Summer Carnival '91

Ten bonus ships:
Pause the game during a play and press I, Select, II, Select, I, Select, II, Select.

Level select:
Highlight the "Option" selection on the title screen and press Up + Select + I. The "Sound Select" option will change into a level selection option.

Level skip:
Pause the game during a play and press Right, Left, Right, Left, Right, Left, Right, Left, II six times. Then, resume game play, hold Left + I + II, and press Run.