Good game - certainly got a lot of cool stuff done in the two weeks! I got a bit overconfident and got taken out at level 17 after I thought I had enough health to take down just one more ship!
If might make a suggestion, perhaps just give a level penalty on death? That's all I can think of, anything else is just polish like maybe letting the player continue right after sinking an enemy ship.
Liked the music a lot! It didn't get repetitive and seemed like there were a lot of distinct tracks.