Cheat codes
During the game, press Esc to pause, then hold down F12 and press the cursor keys in the following order:

up, up, right, right, up, up, up, up	
Unlock all doorsup

up, up, left, left, left, left, left
Full health

up, up, left, left, right, right, left, left
Maximum sword power

left, right, left, up, right, up, up, up
Skip level