void Update()
 {
     if (Ninja.isRecovering)
     {
         return;
     }
     if (Ninja.isJumping)
     {
         return;
     }
     if (Input.GetMouseButton(0))
     {
         holdTime += Time.deltaTime;
         holdTime  = Mathf.Min(holdTime, 1);
         ninja.ChargeJump(holdTime);
     }
     else if (Input.GetMouseButtonUp(0))
     {
         ninja.Jump(holdTime);
         holdTime = 0;
     }
 }