I think the game is great, but some of the ppl reviewing here have a good point, personally:
-love the music, and no, I didnt get tired of it.
-the art style needs some work. it needs to be consistent , so it looks like all elements belong in the same game at least. also I cant believe u coulndt do more with the background other than blue gradient and a couple of clouds(?)
-very important one have to gain additional cash based on how fast the mission is completed, how much damages one took, surviving ships and health, I dont know but something! it was rather irritating to repeat the same missions (no saving feature remember?) and to get the same reward even though I was getting the hang of it and playing better.
-also even though one will fail to beat a mission, an amount of reward should be in order, much less than you would earn if u had beaten the mission obviously.
-I think we should be able to reposition the ships we buy, has the missions get harder one is bound to rethink strategy.
-while fighting the formidable aces, I couldnt help but feel an afterburner feature would be rather useful, even if one have to use it sparingly it would make all the difference in the world.
- the game needs a saving progress feature. or at least a "continue" options next to "new game" thats it.
- the only thing that really bothered me was the fact that there was no final boss fight of sort, or maybe fight the enemy's flee (their robot army have to come from some where arent they?) or maybe a fortress or something, I think I would have liked to at least fight an enemy flee that mirrors the one I build thorough the game.
-at times I wished the enemy attacked from different directions.
-I liked the radar featured on the lower left corner (it is useful enough to even shoot down enemies out of one's view) that being said I wasnt sure why you have dots in the middle of the screen where the same robot u control is to tell where the enemies are coming from, why dont use the same radar at the lower left corner?
over all? love the game, there arent many like this that do it right and you sir certainly did a lot of things right, I wouldnt have played through all the 30 stages if i dint like it. really hope you r planning to work on a second installment.