private void OnCollisionEnter2D(Collision2D collision)
 {
     if (collision.gameObject.name == "Target")
     {
         magnitude = GetComponent <Rigidbody2D>().velocity.magnitude;
         hit       = true;
         GetComponent <Image>().color    = Color.green;
         nn.GetComponent <Image>().color = Color.green;
         nn.Finish();
     }
 }