private void OnCollisionEnter(Collision collision)
 {
     // When ball trigger the trap, resize it.
     if (collision.gameObject.CompareTag("Trap"))
     {
         Traps trap       = collision.gameObject.GetComponent <Traps>();
         bool  randomTrap = Random.Range(0, 10) < 5;
         if (randomTrap)
         {
             StartCoroutine(trap.ScaleUp(gameObject));
         }
         else
         {
             StartCoroutine(trap.Shrinking(gameObject));
         }
     }
 }