A JavaScript library for creating 2D canvas-based games
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README.md

Ω500: JS Game Library

Ω500 is a library for making canvas-based games. It focuses on providing an architecturally old-school, straightforward set of tools for creating games: primarily for game jams and rapid prototyping. Check out the online examples: http://mrspeaker.github.io/Omega500/.

Platform example

Getting Started

Easiest way to start is to copy the /ex/template folder (and rename it), then run it in your browser. Game on! The "game" displays a screen containing a player, which you control left/right with the keyboard keys. The src directory contains a main Ω.Game object, and a Ω.Screen object (called MainScreen) that contains a Ω.Entity object (called Player).

- template
    - lib
        Ω500.js
    - src
        - entities
            Player.js
        - screens
            MainScreen.js
        game.js
    index.html

A real game will have a bunch of screens (TitleScreen, GameOverScreen...) and a bunch of entites (Baddie, Bullet, PowerUp...) - but they will be wired up mostly like the demo. Check out the other examples and games to see how this scales.

Some games using Ω500

DIGIBOTS & CO. DIGIBOTS & CO. Zmore. Time Flies Straight. Time Flies Straight

Ω500 Features:

Main game loop. Screens and dialogs (with transitions). Input handling (keys, mouse, touch, iCade). Image loading and display. SpriteSheet animations. Tile and isometric maps. Repeating maps, with parallax. Entity/Map and Entity/Entity collisions. Velocity acceleration & gravity components. Generate maps from images. Camera'd map, Tracked camera (with box). Audio load/play. Math/random/timer helpers. Asset preloader/progress. Simple particle controller. Raycast against maps. Path finding, QuadTree, Simplex Noise. Auto-genereated tile sets for prototyping. Text helpers. Trig helpers, Font plotter. Mixin system. State machine helper. "Tiled" map editor level support. Fullscreen API support. Flipped spritesheets and images. Spring algo (for camera & entities). Various "effects".

Using Ω500

Best is to dive into the examples, and snippets...

General idea/notes

Old-school, super-simple architecture: Everything has tick and render(gfx) methods. Each object manages its children and passes these calls on so the entire heirachy receives the messages. Everyone gets ticked, then rendered. For example:

.           Game            // extend Ω.Game
.            |
.          Screen           // extend Ω.Screen
.            |
.      _______________
.     |      |        |
.  Player [Baddies]  Map    // extend Ω.Entity, Array of [Ω.Entity], and Ω.Map
.     |
. [Bullets]                 // Array of [extend Ω.Entity]

Every loop the engine calls tick on the main game object. This automatically calls tick on its current screen - but that's the end of the magic. After this the screen must manually call tick on its children (player, all the baddies in the baddie array, map) and so on. Once the tick is done, the same thing happens with render. [In progress: recently added some magic to automate the tick/rendering of children - see Screen and Entity.]

That's the rule: if you want something ticked, then tick it. If you want something rendered, then render it.

Random helpful notes

  • Many positions in maps etc are given as a 2 element [x, y] array (TODO: standardize this!).
  • Uses John Resig's simple class with inheritance (see below)
  • Project setup: copy/paster Ω500.js into your project

Ω.Game

Ω/Game.js

Extend Ω.Game to create your game. If you need to do stuff in init, don't forget to pass the width and height arguments up to the _super class:

var MyGame = Ω.Game.extend({

    init: function (w, h) {

        this._super(w, h);

    },

    load: function () {

        // Called when all resources have loaded

    }

});

var game = new MyGame(640, 480);

The Game super class has some boilerplate, such as accepting a screen object to display as well as the tick and render methods described above (you can override them if you need).

Canvas/DOM container:

The canvas property to sets the game canvas: can be a CSS selector to either the canvas element you want to use, or the containing element you want the canvas to be created inside of. Defaults to "body". If an explicit width or height is set on the canvas element this will be used, otherwise it will use the values passed in - or default to 400x250.

