It's a simple old school side scrolling shooter packed full of wow and funny one liners.
8 great weapons and tons of enemies to kill them with is just the first brilliant thing about the game, the fact that it's so simple is what makes it so much fun and so addictive. Basic job is to get the keycard to exit the level, after you've finished 3, you face and boss and then finish the world. There's 8 worlds total and there's replayabillity in there too.
Because to get the top marks, you've gotta find the Babe on each level and find all of the Nukes too. And the Nukes are well worth seeking out, as they're highly useful, 'cause when you collect them all on a level, your health, ammo and Pipe Bomb capacity increses.
It's just some great old school fun anf for the asking price, it's well worth it. 'cause they don't make them like this anymore :)