I spent WAY too much time playing this...
This is a pretty badass game, but the only problem for me was that endurance mode was waaaaaay too easy. Unless I just figured out the perfect combo of factories; 3 pyramids right of the bat, a radio tower, then a tank factory. Anything else after that was just overkill. Seriously, I left it running while I made breakfast, took a crap, and smoked a cigarette. When I finally came back after an hour my base was still running strong without a single point of damage.
Anyway, I liked the retro-style graphics and the music was pretty catchy. Gameplay/interface was pretty smooth, and the progression of difficulty was just right. Except for the ease of endurance mode, this was a pretty solid game.
-T.