Played this already.
This game doesn't really improve upon anything from the other thousands of defense games that are exactly identical, so one has to question it's existence. The balance of many of the towers are also completely off. For most of the game I simply loaded up on the basic cannon and then upgraded it whenever possible. Everything else is too costly for what it does if not inferior. I think a little more polishing of the combat system and some more innovation would help this otherwise generic tower game out quit a bit.