You need to defeat the bosses in each level and collect their heads. Once you have collected all of the heads you need to, they will be used to construct one huge and crazy powerful gun that you will need to beat the boss of all bosses. Each level you will have to defeat a meaner and more difficult boss than the last. You will be awarded with money for each boss that you defeat and will be able to use this money to upgrade your health and other things that will make you more successful in battle. This game is also full of funny and quirky text.