It's very cool, sound would be good, decrease the number of projectiles in the air or increase the players fire power to take out more ships and/or projectiles. In some screens there seems no way to escape and players will get frustrated quickly and stop playing. I assume your not just doing this for fun so you want lots of people to play it so they can see your work? Well than you might want to think about making it a little more player friendly(easier).
The graphics are very nice!
