//This container contains all the circles that act as a mask for the picture
var container:Sprite = new Sprite();
 
//Assign the container to be the image's mask
picture.mask = container;
 
//Add the container to the stage
addChild (container);
 
/* This timer is responsible for creating a circle every 0.05 seconds. A total of 20 circles will be created. */
var timer = new Timer(50,20);
timer.addEventListener (TimerEvent.TIMER, createMaskBall);
timer.start ();
 
//The timer calls this function every 0.05 seconds
function createMaskBall (e:Event):void {
 
        //Create a new MaskBall
        var maskBall:MaskBall = new MaskBall();
 
        //Set scale to zero so it won't be visible at the beginning
        maskBall.scaleX = 0;
        maskBall.scaleY = 0;
 
        //Assign a random position in the stage
        maskBall.x = Math.random() * stage.stageWidth;
        maskBall.y = Math.random() * stage.stageHeight;
 
        //Add the maskBall to the container
        container.addChild (maskBall);
 
        //We need ENTER_FRAME function to handle the animation
        maskBall.addEventListener (Event.ENTER_FRAME, animateMaskBall);
}
 
//This function is called in every frame
function animateMaskBall (e:Event):void {
 
        //Increase the scale
        e.target.scaleX += 0.05;
        e.target.scaleY += 0.05;
}