God mode:
Press 4, 6, 6, 8 during game play or while on the automap screen.

All items, all keys, full ammo:
Press 4, 9, 9, 6 during game play or while on the automap screen.

Level skip:
Press 4, 7, 8, 6 during game play or while on the automap screen.

Previous level:
Press 4, 6, 9, 6 during game play or while on the automap screen.

Refresh information:
Press 4, 8, 8, 7 during game play or while on the automap screen.

Music test:
Press # when the "ball" appears on the title screen.

Level select:
Hold 1 + 3 + 7 + 9 at the main menu. Note: Levels 3-5 and 6-7 are bonus levels.