What an awesome game! I love it! It doesn't fit the theme, which is a shame, because otherwise it'd be top marks from me! My only minor gripe was that I didnt immediately understand the UI. I would suggest a simple update to the build square to show a ghosted image of what you were about to build would probably be enough - maybe with the tab arrows either side - that way its obvious what the player is about to commit to. Also, I wanted more! More levels, units, buildings etc! Its a great idea and really well executed in such a short amount of time. Well done!