Screen

/screens/Screen.js

Objects inherited from Ω.Screen are scene containers to display stuff in. tick and render will be called automatically by the game if you set using game.setScreen. Changing screens will use a small fade transition between the current and the new:

game.setScreen(new TitleScreen());

setScreen is a method on the Game class (so if you're just calling it from the game's load function then you can do this.setScreen(...). Then for example, in the TitleScreen's tick method you can wait for input and move to the main game:

if (Ω.input.pressed("space")) {
    game.setScreen(new MainScreen());
}

Async operations

If you need to do async stuff on load (like ajax calls etc), then set the screen's loaded property to false. When you're done, set it to true.)

Clearing the screen

In render, you can clear the screen to a color (if you want):

this.clear(gfx, "#333"); // for clearing

Current "Frame" number

Screens also have a property frame that is initialized to 0 and incremented by the game every tick.

Transitions

The default transition is a straight crossfade, but you can choose a colour to fade to (or in/out of):

game.setScreen(screen, {type: "inout", time: 50, color: "#ffff00"});

out // Fade out to a colour inout // Fade in/out to a colour

In progress

NOTE: W.I.P! Currently adding some magic to screens to automate the tick/render cycle on objects. If you pass a tick/renderable object (a body) to screen.add it will be magically ticked and rendered. This is just testing at the moment: it reduces a lot of boilerplate and makes it really simple to get stuff on screen - but I'm still seeing if it's flexible enough.

this.add(new Ω.Entity({})); // Entity will be ticked and renderd by magic.
this.add(new BadGuy(), "baddies"); // Entity added and rennderd with "baddies" group
this.add(new BadGuy(), "baddies", 10); // If first "baddies" member, sets the zIndex for the group to 10

An entity also now has a add method. Bodies added here will be processed by the screen (see Entity).

Entity

Ω/entities/Entity.js

Players, bad guys, monsters etc should inherit from Ω.Entity. Entities know how to move inside maps, and detect collisions with other entities.

var player = new Ω.Entity(100, 100, 18, 24); // x, y, w, h

Has x, y, w, h properties which is used for map/entity collision detection. Width and height are optional if you specify them in the class itself (default is w: 32, h: 32).

There are a couple of conventions for updating collections of entities [NOTE: these conventions are currently being integrated into the system: if you use the magic add method then you don't need to filter to tick, or forEach to render.]. For "ticking", call tick on each object - and inside the object's tick method return true if it's still alive, and false if it should be removed:

this.baddies = this.baddies.filter(function (baddie) {
    return baddie.tick();
});

The entity base class has a remove flag which you can set anywhere in the entity, and return it (negatively) from the tick method:

...
remove: false,

tick: function () {

    return !(this.remove);

},
...

For rendering, just forEach them:

this.baddies.forEach(function (baddie) {
    baddie.tick(gfx);
});

How things are rendered is completely up to you. You get the passed the gfx object which has the 2D graphics context as property ctx. You can draw with canvas primitives, or render images (see images), sprite sheets (see sprite sheets), or animation frames (see animations).

In progress

NOTE: W.I.P! Currently adding some magic to screens to automate the tick/render cycle on objects (see Screen. If you pass a freshly minted tick/renderable object to this.add() it will be magically ticked and rendered.

add: function(body, tag, zIndex)

NOTE: Problem with this approach is that there is no "remove" at the moment - so refreshing is a problem. See my LD29 game how I hacked around it (and refactor this!)

Bounding boxes

Sometimes it's useful to see where the bounding box of your entity is. There's no debug mode, but the default rendering of an entity is something like this:

gfx.ctx.fillStyle = "red";
gfx.ctx.fillRect(this.x, this.y, this.w, this.h);

You can call this._super(gfx) at the end of your entity render function (or draw your own) and you'll get a red box showing where the collision detection is used.

At the moment there is no option to have a different sized bounding box.

Classes

Uses John Resig simple classes:

var MyClass = Ω.Class.extend({
    init: function () {}
});

// Extend a base class
var MySubClass = MyClass.extend({});

// Instanciate the things
myClassGuy = new MyClass();
mySubClassGuy = new MySubClass();

Can call super:

var Baddie = Ω.Entity.extend({

    init: function (x, y) {

        _this.super(x,y);

        // ... do baddie init
    }

});

There's also an init_post method that will be called after init.

