private function frame(event:Event):void {
  var h:Number = systemManager.stage.height;
  var w:Number = systemManager.stage.width;
  var dx:Number = Math.random() * 2 - 1;
  var dy:Number = Math.random() * 2 - 1 ;
  vx += dx; vy += dy;
  var s:Number = w/800;
   ball.scaleX = w/800;
   ball.scaleY = h/600;
  //      vy += gravity;
        ball.x += vx;
        ball.y += vy;
        var left:Number = 0;
        var right:Number = myVid.width;
        var top:Number = 0;
        var bottom:Number = myVid.height;
        
        if(ball.x + radius > right)
        {
            ball.x = right - radius;
            vx *= bounce;
        }
        else if(ball.x - radius < left)
        {
            ball.x = left + radius;
            vx *= bounce;
        }
        if(ball.y + radius > bottom)
        {
            ball.y = bottom - radius;
            vy *= bounce;
        }
        else if(ball.y - radius < top)
        {
            ball.y = top + radius;
            vy *= bounce;
        }
        if (ball.y > (height/2)+(height/5)) gravity =  (-gravity);  
        if (ball.y < (height/5)) gravity =  (-gravity);  
  
                                        // myVid.mask = ball;
        }