Pause the game and enter one of the following codes for the desired effect.

Effect	Code
9 Lives	Up+1, Down+1, Down+1, Up+2, Down+2, Up+2, Up+1, Up+1.
Change Weapon	Up+1, Up+2, Up+2, Up+1, Down+2, Down+1, Down+1, Down+2.
Skip Level	Down+2, Down+1, Up+2, Down+2, Down+2, Up+1, Down+2, Up+1.