Untitled

Disable autoscaling in AS3
private function expand(event:Event):void {
  TweenLite.killTweensOf(this);
  TweenLite.to(this, .2, {
    height: _dimensions.tall_height
  });
  return;
}

var m:Sprite = new Sprite();

var g:Graphics = m.graphics;
g.beginFill(0);
g.drawRect(0, 0, box.width, 200);
g.endFill();

// Apply mask
box.mask = m;

var m:Sprite = Sprite(box.mask);

// Redraw mask, now 400px
var g:Graphics = m.graphics;
g.beginFill(0);
g.drawRect(0, 0, box.width, 400);
g.endFill();

// Reapply mask
box.mask = m;