class TweenPropertyFactory {

 final Tween _tween;

 TweenPropertyFactory._internal(this._tween);

 TweenProperty get x => _tween._addTweenProperty(0);
 TweenProperty get y => _tween._addTweenProperty(1);
 TweenProperty get pivotX => _tween._addTweenProperty(2);
 TweenProperty get pivotY => _tween._addTweenProperty(3);
 TweenProperty get scaleX => _tween._addTweenProperty(4);
 TweenProperty get scaleY => _tween._addTweenProperty(5);
 TweenProperty get skewX => _tween._addTweenProperty(6);
 TweenProperty get skewY => _tween._addTweenProperty(7);
 TweenProperty get rotation => _tween._addTweenProperty(8);
 TweenProperty get alpha => _tween._addTweenProperty(9);
}