
    
      # mixin variant
      # call geometry method function from instance of a Hash class
      puts rect_1.intersect_rect?(rect_2)
    
      # OR
    
      # module variants
      puts args.geometry.intersect_rect?(rect_1, rect_2)
      puts Geometry.intersect_rect?(rect_1, rect_2)
    end
    

    intersect_rect? link

    Invocation variants:

    Given two rectangle primitives this function will return true or false depending on if the two rectangles intersect or not. An optional final parameter can be passed in representing the tolerence of overlap needed to be considered a true intersection. The default value of tolerance is 0.1 which keeps the function from returning true if only the edges of the rectangles overlap.

    :anchor_x, and anchor_y is taken into consideration if the objects respond to these methods.

    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 they intersect.

    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 - 20,
        y: 360 - 20,
        w: 40,
        h: 40,
        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 - 20,
        w: 40,
        h: 40,
        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_1.intersect_rect? args.state.box_2
        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
    

    inside_rect? link

    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.

    :anchor_x, and anchor_y is taken into consideration if the objects respond to these methods.

    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 link

    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 link

    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 link

    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 link

    Invocation variants:

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

    angle_from link

    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, angle link

    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
    

    angle_turn_direction link

    Invocation variants:

    Returns 1 or -1 depending on which direction the angle needs to turn to reach the target_angle most efficiently. The angles are assumed to be in degrees. 1 means turn clockwise, and -1 means turn counter-clockwise.

    distance link

    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? link

    Invocation variants:

    circle_center can also contain the radius value (instead of passing it as a separate argument).

    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 link

    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 link

    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 link

    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
    

    line_intersect link

    Given two lines (:x, :y, :x2, :y2), this function returns point of intersection if the line segments intersect. If the line segments do not intersect, nil is returned. If you want the lines to be treated as infinite lines, use ray_intersect.

    Invocation variants:

    def tick args # define line_one to go from the bottom left to the top right args.state.line_one ||= { x: 0, y: 0, x2: 1280, y2: 720 }

    # have the mouse control the x2 and y2 of line_two line_two = { x: 0, y: 720, x2: args.inputs.mouse.x, y2: args.inputs.mouse.y }

    # calc if line_one and line_two intersect and if so, the point of intersection args.state.intersect_point = args.geometry.line_intersect args.state.line_one, line_two

    # draw line_one args.outputs.lines << { x: 0, y: 0, x2: 1280, y2: 720 }

    # draw line_two args.outputs.lines << line_two

    # draw a rect at the intersection point if args.state.intersect_point args.outputs.solids << { x: args.state.intersect_point.x, y: args.state.intersect_point.y, w: 10, h: 10, anchor_x: 0.5, anchor_y: 0.5, r: 255, g: 0, b: 0 } end end

    ray_intersect link

    Given two lines (:x, :y, :x2, :y2), this function returns point of intersection if the ray (infinite line) intersect. If the lines are parallel, nil is returned. If you do not want the lines to be treated as infinite lines, use line_intersect.

    Invocation variants:

    def tick args # define line_one to go from the bottom left to the top right args.state.line_one ||= { x: 0, y: 0, x2: 1280, y2: 720 }

    # have the mouse control the x2 and y2 of line_two line_two = { x: 0, y: 720, x2: args.inputs.mouse.x, y2: args.inputs.mouse.y }

    # calc if line_one and line_two intersect and if so, the point of intersection args.state.intersect_point = args.geometry.ray_intersect args.state.line_one, line_two

    # draw line_one args.outputs.lines << { x: 0, y: 0, x2: 1280, y2: 720 }

    # draw line_two args.outputs.lines << line_two

    # draw a rect at the intersection point if args.state.intersect_point args.outputs.solids << { x: args.state.intersect_point.x, y: args.state.intersect_point.y, w: 10, h: 10, anchor_x: 0.5, anchor_y: 0.5, r: 255, g: 0, b: 0 } end end

    rotate_point link

    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 link

    Given a rect and a collection of rects, find_intersect_rect returns the first rect that intersects with the the first parameter.

    :anchor_x, and anchor_y is taken into consideration if the objects respond to these methods.

    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 link

    Given a rect and a collection of rects, find_all_intersect_rect returns all rects that intersects with the the first parameter.

    :anchor_x, and anchor_y is taken into consideration if the objects respond to these methods.

    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 link

    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
    

    find_all_intersect_rect_quad_tree link

    This is a faster collision algorithm for determining if a rectangle intersects other rectangles in an array. In order to use find_all_intersect_rect_quad_tree, you must first generate a quad tree data structure using create_quad_tree. Use this function if find_all_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
      collisions = args.geometry.find_all_intersect_rect_quad_tree args.state.player,
                                                                  args.state.quad_tree
    
      # if there is a collision render a red box
      args.outputs.solids << collisions.map { |c| c.merge(r: 255) }
    
      # render player as green
      args.outputs.solids << args.state.player.merge(g: 255)
    
      # render boxes as borders
      args.outputs.borders << args.state.boxes
    end
    

    line_angle link

    Given a line, this function will return the angle of the line in degrees.

    vec2_dot_product link

    Given two Hashes with x and y keys (or Objects that respond to x and y), this function will return the dot product of the two vectors.

    Note: Take a look at this sample app for a non-trivial example of how to use this function: ./samples/04_physics_and_collisions/11_bouncing_ball_with_gravity/

    vec2_normalize link

    Given a Hash with x and y keys (or an Object that responds to x and y), this function will return a Hash with x and y keys that represents the vector normalized.

    Note: Take a look at this sample app for a non-trivial example of how to use this function: ./samples/04_physics_and_collisions/11_bouncing_ball_with_gravity/

    line_vec2 link

    Given a line, this function will return a Hash with x and y keys that represents the vector of the line.

    Note: Take a look at this sample app for a non-trivial example of how to use this function: ./samples/04_physics_and_collisions/11_bouncing_ball_with_gravity/

    vec2_magnitude link

    Given a Hash with x and y keys (or an Object that responds to x and y), this function will return the magnitude of the vector.

    Note: Take a look at this sample app for a non-trivial example of how to use this function: ./samples/04_physics_and_collisions/11_bouncing_ball_with_gravity/

    distance_squared link

    Given two Hashes with x and y keys (or Objects that respond to x and y), this function will return the distance squared between the two points. This is useful when you only want to compare distances, and don't need the actual distance.

    Note: Take a look at this sample app for a non-trivial example of how to use this function: ./samples/04_physics_and_collisions/11_bouncing_ball_with_gravity/

    vec2_normal link

    Given a Hash with x and y keys (or an Object that responds to x and y), this function will return a Hash with x and y keys that represents the normal of the vector.

    Note: Take a look at this sample app for a non-trivial example of how to use this function: ./samples/04_physics_and_collisions/11_bouncing_ball_with_gravity/

    circle_intersect_line? link

    The first parameters is a Hash with x, y, and radius keys (or an Object that responds to x, y, and radius).

    The second parameter is a Hash with x, y, x2, and y2 keys (or an Object that responds to x, y, x2, and y2).

    This function will return true if the circle intersects the line, and false if it does not.

    Note: Take a look at this sample app for a non-trivial example of how to use this function: ./samples/04_physics_and_collisions/11_bouncing_ball_with_gravity/

    line_normal link

    The first parameter is a line (a Hash with x, y, x2, and y2 keys, or an Object that responds to x, y, x2, and y2).

    The second parameter is a Hash with x and y keys (or an Object that responds to x and y).

    This function will return a Hash with x and y keys that represents the normal of the line relative to the point provided.

    Note: Take a look at this sample app for a non-trivial example of how to use this function: ./samples/04_physics_and_collisions/11_bouncing_ball_with_gravity/

    point_on_line? link

    The first parameter is a point (a Hash with x and y keys, or an Object that responds to x and y).

    The second parameter is a line (a Hash with x, y, x2, and y2 keys, or an Object that responds to x, y, x2, and y2).

    This function will return true if the point is on the line, and false if it is not.

    Note: Take a look at this sample app for a non-trivial example of how to use this function: ./samples/04_physics_and_collisions/11_bouncing_ball_with_gravity/

    find_collisions link

    Given an Array of rects, returns a Hash of collisions. Each entry in the return Hash maps two rects from the input Array that intersect.

    Note that in the event of an intersection of rects A and B, the returned Hash will contain two entries: {A=>B,B=>A}

    def tick(args)
      args.state.squares ||= []
      args.state.alphabet ||= ('A'..'Z').to_a
    
      # reset the squares if the user presses 'R'
      args.state.squares = [] if args.inputs.keyboard.r
    
      # add a new square every 4 ticks until we get to 26
      # the last part of the condition is to make sure we always have at least 1 square before
      # we start checking for collisions, otherwise #find_collisions will throw an error
      if (args.state.tick_count % 4 == 0 && args.state.squares.size < 26) || args.state.squares.size == 0
    
        # add a new square to the array with a random position, with some padding
        # so that the squares don't spawn too close to the edge of the screen
        # we also set the text to a random letter from the alphabet so we can re-use
        # the same hash for both the squares and their labels
        args.state.squares << {
          x: rand(1280 - 200) + 100, y: rand(720 - 300) + 100,
          w: 50, h: 50,
          text: args.state.alphabet[args.state.squares.size],
          alignment_enum: 1, # center the text
          r: 0, g: 255, b: 0, a: 128
        }
      end
    
      # check for collisions between the squares. this returns a hash of the
      # colliding squares, with the key being the first square and the value
      # being the second square
      collisions = args.geometry.find_collisions(args.state.squares)
      collisions.each do |key, value|
        key.merge!(r: 255, g: 0, b: 0)
        value.merge!(r: 0, g: 0, b: 255)
      end
    
      # render instructions and collision info
      args.outputs.labels << {x: 30, y: 20.from_top, text: "Press 'R' to reset" }
      args.outputs.labels << {x: 30, y: 45.from_top, text: "#{args.state.squares.size} squares, #{collisions.size} collisions" }
      args.outputs.labels << {x: 30, y: 70.from_top, text: "#{collisions.map { |k, v| "{#{k.text}=>#{v.text}}" }.join(', ')}" }
    
      # render the squares and their labels
      args.outputs.solids << args.state.squares
      args.outputs.labels << args.state.squares.map_with_index do |square, i|
        square.merge(
          x: square.x + 25, y: square.y + 35, # center the text in the square
          r: 0, g: 0, b: 0                    # make it black
        )
      end
    end
    

    create_quad_tree link

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

    Audio (args.audio) link

    Hash that contains audio sources that are playing.

    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).

    volume link

    You can globally control the volume for all audio using args.audio.volume. Example:

    def tick args
      if args.inputs.down
        args.audio.volume -= 0.01
      elsif args.inputs.up
        args.audio.volume += 0.01
      end
    end
    

    One-Time Sounds link

    Here's how to play audio one-time (does not loop).

    def tick args
      # play a one-time non-looping sound every second
      if (args.state.tick_count % 60) == 0
        args.audio[:coin] = { input: "sounds/coin.wav" }
        # OR
        args.outputs.sounds << "sounds/coin.wav"
      end
    end
    

    Looping Audio link

    Here's how to play audio that loops (eg background music), and how to stop the sound.

    def tick args
      if args.state.tick_count == 0
        args.audio[:bg_music] = { input: "sounds/bg-music.ogg", looping: true }
      end
    
      # stop sound if space key is pressed
      if args.inputs.keyboard.key_down.space
        args.audio[:bg_music] = nil
        # OR
        args.audio.delete :bg_music
      end
    end
    

    Setting Additional Audio Properties link

    Here are additional properties that can be set.

    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',  # file path relative to mygame directory
        gain:    1.0,             # Volume (float value 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: true,            # Set to true to loop the sound/music until you stop it
        foobar:  :baz,            # additional keys/values can be safely added to help with context/game logic (ie metadata)
        x: 0.0, y: 0.0, z: 0.0    # Relative position to the listener, x, y, z from -1.0 to 1.0
      }
    end
    

    IMPORTANT: Please take note that gain and pitch must be given float values (eg gain: 1.0, not gain: 1 or game: 0).

    Advanced Audio Manipulation (Crossfade) link

    Take a look at the Audio Mixer sample app for a non-trival example of how to use these properties. The sample app is located within the DragonRuby zip file at ./samples/07_advanced_audio/01_audio_mixer.

    Here's an example of crossfading two bg music tracks.

    def tick args
      # start bg-1.ogg at the start
      if args.state.tick_count == 0
        args.audio[:bg_music] = { input: "sounds/bg-1.ogg", looping: true, gain: 0.0 }
      end
    
      # if space is pressed cross fade to new bg music
      if args.inputs.keyboard.key_down.space
        # get the current bg music and create a new audio entry that represents the crossfade
        current_bg_music = args.audio[:bg_music]
    
        # cross fade audio entry
        args.audio[:bg_music_fade] = {
          input:    current_bg_music[:input],
          looping:  true,
          gain:     current_bg_music[:gain],
          pitch:    current_bg_music[:pitch],
          paused:   false,
          playtime: current_bg_music[:playtime]
        }
    
        # replace the current playing background music (toggling between bg-1.ogg and bg-2.ogg)
        # set the gain/volume to 0.0 (this will be increased to 1.0 accross ticks)
        new_background_music = { looping: true, gain: 0.0 }
    
        # determine track to play (swap between bg-1 and bg-2)
        new_background_music[:input] = if current_bg_music.input == "sounds/bg-1.ogg"
                                         "sounds/bg-2.ogg"
                                       else
                                         "sounds/bg-2.ogg"
                                       end
    
        # bg music audio entry
        args.audio[:bg_music] = new_background_music
      end
    
      # process cross fade (happens every tick)
      # increase the volume of bg_music every tick until it's at 100%
      if args.audio[:bg_music] && args.audio[:bg_music].gain < 1.0
        # increase the gain 1% every tick until we are at 100%
        args.audio[:bg_music].gain += 0.01
        # clamp value to 1.0 max value
        args.audio[:bg_music].gain = 1.0 if args.audio[:bg_music].gain > 1.0
      end
    
      # decrease the volume of cross fade bg music until it's 0.0, then delete it
      if args.audio[:bg_music_fade] && args.audio[:bg_music_fade].gain > 0.0
        # decrease by 1% every frame
        args.audio[:bg_music_fade].gain -= 0.01
        # delete audio when it's at 0%
        if args.audio[:bg_music_fade].gain <= 0.0
          args.audio[:bg_music_fade] = nil
        end
      end
    end
    

    Audio encoding trouble shooting link

    If audio doesn't seem to be working, try re-encoding it via ffmpeg:

    # re-encode ogg
    ffmpeg -i ./mygame/sounds/SOUND.ogg -ac 2 -b:a 160k -ar 44100 -acodec libvorbis ./mygame/sounds/SOUND-converted.ogg
    
    # convert wav to ogg
    ffmpeg -i ./mygame/sounds/SOUND.wav -ac 2 -b:a 160k -ar 44100 -acodec libvorbis ./mygame/sounds/SOUND-converted.ogg
    

    Sound Synthesis link

    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 link

    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.

