Very strong defense game
Very well done. The variety of offensive and defensive units you can build is just right for this kind of game. It is challenging yet not too hard to be frustrating. This balance is not easy to get, so kudos on that. Usually, after getting my ass kicked by the A.I., I can figure out what to do to avoid the same fate on the next try. If I fail again, at least I know what I did wrong and I can tune my strategy.
Good job on making stages that require different strategies. I especially love the ship escort missions. The sound is great, as the visuals.