Is it fun? Yes. However, there are problems. For example, when you get bigger, if you move up, you can get eaten by something from below because of your size, making manuevering nearly impossible. The other thing is the music. I loved it to begin with, but towards the end, the clown like music was manic and annoying!
As for the good, I love the retro look, it is colorful fun. And, the idea is silly fun. Good job overall, just fix those issue and you have a 5 star game.