    For sound synthesis, gain can be initially set, but changing the value while the sound is playing will produce clicking/popping sounds. The attack and release of the sound should be baked into the array.

    Example: link

    def generate_sine_wave frequency:, duration:, fade_out: true
      samples_per_period = (48000 / frequency).ceil
      count = (samples_per_period * duration.fdiv(60)).floor * frequency
      count.map_with_index do |i|
        attack_perc = (i / samples_per_period).clamp(0, 1)
        release_perc = if fade_out
                          1 - (i / count)
                       elsif i > count - samples_per_period
                         (count - i) / samples_per_period
                       else
                         1
                       end
        Math.sin((2 * Math::PI) * (i / samples_per_period)) * attack_perc * release_perc
      end
    end
    
    def tick args
      if args.state.tick_count == 0
        wave_data = generate_sine_wave frequency: 440.0,
                                       duration: 60 * 1.5,
                                       fade_out: true
        args.audio[:my_audio] = {
          input: [1, 48000, wave_data],
        }
      end
    end
    

    Easing (args.easing) link

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

    ease link

    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

    Examples link

    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
    

    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
    

    Easing Definitions link

    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, :quint

    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
    

    easing.ease_spline start_tick, current_tick, duration, spline link

    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
    

    Pixel Arrays (args.pixel_arrays) link

    A PixelArray object with a width, height and an Array of pixels which are hexadecimal color values in ABGR format.

    You can create a pixel array like this:

    w = 200
    h = 100
    args.pixel_array(:my_pixel_array).w = w
    args.pixel_array(:my_pixel_array).h = h
    

    You'll also need to fill the pixels with values, if they are nil, the array will render with the checkerboard texture. You can use #00000000 to fill with transparent pixels if desired.

    args.pixel_array(:my_pixel_array).pixels.fill #FF00FF00, 0, w * h
    

    Note: To convert from rgb hex (like skyblue #87CEEB) to abgr hex, you split it in pairs pair (eg 87 CE EB) and reverse the order (eg EB CE 87) add join them again: #EBCE87. Then add the alpha component in front ie: FF for full opacity: #FFEBCE87.

    You can draw it by using the symbol for :path

    args.outputs.sprites << { x: 500, y: 300, w: 200, h: 100, path: :my_pixel_array) }
    

    If you want access a specific x, y position, you can do it like this for a bottom-left coordinate system:

    x = 150
    y = 33
    args.pixel_array(:my_pixel_array).pixels[(height - y) * width + x] = 0xFFFFFFFF
    

    CVars (args.cvars) link

    Hash contains metadata pulled from the files under the ./metadata directory. To get the keys that are available type $args.cvars.keys in the Console. Here is an example of how to retrieve the game version number:

    def tick args
      args.outputs.labels << {
        x: 640,
        y: 360,
        text: args.cvars["game_metadata.version"].value.to_s
      }
    end
    

    Each CVar has the following properties value, name, description, type, locked.

    Layout (args.layout) link

    Layout provides apis for placing primitives on a virtual grid that's within the "safe area" accross all platforms. This virtual grid is useful for rendering static controls (buttons, menu items, configuration screens, etc).

    For reference implementations, take a look at the following sample apps:

    The following example creates two menu items and updates a label with the button that was clicked:

    def tick args
      # render debug_primitives of args.layout for help with placement
      # args.outputs.primitives << args.layout.debug_primitives
    
      # capture the location for a label centered at the top
      args.state.label_rect ||= args.layout.rect(row: 0, col: 10, w: 4, h: 1)
      # state variable to hold the current click status
      args.state.label_message ||= "click a menu item"
    
      # capture the location of two menu items positioned in the center
      # with a cell width of 4 and cell height of 2
      args.state.menu_item_1_rect ||= args.layout.rect(row: 1, col: 10, w: 4, h: 2)
      args.state.menu_item_2_rect ||= args.layout.rect(row: 3, col: 10, w: 4, h: 2)
    
      # render the label at the center of the label_rect
      args.outputs.labels << args.state.label_rect.center.merge(text: args.state.label_message,
                                                                anchor_x: 0.5,
                                                                anchor_y: 0.5)
    
      # render menu items
      args.outputs.sprites << args.state.menu_item_1_rect.merge(path: :solid,
                                                                r: 100,
                                                                g: 100,
                                                                b: 200)
      args.outputs.labels << args.state.menu_item_1_rect.center.merge(text: "item 1",
                                                                      r: 255,
                                                                      g: 255,
                                                                      b: 255,
                                                                      anchor_x: 0.5,
                                                                      anchor_y: 0.5)
    
      args.outputs.sprites << args.state.menu_item_2_rect.merge(path: :solid,
                                                                r: 100,
                                                                g: 100,
                                                                b: 200)
      args.outputs.labels << args.state.menu_item_2_rect.center.merge(text: "item 2",
                                                                      r: 255,
                                                                      g: 255,
                                                                      b: 255,
                                                                      anchor_x: 0.5,
                                                                      anchor_y: 0.5)
    
      # if click occurs, then determine which menu item was clicked
      if args.inputs.mouse.click
        if args.inputs.mouse.intersect_rect?(args.state.menu_item_1_rect)
          args.state.label_message = "menu item 1 clicked"
        elsif args.inputs.mouse.intersect_rect?(args.state.menu_item_2_rect)
          args.state.label_message = "menu item 2 clicked"
        else
          args.state.label_message = "click a menu item"
        end
      end
    end
    

    rect link

    Given a row:, col:, w:, h:, returns a Hash with properties x, y, w, h, and center (which contains a Hash with x, y). The virtual grid is 12 rows by 24 columns (or 24 columns by 12 rows in portrait mode).

    debug_primitives link

    Function returns an array of primities that can be rendered to the screen to help you place items within the grid.

    Example:

    def tick args
      args.outputs.primitives << args.layout.debug_primitives
    end
    

    Array link

    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 link

    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? link

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

    l1 = [:a, :b, :c]
    result = l1.include_any?(:b, :c, :d)
    puts result # true
    
    l1 = [:a, :b, :c]
    l2 = [:b, :c, :d]
    # returns true, but requires the parameter to be "splatted"
    # consider using (l1 & l2) instead
    result = l1.include_any?(*l2)
    puts result # true
    
    # & (bit-wise and) operator usage
    l1 = [:a, :b, :c]
    l2 = [:d, :c]
    result = (l1 & l2)
    puts result # [:c]
    
    # | (bit-wise or) operator usage
    l1 = [:a, :b, :c, :a]
    l2 = [:d, :f, :a]
    result = l1 | l2
    puts result # [:d, :f, :a, :b, :c]
    

    any_intersect_rect? link

    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 link

    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 link

    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 link

    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 link

    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 link

    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
    

    Numeric link

    The Numeric class has been extend to provide methods that will help in common game development tasks.

    frame_index link

    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. The named parameters version allows you to also specify a repeat_index which is useful if your animation has starting frames that shouldn't be considered when looped:

    def tick args
      start_looping_at = 0
    
      sprite_index =
        start_looping_at.frame_index count: 6,
                                     hold_for: 4,
                                     repeat: true,
                                     repeat_index: 0,
                                     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
    

    The named parameter variant of frame_index is also available on Numeric:

    def tick args
      sprite_index =
        Numeric.frame_index start_at: 0,
                            count: 6, # or frame_count: 6 (if both are provided frame_count will be used)
                            hold_for: 4,
                            repeat: true,
                            repeat_index: 0,
                            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
    

    Another example where frame_index is applied to a sprite sheet.

    def tick args
      index = Numeric.frame_index start_at: 0,
                                  frame_count: 7,
                                  repeat: true
      args.outputs.sprites << {
        x: 0,
        y: 0,
        w: 32,
        h: 32,
        source_x: 32 * index,
        source_y: 0,
        source_w: 32,
        source_h: 32,
        path: "sprites/misc/explosion-sheet.png"
      }
    end
    

    elapsed_time link

    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? link

    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? link

    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 link

    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 link

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

    global_tick_count link

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

    Grid (args.grid) link

    Returns the virtual grid for the game.

    name link

    Returns either :origin_bottom_left or :origin_center.

    bottom link

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

    top link

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

    left link

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

    right link

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

    rect link

    Returns a rectangle Primitive that represents the grid.

    origin_bottom_left! link

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

    origin_center! link

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

    orientation link

    Returns either :portrait or :landscape. The orientation of your game is set within ./mygame/metadata/game_metadata.txt.

    w link

    Returns the grid's width (value is 1280 if orientation :landscape, and 720 if orientation is :portrait).

    h link

    Returns the grid's width (value is 720 if orientation :landscape, and 1280 if orientation is :portrait).

    Grid HD Properties link

    The following properties are available to Pro license holders. Setting hd=true and hd=true in ./mygame/metadata/game_metadata.txt will enable All Screen Mode.

    Please review the sample app located at ./samples/07_advanced_rendering_hd/03_allscreen_properties.

    When All Screen mode is enabled, you can render outside of the 1280x720 safe area. The 1280x720 logical canvas will be centered within the screen and scaled to one of the following closest/bess-fit resolutions.

    Regardless of the rendering resolution, your logical canvas will always be 1280x720 and all hd_* values will be at this same logical scale.

    hd_left link

    Returns the position of the left edge of the screen at the logical scale of 1280x720. For example, if the window's width is 1290x720, then hd_left will be -5.

    hd_right link

    Returns the position of the right edge of the screen at the logical scale of 1280x720. For example, if the window's width is 1290x720, then hd_right will be 1285.

    hd_bottom link

    Returns the position of the bottom edge of the screen at the logical scale of 1280x720. For example, if the window's width is 1280x730, then hd_bottom will be -5.

    hd_top link

    Returns the position of the top edge of the screen at the logical scale of 1280x720. For example, if the window's width is 1280x730, then hd_top will be 725.

    hd_offset_x link

    Returns the number of pixels that the 1280x720 canvas is offset from the left so that it's centered in the screen.

    hd_offset_y link

    Returns the number of pixels that the 1280x720 canvas is offset from the bottom so that it's centered in the screen.

    window_width link

    Returns the true width of the window. High DPI settings are not taken into consideration.

    window_height link

    Returns the true height of the window. High DPI settings are not taken into consideration.

    native_width link

    Returns the true width of the window. High DPI settings (macOS, iOS, Android) are taken into consideration.

    native_height link

    Returns the true height of the window. High DPI settings (macOS, iOS, Android) are taken into consideration.

    native_scale link

    Returns a decimal value representing the rendering scale of the game.

    native_scale_enum link

    Returns an integer value representing the rendering scale of the game.

    The enum value is taken into consideration when rendering a sprite through texture atlases.

    Given the following code:

    def tick args
      args.outputs.sprites << { x: 0, y: 0, w: 100, h: 100, path: "sprites/player.png" }
    end
    

    The sprite path of sprites/player.png will be replaced according to the following naming conventions (fallback to a lower resolution is automatically handled if a sprite with naming convention isn't found):

    Samples link

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

    Learn Ruby Optional link

    Beginner Ruby Primer - automation.rb link

    # ./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
    
    

    Beginner Ruby Primer - main.rb link

    # ./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
    
    

    Intermediate Ruby Primer - printing.txt link

    # ./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
    
    

    Intermediate Ruby Primer - strings.txt link

    # ./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
    
    

    Intermediate Ruby Primer - numbers.txt link

    # ./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
    
    

    Intermediate Ruby Primer - booleans.txt link

    # ./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
    
    

    Intermediate Ruby Primer - conditionals.txt link

    # ./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
    
    

    Intermediate Ruby Primer - looping.txt link

    # ./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
    
    

    Intermediate Ruby Primer - functions.txt link

    # ./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
    
    

    Intermediate Ruby Primer - arrays.txt link

    # ./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
    # ====================================================================================
    
    

    Intermediate Ruby Primer - main.rb link

    # ./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
    
    

    Intermediate Ruby Primer - repl.rb link

    # ./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 link

    Labels - main.rb link

    # ./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.
    
    =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 LABEL is the ARRAY:
    #     [320, 640, "Example
    #     [ X ,  Y,    TEXT]
    # 4. It's recommended to use hashes so that you're not reliant on positional values:
    #    { x: 320,
    #      y: 640,
    #      text: "Text",
    #      font: "fonts/font.ttf",
    #      anchor_x: 0.5, # or alignment_enum: 0, 1, or 2
    #      anchor_y: 0.5, # or vertical_alignment_enum: 0, 1, or 2
    #      r: 0,
    #      g: 0,
    #      b: 0,
    #      a: 255,
    #      size_px: 20,   # or size_enum: -10 to 10 (0 means "ledgible on small devices" ie: 20px)
    #      blendmode_enum: 1 }
    
    
    # The tick method is called by DragonRuby every frame
    # args contains all the information regarding the game.
    def tick args
      # render the current frame to the screen using a simple array
      # this is useful for quick and dirty output and is recommended to use
      # a Hash to render long term.
      args.outputs.labels << [580.5, 650, "frame: #{args.state.tick_count}"]
    
