Neat game! I have a couple suggestions:
- I would put the controls in-game somewhere
- I'm always hesitant to differentiate things by colour in games. There are various type of colourblindness and some people might have difficulty telling the notes apart. The two colours here are probably different enough, but I might still add some other difference (e.g., make one a circle and the other a star). Something to think about!
Overall, great job!