Unlimited continues:
Quickly press Left, Up, Right, Up, Left(3), Right, Down(2) at the title screen. The sound of a boom will confirm correct code entry. Note: The code must be entered before the high score screen appears. Press R during game play to get nine credits.

Level skip:
Enable the "Unlimited continues" code. When the high score screen appears, press Right, Up(2), Left, Right(3), Left, Down(2), Right, Up. The sound of a boom will confirm correct code entry. Press L during game play to jump to the next level.