      # render the current frame to the screen centered vertically and horizontally at 640, 620
      args.outputs.labels << { x: 640, y: 620, anchor_x: 0.5, anchor_y: 0.5, text: "frame: #{args.state.tick_count}" }
    
      # 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 << { x: 5,          y: 720 - 5, text: "This is a label located at the top left." }
      args.outputs.labels << { x: 5,          y:      30, text: "This is a label located at the bottom left." }
      args.outputs.labels << { x: 1280 - 420, y: 720 - 5, text: "This is a label located at the top right." }
      args.outputs.labels << { x: 1280 - 440, y: 30,      text: "This is a label located at the bottom right." }
    
      # Demonstration of the Size Enum Parameter
    
      # size_enum of -2 is equivalent to using size_px: 18
      args.outputs.labels << { x: 175 + 150, y: 610 - 50, text: "Smaller label.",  size_enum: -2 }
    
      # size_enum of -1 is equivalent to using size_px: 20
      args.outputs.labels << { x: 175 + 150, y: 580 - 50, text: "Small label.",    size_enum: -1 }
    
      # size_enum of  0 is equivalent to using size_px: 22
      args.outputs.labels << { x: 175 + 150, y: 550 - 50, text: "Medium label.",   size_enum:  0 }
    
      # size_enum of  0 is equivalent to using size_px: 24
      args.outputs.labels << { x: 175 + 150, y: 520 - 50, text: "Large label.",    size_enum:  1 }
    
      # size_enum of  0 is equivalent to using size_px: 26
      args.outputs.labels << { x: 175 + 150, y: 490 - 50, text: "Larger label.",   size_enum:  2 }
    
      # Demonstration of the Align Parameter
      args.outputs.lines  << { x: 175 + 150, y: 0, h: 720 }
    
      # alignment_enum: 0 is equivalent to anchor_x: 0
      args.outputs.labels << { x: 175 + 150, y: 345 - 50, text: "Left aligned.",   alignment_enum: 0 }
    
      # alignment_enum: 1 is equivalent to anchor_x: 0.5
      args.outputs.labels << { x: 175 + 150, y: 325 - 50, text: "Center aligned.", alignment_enum: 1 }
    
      # alignment_enum: 2 is equivalent to anchor_x: 1
      args.outputs.labels << { x: 175 + 150, y: 305 - 50, text: "Right aligned.",  alignment_enum: 2 }
    
      # Demonstration of the RGBA parameters
      args.outputs.labels << { x: 600  + 150, y: 590 - 50, text: "Red Label.",   r: 255, g:   0, b:   0 }
      args.outputs.labels << { x: 600  + 150, y: 570 - 50, text: "Green Label.", r:   0, g: 255, b:   0 }
      args.outputs.labels << { x: 600  + 150, y: 550 - 50, text: "Blue Label.",  r:   0, g:   0, b: 255 }
      args.outputs.labels << { x: 600  + 150, y: 530 - 50, text: "Faded Label.", r:   0, g:   0, b:   0, a: 128 }
    
      # providing a custom font
      args.outputs.labels << { x: 690 + 150,
                               y: 330 - 50,
                               text: "Custom font (Hash)",
                               size_enum: 0,                 # equivalent to size_px:  22
                               alignment_enum: 1,            # equivalent to anchor_x: 0.5
                               vertical_alignment_enum: 2,   # equivalent to anchor_y: 1
                               r: 125,
                               g: 0,
                               b: 200,
                               a: 255,
                               font: "manaspc.ttf" }
    
      # Primitives can hold anything, and can be given a label in the following forms
      args.outputs.primitives << { x: 690 + 150,
                                   y: 330 - 80,
                                   text: "Custom font (.primitives Hash)",
                                   size_enum: 0,
                                   alignment_enum: 1,
                                   r: 125,
                                   g: 0,
                                   b: 200,
                                   a: 255,
                                   font: "manaspc.ttf" }
    end
    
    

    Labels Text Wrapping - main.rb link

    # ./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
    
    

    Lines - main.rb link

    # ./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: Provided an Array or a Hash, lines will be rendered to the screen.
    - args.state.tick_count: This property contains an integer value that
      represents the current frame. DragonRuby 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)
    #    Creating a line using an Array (quick and dirty):
    #    [x, y, x2, y2, r, g, b, a]
    #    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
    # 4. Using Hashes, the keys are :x, :y, :x2, :y2, :r, :g, :b, and :a
    def tick args
      args.outputs.labels << { x: 640,
                               y: 700,
                               text: "Sample app shows how to create lines.",
                               size_px: 22,
                               anchor_x: 0.5,
                               anchor_y: 0.5 }
    
      # Render lines using Arrays/Tuples
      # This is quick and dirty and it's recommended to use Hashes long term
      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  << { x:  380,
                               y:  370,
                               x2: 875,
                               y2: 370,
                               r:  args.state.tick_count % 255,
                               g:  0,
                               b:  0,
                               a:  255 }
    
      args.outputs.lines  << { x:  380,
                               y:  330 - args.state.tick_count % 25,
                               x2: 875,
                               y2: 330,
                               r:  0,
                               g:  0,
                               b:  0,
                               a:  255 }
    
      args.outputs.lines  << { x:  380 + args.state.tick_count % 400,
                               y:  290,
                               x2: 875,
                               y2: 290,
                               r:  0,
                               g:  0,
                               b:  0,
                               a:  255 }
    end
    
    

    Solids Borders - main.rb link

    # ./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: Provided an Array or a Hash, solid squares will be
      rendered to the screen.
    - args.outputs.borders: Provided an Array or a Hash, borders
      will be rendered to the screen.
    - args.outputs.primitives: Provided an Hash with a :primitive_marker key,
      either a solid square or border will be rendered to the screen.
    =end
    
    # The parameters required for rects are:
    # 1. The bottom left corner (x, y)
    # 2. The width (w)
    # 3. The height (h)
    # 4. The rgba values for the color and transparency (r, g, b, a)
    # [100, 100, 400, 500, 0, 255, 0, 180]
    # Whether the rect would be filled or not depends on if
    # it is added to args.outputs.solids or args.outputs.borders
    # (or its :primitive_marker if Hash is sent to args.outputs.primitives)
    def tick args
      args.outputs.labels << { x: 640,
                               y: 700,
                               text: "Sample app shows how to create solid squares and borders.",
                               size_px: 22,
                               anchor_x: 0.5,
                               anchor_y: 0.5 }
    
      # Render solids/borders using Arrays/Tuples
      # This is quick and dirty and it's recommended to use Hashes long term
      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.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]
    
      # using Hashes
      args.outputs.solids << { x: 710,
                               y: 520,
                               w: 50,
                               h: 50,
                               r: 0,
                               g: 80,
                               b: 40,
                               a: args.state.tick_count % 255 }
    
      # primitives outputs requires a primitive_marker to differentiate
      # between a solid or a border
      args.outputs.primitives << { x: 770,
                                   y: 520,
                                   w: 50,
                                   h: 50,
                                   r: 0,
                                   g: 80,
                                   b: 40,
                                   a: args.state.tick_count % 255,
                                   primitive_marker: :solid }
    
      args.outputs.borders << { x: 710,
                                y: 320,
                                w: 50,
                                h: 50,
                                r: 0,
                                g: 80,
                                b: 40,
                                a: args.state.tick_count % 255 }
    
      # primitives outputs requires a primitive_marker to differentiate
      # between a solid or a border
      args.outputs.borders << { x: 770,
                                y: 320,
                                w: 50,
                                h: 50,
                                r: 0,
                                g: 80,
                                b: 40,
                                a: args.state.tick_count % 255,
                                primitive_marker: :border }
    end
    
    

    Sprites - main.rb link

    # ./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: Provided an Array or a Hash, a sprite will be
      rendered to the screen.
    
    Properties of a sprite:
    {
      # common properties
      x: 0,
      y: 0,
      w: 100,
      h: 100,
      path: "sprites/square/blue.png",
      angle: 90,
      a: 255,
    
      # anchoring (float value representing a percentage to offset w and h)
      anchor_x: 0,
      anchor_y: 0,
      angle_anchor_x: 0,
      angle_anchor_y: 0,
    
      # color saturation
      r: 255,
      g: 255,
      b: 255,
    
      # flip rendering
      flip_horizontally: false,
      flip_vertically: false
    
      # sprite sheet properties/clipped rect (using the top-left as the origin)
      tile_x: 0,
      tile_y: 0,
      tile_w: 20,
      tile_h: 20
    
      # sprite sheet properties/clipped rect (using the bottom-left as the origin)
      source_x: 0,
      source_y: 0,
      source_w: 20,
      source_h: 20,
    }
    =end
    def tick args
      args.outputs.labels << { x: 640,
                               y: 700,
                               text: "Sample app shows how to render a sprite.",
                               size_px: 22,
                               anchor_x: 0.5,
                               anchor_y: 0.5 }
    
      # ==================
      # ROW 1 Simple Rendering
      # ==================
      args.outputs.labels << { x: 460,
                               y: 600,
                               text: "Simple rendering." }
    
      # using quick and dirty Array (use Hashes for long term maintainability)
      args.outputs.sprites << [460, 470, 128, 101, 'dragonruby.png']
    
      # using Hashes
      args.outputs.sprites << { x: 610,
                                y: 470,
                                w: 128,
                                h: 101,
                                path: 'dragonruby.png',
                                a: args.state.tick_count % 255 }
    
      args.outputs.sprites << { x: 760 + 64,
                                y: 470 + 50,
                                w: 128,
                                h: 101,
                                anchor_x: 0.5,
                                anchor_y: 0.5,
                                path: 'dragonruby.png',
                                flip_horizontally: true,
                                flip_vertically: true,
                                a: args.state.tick_count % 255 }
    
      # ==================
      # ROW 2 Angle/Angle Anchors
      # ==================
      args.outputs.labels << { x: 460,
                               y: 400,
                               text: "Angle/Angle Anchors." }
      # rotation using angle (in degrees)
      args.outputs.sprites << { x: 460,
                                y: 270,
                                w: 128,
                                h: 101,
                                path: 'dragonruby.png',
                                angle: args.state.tick_count % 360 }
    
      # rotation anchor using angle_anchor_x
      args.outputs.sprites << { x: 760,
                                y: 270,
                                w: 128,
                                h: 101,
                                path: 'dragonruby.png',
                                angle: args.state.tick_count % 360,
                                angle_anchor_x: 0,
                                angle_anchor_y: 0 }
    
      # ==================
      # ROW 3 Sprite Cropping
      # ==================
      args.outputs.labels << { x: 460,
                               y: 200,
                               text: "Cropping (tile sheets)." }
    
      # tiling using top left as the origin
      args.outputs.sprites << { x: 460,
                                y: 90,
                                w: 80,
                                h: 80,
                                path: 'dragonruby.png',
                                tile_x: 0,
                                tile_y: 0,
                                tile_w: 80,
                                tile_h: 80 }
    
      # overlay to see how tile_* crops
      args.outputs.sprites << { x: 460,
                                y: 70,
                                w: 128,
                                h: 101,
                                path: 'dragonruby.png',
                                a: 80 }
    
      # tiling using bottom left as the origin
      args.outputs.sprites << { x: 610,
                                y: 70,
                                w: 80,
                                h: 80,
                                path: 'dragonruby.png',
                                source_x: 0,
                                source_y: 0,
                                source_w: 80,
                                source_h: 80 }
    
      # overlay to see how source_* crops
      args.outputs.sprites << { x: 610,
                                y: 70,
                                w: 128,
                                h: 101,
                                path: 'dragonruby.png',
                                a: 80 }
    end
    
    

    Sounds - main.rb link

    # ./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 link

    Keyboard - main.rb link

    # ./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
      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."]
        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
    
    

    Moving A Sprite - main.rb link

    # ./samples/02_input_basics/01_moving_a_sprite/app/main.rb
    def tick args
      # Create a player and set default values
      # NOTE: args.state is a construct that lets you define properties on the fly
      args.state.player ||= { x: 100,
                              y: 100,
                              w: 50,
                              h: 50,
                              path: 'sprites/square/green.png' }
    
      # move the player around by consulting args.inputs
      # the top level args.inputs checks the keyboard's arrow keys, WASD,
      # and controller one
      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
    
      # Render the player to the screen
      args.outputs.sprites << args.state.player
    end
    
    

    Mouse - main.rb link

    # ./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
      args.outputs.labels << { x: 640,
                               y: 700,
                               anchor_x: 0.5,
                               anchor_y: 0.5,
                               text: "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
      { x: x,
        y: 720 - 5 - 20 * row,
        text: message }
    end
    
    

    Mouse Point To Rect - main.rb link

    # ./samples/02_input_basics/03_mouse_point_to_rect/app/main.rb
    =begin
    - Example usage of Hash#inside_rect? to determine if a mouse click happened
      inside of a box.
      ```
      rect_1 = { x: 100, y: 100, w:   1, h:   1 }
      rect_2 = { x:   0, y:   0, w: 500, h: 500 }
      result = rect_1.inside_rect? rect_2
      ```
    =end
    def tick args
      # initialize the rectangle
      args.state.box ||= { x: 785, y: 370, w: 50, h: 50, r: 0, g: 0, b: 170 }
    
      # store the mouse click and the frame the click occured
      # and whether it was inside or outside the box
      if args.inputs.mouse.click
        args.state.last_mouse_click = args.inputs.mouse.click
        args.state.last_mouse_click_at = args.state.tick_count
        if args.state.last_mouse_click.inside_rect? args.state.box
          args.state.was_inside_rect = true
        else
          args.state.was_inside_rect = false
        end
      end
    
