At the main menu, hold [Shift] and type "mensaaaa" to enable cheat mode. If you entered the code correctly, the phrase "That's what I need" will be spoken. Then, enter one of the following codes during a game to activate the corresponding cheat function:
Result
Cheat Code
God mode G
Level skip [Left Shift] + [Left Ctrl] + A
Level restart [Left Shift] + [Left Ctrl] + R
Continue mission if failed [Left Shift] + [Left Ctrl] + C