01 Enable sensors (iPhone asks once). On a computer, drag the ring to tilt.
02 Hold the pose. Tap LOCK. All 24 LEDs pulse green twice.
03 Stay inside ±5° — solid green. 90° from lock is the blue target.
04 Off axis: the tilt side fades yellow over the next 5°, then red over 5° more. The rest of the ring holds the previous color — nothing goes dark. One yellow LED opposite points you home.
05 Attitude is the phone OS 9-DOF quaternion (gyro + gravity + magnetometer). No extra filter.