SerialTween, ParallelTween を slice しないとちゃんと動く

/**
 * Copyright soundkitchen ( http://wonderfl.net/user/soundkitchen )
 * MIT License ( http://www.opensource.org/licenses/mit-license.php )
 * Downloaded from: http://wonderfl.net/c/yHsR
 */

// forked from soundkitchen's SerialTween, ParallelTween を slice するとオカしい
/**
 *  SerialTween, ParallelTween を slice すると最後まで tween されない :-(
 */
package
{
    import flash.display.Sprite;
    import flash.events.Event;
    import flash.events.MouseEvent;

    import org.libspark.betweenas3.BetweenAS3;
    import org.libspark.betweenas3.easing.*;
    import org.libspark.betweenas3.tweens.ITween;

    [SWF(width=465, height=465, frameRate=30, backgroundColor=0xffffff)]
    public class Main extends Sprite
    {
        public function Main()
        {
            var s:Sprite = addChild(new Sprite()) as Sprite;
            s.x = 100;
            s.y = 100;
            
            with (s.graphics)
            {
                beginFill(0);
                drawCircle(0, 0, 20);
                endFill();
            }
            
            var t:ITween = BetweenAS3.serial(
                    BetweenAS3.to(s, {$x: 200, $y: 200}, 2, Sine.easeOut),
                    BetweenAS3.to(s, {alpha: 0}, 2, Expo.easeOut)
            );

            //t = BetweenAS3.slice(t, 0, 1);
            
            t.play();
        }
    }
}