Easy to abuse mechanism.
Fun, but it becomes really easy when you figure out how it works. Dual pistols make it too easy, and the zombie clones never get stronger, so it's just endlessly mowing them down at that point. It's also weird how you can make two giant towers on either side of you, and somehow the bottom of the screen will magically push you up. It'd be nice if there was a penalty for doing that, like if the clones used their height advantage to jump down on you, or the towers would collapse and bury you.
Really, once we get the pistols, we'd never lose, if it wasn't for the clones' greatest weapon: The mofunzone link. Well, if your goal was to raise the # of hits at mofunzone, you accomplished it well.