Good game
Graphics: These were deffinatly not bad. Everything looks pretty good to me. I like your drawing style a lot, the special effects were alright as well, not much to complain about.
Sound: I think the machine gun has a good sound when you fire. Normally you would get a little annoyed, but this machine guns sound was not annoying at all. As for the music, I think you should turn that up a little, I could barely hear it.
Interactivity: Simple controls, which is nice. I also liked the high score list, but I don´t think it was really a high score list. I was ranked 1st, 2nd, 3rd and 4th and I didn´t even got passed level 2. Maybe you should turn that into a real high score list, would be much better.
Stuff that needs improvement:
-Well some enemies fired way to quickly. Sometimes I didn´t even saw them yet and they already shot me. This is alright for the higher levels, but not at level one.
-There´s plenty of ammo coming from the air, but it´s still not enough. You get about 30 bullets for every package now right? I think you should make that 50 or 60.
Overall 8 out of 10, 4 out of 5. This was a very nice game in my opinion. I don´t think you can improve this game much. Hope to see some more of this stuff from you. Keep up the excellent work.