Presse escape, then hold F12 and type the following arrow keys:
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Up,Up,Right,Right,Up,Up,Up,Up       - Unlock all doors
Up,Up,Up,Left,Left,Left,Left,Left        - Full Health
Up,Up,Left,Left,Right,Right,Left,Left  - Max Sword Power
Left,Right,Left,Up,Right,Up,Up,Up    - Level Skip