//前後移動，左右轉向
    private int Speed_run = 5;
    private int Speed_rot = 20;
private void key_hold()
    {
         if (Input.GetKey(KeyCode.W))
        {
            transform.Translate(Vector3.forward* Time.deltaTime*Speed_run);
        }

        if (Input.GetKey(KeyCode.S))
        {
            transform.Translate(Vector3.back* Time.deltaTime*Speed_run);
        }

        if (Input.GetKey(KeyCode.A))
        {
            this.transform.Rotate(Vector3.up  * Time.deltaTime * -Speed_rot);
        }

        if (Input.GetKey(KeyCode.D))
        {
            this.transform.Rotate(Vector3.up * Time.deltaTime * Speed_rot);
        }
    }