I really like the concept! I've been working on projects in the infinite-builder genre so it's fun to see someone else's take (on a limited time scale). The art is nice and I really enjoyed the tower placement animation. The automation aspect is also cool and it's fun to watch the guys run around and do your work for you. There also some nice personality to the actual build items. Things I'd like to see: more tower defense elements, more expansion, and a cleaner menu (have the menu close by clicking "build" again, for example).