Boring
the problem with this game is that it takes too long to buy anything due to the fact that fighting back is hard as hell.
You cant aim at all (until you save up 1000$ which takes practically 8-10 levels)
The enemies end up wiht more life and get stronger which makes things much MUCH more annoying and when that happens you can barely make any money at all because they take so long too kill.
Personally, I think that you should either start out with that sticky shield or make it cheaper. players wont get any where if they cant kill any tanks