I'm not sure the theme comes out of this one very well, it almost feels like a tacked on thing that makes the game worse. Because the game itself is quite fun, fun enough to make me play several times and try to do better.
I get the feeling that the reload may not have been the right choice, I think it doesn't necessarily add anything to the game, and a simple shooting delay may have been a better fit.
Decent amount of enemy variation, but sometimes the drop pods come a little abruptly. It would be fairly simple to fix; just make the pods that fall on the left half of the screen to come down from the right, and vice versa.