I really liked how shooting the bullets felt like it matched the tempo of the song, I think that the audio was the best part of your game! You did a really good job, you should make more!
Besides that I recommend having more enemy types, and maybe more possible attacks for the player (maybe something that will push bullets away?) - although you used your time fairly well! I'm trying to rate a lot of games, so if you could rate mine that would be greatly appreciated.