Circle of Particles

var canvas:BitmapData = new BitmapData(400,400, false, 0xFFFFFF);
addChild(new Bitmap(canvas));
var eraser:BitmapData = new BitmapData(400,400, true, 0x33FFFFFF);

var particles:Array = new Array();
for (var i:int = 0; i < 1000; i++){
	particles.push(makeParticle());
}

addEventListener(Event.ENTER_FRAME, onLoop);
function onLoop(evt:Event):void {
	canvas.copyPixels(eraser, eraser.rect, new Point(0,0), null, null, true);
	for (var i:int = 0; i < particles.length; i++){
		particles[i]();
	}
}

function makeParticle():Function {
	var dx:Number, dy:Number;
	var x:Number = 200;
	var y:Number = 200;
	var vx:Number = Math.random() * 4 - 2;
	var vy:Number = Math.random() * 4 - 2;
	return function():void {
			  x += vx;
		      y += vy;
		      dx = x - 200;
		      dy= y - 200;
			   if (Math.sqrt((dx * dx) + (dy * dy)) > 100){
				 vx *= -1;
				 vy *= -1;
			   }
		       canvas.setPixel(x, y, 0x000000);
	}
}

This creates a circular area filled with moving particles/pixels. It makes use of yesterdays functional programming techniques.