void OnCollisionEnter(Collision collision)
    {
        Collider collider = collision.collider;

        if (collider.CompareTag("bullet") && alive)
        {
            animation.Play("death01");
            alive = false;
            serialPort.KillZombie(id);
            print("kill zombie" + id);
            //queue.Dequeue();
        }
    }