Input

Ω/input/input.js

Bind "actions" to key codes. The actions are just strings that make sense for your game... "fire", "jump", "decapitate"... whatever... You match the keycode (or a aliases like "up", "down" - see Ω.input for the full list) to the action:

Ω.input.bind("explodeThings", 32); // Bind space bar (code 32) to action "explodeThings"

Can map multiple at once:

Ω.input.bind({
    "fire": ["space", "touch", 13], // Bind multiple keys to the action "fire"
    "left": "left",
    "right": "right",
    "up": "up",
    "down": "down"
});

This lets you have multiple keys bind to the same action. In the example above the touch screen, space bar, and the enter key (keycode 13 (which incidentally also has the alias "enter")) all trigger the action "fire".

Then to test:

if (Ω.input.pressed("fire")) // A button with the action "fire" was pressed
if (Ω.input.released("fire")) // A button with the action "fire" was released
if (Ω.input.isDown("up")) // Button is being held down
if (Ω.input.wasDown("left")) // Button was down in the last frame

To force an action to be released (even if user still holding down button):

Ω.input.release("left")

Reset all keys (stops stuck keys when transitioning screens):

Ω.input.reset();

Image

Ω/assets/Image.js

Usually you load the image as a class property (so it is preloaded). If you preload it in many classes it will only be loaded once.

var img = new Ω.Image("res/minecraft.png");

In container render:

img.render(gfx, 10, 10);

The image can be loaded "flipped" (flip x = 1, flip y = 2, flip both = 3):

// Load the image upside down
new Ω.Image("res/minecraft.png", 2)

And scaled:

// Non-flipped, 50% size
new Ω.Image("res/minecraft.png", null, 0.5);
// Flipped Y, 150% size
new Ω.Image("res/minecraft.png", 2, 1.5);

Sound

Ω/assets/Sound.js

Usually you load the sound as a class property (so it is preloaded).

{
    ...
    sound: new Ω.Sound("res/boink");
}

If you don't put an extension it'll choose .mp3 if supported, else it will play .ogg - so be sure to export in both formats!

To set the volume (between 0 and 1):

var sound = new Ω.Sound("res/boink.wav", 0.5);

To play a sound:

sound.play();

There's also a couple of static methods on Ω.Sound.

Ω.Sound._reset(); // stop and rewind all sounds
Ω.Sound._setVolume(0.5); // sets all sounds 50% of thier original volume

TODOs:

- Why are these underscored?
- Add fade out/fade in helpers

Sprite sheets

Ω/gfx/SpriteSheet

Specify tile sheet, tile w and tile h.

var sheet = new Ω.SpriteSheet("res/chars.png", 25, 45);

To draw a tile:

sheet.render(gfx, frameX, frameY, posX, posY);

Optional param: flipFlags: only flip x = 1, only flip y = 2, flip both=3

new Ω.SpriteSheet("res/chars.png", 25, 45, 3)

This will create a spritesheet twice as wide, and twice as high as the original. The top left part of the sheet will be the original sprites. The top right will have each cell flipped horizontally. The bottom left will have each cell flipped vertically, and the bottom right will be flipped both horizontally and vertically.

Animation

Ω/anim/Anim.js Ω/anim/Anims.js

Animations are for flipbook-style sprite sheet animation. They take a name, a spritesheet, a time-per-frame, and an array of [x,y] indexes into the spritesheet.

They can be grouped with Ω.Anims:

this.anims = new Ω.Anims([
    new Ω.Anim("idle", this.sheet, 500, [[8, 0], [9, 0]]),
    new Ω.Anim("walk", this.sheet, 60, [[0, 0], [1, 0], [2, 0]])
]);

In the example, the "idle" animation will loop over the spritesheet frames 8,0 and 9,0 showing each frame for 500 milliseconds.

