Cheat codes
At the main menu, type 'levelx' and then press the spacebar. Alternatively, type 'oh dear' and hit the spacebar again.

Alt-0	Speed
Alt-1	Full ammunition
Alt-2	Upgrade weapons
Alt-3	Restore energy
Alt-4	God mode
Alt-6	End mission
Alt-7	Deactivate enemies
Alt-8	Helicopter
Alt-9	Tank