Very good but challenging
First things first, the loading scene got my attention with that chaotic background, I like that. The retro gaming design of the game is very well thought out too, for a guy that likes high quality games this actually pleases me. The fact that you added a story to each mission is cool too, but if you could've taken that story and turned it into a narrator's dialogue that would've been awesome. The thing that bother's me though is the limit of troops to stop the attacks. There isn't enough, and when the game gets harder its very difficult to take care of all the enemies. Maybe you should work on adding little soldiers with the heros. But over all, this is pretty good, keep it up.