Start game as usual. During gameplay press [~] to go to console,
 then enter the following cheats:

 elvis lives            - Become Invulnerable
 no i am winner         - Win Level
 oppenheimer            - Extra Powerful Fireballs
 xmas tree              - Get Lots Of Bonuses
 tabasco                - Shoot fireballs
 system visor           - Show Game Info (FPS etc)
 i love carnage         - More Monsters ?
 extra mess             - ?
 force with me          - ?
 bonus bambus           - ?
 columbus               - ?
 yagas revenge          - ?