Enter the following words as passwords (each can only be used once) - then hold the SPACE key until you exit the password entry screen to start the game:

"BOEBOYRULZ" - Infinite lives
"GOTDAPOWER" - Right mouse button = level skip
"NOMANSLAND" - Infinite time
"TILITSLEEP" - No enemies
"SHELTERME." - Infinite shields
"ONLY55KGS." - Bombs harmless