Been playing this game since I first saw it on the front page a few months back, can't believe I haven't written a review yet. One of the best real-time strategy games I've played on this site, zombies or no zombies. At first I was a little ticked because there was only one type of tower, but as I played more and more, I realized that additional towers wouldn't have fit too well. The custom map maker is incredible, I've poured hours into that making several maps (most of which I forget to save), and then several more hours playing said maps. I really can't think of anything that you could add to make this game better than it already is. Keep up the amazing work.
Oh, and if anyone wants to give a map I did save a try:
It's called Hope Island. 3 bridges, 1000 zombies. Not too difficult, but a good challenge I think.