The game is GREAT, but some things could be added:
1. Like some people said, a sideways dash would be great.
2. Also, like some other people said, maybe hit the target just by going over it.
3. A level select would be great. Then we can unlock/choose levels, and then choose the levels we want.
4. Some more effects could be added, like a music-themed background,(When ever a note plays, add a water-droplet effect or something like that, themed on what the music sounds like), etc.
Great things about your game too:
1. The thingy where it moves over exactly a certain amount like a real classic game, but with a nice shooter like feel to it.
2. Music. Great music.
3. Levels. Theres a good amount of levels to play at.
Good lasting appeal
9/10 EXCELLENT game!