Set the anim you want to use (defaults to first). You don't have to do this if you are just using a single Anim, rather than grouped Ω.Anims:

this.anims.set("walk");

Tick it inside the container's tick:

this.anims.tick();

Render it inside the container's render:

this.anims.render(gfx, this.x, this.y);

TODOs:

- Add more precise (per-frame) timing
- Add ping-poing/reverse playback

Map

Ω/maps/Map.js

Maps take a Ω.SpriteSheet, and a bunch of 2D cells to show what to draw. Also, you'll usually give it a camera to render (for scrolling around a larger map).

sheet: new Ω.SpriteSheet("../res/images/tiles.png", 32, 32)

...

var map = new Ω.Map(this.sheet, [
    [1,1,1,1,1,],
    [1,0,0,0,0,],
    [1,0,1,1,0,],
    [1,0,0,0,0,],
    [1,1,1,1,1,]
]);

Optional 3rd parameter that indicates the last number that is "walkable" (or "not solid") for entity collision detection. Default is 0 - so when you have an Ω.Entity and you call its move method it will collide with everything except "0" tiles (see "Collisions" below).

Can check the map.walkable property to see.

Debug Map

Ω/maps/DebugMap.js

Doesn't require a spritesheet - it's magically generated (for quick prototyping)

Iso Map

Ω/maps/IsoMap.js

There's nothing done for iso stuff yet - renders an iso map, but that's about it.

Blocks

map.getBlock()
map.getBlocks()
map.setBlock()

Flags

map.repeat
map.parallax

Collisions

In your entity's tick method, determine the distance you want it to move for the frame and call move. If the entity would end up inside a wall, the move function will push the entity back to be snug up against it. The entity can slide along a wall.

entity.move(xAmount, yAmount, map);

If an entity hits a one or map cells then the entity's hitBlocks method will be triggered.

hitBlocks: function (xBlocks, yBlocks) {
    // x/y is collisions when checking horizontal vs checking vertical
    // blocks are array: [Top Left block, Bottom Left block, Top Right block, Bottom Right block]
    // will be `undefined` if no collision
}

Loading a map from an image*

You can paint pixels and use that as your map - mapping different colours to different tiles. Other colours can then be used to set the locations of entities and spawn points etc. Good for rapid prototying and game jams.

map.imgToCells(path, colorMap, callback, flipFlags)

The callback (if you provide a path to an image, otherwise the return value if you provide an image directly) returns colours from the colour map that were not matched. These (it's assumed) are used for entity locations etc.

"Tiled Editor" Map loader

Ω/assets/Tiled.js

For loading maps created with Tiled Editor

Physics

Ω/physics/Physics.js

Collision detection

Check for collision against all entities against each other, and call the enitity's hit method, passing the entity that hit it.

Ω.Physics.checkCollisions([
    this.players,
    this.baddies
]);

You can provide an optional second paramater that is the entity method name to call instead of hit.

If you only want to check a single entity against other then checkCollision (singluar!) checks for a single entity agains an array (or array of arrays) of other entities:

Ω.Physics.checkCollision(
    this.player,
    [this.baddies, this.monsters],
    "hitEnemy"
);

You can check for collision via collision points, if the entity has an array property called points (containing elements that are [x, y])

Ω.Physics.checkPointsCollision(
    entityWithPoints,
    entitiesArray,
    cbName
);

Dialog

Ω/screens/Dialog.js

Overlay for displaying menus etc.

game.setDialog(new Ω.Dialog())

Time stops when dialogs are up (assuming you are using Ω.utils.now() for tracking current time)

Customiseable "kill action" to remove the dialog. Defaults to the action "escape" (see Input).

Camera

Ω/cameras/Camera.js

Camera lets you define a viewport and draws only a small part of the world at a time. Pass in anything you want to draw to the camera and it'll be rendered in the correct world location.

It accepts an array of entities, or arrays of entities to render. They are drawn using the painters alogrithm:

// Camera at pos 0, 0 with viewport size 320x240.
var camera = new Ω.Camera(0, 0, 320, 240);

// Draw the map, player and baddies (anything (or array of things) with a render function!)
camera.render(gfx, [map, player, baddies]);

To move a camera, change it's x and y properties, or use the helper methods:

moveTo(x, y) // Move directly to an x/y location. moveBy(x, y) // Move relatively by x/y pixels.