      # render
      args.outputs.labels << { x: 640, y: 700, anchor_x: 0.5, anchor_y: 0.5, text: "Sample app shows how to determine if a click happened inside a rectangle." }
      args.outputs.labels << { x: 340, y: 420, text:  "Click inside (or outside) the blue box ---->" }
    
      args.outputs.borders << args.state.box
    
      if args.state.last_mouse_click
        if args.state.was_inside_rect
          args.outputs.labels << { x: 810,
                                   y: 340,
                                   anchor_x: 0.5,
                                   anchor_y: 0.5,
                                   text: "Mouse click happened *inside* the box [frame #{args.state.last_mouse_click_at}]." }
        else
          args.outputs.labels << { x: 810,
                                   y: 340,
                                   anchor_x: 0.5,
                                   anchor_y: 0.5,
                                   text: "Mouse click happened *outside* the box [frame #{args.state.last_mouse_click_at}]." }
        end
      else
        args.outputs.labels << { x: 810,
                                 y: 340,
                                 anchor_x: 0.5,
                                 anchor_y: 0.5,
                                 text: "Waiting for mouse click..." }
      end
    end
    
    

    Mouse Drag And Drop - main.rb link

    # ./samples/02_input_basics/04_mouse_drag_and_drop/app/main.rb
    def tick args
      # create 10 random squares on the screen
      if !args.state.squares
        # the squares will be contained in lookup/Hash so that we can access via their id
        args.state.squares = {}
        10.times_with_index do |id|
          # for each square, store it in the hash with
          # the id (we're just using the index 0-9 as the index)
          args.state.squares[id] = {
            id: id,
            x: 100 + (rand * 1080),
            y: 100 + (520 * rand),
            w: 100,
            h: 100,
            path: "sprites/square/blue.png"
          }
        end
      end
    
      # two key variables are set here
      # - square_reference: this represents the square that is currently being dragged
      # - square_under_mouse: this represents the square that the mouse is currently being hovered over
      if args.state.currently_dragging_square_id
        # if the currently_dragging_square_id is set, then set the "square_under_mouse" to
        # the same square as square_reference
        square_reference = args.state.squares[args.state.currently_dragging_square_id]
        square_under_mouse = square_reference
      else
        # if currently_dragging_square_id isn't set, then see if there is a square that
        # the mouse is currently hovering over (the square reference will be nil since
        # we haven't selected a drag target yet)
        square_under_mouse = args.geometry.find_intersect_rect args.inputs.mouse, args.state.squares.values
        square_reference = nil
      end
    
    
      # if a click occurs, and there is a square under the mouse
      if args.inputs.mouse.click && square_under_mouse
        # capture the id of the square that the mouse is hovering over
        args.state.currently_dragging_square_id = square_under_mouse.id
    
        # also capture where in the square the mouse was clicked so that
        # the movement of the square will smoothly transition with the mouse's
        # location
        args.state.mouse_point_inside_square = {
          x: args.inputs.mouse.x - square_under_mouse.x,
          y: args.inputs.mouse.y - square_under_mouse.y,
        }
      elsif args.inputs.mouse.held && args.state.currently_dragging_square_id
        # if the mouse is currently being held and the currently_dragging_square_id was set,
        # then update the x and y location of the referenced square (taking into consideration the
        # relative position of the mouse when the square was clicked)
        square_reference.x = args.inputs.mouse.x - args.state.mouse_point_inside_square.x
        square_reference.y = args.inputs.mouse.y - args.state.mouse_point_inside_square.y
      elsif args.inputs.mouse.up
        # if the mouse is released, then clear out the currently_dragging_square_id
        args.state.currently_dragging_square_id = nil
      end
    
      # render all the squares on the screen
      args.outputs.sprites << args.state.squares.values
    
      # if there was a square under the mouse, add an "overlay"
      if square_under_mouse
        args.outputs.sprites << square_under_mouse.merge(path: "sprites/square/red.png")
      end
    end
    
    

    Mouse Rect To Rect - main.rb link

    # ./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
    
    

    Controller - main.rb link

    # ./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
    
    

    Touch - main.rb link

    # ./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
    
    

    Managing Scenes - main.rb link

    # ./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 link

    Animation Using Separate Pngs - main.rb link

    # ./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" }
    
      args.outputs.labels << { x: 640,
                               y: 700,
                               text: "Sample app shows how to use Numeric#frame_index to animate a sprite over time.",
                               anchor_x: 0.5,
                               anchor_y: 0.5 }
    end
    
    

    Animation Using Sprite Sheet - main.rb link

    # ./samples/03_rendering_sprites/02_animation_using_sprite_sheet/app/main.rb
    def tick args
      args.state.player ||= { x: 100,
                              y: 100,
                              w: 64,
                              h: 64,
                              direction: 1,
                              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
    
    

    Animation States 1 - main.rb link

    # ./samples/03_rendering_sprites/03_animation_states_1/app/main.rb
    class Game
      attr_gtk
    
      def defaults
        state.show_debug_layer = true if state.tick_count == 0
    
        state.player ||= {
          tile_size: 64,
          speed: 3,
          slash_frames: 15,
          x: 50,
          y: 400,
          dir_x: 1,
          dir_y: -1,
          is_moving: false
        }
    
        state.enemies ||= []
      end
    
      def add_enemy
        state.enemies << {
          x: 1200 * rand,
          y: 600 * rand,
          w: 64,
          h: 64,
          anchor_x: 0.5,
          anchor_y: 0.5,
          path: 'sprites/enemy.png'
        }
      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,
          anchor_x: 0.5,
          anchor_y: 0.5,
          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,
        }
      end
    
      def sprite_horizontal_stand
        {
          x: player.x,
          y: player.y,
          w: player.tile_size,
          h: player.tile_size,
          anchor_x: 0.5,
          anchor_y: 0.5,
          path: 'sprites/horizontal-stand.png',
          flip_horizontally: player.dir_x > 0,
        }
      end
    
      def sprite_horizontal_slash
        tile_index   = player.slash_at.frame_index(5, player.slash_frames.idiv(5), false) || 0
    
        {
          x: player.x + player.dir_x.sign * 9.25,
          y: player.y + 9.25,
          w: 165,
          h: 165,
          anchor_x: 0.5,
          anchor_y: 0.5,
          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.borders << player.slash_collision_rect
      end
    
      def slash_initiate?
        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 if vector.x != 0
          player.dir_y = vector.y if vector.y != 0
          player.is_moving = true
        else
          state.debug_label = vector
          player.is_moving = false
        end
      end
    
      def calc_slash
        player.slash_collision_rect = {
          x: player.x + player.dir_x.sign * 52,
          y: player.y,
          w: 40,
          h: 20,
          anchor_x: 0.5,
          anchor_y: 0.5,
          path: "sprites/debug-slash.png"
        }
    
        # 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
    
    

    Animation States 2 - main.rb link

    # ./samples/03_rendering_sprites/03_animation_states_2/app/main.rb
    def tick args
      defaults args
      input args
      calc args
      render args
    end
    
    def defaults args
      # uncomment the line below to slow the game down by a factor of 4 -> 15 fps (for debugging)
      # args.gtk.slowmo! 4
    
      args.state.player ||= {
        x: 144,                # render x of the player
        y: 32,                 # render y of the player
        w: 144 * 2,            # render width of the player
        h: 72 * 2,             # render height of the player
        dx: 0,                 # velocity x of the player
        action: :standing,     # current action/status of the player
        action_at: 0,          # frame that the action occurred
        previous_direction: 1, # direction the player was facing last frame
        direction: 1,          # direction the player is facing this frame
        launch_speed: 4,       # speed the player moves when they start running
        run_acceleration: 1,   # how much the player accelerates when running
        run_top_speed: 8,      # the top speed the player can run
        friction: 0.9,         # how much the player slows down when have stopped attempting to run
        anchor_x: 0.5,         # render anchor x of the player
        anchor_y: 0            # render anchor y of the player
      }
    end
    
    def input args
      # if the directional has been pressed on the input device
      if args.inputs.left_right != 0
        # determine if the player is currently running or not,
        # if they aren't, set their dx to their launch speed
        # otherwise, add the run acceleration to their dx
        if args.state.player.action != :running
          args.state.player.dx = args.state.player.launch_speed * args.inputs.left_right.sign
        else
          args.state.player.dx += args.inputs.left_right * args.state.player.run_acceleration
        end
    
        # capture the direction the player is facing and the previous direction
        args.state.player.previous_direction = args.state.player.direction
        args.state.player.direction = args.inputs.left_right.sign
      end
    end
    
    def calc args
      # clamp the player's dx to the top speed
      args.state.player.dx = args.state.player.dx.clamp(-args.state.player.run_top_speed, args.state.player.run_top_speed)
    
      # move the player by their dx
      args.state.player.x += args.state.player.dx
    
      # capture the player's hitbox
      player_hitbox = hitbox args.state.player
    
      # check boundary collisions and stop the player if they are colliding with the ednges of the screen
      if (player_hitbox.x - player_hitbox.w / 2) < 0
        args.state.player.x = player_hitbox.w / 2
        args.state.player.dx = 0
        # if the player is not standing, set them to standing and capture the frame
        if args.state.player.action != :standing
          args.state.player.action = :standing
          args.state.player.action_at = args.state.tick_count
        end
      elsif (player_hitbox.x + player_hitbox.w / 2) > 1280
        args.state.player.x = 1280 - player_hitbox.w / 2
        args.state.player.dx = 0
    
        # if the player is not standing, set them to standing and capture the frame
        if args.state.player.action != :standing
          args.state.player.action = :standing
          args.state.player.action_at = args.state.tick_count
        end
      end
    
      # if the player's dx is not 0, they are running. update their action and capture the frame if needed
      if args.state.player.dx.abs > 0
        if args.state.player.action != :running || args.state.player.direction != args.state.player.previous_direction
          args.state.player.action = :running
          args.state.player.action_at = args.state.tick_count
        end
      elsif args.inputs.left_right == 0
        # if the player's dx is 0 and they are not currently trying to run (left_right == 0), set them to standing and capture the frame
        if args.state.player.action != :standing
          args.state.player.action = :standing
          args.state.player.action_at = args.state.tick_count
        end
      end
    
      # if the player is not trying to run (left_right == 0), slow them down by the friction amount
      if args.inputs.left_right == 0
        args.state.player.dx *= args.state.player.friction
    
        # if the player's dx is less than 1, set it to 0
        if args.state.player.dx.abs < 1
          args.state.player.dx = 0
        end
      end
    end
    
    def render args
      # determine if the player should be flipped horizontally
      flip_horizontally = args.state.player.direction == -1
      # determine the path to the sprite to render, the idle sprite is used if action == :standing
      path = "sprites/link-idle.png"
    
      # if the player is running, determine the frame to render
      if args.state.player.action == :running
        # the sprite animation's first 3 frames represent the launch of the run, so we skip them on the animation loop
        # by setting the repeat_index to 3 (the 4th frame)
        frame_index = args.state.player.action_at.frame_index(count: 9, hold_for: 8, repeat: true, repeat_index: 3)
        path = "sprites/link-run-#{frame_index}.png"
    
        args.outputs.labels << { x: args.state.player.x - 144, y: args.state.player.y + 230, text: "action:      #{args.state.player.action}" }
        args.outputs.labels << { x: args.state.player.x - 144, y: args.state.player.y + 200, text: "action_at:   #{args.state.player.action_at}" }
        args.outputs.labels << { x: args.state.player.x - 144, y: args.state.player.y + 170, text: "frame_index: #{frame_index}" }
      else
        args.outputs.labels << { x: args.state.player.x - 144, y: args.state.player.y + 230, text: "action:      #{args.state.player.action}" }
        args.outputs.labels << { x: args.state.player.x - 144, y: args.state.player.y + 200, text: "action_at:   #{args.state.player.action_at}" }
        args.outputs.labels << { x: args.state.player.x - 144, y: args.state.player.y + 170, text: "frame_index: n/a" }
      end
    
    
      # render the player's hitbox and sprite (the hitbox is used to determine boundary collision)
      args.outputs.borders << hitbox(args.state.player)
      args.outputs.borders << args.state.player
    
      # render the player's sprite
      args.outputs.sprites << args.state.player.merge(path: path, flip_horizontally: flip_horizontally)
    end
    
    def hitbox entity
      {
        x: entity.x,
        y: entity.y + 5,
        w: 64,
        h: 96,
        anchor_x: 0.5,
        anchor_y: 0
      }
    end
    
    
    $gtk.reset
    
    

    Animation States 3 - main.rb link

    # ./samples/03_rendering_sprites/03_animation_states_3/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].transient!
        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
    
    

    Color And Rotation - main.rb link

    # ./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.background_color = [70, 70, 70]
      outputs.sprites <<  { **destination_rect(state), # sets first four parameters of car sprite
                            path: 'sprites/86.png',    # image path of car
                            angle: state.angle,
                            a: opacity,                # alpha
                            **saturation,
                            **source_rect(state),      # sprite sub division/tile (source x, y, w, h)
                            flip_horizontally: false,
                            flip_vertically: false,    # don't flip sprites
                            **rotation_anchor }
    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
      { angle_anchor_x: 0.7, angle_anchor_y: 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
      { r: 255, g: 255, b: 255 }
    end
    
    # Sets definition of destination_rect (used to define the car sprite)
    def destination_rect state
      { x: state.x,
        y: state.y,
        w: state.sprite.width  * state.sprite.scale, # multiplies by 4 to set size
        h: 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
      { source_x: 0,
        source_y: 0,
        source_w: state.sprite.width,
        source_h: state.sprite.height }
    end
    
    

    Physics And Collisions link

    Simple - main.rb link

    # ./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
    
    

    Simple Aabb Collision - main.rb link

    # ./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
    
    

    Simple Aabb Collision With Map Editor - main.rb link

    # ./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
    
    

    Simple Aabb Collision With Map Editor - Data - terrain.txt link

    # ./samples/04_physics_and_collisions/01_simple_aabb_collision_with_map_editor/data/terrain.txt
    352,320,32,32
    352,352,32,32
    352,384,32,32
    352,256,32,32
    352,192,32,32
    352,224,32,32
    

    Moving Objects - main.rb link

    # ./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
    
    

    Entities - main.rb link

    # ./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
    
    

    Box Collision - main.rb link

    # ./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
    
    

    Box Collision 2 - main.rb link

    # ./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
    
    

