it's simple but...
it gets hard too fast. I mean I like the graphics and everything but the game play just gets hard too fast. You need to tone it don't just a little bit. And just some suggestions:
1. Make more music so we can choose a music we want to listen too.
2. Make the direction keys with the arrow keys and not AS D W.
3. Make different ships avialible.
4. Make a health/shield restoring in the shop.
5. Make a health and shield upgrading availible in the shop.
6. Cooldown time after each wave of enemies.
That's all I can think of right now.
Anywho... try to spend much more time then two days to make a great game. This one... just needs ALOT more work done to it when what you have right now.