If it werent for my previous experience with Warcraft 3 tower defenses (Which i stopped playing because there were WAY too many, as is where this started as...) i may have not beat this. First i started making a small amount of towers near the center and focused on upgrades, as in Warcraft 3 it often did better than mazing. But that was not the case here... Good job on this!
Very fun, and i'd love to see more like this, but... If it did'nt cost as much as a full-fledged pc game that has had more effort put into it and has more replay value...