Created
December 14, 2013 08:17
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The code powering http://andrewberls.com/demos/tracetext/
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| tracerColors = [ | |
| '#1B184F', | |
| '#312c91', | |
| '#423ac0', | |
| '#9c4274' | |
| ] | |
| class Tracer extends Kona.Entity | |
| @group = 'tracers' | |
| constructor: (opts={}) -> | |
| super(opts) | |
| @gravity = false | |
| @box = { | |
| width: 10, | |
| height: 10 | |
| } | |
| @color = Kona.Utils.sample(tracerColors) | |
| # Survive for some number of collisions before disappearing | |
| @lifetime = 3 | |
| @pixels = [] | |
| @pixelSize = 2 | |
| @pixelColor = '#b8b8b8' | |
| @pushFlag = 0 | |
| @pushLimit = 5 | |
| @sweepFlag = 0 | |
| @sweepLimit = 7 | |
| drawPixels: -> | |
| for pixel in @pixels | |
| Kona.Canvas.safe => | |
| Kona.Canvas.ctx.fillStyle = @pixelColor | |
| Kona.Canvas.ctx.fillRect(pixel.x,pixel.y,@pixelSize,@pixelSize) | |
| update: -> | |
| super() | |
| # Reverse direction if we hit a wall on any side | |
| if @left() <= 0 || @right() >= Kona.Canvas.width | |
| @lifetime -= 1 | |
| @direction.dx *= -1 | |
| if @top() <= 0 || @bottom() >= Kona.Canvas.height | |
| @lifetime -= 1 | |
| @direction.dy *= -1 | |
| @drawPixels() | |
| if @pushFlag == 0 | |
| @pixels.push { x: @midx(), y: @midy() } | |
| if @sweepFlag == 0 | |
| @pixels.shift() | |
| @pushFlag = cycle(@pushFlag, @pushLimit) | |
| @sweepFlag = cycle(@sweepFlag, @sweepLimit) | |
| if @lifetime == 0 | |
| Kona.Scenes.currentScene.removeEntity(@) | |
| draw: -> | |
| Kona.Canvas.safe => Kona.Canvas.drawRect(@position, @box, color: @color) | |
| # Increment a number, cycling to 0 if it exceeds `limit` | |
| cycle = (num, limit) -> | |
| if num > limit then 0 else num+1 | |
| # Choose a random nonzero value for dx or dy | |
| randomMotion = -> | |
| res = Kona.Utils.random(-2,2) | |
| if res == 0 then randomMotion() else res | |
| # Choose a random speed value | |
| randomSpeed = -> | |
| Kona.Utils.sample(Kona._.range(0.5,1,0.1)) | |
| # Choose a random point on the canvas | |
| randomX = -> Kona.Utils.random(0, Kona.Canvas.width) | |
| randomY = -> Kona.Utils.random(0, Kona.Canvas.height) | |
| # Add a Tracer entity to the canvas | |
| addTracer = (opts) -> | |
| tracer = new Tracer(opts) | |
| Kona.Scenes.currentScene.addEntity(tracer) | |
| Kona.ready -> | |
| Kona.Canvas.init('gameCanvas') | |
| main = new Kona.Scene { name: 'main', active: true } | |
| addTracer { x: 200, y: 200, dx: -2, dy: -1, speed: 0.75 } | |
| setInterval -> | |
| addTracer { | |
| x: randomX() | |
| y: randomY() | |
| dx: randomMotion() | |
| dy: randomMotion() | |
| speed: randomSpeed() | |
| } | |
| , 3000 | |
| Kona.Engine.start() |
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