BASIC CLIPPING...

var root = new StrikeDisplay("main","#000000",30,false);
var wid = root.stage.stageWidth;
var hei = root.stage.stageHeight;

var bg = new Sprite();
bg.graphics.drawImage("bg","gradientbg.jpg");
root.stage.addChild(bg);

var bg2 = new Sprite();
bg2.graphics.drawImage("bg","gradientbg.jpg");
bg2.alpha = .3;
root.stage.addChildAt(bg2,0);

var circs = new Sprite();
var numcircs = 20;
var rad = 120;
circs.x = circs.y = 150;
bg.clippingSprite = circs;

function circDraw(evt) {
   circs.graphics.clear();
   circs.graphics.beginFill("#333333",1);
   for (var i = 0;i<numcircs;i++) {
   	circs.graphics.drawCircle(Math.cos(i*Math.PI*2/numcircs)*rad,Math.sin(i*Math.PI*2/numcircs)*rad,10);
   }
}

root.stage.addEventListener("enterFrame",loop);

var dir = -1;

function loop(evt) {
   rad+=dir;
   circs.rotation+=dir*3;
   circDraw();
   if (rad<1 || rad>120) {
   	dir*=-1;
   }
}

function setClip() {
   var c = document.getElementById('clip').checked;
   if (c) {
   	bg.clippingSprite = circs;
   } else {
   	bg.clippingSprite = null;
   	bg.addChild(circs);
   }
}