Great music and fine sfx as mentioned, but had a lot of trouble seeing what was happening, mostly because the ships were pretty close to the same color as the background. On top of that, the clouds actually interfered with visibility, which made it nearly impossible to not take damage at points. Overall, I liked the idea and the game generally, especially the music, but had a really difficult time playing the game. Would be nice to have larger sprites generally next time - I recognize it is a shoot-em-up type game, but doesn't mean it shouldn't scale up properly. In any case, nice work!
Edit: Oops! That was my bad, didn't see the expand button. :D It scaled up fine, so ignore most stuff about it being too small. I still found the contrast to be too low, but I changed my rating after finding the expand button in another game.