Hold Shift and type mensaaaa at the main menu to enable cheat mode. The phrase "That's what I need" will be spoken to confirm correct code entry. Enter one of the following codes:

Effect - CheatCode

Level skip - [Left Shift] + [Left Ctrl] + A
Continue mission if failed - [Left Shift] + [Left Ctrl] + C
God mode - G
Level restart - [Left Shift] + [Left Ctrl] + R