void OnTriggerEnter2D(Collider2D collider)
    {
        ProjectileController missile = collider.gameObject.GetComponent <ProjectileController>();

        if (missile)
        {
            missile.Hit();
            health -= missile.GetDamage();
            if (health <= 0)
            {
                Death();
            }
            Debug.Log("Hit by a missile");
        }
    }