For a first game, well done! The loop and the idea is there, you just need to refine it more. Hit/miss feedback is very importand in these games, it is a bit lacking, same goes to actually explaining to hit the notes. Otherwiseit is a fun little note smasher
Graphics are not bad, but the font does break the resolution rules in the “introduction” part, and the spritework needs a bit more cohesion and refining, but other than these, it is not bad.
Music is by far the best part of the game, super cool job with it, sounds gameboys enough!
Overall, cool first game, well done!