package {
 
        import flash.display.MovieClip;
 
        public class MyMask extends MovieClip {
 
                //Mask's x and y speed
                public var speedX:Number;
                public var speedY:Number;
 
                //Set the given scale for this mask, when we create a new
                //mask object
                public function MyMask(scale:Number) {
                        this.scaleX = scale;
                        this.scaleY = scale;
                }
        }
}

//We use an array to hold all our masks.
//(Except the mask that follows our cursor)
var masks:Array = new Array();
 
//We add all of the masks to a container
var maskContainer:Sprite = new Sprite();
 
//Set the maskContainer to be the image's mask
backgroundImage.mask=maskContainer;
 
//Add the container on the stage
addChild(maskContainer);
 
//Create the mask which follows cursor movement (master mask)
var masterMask:MyMask=new MyMask(1);
 
//Set the master masks's coordinates to match cursor's coordinates
masterMask.x=mouseX;
masterMask.y=mouseY;
 
//Add the master mask to a container
maskContainer.addChild(masterMask);
 
//Cache the image and container as bitmap, so we
//can animate the alpha of the masks
maskContainer.cacheAsBitmap=true;
backgroundImage.cacheAsBitmap=true;
 
//Create a timer that is called every 0.2 seconds
var timer:Timer=new Timer(200,0);
timer.addEventListener(TimerEvent.TIMER, timerEvent);
timer.start();
 
//This function is called every 0.2 seconds.
//We create a new mask in this function.
function timerEvent(e:TimerEvent):void {
 
        //Calculate a random scale for the new mask (0 to 1.5)
        var scale:Number=Math.random()*1.5 + 0.5;
 
        //Create a new mask with random scale
        var newMask:MyMask=new MyMask(scale);
 
        //Set the position for the new mask
        newMask.x=mouseX;
        newMask.y=mouseY;
 
        //Assign a random x and y speed for the mask
        newMask.speedX=Math.random()*20-10;
        newMask.speedY=Math.random()*20-10;
 
        //Add the mask to the container
        maskContainer.addChild(newMask);
 
        //Add the mask to the array
        masks.push(newMask);
}
 
//We need ENTER_FRAME to animate the masks
addEventListener(Event.ENTER_FRAME, enterFrameHandler);
 
//This function is called in each frame
function enterFrameHandler(e:Event):void {
 
        //Loop through the mask array
        for (var i:uint = 0; i < masks.length; i++) {
 
                //Save a mask to a local variable
                var myMask:MyMask = (MyMask)(masks[i]);
 
                //Update the x and y position
                myMask.x+=myMask.speedX;
                myMask.y+=myMask.speedY;
 
                //Increase the scale
                myMask.scaleX+=0.1;
                myMask.scaleY+=0.1;
 
                //Reduce the alpha
                myMask.alpha-=0.01;
 
                //If the alpha is below 0, remove the mask
                //from the container and from the array
                if (myMask.alpha<0) {
                        masks.splice(i,1);
                        maskContainer.removeChild(myMask);
                }
        }
 
        //Update the master mask position
        masterMask.x=mouseX;
        masterMask.y=mouseY;
}