public void UpgradeSpeed()
 {
     try{
         if (tower)
         {
             MonekeyThroeDart monkeyThrowDart = tower.GetComponent <MonekeyThroeDart> ();
             if (monkeyThrowDart.BuyShootFaster())
             {
             }
         }
     }
     catch (Exception e) {
     }
 }