private void OnTriggerExit(Collider other)
        {
            InteractionUser user = other.GetComponent <InteractionUser>();

            if (user != null)
            {
                user.Unselect(this);
            }
        }
        private void OnTriggerStay(Collider other)
        {
            InteractionUser user = other.GetComponent <InteractionUser>();

            if (user != null)
            {
                if (IsFacingMe(other.transform))
                {
                    user.Select(this);
                }
                else
                {
                    user.Unselect(this);
                }
            }
        }