    Box Collision 3 - main.rb link

    # ./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
    
    

    Jump Physics - main.rb link

    # ./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
    
    

    Bouncing On Collision - ball.rb link

    # ./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
    
    

    Bouncing On Collision - block.rb link

    # ./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
    
    

    Bouncing On Collision - cannon.rb link

    # ./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
    
    

    Bouncing On Collision - main.rb link

    # ./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
    
    

    Bouncing On Collision - peg.rb link

    # ./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
    
    

    Bouncing On Collision - vector2d.rb link

    # ./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
    
    

    Arbitrary Collision - ball.rb link

    # ./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
    
    

    Arbitrary Collision - blocks.rb link

    # ./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
    
    

    Arbitrary Collision - linear_collider.rb link

    # ./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
    
    

    Arbitrary Collision - main.rb link

    # ./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
    
    

    Arbitrary Collision - paddle.rb link

    # ./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
    
    

    Arbitrary Collision - rectangle.rb link

    # ./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
    
    

    Arbitrary Collision - square_collider.rb link

    # ./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
    
    

    Arbitrary Collision - vector2d.rb link

    # ./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
    

    Collision With Object Removal - ball.rb link

    # ./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
    
    

    Collision With Object Removal - linear_collider.rb link

    # ./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
    
    

    Collision With Object Removal - main.rb link

    # ./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
    
    

    Collision With Object Removal - paddle.rb link

    # ./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
    
    

    Collision With Object Removal - tests.rb link

    # ./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
    
    

    Collision With Object Removal - vector2d.rb link

    # ./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
    
    

    Bouncing Ball With Gravity - main.rb link

    # ./samples/04_physics_and_collisions/11_bouncing_ball_with_gravity/app/main.rb
    class Game
      attr_gtk
    
      def tick
        outputs.labels << { x: 30, y: 30.from_top,
                            text: "left/right arrow keys to spin, up arrow to jump, ctrl+r to reset, click two points to place terrain" }
        defaults
        calc
        render
      end
    
      def defaults
        state.terrain ||= []
    
        state.player ||= { x: 100,
                           y: 640,
                           dx: 0,
                           dy: 0,
                           radius: 12,
                           drag: 0.05477,
                           gravity: 0.03,
                           entropy: 0.9,
                           angle: 0,
                           facing: 1,
                           angle_velocity: 0,
                           elasticity: 0.5 }
    
        state.grid_points ||= (1280.idiv(40) + 1).flat_map do |x|
          (720.idiv(40) + 1).map do |y|
            { x: x * 40,
              y: y * 40,
              w: 40,
              h: 40,
              anchor_x: 0.5,
              anchor_y: 0.5 }
          end
        end
      end
    
      def calc
        player.y = 720  if player.y < 0
        player.x = 1280 if player.x < 0
        player.x = 0    if player.x > 1280
        player.angle_velocity = player.angle_velocity.clamp(-30, 30)
        calc_edit_mode
        calc_play_mode
      end
    
      def calc_edit_mode
        state.current_grid_point = geometry.find_intersect_rect(inputs.mouse, state.grid_points)
        calc_edit_mode_click
      end
    
      def calc_edit_mode_click
        return if !state.current_grid_point
        return if !inputs.mouse.click
    
        if !state.start_point
          state.start_point = state.current_grid_point
        else
          state.terrain << { x: state.start_point.x,
                             y: state.start_point.y,
                             x2: state.current_grid_point.x,
                             y2: state.current_grid_point.y }
          state.start_point = nil
        end
      end
    
      def calc_play_mode
        player.x += player.dx
        player.dy -= player.gravity
        player.y += player.dy
        player.angle += player.angle_velocity
        player.dy += player.dy * player.drag ** 2 * -1
        player.dx += player.dx * player.drag ** 2 * -1
        player.colliding = false
        player.colliding_with = nil
    
        if inputs.keyboard.key_down.up
          player.dy += 5 * player.angle.vector_y
          player.dx += 5 * player.angle.vector_x
        end
        player.angle_velocity += inputs.left_right * -1
        player.facing = if inputs.left_right == -1
                          -1
                        elsif inputs.left_right == 1
                          1
                        else
                          player.facing
                        end
    
        collisions = player_terrain_collisions
        collisions.each do |collision|
          collide! player, collision
        end
    
        if player.colliding_with
          roll! player, player.colliding_with
        end
      end
    
      def reflect_velocity! circle, line
        slope = geometry.line_slope line, replace_infinity: 1000
        slope_angle = geometry.line_angle line
        if slope_angle == 90 || slope_angle == 270
          circle.dx *= -circle.elasticity
        else
          circle.angle_velocity += slope * (circle.dx.abs + circle.dy.abs)
          vec = line.x2 - line.x, line.y2 - line.y
          len = Math.sqrt(vec.x**2 + vec.y**2)
    
          vec.x /= len
          vec.y /= len
    
          n = geometry.vec2_normal vec
    
          v_dot_n = geometry.vec2_dot_product({ x: circle.dx, y: circle.dy }, n)
    
          circle.dx = circle.dx - n.x * (2 * v_dot_n)
          circle.dy = circle.dy - n.y * (2 * v_dot_n)
          circle.dx *= circle.elasticity
          circle.dy *= circle.elasticity
          half_terminal_velocity = 10
          impact_intensity = (circle.dy.abs) / half_terminal_velocity
          impact_intensity = 1 if impact_intensity > 1
    
          final = (0.9 - 0.8 * impact_intensity)
          next_angular_velocity = circle.angle_velocity * final
          circle.angle_velocity *= final
    
          if (circle.dx.abs + circle.dy.abs) <= 0.2
            circle.dx = 0
            circle.dy = 0
            circle.angle_velocity *= 0.99
          end
    
          if circle.angle_velocity.abs <= 0.1
            circle.angle_velocity = 0
          end
        end
      end
    
      def position_on_line! circle, line
        circle.colliding = true
        point = geometry.line_normal line, circle
        if point.y > circle.y
          circle.colliding_from_above = true
        else
          circle.colliding_from_above = false
        end
    
        circle.colliding_with = line
    
        if !geometry.point_on_line? point, line
          distance_from_start_of_line = geometry.distance_squared({ x: line.x, y: line.y }, point)
          distance_from_end_of_line = geometry.distance_squared({ x: line.x2, y: line.y2 }, point)
          if distance_from_start_of_line < distance_from_end_of_line
            point = { x: line.x, y: line.y }
          else
            point = { x: line.x2, y: line.y2 }
          end
        end
        angle = geometry.angle_to point, circle
        circle.y = point.y + angle.vector_y * (circle.radius)
        circle.x = point.x + angle.vector_x * (circle.radius)
      end
    
      def collide! circle, line
        return if !line
        position_on_line! circle, line
        reflect_velocity! circle, line
        next_player = { x: player.x + player.dx,
                        y: player.y + player.dy,
                        radius: player.radius }
      end
    
      def roll! circle, line
        slope_angle = geometry.line_angle line
        return if slope_angle == 90 || slope_angle == 270
    
        ax = -circle.gravity * slope_angle.vector_y
        ay = -circle.gravity * slope_angle.vector_x
    
        if ax.abs < 0.05 && ay.abs < 0.05
          ax = 0
          ay = 0
        end
    
        friction_coefficient = 0.0001
        friction_force = friction_coefficient * circle.gravity * slope_angle.vector_x
    
        circle.dy += ay
        circle.dx += ax
    
        if circle.colliding_from_above
          circle.dx += circle.angle_velocity * slope_angle.vector_x * 0.1
          circle.dy += circle.angle_velocity * slope_angle.vector_y * 0.1
        else
          circle.dx += circle.angle_velocity * slope_angle.vector_x * -0.1
          circle.dy += circle.angle_velocity * slope_angle.vector_y * -0.1
        end
    
        if circle.dx != 0
          circle.dx -= friction_force * (circle.dx / circle.dx.abs)
        end
    
        if circle.dy != 0
          circle.dy -= friction_force * (circle.dy / circle.dy.abs)
        end
      end
    
      def player_terrain_collisions
        terrain.find_all do |terrain|
                 geometry.circle_intersect_line? player, terrain
               end
               .sort_by do |terrain|
                 if player.facing == -1
                   -terrain.x
                 else
                   terrain.x
                 end
               end
      end
    
      def render
        render_current_grid_point
        render_preview_line
        render_grid_points
        render_terrain
        render_player
        render_player_terrain_collisions
      end
    
      def render_player_terrain_collisions
        collisions = player_terrain_collisions
        outputs.lines << collisions.map do |collision|
                           { x: collision.x,
                             y: collision.y,
                             x2: collision.x2,
                             y2: collision.y2,
                             r: 255,
                             g: 0,
                             b: 0 }
                         end
      end
    
      def render_current_grid_point
        return if state.game_mode == :play
        return if !state.current_grid_point
        outputs.sprites << state.current_grid_point
                                .merge(w: 8,
                                       h: 8,
                                       anchor_x: 0.5,
                                       anchor_y: 0.5,
                                       path: :solid,
                                       g: 0,
                                       r: 0,
                                       b: 0,
                                       a: 128)
      end
    
      def render_preview_line
        return if state.game_mode == :play
        return if !state.start_point
        return if !state.current_grid_point
    
        outputs.lines << { x: state.start_point.x,
                           y: state.start_point.y,
                           x2: state.current_grid_point.x,
                           y2: state.current_grid_point.y }
      end
    
      def render_grid_points
        outputs
          .sprites << state
                        .grid_points
                        .map do |point|
          point.merge w: 8,
                      h: 8,
                      anchor_x: 0.5,
                      anchor_y: 0.5,
                      path: :solid,
                      g: 255,
                      r: 255,
                      b: 255,
                      a: 128
        end
      end
    
      def render_terrain
        outputs.lines << state.terrain
      end
    
      def render_player
        outputs.sprites << player_prefab
      end
    
      def player_prefab
        flip_horizontally = player.facing == -1
        { x: player.x,
          y: player.y,
          w: player.radius * 2,
          h: player.radius * 2,
          angle: player.angle,
          anchor_x: 0.5,
          anchor_y: 0.5,
          path: "sprites/circle/blue.png" }
      end
    
      def player
        state.player
      end
    
      def terrain
        state.terrain
      end
    end
    
    def tick args
      $game ||= Game.new
      $game.args = args
      $game.tick
    end
    
    def reset args
      $terrain = args.state.terrain
      $game = nil
    end
    
    

    Ramp Collision - main.rb link

    # ./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
    
    

    Ramp Collision - toolbar.rb link

    # ./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: 64, 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, r: 128, a: 64)
    
      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,
            g: 128
          },
          {
            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 link

    Mouse Click - main.rb link

    # ./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:
    
     - Hash#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_gtk # class macro that adds outputs, inputs, state, etc to class
    
      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
        if !state.spaces
          state.square_size ||= 80
          state.board_left  ||= grid.w_half - state.square_size * 1.5
          state.board_top   ||= grid.h_half - state.square_size * 1.5
          state.spaces = {}
          state.space_combinations.each do |x, y|
            state.spaces[x]    ||= {}
            state.spaces[x][y] ||= {}
            state.spaces[x][y].hitbox ||= {
              x: state.board_left + (x + 1) * state.square_size,
              y: state.board_top  + (y + 1) * state.square_size,
              w: state.square_size,
              h: state.square_size
            }
          end
        end
      end
    
      # Uses borders to create grid squares for the game's board. Also outputs the game pieces using labels.
      def render_board
        # 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.map do |space| # outputs borders for all board spaces
                             space.hitbox
                           end
    
        hovered_box = all_spaces.find do |space|
          inputs.mouse.inside_rect?(space.hitbox) && !space.piece
        end
    
        if hovered_box && !state.game_over
          args.outputs.solids << { x: hovered_box.hitbox.x,
                                   y: hovered_box.hitbox.y,
                                   w: hovered_box.hitbox.w,
                                   h: hovered_box.hitbox.h,
                                   r: 0,
                                   g: 100,
                                   b: 200,
                                   a: 80 }
        end
    
        # put label in each filled space of board
        outputs.labels << filled_spaces.map do |space|
          { x: space.hitbox.x + space.hitbox.w / 2,
            y: space.hitbox.y + space.hitbox.h / 2,
            anchor_x: 0.5,
            anchor_y: 0.5,
            size_px: 40,
            text: space.piece }
        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
                            { x: 640, y: 600, text: "x won", size_px: 40, anchor_x: 0.5, anchor_y: 0.5 }
                          elsif state.o_won
                            { x: 640, y: 600, text: "o won", size_px: 40, anchor_x: 0.5, anchor_y: 0.5 }
                          elsif state.draw
                            { x: 640, y: 600, text: "draw", size_px: 40, anchor_x: 0.5, anchor_y: 0.5 }
                          else
                            { x: 640, y: 600, text: "turn: #{state.current_turn}", size_px: 40, anchor_x: 0.5, anchor_y: 0.5 }
                          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.hitbox) && !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
        all_spaces.reject { |space| !space.piece } # reject spaces with no pieces in them
      end
    
      # Defines all spaces on the board.
      def all_spaces
        state.space_combinations.map do |x, y|
          state.spaces[x][y] # yield if a block is given
        end
      end
    end
    
    $tic_tac_toe = nil
    
    def tick args
      args.outputs.labels << { x: 640,
                               y: 700,
                               anchor_x: 0.5,
                               anchor_y: 0.5,
                               text: "Sample app shows how to work with mouse clicks and hitboxes." }
      $tic_tac_toe ||= TicTacToe.new
      $tic_tac_toe.args = args
      $tic_tac_toe.tick
    end
    
    

    Mouse Move - main.rb link

    # ./samples/05_mouse/02_mouse_move/app/main.rb
    =begin
    
     Reminders:
    
     - 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 ||= { x: 640,
                           y: 360,
                           w: 4 * 3,
                           h: 8 * 3,
                           attack_angle: 0,
                           dx: 0,
                           dy: 0,
                           created_at: state.tick_count }
      end
    
