I love this game, but I hate the fact that it's a neutered version. You have to go to its website and become a "Gold" (Paying) member to save your game..
Great game, entirely too unforgiving at the latter levels though. I don't know why the 30-level badge is listed as "Hard" instead of "IMPOSSIBLE," even the headshots for last stand was way easier than this!
Repairs are FAR too expensive, the weapon damage upgrade apparently does nothing, the cannon fires too slowly even fully upgraded, to stop the enemies which rush in swarms. Never figured out how to use the mines until I quit. 1/5