I hardly ever write reviews, but this game has earned my praise. My only complaint (if youd call it that) is that it needs more levels. There are some in-app purchases, but you dont have to buy anything to beat the game. I did make a couple of in-app purchases, but I paid in because I wanted to - not because I had to. For me, its not about the money and more about the principle).
I did have a small problem when playing the game, though... but maybe it was just on my phone. When I would spend some of my "toes" to hire allies, and then had to stop playing for a bit, the level wouldnt resume when I brought the game back up. It would relaunch the game from the beginning, but the toes that I spent earlier would be gone. So, I quickly learned not to spend toes on a level unless I had a window of time that I could play the level all the way through.
So, in summary, near-perfect tower defense game... but keep the levels coming (or release a new game as a continuation of this one).