      # Outputs a gray background.
      # Calls the methods needed to output the player, zombies, etc onto the screen.
      def render
        outputs.background_color = [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.merge path: animation_sprite(z)  # sets definition for sprite, calls animation_sprite method
        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
          zombie = { x: z.x,
                     y: z.y,
                     w: 4 * 3,
                     h: 8 * 3,
                     path: animation_sprite(z, z.death_at), # calls animation_sprite method
                     a: 255 * z.death_at.ease(30, :flip) }  # transparency of a zombie changes when they die
    
          # 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.
          [zombie,
           zombie.merge(path: 'sprites/slash.png',
                        angle: 45 + (state.player.attack_angle_on_click || 0)).scale_rect(3, 0.5, 0.5)]
        end
      end
    
      # Outputs the player sprite using the images in the sprites folder.
      def render_player
        # 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.sprites << { x: state.player.x + state.player.attack_angle.vector_x(60),
                             y: state.player.y + state.player.attack_angle.vector_y(60),
                             w: 3,
                             h: 3,
                             r: 255,
                             g: 0,
                             b: 0,
                             path: :solid }
    
        outputs.sprites << { x: state.player.x,
                             y: state.player.y,
                             w: 4 * 3,
                             h: 8 * 3,
                             path: "sprites/player-#{animation_index(state.player.created_at.elapsed_time)}.png" } # string interpolation
      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, r: 255, g: 255, b: 255, a: 255 * state.flash_at.ease(10, :flip), path: :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 << (if rand > 0.5
                           {
                             x: grid.rect.w.randomize(:ratio), # random x position on screen (within grid scope)
                             y: [-10, 730].sample, # y position is set to either -10 or 730 (randomly chosen)
                             w: 4 * 3, h: 8 * 3,
                             created_at: state.tick_count
                           }
                          else
                           {
                             x: [-10, 1290].sample, # x position is set to either -10 or 1290 (randomly chosen)
                             y: grid.rect.w.randomize(:ratio), # random y position on screen
                             w: 4 * 3, h: 8 * 3,
                             created_at: state.tick_count
                           }
                          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.clamp(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.clamp(0, 1280)
        state.player.y = state.player.y.clamp(0, 720) # 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.intersect_rect? state.player) }
        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_time # 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 Move Paint App - main.rb link

    # ./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
    
    

    Coordinate Systems - main.rb link

    # ./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
    
    

    Clicking Buttons - main.rb link

    # ./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 link

    Reading Writing Files - main.rb link

    # ./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 Game - main.rb link

    # ./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 link

    Audio Mixer - main.rb link

    # ./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.rect.x).to_f / (results.pitch_slider_rect.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.rect.x).to_f / (results.playtime_slider_rect.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.rect.x).to_f / (results.gain_slider_rect.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.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
    
    

    Audio Mixer - server_ip_address.txt link

    # ./samples/07_advanced_audio/01_audio_mixer/app/server_ip_address.txt
    192.168.1.65
    

    Sound Synthesis - main.rb link

    # ./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]  }
      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 link

    Labels With Wrapped Text - main.rb link

    # ./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].transient!
      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
    
    

    Rotating Label - main.rb link

    # ./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].transient!
      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
    
    

    Render Targets Clip Area - main.rb link

    # ./samples/07_advanced_rendering/01_render_targets_clip_area/app/main.rb
    def tick args
      # define your state
      args.state.player ||= { x: 0, y: 0, w: 300, h: 300, path: "sprites/square/blue.png" }
    
      # controller input for player
      args.state.player.x += args.inputs.left_right * 5
      args.state.player.y += args.inputs.up_down * 5
    
      # create a render target that holds the
      # full view that you want to render
    
      # make the background transparent
      args.outputs[:clipped_area].background_color = [0, 0, 0, 0]
    
      # set the w/h to match the screen
      args.outputs[:clipped_area].w = 1280
      args.outputs[:clipped_area].h = 720
    
      # mark it as transient so that the render target
      # isn't cached (since we are going to be changing it every frame)
      args.outputs[:clipped_area].transient!
    
      # render the player in the render target
      args.outputs[:clipped_area].sprites << args.state.player
    
      # render the player and clip area as borders to
      # keep track of where everything is at regardless of clip mode
      args.outputs.borders << args.state.player
      args.outputs.borders << { x: 540, y: 460, w: 200, h: 200 }
    
      # render the render target, but only the clipped area
      args.outputs.sprites << {
        # where to render the render target
        x: 540,
        y: 460,
        w: 200,
        h: 200,
        # what part of the render target to render
        source_x: 540,
        source_y: 460,
        source_w: 200,
        source_h: 200,
        # path of render target to render
        path: :clipped_area
      }
    
      # mini map
      args.outputs.borders << { x: 1280 - 160, y: 0, w: 160, h: 90 }
      args.outputs.sprites << { x: 1280 - 160, y: 0, w: 160, h: 90, path: :clipped_area }
    end
    
    $gtk.reset
    
    

    Render Targets Combining Sprites - main.rb link

    # ./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].transient!
      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
    
    

    Simple Render Targets - main.rb link

    # ./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
    
    

    Coordinate Systems And Render Targets - main.rb link

    # ./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].transient!
      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].transient!
      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
    
    

    Render Targets Repeating Texture - main.rb link

    # ./samples/07_advanced_rendering/02_render_targets_repeating_texture/app/main.rb
    # Sample app shows how to leverage render targets to create a repeating
    # texture given a source sprite.
    def tick args
      args.outputs.sprites << repeating_texture(args,
                                                x: 640,
                                                y: 360,
                                                w: 1280,
                                                h: 720,
                                                anchor_x: 0.5,
                                                anchor_y: 0.5,
                                                path: 'sprites/square/blue.png')
    end
    
    def repeating_texture args, x:, y:, w:, h:, path:, anchor_x: 0, anchor_y: 0
      # create an area to store state for function
      args.state.repeating_texture_lookup ||= {}
    
      # create a unique name for the repeating texture
      rt_name = "#{path.hash}-#{w}-#{h}"
    
      # if the repeating texture has not been created yet, create it
      if args.state.repeating_texture_lookup[rt_name]
        return { x: x,
                 y: y,
                 w: w,
                 h: h,
                 anchor_x: anchor_x,
                 anchor_y: anchor_y,
                 path: rt_name }
      end
    
      # create a render target to store the repeating texture
      args.outputs[rt_name].w = w
      args.outputs[rt_name].h = h
    
      # calculate the sprite box for the repeating texture
      sprite_w, sprite_h = args.gtk.calcspritebox path
    
      # calculate the number of rows and columns needed to fill the repeating texture
      rows = h.idiv(sprite_h) + 1
      cols = w.idiv(sprite_w) + 1
    
      # generate the repeating texture using a render target
      # this only needs to be done once and will be cached
      args.outputs[rt_name].sprites << rows.map do |r|
                                         cols.map do |c|
                                           { x: sprite_w * c,
                                             y:  h - sprite_h * (r + 1),
                                             w: sprite_w,
                                             h: sprite_h,
                                             path: path }
                                         end
                                       end
    
      # store a flag in state denoting that the repeating
      # texture has been generated
      args.state.repeating_texture_lookup[rt_name] = true
    
      # return the repeating texture
      repeating_texture args, x: x, y: y, w: w, h: h, path: path
    end
    
    $gtk.reset
    
    

    Render Targets Thick Lines - main.rb link

    # ./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
    
    

    Render Targets With Tile Manipulation - main.rb link

    # ./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
    
    

    Render Target Viewports - main.rb link

    # ./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.outputs.transient = true
      $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
    
    

    Render Primitive Hierarchies - main.rb link

    # ./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
    
    

    Render Primitives As Hash - main.rb link

    # ./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
    
    

    Buttons As Render Targets - main.rb link

    # ./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
    
    

    Pixel Arrays - main.rb link

    # ./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
    
    

    Pixel Arrays From File - main.rb link

    # ./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
    
    

    Shake Camera - main.rb link

    # ./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].transient!
        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
    
    

    Simple Camera - main.rb link

    # ./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].transient!
      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
    
    

    Simple Camera Multiple Targets - main.rb link

    # ./samples/07_advanced_rendering/07_simple_camera_multiple_targets/app/main.rb
    def tick args
      args.outputs.background_color = [0, 0, 0]
    
      # variables you can play around with
      args.state.world.w                ||= 1280
      args.state.world.h                ||= 720
      args.state.target_hero            ||= :hero_1
      args.state.target_hero_changed_at ||= -30
      args.state.hero_size              ||= 32
    
      # initial state of heros and camera
      args.state.hero_1 ||= { x: 100, y: 100 }
      args.state.hero_2 ||= { x: 100, y: 600 }
      args.state.camera ||= { x: 640, y: 360, scale: 1.0 }
    
      # render 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: "+/- to change zoom of camera", r: 255, g: 255, b: 255}.label!
      args.outputs.primitives << { x: 10, y: 30.from_top, text: "arrow keys to move target hero", r: 255, g: 255, b: 255}.label!
      args.outputs.primitives << { x: 10, y: 50.from_top, text: "space to cycle target hero", r: 255, g: 255, b: 255}.label!
    
      # render scene
      args.outputs[:scene].transient!
      args.outputs[:scene].w = args.state.world.w
      args.outputs[:scene].h = args.state.world.h
    
      # render world
      args.outputs[:scene].solids << { x: 0, y: 0, w: args.state.world.w, h: args.state.world.h, r: 20, g: 60, b: 80 }
    
      # render hero_1
      args.outputs[:scene].solids << { x: args.state.hero_1.x, y: args.state.hero_1.y,
                                       w: args.state.hero_size, h: args.state.hero_size, r: 255, g: 155, b: 80 }
    
      # render hero_2
      args.outputs[:scene].solids << { x: args.state.hero_2.x, y: args.state.hero_2.y,
                                       w: args.state.hero_size, h: args.state.hero_size, r: 155, g: 255, b: 155 }
    
      # render scene relative to 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 }
    
      # mini map
      args.outputs.borders << { x: 10,
                                y: 10,
                                w: args.state.world.w.idiv(8),
                                h: args.state.world.h.idiv(8),
                                r: 255,
                                g: 255,
                                b: 255 }
      args.outputs.sprites << { x: 10,
                                y: 10,
                                w: args.state.world.w.idiv(8),
                                h: args.state.world.h.idiv(8),
                                path: :scene }
    
      # cycle target hero
      if args.inputs.keyboard.key_down.space
        if args.state.target_hero == :hero_1
          args.state.target_hero = :hero_2
        else
          args.state.target_hero = :hero_1
        end
        args.state.target_hero_changed_at = args.state.tick_count
      end
    
      # move target hero
      hero_to_move = if args.state.target_hero == :hero_1
                       args.state.hero_1
                     else
                       args.state.hero_2
                     end
    
      if args.inputs.directional_angle
        hero_to_move.x += args.inputs.directional_angle.vector_x * 5
        hero_to_move.y += args.inputs.directional_angle.vector_y * 5
        hero_to_move.x  = hero_to_move.x.clamp(0, args.state.world.w - hero_to_move.size)
        hero_to_move.y  = hero_to_move.y.clamp(0, args.state.world.h - hero_to_move.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
      end
    
      args.state.camera.scale = 0.1 if args.state.camera.scale < 0.1
    end
    
    def other_hero args
      if args.state.target_hero == :hero_1
        return args.state.hero_2
      else
        return args.state.hero_1
      end
    end
    
    def calc_scene_position args
      target_hero = if args.state.target_hero == :hero_1
                      args.state.hero_1
                    else
                      args.state.hero_2
                    end
    
      other_hero = if args.state.target_hero == :hero_1
                     args.state.hero_2
                   else
                     args.state.hero_1
                   end
    
      # calculate the lerp percentage based on the time since the target hero changed
      lerp_percentage = args.easing.ease args.state.target_hero_changed_at,
                                         args.state.tick_count,
                                         30,
                                         :smooth_stop_quint,
                                         :flip
    
      # calculate the angle and distance between the target hero and the other hero
      angle_to_other_hero = args.geometry.angle_to target_hero, other_hero
    
      # calculate the distance between the target hero and the other hero
      distance_to_other_hero = args.geometry.distance target_hero, other_hero
    
      # the camera position is the target hero position plus the angle and distance to the other hero (lerped)
      { x: args.state.camera.x - (target_hero.x + (angle_to_other_hero.vector_x * distance_to_other_hero * lerp_percentage)) * args.state.camera.scale,
        y: args.state.camera.y - (target_hero.y + (angle_to_other_hero.vector_y * distance_to_other_hero * lerp_percentage)) * args.state.camera.scale,
        w: args.state.world.w * args.state.camera.scale,
        h: args.state.world.h * args.state.camera.scale }
    end
    
    

    Splitscreen Camera - main.rb link

    # ./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].transient!
        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].transient!
         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].transient!
        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
    
    

    Z Targeting Camera - main.rb link

    # ./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].transient!
        outputs[:scene].sprites << ({ x: 0, y: 0, w: 933, h: 700, path: '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
    
    

    Camera And Large Map - main.rb link

    # ./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].transient!
        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
    
    

    Blend Modes - main.rb link

    # ./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
    
    

    Render Target Noclear - main.rb link

    # ./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).transient = true
      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
    
    

    Lighting - main.rb link

    # ./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].transient!
      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].transient!
      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].transient!
      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
    
    

    Triangles - main.rb link

    # ./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
    
    

    Triangles Trapezoid - main.rb link

    # ./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
    
    

    Camera Space World Space Simple - main.rb link

    # ./samples/07_advanced_rendering/16_camera_space_world_space_simple/app/main.rb
    def tick args
      # camera must have the following properties (x, y, and scale)
      args.state.camera ||= {
        x: 0,
        y: 0,
        scale: 1
      }
    
      args.state.camera.x += args.inputs.left_right * 10 * args.state.camera.scale
      args.state.camera.y += args.inputs.up_down * 10 * args.state.camera.scale
    
