Invincibility:
Hold Start on controller two at the title screen and keep it pressed until the weapon selection screen is displayed. This effect will last until the game is paused.

Nine lives:
Begin game play and pass level 2. After the game ends, enter the options screen and press Start. A woman will appear and say "Continue Up" to confirm correct code entry. This may be repeated any time your lives have dropped below three.

Extra continues:
Begin game play and destroy your ship. Allow Rex to die on his way to the shuttle. Enter the options screen, set the pad reset selection to "Enable", and press C + Start.

Switch firing mode:
Press A + B + C during game play.

All weapons:
Do not collect any bonus weapons or destroy anything except the Widerum ship at the end of level 1. You score after the level has completed should be 2,800 points.

Rotate logo:
Press A + C + [Left or Right] on controller two at the logo screen. Use the D-pad, A, and C to change the size and rotation of the logo.

Two player mode:
Wait until the first green alien appear on the right side of the screen on level 1. Press Start on controller two. One can control the normal robot while the other player controls the next enemy robot.