First make your score end in a three (by shooting the bubbles). Then hit 'P' to pause the game. Hit 'Esc' and then click on "No" when asked if you want to play again. Doing so takes you to the title screen with the drooling barbarian. Now type the following: "KOM JE ILLEGAAL DOOR DE PLAAG DAN GRIKPT DE JUNGLE COMMAND JE IN DE KRAGG" followed by 'Return'. The border should have become green. Hit the 'Fire' button to return to the game. You now have infinite lives. You must do this on Level 1 before being killed even once.