      # generate 500 shapes with random positions
      args.state.objects ||= 500.map do
        {
          x: -2000 + rand(4000),
          y: -2000 + rand(4000),
          w: 16,
          h: 16,
          path: 'sprites/square/blue.png'
        }
      end
    
      # "i" to zoom in, "o" to zoom out
      if args.inputs.keyboard.key_down.i || args.inputs.keyboard.key_down.equal_sign || args.inputs.keyboard.key_down.plus
        args.state.camera.scale += 0.1
      elsif args.inputs.keyboard.key_down.o || args.inputs.keyboard.key_down.minus
        args.state.camera.scale -= 0.1
        args.state.camera.scale = 0.1 if args.state.camera.scale < 0.1
      end
    
      # "zero" to reset zoom and camera
      if args.inputs.keyboard.key_down.zero
        args.state.camera.scale = 1
        args.state.camera.x = 0
        args.state.camera.y = 0
      end
    
      # if mouse is clicked
      if args.inputs.mouse.click
        # convert the mouse to world space and delete any objects that intersect with the mouse
        rect = Camera.to_world_space args.state.camera, args.inputs.mouse
        args.state.objects.reject! { |o| rect.intersect_rect? o }
      end
    
      # "r" to reset
      if args.inputs.keyboard.key_down.r
        $gtk.reset_next_tick
      end
    
      # define scene
      args.outputs[:scene].transient!
      args.outputs[:scene].w = Camera::WORLD_SIZE
      args.outputs[:scene].h = Camera::WORLD_SIZE
    
      # render diagonals and background of scene
      args.outputs[:scene].lines << { x: 0, y: 0, x2: 1500, y2: 1500, r: 0, g: 0, b: 0, a: 255 }
      args.outputs[:scene].lines << { x: 0, y: 1500, x2: 1500, y2: 0, r: 0, g: 0, b: 0, a: 255 }
      args.outputs[:scene].solids << { x: 0, y: 0, w: 1500, h: 1500, a: 128 }
    
      # find all objects to render
      objects_to_render = Camera.find_all_intersect_viewport args.state.camera, args.state.objects
    
      # for objects that were found, convert the rect to screen coordinates and place them in scene
      args.outputs[:scene].sprites << objects_to_render.map { |o| Camera.to_screen_space args.state.camera, o }
    
      # render scene to screen
      args.outputs.sprites << { **Camera.viewport, path: :scene }
    
      # render instructions
      args.outputs.sprites << { x: 0, y: 110.from_top, w: 1280, h: 110, path: :pixel, r: 0, g: 0, b: 0, a: 128 }
      label_style = { r: 255, g: 255, b: 255, anchor_y: 0.5 }
      args.outputs.labels << { x: 30, y: 30.from_top, text: "Arrow keys to move around. I and O Keys to zoom in and zoom out (0 to reset camera, R to reset everything).", **label_style }
      args.outputs.labels << { x: 30, y: 60.from_top, text: "Click square to remove from world.", **label_style }
      args.outputs.labels << { x: 30, y: 90.from_top, text: "Mouse locationin world: #{(Camera.to_world_space args.state.camera, args.inputs.mouse).to_sf}", **label_style }
    end
    
    # helper methods to create a camera and go to and from screen space and world space
    class Camera
      SCREEN_WIDTH = 1280
      SCREEN_HEIGHT = 720
      WORLD_SIZE = 1500
      WORLD_SIZE_HALF = WORLD_SIZE / 2
      OFFSET_X = (SCREEN_WIDTH - WORLD_SIZE) / 2
      OFFSET_Y = (SCREEN_HEIGHT - WORLD_SIZE) / 2
    
      class << self
        # given a rect in screen space, converts the rect to world space
        def to_world_space camera, rect
          rect_x = rect.x
          rect_y = rect.y
          rect_w = rect.w || 0
          rect_h = rect.h || 0
          x = (rect_x - WORLD_SIZE_HALF + camera.x * camera.scale - OFFSET_X) / camera.scale
          y = (rect_y - WORLD_SIZE_HALF + camera.y * camera.scale - OFFSET_Y) / camera.scale
          w = rect_w / camera.scale
          h = rect_h / camera.scale
          rect.merge x: x, y: y, w: w, h: h
        end
    
        # given a rect in world space, converts the rect to screen space
        def to_screen_space camera, rect
          rect_x = rect.x
          rect_y = rect.y
          rect_w = rect.w || 0
          rect_h = rect.h || 0
          x = rect_x * camera.scale - camera.x * camera.scale + WORLD_SIZE_HALF
          y = rect_y * camera.scale - camera.y * camera.scale + WORLD_SIZE_HALF
          w = rect_w * camera.scale
          h = rect_h * camera.scale
          rect.merge x: x, y: y, w: w, h: h
        end
    
        # viewport of the scene
        def viewport
          {
            x: OFFSET_X,
            y: OFFSET_Y,
            w: 1500,
            h: 1500
          }
        end
    
        # viewport in the context of the world
        def viewport_world camera
          to_world_space camera, viewport
        end
    
        # helper method to find objects within viewport
        def find_all_intersect_viewport camera, os
          Geometry.find_all_intersect_rect viewport_world(camera), os
        end
      end
    end
    
    $gtk.reset
    
    

    Camera Space World Space Simple Grid Map - main.rb link

    # ./samples/07_advanced_rendering/16_camera_space_world_space_simple_grid_map/app/main.rb
    def tick args
      defaults args
      calc args
      render args
    end
    
    def defaults args
      tile_size = 100
      tiles_per_row = 32
      number_of_rows = 32
      number_of_tiles = tiles_per_row * number_of_rows
    
      # generate map tiles
      args.state.tiles ||= number_of_tiles.map_with_index do |i|
        row = i.idiv(tiles_per_row)
        col = i.mod(tiles_per_row)
        {
          x: row * tile_size,
          y: col * tile_size,
          w: tile_size,
          h: tile_size,
          path: 'sprites/square/blue.png'
        }
      end
    
      center_map = {
        x: tiles_per_row.idiv(2) * tile_size,
        y: number_of_rows.idiv(2) * tile_size,
        w: 1,
        h: 1
      }
    
      args.state.center_tile ||= args.state.tiles.find { |o| o.intersect_rect? center_map }
      args.state.selected_tile ||= args.state.center_tile
    
      # camera must have the following properties (x, y, and scale)
      if !args.state.camera
        args.state.camera = {
          x: 0,
          y: 0,
          scale: 1,
          target_x: 0,
          target_y: 0,
          target_scale: 1
        }
    
        args.state.camera.target_x = args.state.selected_tile.x + args.state.selected_tile.w.half
        args.state.camera.target_y = args.state.selected_tile.y + args.state.selected_tile.h.half
        args.state.camera.x = args.state.camera.target_x
        args.state.camera.y = args.state.camera.target_y
      end
    end
    
    def calc args
      calc_inputs args
      calc_camera args
    end
    
    def calc_inputs args
      # "i" to zoom in, "o" to zoom out
      if args.inputs.keyboard.key_down.i || args.inputs.keyboard.key_down.equal_sign || args.inputs.keyboard.key_down.plus
        args.state.camera.target_scale += 0.1 * args.state.camera.scale
      elsif args.inputs.keyboard.key_down.o || args.inputs.keyboard.key_down.minus
        args.state.camera.target_scale -= 0.1 * args.state.camera.scale
        args.state.camera.target_scale = 0.1 if args.state.camera.scale < 0.1
      end
    
      # "zero" to reset zoom and camera
      if args.inputs.keyboard.key_down.zero
        args.state.camera.target_scale = 1
        args.state.selected_tile = args.state.center_tile
      end
    
      # if mouse is clicked
      if args.inputs.mouse.click
        # convert the mouse to world space and delete any tiles that intersect with the mouse
        rect = Camera.to_world_space args.state.camera, args.inputs.mouse
        selected_tile = args.state.tiles.find { |o| rect.intersect_rect? o }
        if selected_tile
          args.state.selected_tile = selected_tile
          args.state.camera.target_scale = 1
        end
      end
    
      # "r" to reset
      if args.inputs.keyboard.key_down.r
        $gtk.reset_next_tick
      end
    end
    
    def calc_camera args
      args.state.camera.target_x = args.state.selected_tile.x + args.state.selected_tile.w.half
      args.state.camera.target_y = args.state.selected_tile.y + args.state.selected_tile.h.half
      dx = args.state.camera.target_x - args.state.camera.x
      dy = args.state.camera.target_y - args.state.camera.y
      ds = args.state.camera.target_scale - args.state.camera.scale
      args.state.camera.x += dx * 0.1 * args.state.camera.scale
      args.state.camera.y += dy * 0.1 * args.state.camera.scale
      args.state.camera.scale += ds * 0.1
    end
    
    def render args
      args.outputs.background_color = [0, 0, 0]
    
      # define scene
      args.outputs[:scene].transient!
      args.outputs[:scene].w = Camera::WORLD_SIZE
      args.outputs[:scene].h = Camera::WORLD_SIZE
      args.outputs[:scene].background_color = [0, 0, 0, 0]
    
      # render diagonals and background of scene
      args.outputs[:scene].lines << { x: 0, y: 0, x2: 1500, y2: 1500, r: 0, g: 0, b: 0, a: 255 }
      args.outputs[:scene].lines << { x: 0, y: 1500, x2: 1500, y2: 0, r: 0, g: 0, b: 0, a: 255 }
      args.outputs[:scene].solids << { x: 0, y: 0, w: 1500, h: 1500, a: 128 }
    
      # find all tiles to render
      objects_to_render = Camera.find_all_intersect_viewport args.state.camera, args.state.tiles
    
      # convert mouse to world space to see if it intersects with any tiles (hover color)
      mouse_in_world = Camera.to_world_space args.state.camera, args.inputs.mouse
    
      # for tiles that were found, convert the rect to screen coordinates and place them in scene
      args.outputs[:scene].sprites << objects_to_render.map do |o|
        if o == args.state.selected_tile
          tile_to_render = o.merge path: 'sprites/square/green.png'
        elsif o.intersect_rect? mouse_in_world
          tile_to_render = o.merge path: 'sprites/square/orange.png'
        else
          tile_to_render = o.merge path: 'sprites/square/blue.png'
        end
    
        Camera.to_screen_space args.state.camera, tile_to_render
      end
    
      # render scene to screen
      args.outputs.sprites << { **Camera.viewport, path: :scene }
    
      # render instructions
      args.outputs.sprites << { x: 0, y: 110.from_top, w: 1280, h: 110, path: :pixel, r: 0, g: 0, b: 0, a: 200 }
      label_style = { r: 255, g: 255, b: 255, anchor_y: 0.5 }
      args.outputs.labels << { x: 30, y: 30.from_top, text: "I/O or +/- keys to zoom in and zoom out (0 to reset camera, R to reset everything).", **label_style }
      args.outputs.labels << { x: 30, y: 60.from_top, text: "Click to center on square.", **label_style }
      args.outputs.labels << { x: 30, y: 90.from_top, text: "Mouse location in world: #{(Camera.to_world_space args.state.camera, args.inputs.mouse).to_sf}", **label_style }
    end
    
    # helper methods to create a camera and go to and from screen space and world space
    class Camera
      SCREEN_WIDTH = 1280
      SCREEN_HEIGHT = 720
      WORLD_SIZE = 1500
      WORLD_SIZE_HALF = WORLD_SIZE / 2
      OFFSET_X = (SCREEN_WIDTH - WORLD_SIZE) / 2
      OFFSET_Y = (SCREEN_HEIGHT - WORLD_SIZE) / 2
    
      class << self
        # given a rect in screen space, converts the rect to world space
        def to_world_space camera, rect
          rect_x = rect.x
          rect_y = rect.y
          rect_w = rect.w || 0
          rect_h = rect.h || 0
          x = (rect_x - WORLD_SIZE_HALF + camera.x * camera.scale - OFFSET_X) / camera.scale
          y = (rect_y - WORLD_SIZE_HALF + camera.y * camera.scale - OFFSET_Y) / camera.scale
          w = rect_w / camera.scale
          h = rect_h / camera.scale
          rect.merge x: x, y: y, w: w, h: h
        end
    
        # given a rect in world space, converts the rect to screen space
        def to_screen_space camera, rect
          rect_x = rect.x
          rect_y = rect.y
          rect_w = rect.w || 0
          rect_h = rect.h || 0
          x = rect_x * camera.scale - camera.x * camera.scale + WORLD_SIZE_HALF
          y = rect_y * camera.scale - camera.y * camera.scale + WORLD_SIZE_HALF
          w = rect_w * camera.scale
          h = rect_h * camera.scale
          rect.merge x: x, y: y, w: w, h: h
        end
    
        # viewport of the scene
        def viewport
          {
            x: OFFSET_X,
            y: OFFSET_Y,
            w: WORLD_SIZE,
            h: WORLD_SIZE
          }
        end
    
        # viewport in the context of the world
        def viewport_world camera
          to_world_space camera, viewport
        end
    
        # helper method to find objects within viewport
        def find_all_intersect_viewport camera, os
          Geometry.find_all_intersect_rect viewport_world(camera), os
        end
      end
    end
    
    $gtk.reset
    
    

    Matrix And Triangles 2d - main.rb link

    # ./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
    
    

    Matrix And Triangles 3d - main.rb link

    # ./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
    
    

    Matrix Camera Space World Space - main.rb link

    # ./samples/07_advanced_rendering/16_matrix_camera_space_world_space/app/main.rb
    # sample app shows how to translate between screen and world coordinates using matrix multiplication
    class Game
      attr_gtk
    
      def tick
        defaults
        input
        calc
        render
      end
    
      def defaults
        return if state.tick_count != 0
    
        # define the size of the world
        state.world_size = 1280
    
        # initialize the camera
        state.camera = {
          x: 0,
          y: 0,
          zoom: 1
        }
    
        # initialize entities: place entities randomly in the world
        state.entities = 200.map do
          {
            x: (rand * state.world_size - 100).to_i * (rand > 0.5 ? 1 : -1),
            y: (rand * state.world_size - 100).to_i * (rand > 0.5 ? 1 : -1),
            w: 32,
            h: 32,
            angle: 0,
            path: "sprites/square/blue.png",
            rotation_speed: rand * 5
          }
        end
    