There's also a TrackingCamera that will follow the entity you pass to it. Ω/cameras/TrackingCamera.js

In Progress

Note: Cameras are part of the magic being added to Screens. Define a Camera object on a Screen and it will be applied to screen bodies. If you don't want the magic, don't call your camera camera. May I suggest cam?

Preloading

Ω/Ω.js

Instanciate resources as properties in your classes to preloaded them:

var me = new Ω.Entity({
    img: new Ω.Image("res/images/me.png") // These will be preloaded
    snd: new Ω.Sound("res/audio/hey")
});

You can track the loading progress in your game object (for making a loading bar, for example):

Ω.evt.progress.push(function (loadedSoFar, maxToLoad) {
    // console.log(loadedSoFar, maxToLoad);
});

TODOs: - build in some kind of "incremental" loading - so not everything needs to be loaded at once.

Font plotting

Ω/text/Font.js

Rather than using borin' old ctx.fillText you can use a bitmap font.

font: new Ω.Font("myfont.png", 16, 16)

in render:

this.font.render(gfx, "hello, world!", 100, 100)

The font assumes a specific ordering of letters (that seemed to show up on a bunch of different bitmapped fonts I found:

!"#$%&'()*+,-./0123456789:;<=>?@abcdefghijklmnopqrstuvwxyz[/]^_`abcdefghijklmnopqrstuvwxyz{|}~

If you have a font with a different ordering of characters, supply this as an argument:

font: new Ω.Font("myfont.png", 16, 16, "!?abcdefghijklmnopqrstuvwyz.[]")

Ray casting

Ω/utils/rays.js

Just for hitting maps, not other entities.

Effects

Particles

Ω/effects/Particle.js

var p = new Ω.Particle({});
p.play(20, 20); // Starts the particles

...
p.tick();
...
p.render(gfx);

Shake.

Ω/effects/Shake.js

Flash.

Ω/effects/Flash.js

Utils - Math

Ω/utils/math

Ω.math.dist(a, b) // Distance between two entities (or [x,y] arrays)
Ω.math.distCenter(a, b) // Distance between center of two entities
Ω.math.angleBetween(a, b)
Ω.math.clamp(val, min, max) // clamp value to a range
Ω.math.ratio(start, finish, amount)
Ω.math.lerp(start, finish, amount)
Ω.math.lerpPerc // for a percent
Ω.math.smoothstep(start, finish, amount)
Ω.math.snap(value, snapSize) // Snap given value to snap size (floored)
Ω.math.snapRound(value, snapSize) // // Snap given value to snap size (rounded)
Ω.math.center(entity) // get the middle of a rectangle
Ω.math.constrain(pos, bounds) // given a [x,y] pos, keep inside a rectangle
Ω.math.degToRad()
Ω.math.radToDeg()

Utils

Ω/utils/utils

Note about time: use Ω.utils.now() for everything time related. Time is not incremented in dialogs, so you can pause the game without time-dependent functions being affected.

Randoms

Ω.utils.rand(10)  // Random whole number between 0 and 9
Ω.utils.oneIn(10) // 1 in 10 chance of being true
Ω.utils.rnd.seed = 42 // For seeded random: set the seed
Ω.utils.rnd.rand(max, min) // Seeded int between min and max

Time

Ω.utils.now()
Ω.utils.since(time)
Ω.utils.toggle(ms, steps) // cycles through 0-steps every ms milliseconds
Ω.utils.formatTime(time)

Ajax

Ω.utils.ajax(url, callback)

Fullscreen API

Sends an element fullscreen (using HTML5 fullscreen API). Needs to be done inside a user interaction (like a click, keypress) handler:

document
    .querySelector("#fsButton")
    .addEventListener("click", function () {
        Ω.utils.fullscreen.toggle("#myGameCanvas");
    }, false);

Mathods:

Ω.utils.fullscreen.request("#board")
Ω.utils.fullscreen.cancel()
Ω.utils.fullscreen.toggle("#board") //toggle between request/cancel

