At the Title screen, press A, A, Down, C, B, A, Up, Up, Down.

At the Title screen, press A, Down, Down, B, B, B, C, Left, Right.

Level 2: AFHT-CAA8
Level 3: AKHT-CAA8
Level 4: APHT-CAA8
Level 5: AZHT-CAA8
Level 6: A3AT-CAA8
Level 7: A7HT-CAA8
Level 8: BFHT-CAA8
Level 9: BKHT-CAA8
Level 10: BPHT-CAA8
Level 11: BZHT-CAA8
Level 12: B3HT-CAA8
Level 13: CBHT-CAA8