duck

        var rollAngle = Mathf.Atan2(transform.up.x, transform.up.y);
        var pitchAngle = Mathf.Atan2(transform.up.z, transform.up.y);

    var h = Input.GetAxis ("Horizontal");
    var v = Input.GetAxis ("Vertical");

    if (h == 0 && v == 0)
    {
        // auto level
        h = -rollAngle / 90f;
        v = -pitchAngle / 90f;
    }

    rigidbody.AddRelativeTorque (Vector3(1, 0, 0) * v *0.005);
    rigidbody.AddRelativeTorque (Vector3(0, 0, 1) * h *-0.005);