Cheat mode:
Press A, B, Y, X on controller two during game play. Press A on controller one to display a cheat number in the top left corner of the screen. To change the cheat number, press A on controller two to toggle invincibility, B on controller two to toggle no damage, or C on controller two to toggle unlimited weapons. The cheat number corresponds to the following status:

1 - Invincibility
2 - No damage
3 - Invincibility
4 - Unlimited weapons
5 - Unlimited weapons and invincibility
6 - Unlimited weapons and no damage
7 - All cheats activated

Level skip:
Press C, Up, Right, Down, Left, A, Right, Down on controller two at the options menu. A sound will confirm correct code entry. Pause game play and press C, A, B or C + A + B. A green flame around the screen will confirm correct code entry. Resume game play to advance to the next level.

Level Password
2 QUESTION
3 MASTERED
4 MOTORWAY
5 CABINETS
6 SQUIRREL
End OVERGAME

Alien movement:
There are some places where the aliens will not follow you or enter.

Weapons:
Use your weapons wisely. When you are out of ammunition, you cannot use fists or hit the aliens with your guns.