private void OnTriggerEnter(Collider other)
        {
            switch (other.gameObject.tag)
            {
            case Tags.POWERUP:
                Powerup powerup = other.GetComponent <Powerup>();
                powerup.ApplyPowerupEffect();
                powerup.Relocate();
                break;

            default:
                // Nothing to do!
                break;
            }
        }