        # backdrop for the world
        state.backdrop = { x: -state.world_size,
                           y: -state.world_size,
                           w: state.world_size * 2,
                           h: state.world_size * 2,
                           r: 200,
                           g: 100,
                           b: 0,
                           a: 128,
                           path: :pixel }
    
        # rect representing the screen
        state.screen_rect = { x: 0, y: 0, w: 1280, h: 720 }
    
        # update the camera matricies (initial state)
        update_matricies!
      end
    
      # if the camera is ever changed, recompute the matricies that are used
      # to translate between screen and world coordinates. we want to cache
      # the resolved matrix for speed
      def update_matricies!
        # camera space is defined with three matricies
        # every entity is:
        # - offset by the location of the camera
        # - scaled
        # - then centered on the screen
        state.to_camera_space_matrix = MatrixFunctions.mul(mat3_translate(state.camera.x, state.camera.y),
                                                           mat3_scale(state.camera.zoom),
                                                           mat3_translate(640, 360))
    
        # world space is defined based off the camera matricies but inverted:
        # every entity is:
        # - uncentered from the screen
        # - unscaled
        # - offset by the location of the camera in the opposite direction
        state.to_world_space_matrix = MatrixFunctions.mul(mat3_translate(-640, -360),
                                                          mat3_scale(1.0 / state.camera.zoom),
                                                          mat3_translate(-state.camera.x, -state.camera.y))
    
        # the viewport is computed by taking the screen rect and moving it into world space.
        # what entities get rendered is based off of the viewport
        state.viewport = rect_mul_matrix(state.screen_rect, state.to_world_space_matrix)
      end
    
      def input
        # if the camera is changed, invalidate/recompute the translation matricies
        should_update_matricies = false
    
        # + and - keys zoom in and out
        if inputs.keyboard.equal_sign || inputs.keyboard.plus || inputs.mouse.wheel && inputs.mouse.wheel.y > 0
          state.camera.zoom += 0.01 * state.camera.zoom
          should_update_matricies = true
        elsif inputs.keyboard.minus || inputs.mouse.wheel && inputs.mouse.wheel.y < 0
          state.camera.zoom -= 0.01 * state.camera.zoom
          should_update_matricies = true
        end
    
        # clamp the zoom to a minimum of 0.25
        if state.camera.zoom < 0.25
          state.camera.zoom = 0.25
          should_update_matricies = true
        end
    
        # left and right keys move the camera left and right
        if inputs.left_right != 0
          state.camera.x += -1 * (inputs.left_right * 10) * state.camera.zoom
          should_update_matricies = true
        end
    
        # up and down keys move the camera up and down
        if inputs.up_down != 0
          state.camera.y += -1 * (inputs.up_down * 10) * state.camera.zoom
          should_update_matricies = true
        end
    
        # reset the camera to the default position
        if inputs.keyboard.key_down.zero
          state.camera.x = 0
          state.camera.y = 0
          state.camera.zoom = 1
          should_update_matricies = true
        end
    
        # if the update matricies flag is set, recompute the matricies
        update_matricies! if should_update_matricies
      end
    
      def calc
        # rotate all the entities by their rotation speed
        # and reset their hovered state
        state.entities.each do |entity|
          entity.hovered = false
          entity.angle += entity.rotation_speed
        end
    
        # find all the entities that are hovered by the mouse and update their state back to hovered
        mouse_in_world = rect_to_world_coordinates inputs.mouse.rect
        hovered_entities = geometry.find_all_intersect_rect mouse_in_world, state.entities
        hovered_entities.each { |entity| entity.hovered = true }
      end
    
      def render
        # create a render target to represent the camera's viewport
        outputs[:scene].transient!
        outputs[:scene].w = state.world_size
        outputs[:scene].h = state.world_size
    
        # render the backdrop
        outputs[:scene].primitives << rect_to_screen_coordinates(state.backdrop)
    
        # get all entities that are within the camera's viewport
        entities_to_render = geometry.find_all_intersect_rect state.viewport, state.entities
    
        # render all the entities within the viewport
        outputs[:scene].primitives << entities_to_render.map do |entity|
          r = rect_to_screen_coordinates entity
    
          # change the color of the entity if it's hovered
          r.merge!(path: "sprites/square/red.png") if entity.hovered
    
          r
        end
    
        # render the camera's viewport
        outputs.sprites << {
          x: 0,
          y: 0,
          w: state.world_size,
          h: state.world_size,
          path: :scene
        }
    
        # show a label that shows the mouse's screen and world coordinates
        outputs.labels << { x: 30, y: 30.from_top, text: "#{gtk.current_framerate.to_sf}" }
    
        mouse_in_world = rect_to_world_coordinates inputs.mouse.rect
    
        outputs.labels << {
          x: 30,
          y: 55.from_top,
          text: "Screen Coordinates: #{inputs.mouse.x}, #{inputs.mouse.y}",
        }
    
        outputs.labels << {
          x: 30,
          y: 80.from_top,
          text: "World Coordinates: #{mouse_in_world.x.to_sf}, #{mouse_in_world.y.to_sf}",
        }
      end
    
      def rect_to_screen_coordinates rect
        rect_mul_matrix rect, state.to_camera_space_matrix
      end
    
      def rect_to_world_coordinates rect
        rect_mul_matrix rect, state.to_world_space_matrix
      end
    
      def rect_mul_matrix rect, matrix
        # the bottom left and top right corners of the rect
        # are multiplied by the matrix to get the new coordinates
        bottom_left = MatrixFunctions.mul (MatrixFunctions.vec3 rect.x, rect.y, 1), matrix
        top_right   = MatrixFunctions.mul (MatrixFunctions.vec3 rect.x + rect.w, rect.y + rect.h, 1), matrix
    
        # with the points of the rect recomputed, reconstruct the rect
        rect.merge x: bottom_left.x,
                   y: bottom_left.y,
                   w: top_right.x - bottom_left.x,
                   h: top_right.y - bottom_left.y
      end
    
      # this is the definition of how to move a point in 2d space using a matrix
      def mat3_translate x, y
        MatrixFunctions.mat3 1, 0, x,
                             0, 1, y,
                             0, 0, 1
      end
    
      # this is the definition of how to scale a point in 2d space using a matrix
      def mat3_scale scale
        MatrixFunctions.mat3 scale, 0, 0,
                             0, scale, 0,
                             0,     0, 1
      end
    end
    
    $game = Game.new
    
    def tick args
      $game.args = args
      $game.tick
    end
    
    $gtk.reset
    
    

    Matrix Cubeworld - main.rb link

    # ./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
    
    

    Matrix Cubeworld - modeling-api.rb link

    # ./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
    
    

    Override Core Rendering - main.rb link

    # ./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
    
    

    Layouts - main.rb link

    # ./samples/07_advanced_rendering/18_layouts/app/main.rb
    def tick args
      args.outputs.solids << args.layout.rect(row: 0,
                                              col: 0,
                                              w: 24,
                                              h: 12,
                                              include_row_gutter: true,
                                              include_col_gutter: true).merge(b: 255, a: 80)
      render_row_examples args
      render_column_examples args
      render_max_width_max_height_examples args
      render_points_with_anchored_label_examples args
      render_centered_rect_examples args
      render_rect_group_examples args
    end
    
    def render_row_examples args
      # rows (light blue)
      args.outputs.labels << args.layout.rect(row: 1, col: 6 + 3).merge(text: "row examples", anchor_x: 0.5, anchor_y: 0.5)
      4.map_with_index do |row|
        args.outputs.solids << args.layout.rect(row: row, col: 6, w: 1, h: 1).merge(**light_blue)
      end
    
      2.map_with_index do |row|
        args.outputs.solids << args.layout.rect(row: row * 2, col: 6 + 1, w: 1, h: 2).merge(**light_blue)
      end
    
      4.map_with_index do |row|
        args.outputs.solids << args.layout.rect(row: row, col: 6 + 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: 6 + 4, w: 2, h: 2).merge(**light_blue)
      end
    end
    
    def render_column_examples args
      # columns (yellow)
      yellow = { r: 255, g: 255, b: 128 }
      args.outputs.labels << args.layout.rect(row: 1, col: 12 + 3).merge(text: "column examples", anchor_x: 0.5, anchor_y: 0.5)
      6.times do |col|
        args.outputs.solids << args.layout.rect(row: 0, col: 12 + col, w: 1, h: 1).merge(**yellow)
      end
    
      3.times do |col|
        args.outputs.solids << args.layout.rect(row: 1, col: 12 + col * 2, w: 2, h: 1).merge(**yellow)
      end
    
      6.times do |col|
        args.outputs.solids << args.layout.rect(row: 2, col: 12 + col, w: 1, h: 2).merge(**yellow)
      end
    end
    
    def render_max_width_max_height_examples args
      # max width/height baseline (transparent green)
      args.outputs.labels << args.layout.rect(row: 4, col: 12).merge(text: "max width/height examples", anchor_x: 0.5, anchor_y: 0.5)
      args.outputs.solids << args.layout.rect(row: 4, col: 0, w: 24, h: 2).merge(a: 64, **green)
    
      # max height
      args.outputs.solids << args.layout.rect(row: 4, col: 0, w: 24, h: 2, max_height: 1).merge(a: 64, **green)
    
      # max width
      args.outputs.solids << args.layout.rect(row: 4, col: 0, w: 24, h: 2, max_width: 12).merge(a: 64, **green)
    end
    
    def render_points_with_anchored_label_examples args
      # labels relative to rects
      label_color = { r: 0, g: 0, b: 0 }
    
      # labels realtive to point, achored at 0.0, 0.0
      args.outputs.borders << args.layout.rect(row: 6, col: 3, w: 6, h: 5)
      args.outputs.labels << args.layout.rect(row: 6, col: 3, w: 6, h: 1).center.merge(text: "layout.point anchored to 0.0, 0.0", anchor_x: 0.5, anchor_y: 0.5, size_px: 15)
      grey = { r: 128, g: 128, b: 128 }
      args.outputs.solids << args.layout.rect(row: 7, col: 4.5).merge(**grey)
      args.outputs.labels << args.layout.point(row: 7, col: 4.5, row_anchor: 1.0, col_anchor: 0.0).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)
    
      args.outputs.solids << args.layout.rect(row: 7, col: 5.5).merge(**grey)
      args.outputs.labels << args.layout.point(row: 7, col: 5.5, row_anchor: 1.0, col_anchor: 0.5).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)
    
      args.outputs.solids << args.layout.rect(row: 7, col: 6.5).merge(**grey)
      args.outputs.labels << args.layout.point(row: 7, col: 6.5, row_anchor: 1.0, col_anchor: 1.0).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)
    
      args.outputs.solids << args.layout.rect(row: 8, col: 4.5).merge(**grey)
      args.outputs.labels << args.layout.point(row: 8, col: 4.5, row_anchor: 0.5, col_anchor: 0.0).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)
    
      args.outputs.solids << args.layout.rect(row: 8, col: 5.5).merge(**grey)
      args.outputs.labels << args.layout.point(row: 8, col: 5.5, row_anchor: 0.5, col_anchor: 0.5).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)
    
      args.outputs.solids << args.layout.rect(row: 8, col: 6.5).merge(**grey)
      args.outputs.labels << args.layout.point(row: 8, col: 6.5, row_anchor: 0.5, col_anchor: 1.0).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)
    
      args.outputs.solids << args.layout.rect(row: 9, col: 4.5).merge(**grey)
      args.outputs.labels << args.layout.point(row: 9, col: 4.5, row_anchor: 0.0, col_anchor: 0.0).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)
    
      args.outputs.solids << args.layout.rect(row: 9, col: 5.5).merge(**grey)
      args.outputs.labels << args.layout.point(row: 9, col: 5.5, row_anchor: 0.0, col_anchor: 0.5).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)
    
      args.outputs.solids << args.layout.rect(row: 9, col: 6.5).merge(**grey)
      args.outputs.labels << args.layout.point(row: 9, col: 6.5, row_anchor: 0.0, col_anchor: 1.0).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)
    end
    
    def render_centered_rect_examples args
      # centering rects
      args.outputs.borders << args.layout.rect(row: 6, col: 9, w: 6, h: 5)
      args.outputs.labels << args.layout.rect(row: 6, col: 9, w: 6, h: 1).center.merge(text: "layout.rect centered inside another rect", anchor_x: 0.5, anchor_y: 0.5, size_px: 15)
      outer_rect = args.layout.rect(row: 7, col: 10.5, 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
      )
    end
    
    def render_rect_group_examples args
      args.outputs.labels << args.layout.rect(row: 6, col: 15, w: 6, h: 1).center.merge(text: "layout.rect_group usage", anchor_x: 0.5, anchor_y: 0.5, size_px: 15)
      args.outputs.borders << args.layout.rect(row: 6, col: 15, w: 6, h: 5)
    
      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 },
      ]
    
      args.outputs.solids << args.layout.rect_group(row: 7,
                                                    col: 15,
                                                    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 }
      ]
    
      args.outputs.solids << args.layout.rect_group(row: 7,
                                                    col: 15,
                                                    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 },
        { r: 250, g: 250, b: 250 },
      ]
    
      args.outputs.solids << args.layout.rect_group(row: 8,
                                                    col: 15,
                                                    dcol: 1,
                                                    w: 1,
                                                    h: 1,
                                                    group: colors)
    end
    
    def light_blue
      { r: 128, g: 255, b: 255 }
    end
    
    def yellow
      { r: 255, g: 255, b: 128 }
    end
    
    def green
      { r: 0, g: 128, b: 80 }
    end
    
    def white
      { r: 255, g: 255, b: 255 }
    end
    
    def label_color
      { r: 0, g: 0, b: 0 }
    end
    
    $gtk.reset
    
    

    Advanced Rendering Hd link

    Hd Labels - main.rb link

    # ./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].transient!
      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
    
    

    Texture Atlases - main.rb link

    # ./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 |  3200x18