One issue
I really like the game, I have played through it twice now. I do have one issue with it however. The fact that once you lose one level you have to start all the way back at the beginning is very frustrating. Also that you do not have enough levels to get all the upgrades. It would be really nice to have some sort of a Free mode, where you can just keep getting upgrades until you get tired of the game. Just an Idea, but I think it could add quite a bit to the game.