void OnTriggerEnter2D(Collider2D other)
    {
        if (other.gameObject.tag == "prize")
        {
            Debug.Log("Collision with " + other.gameObject.tag);
            Player.Instance.Points += 10;
            AudioSource coinSound =
                gameObject.GetComponent <AudioSource> ();
            if (coinSound != null)
            {
                coinSound.Play();
            }
        }
        else if (other.gameObject.tag == "fire")
        {
            Debug.Log("Collision with " + other.gameObject.tag);
            Player.Instance.Health -= 10;
        }

        ArrowController sp = other.gameObject.GetComponent <ArrowController> ();

        if (sp != null)
        {
            sp.Reset();
        }
    }