In the game press [`] and a menu screen comes up here type in:

 god            God mode
 weapons        All weapons
 healthr        Restore health
 ammo           Ammo

 Level codes:

 1 - HotWetSoap
 2 - yFishTankW
 3 - ankelRotar
 4 - yEngineVib
 5 - raphoneKin
 6 - gSolomonsW
 7 - inesTheArc
 8 - hitectSket