This game has a lot of replay value; you just have to be creative. Like, I tried to replay levels with the goal of not destroying any red cars at all. If you DO destroy a car, add a 5 second penalty to your time at the end. Try it. Time trials are much more interesting this way. Game deserves a 5/5.
I really enjoyed this game. It's very original and shows that there was thought and effort behind every aspect. Inversely, I'd also believe that Spewer would make an interesting first-person shooter. Imagine if the mad doctor let loose a half a million of these into the city. With their different transformations and abilities, it would be a generous step-up from any post-apocalypse zombie shooter. Just something to think about. =P In any case, great game.