State helper

Ω/utils/State.js

this.state = new Ω.utils.State("BORN") // Init to a state
this.state.set("RUNNING"); // Set to a state

In container tick:

this.state.tick();

switch (this.state.get()) {
    case "BORN": ...
    case "RUNNING": ...
    case "DEAD": ...
}

Testing state:

if (this.state.first()) // first frame....
if (this.state.count > 40) // 40th frame
if (this.state.is("BORN") // is "BORN"
if (this.state.isNot("DEAD") // is not "DEAD"
if (this.state.in("BORN", "RUNNING")) // is any of these
if (this.state.notIn("DEAD", "RUNNING")) // none of these

TODOs:

- isIn, notIn uses multiple args: but most APIs take array. Should only accept array?
- has a `locked` property that prevents changing state. Why?

Mixins

Not quite a component/entity system - but will do in a pinch. Just experimenting with some mixins/traits... stay tuned.

Some pre-defined traits

this.player.mixin([
    {trait: Ω.traits.RemoveAfter, life: 300},
    {trait: Ω.traits.Sin, speed: 70, amp: 10}
]);

Using with Ejecta

Currently Ω500 needs a few hacks to integrate with the awesome Ejecta project. For now, hack out the following things in Ω500:

  • Call Ω.pageload() manually when ready
  • Replace all getAttribute and setAttribute (TODO: submit patch to Ejecta)
  • Replace querySelector with getElementById

Then build add your project to the Ejecta /App folder, and build with Xcode.

WIP / TODO / Roadmap

The development of Ω500 has thus-far followed a "games first" evolution: with a focus on getting games out the door, rather than making beautiful APIs. Hence, there are some warts around. Now that it has proven itself in the field, Ω500 will enter a grand period of refactoring, consolidation, and unit testing.

High priority:

  • auto system: add this commit? Screen.js: https://github.com/mrspeaker/ld29/commit/5d0b7909426fc6253a8323ce12877a5995f7f2e2
  • and this one? https://github.com/mrspeaker/ld29/commit/db480929aa9e300a89f7877c53f3948eb70d32b0
  • data to state? State.js: https://github.com/mrspeaker/ld29/commit/cb0f89d64316d2c5097c954390021c0687700de3

  • API: standardise and consolidate api methods, parameter types, and parameter order.

  • API: remove/fix references to global instantiated "game" object (move to evt system)
  • API: move traits to game object, maybe
  • API: Input should be a class, not an object
  • Examples: add example using Box2D or other physics lib (see "Oscillator" game)
  • Examples: do a "how to make a game" tutorial.
  • BUG: bad map collision if entity taller/wider than block (can work around with collision points)
  • BUG: bad map collision with velocity/gravity when jammed hard left into block (jump straight up and get stuck on upper block)
  • BUG: tracking camera box moves on zoom.
  • BUG: tracking camera box jumps when map is not as wide as screen, but needs to scroll.
  • Perf: dirty rectangles
  • Perf: profiling - offscreen canvas, collection methods
  • Perf: object pooling
  • Physics: Alternate hit box size for collisions
  • Assets: Partial loader - per-screen asset loading

Low priority:

  • Audio: add multi-voice sounds through some kind of pool.
  • Gfx: DSP on spritesheets (especially a "tint" for images)
  • Maps: block selecting (iso)
  • Maps: Tiled image background
  • Better website and examples
  • Font - individual letter widths
  • GUI: button implementation for canvas only games
  • Screens: Multiple screens (as layers)
  • BUG: Load from image on retina devices (cross browser problems with picking a pixel colour)
  • Math: Swarm/flock algo
  • Maps: Auto-tiling
  • Gfx: "Post" effects in webgl (see DIGIBOTS & CO.)
  • Polygon objects
  • WebGL renderer

inFAQ:

Q. How do you do that omega symbol thing? A. Ω symbol is alt-z, on a mac. I should probably change this stupid name if the lib becomes any good.

Q. When do we get a version bump? A. Every time I finish a game with it. Version 1.0 in 5 more games!

Q. License? A. Unlicense!