/// <summary>
 /// Flag a Tweener that implements IAutoKillableTweener to be auto killed if another tween targeting the same object is played. 
 /// Until the Tweener is either killed, or finished, it will be eligible for being automatically 
 /// killed if another Tweener starts playing that tweens the same target object. Note that other tweener 
 /// must implement IAutoKillableTweener as well (though doesn't have to be flagged to AutoKill).
 /// </summary>
 /// <param name="tween"></param>
 public static void AutoKill(Tweener tween)
 {
     if (tween == null || !(tween is IAutoKillableTweener)) return;
     if (GameLoopEntry.ApplicationClosing) return;
     if (_instance == null) _instance = Singleton.CreateSpecialInstance<SPTween>(SPECIAL_NAME, true);
     _instance.AutoKill_Imp(tween as IAutoKillableTweener);
 }
 internal static void AddReference(Tweener tween)
 {
     if (GameLoopEntry.ApplicationClosing) return;
     if (_instance == null) _instance = Singleton.CreateSpecialInstance<SPTween>(SPECIAL_NAME, true);
     _instance.AddReference_Imp(tween);
 }