oldschool particle fun

//2017 - http://lifesine.eu

import flash.display.*;
import flash.filters.BlurFilter;

var w = stage.stageWidth;
var h = stage.stageHeight;
var hw = w * .5;
var hh = h * .5;
var dsqr = hw*hw + hh*hh;

var np = 1000;
var p = [];
for(var i = 0 ; i < np; i++){
    var d = 3 + Math.random() * 3;
    p[i] = addChild(new MovieClip()) as MovieClip;
    p[i].graphics.beginFill(0xFFFFFF);
    //p[i].graphics.drawEllipse(-d * .5,-d * .5, d , d);
    p[i].graphics.drawRect(-d * .5,-d * .5, d , d);
    p[i].graphics.endFill();
    p[i].filters = [new BlurFilter()];
    resetParticle(p[i]);
}

function resetParticle(particle:MovieClip):void{
    var s = 3.0;
    particle.vx = Math.random() * 2 * s - s;
    particle.vy = Math.random() * 2 * s - s;
    particle.x = hw;
    particle.y = hh;
}

function updateParticle(particle:MovieClip):void{
    if((particle.x < 0 || particle.x > w) ||
        (particle.y < 0 || particle.y > w)){
        resetParticle(particle);
    }

    var a = flash.utils.getTimer() * 0.001;
    var r = 0.01;

    particle.vx += Math.cos(a) * r;
    particle.vy += Math.sin(a) * r;

    particle.x += particle.vx;
    particle.y += particle.vy;

    var dx = hw - particle.x;
    var dy = hh - particle.y;
    var d = (dx*dx + dy*dy);
    var s = map(d,0,dsqr,1.0,10.0);
    particle.scaleX = particle.scaleY = s;

    var dmx = particle.x - stage.mouseX;
    var dmy = particle.y - stage.mouseY;
    var dmsqr = (dmx*dmx + dmy * dmy);

    var t = s * 25.5;
    var ct = particle.transform.colorTransform;
    ct.redOffset = ct.greenOffset = ct.blueOffset = (-t);
    ct.redMultiplier = map(dmsqr,0,dsqr * .25,0,255);
    ct.greenMultiplier = map(dmsqr,0,dsqr,0,255);
    //ct.blueMultiplier = map(dmsqr,0,dsqr * 2,-255,255);
    ct.alphaMultiplier = map(dmsqr,0,dsqr * .25,0.0,1.0);
    particle.transform.colorTransform = ct;

    particle.rotation += particle.vx+particle.vy;

    /*
    var blur = particle.filters[0];
    blur.blurX = blur.blurY = map(dmsqr,0,dsqr * .25,0.0,2.0);
    particle.filters = [blur];
    //*/
}

function update(event:Event):void{
    for(var i = 0 ; i < np; i++){
        updateParticle(p[i]);
    }
}

this.addEventListener(Event.ENTER_FRAME,update,false,0,true);

function map(value:Number,
                                start1:Number, stop1:Number,
                                start2:Number, stop2:Number) {
    var outgoing =
      start2 + (stop2 - start2) * ((value - start1) / (stop1 - start1));
    var badness:String = null;
    if (outgoing != outgoing) {
      badness = "NaN (not a number)";

    } else if (outgoing == Number.NEGATIVE_INFINITY ||
               outgoing == Number.POSITIVE_INFINITY) {
      badness = "infinity";
    }
    if (badness != null) {
        trace("map(%s, %s, %s, %s, %s) called, which returns %s",
                      value, start1, stop1,
                      start2, stop2, badness);
    }
    return outgoing;
}