Great game! The visuals and music fit very well. I did have a bit of a hard time remembering which keyboard buttons to hit to swap which was mostly since triangle looks like an up arrow, which is a bit counter intuitive, but that's a nit pick since its easy to get used to after a bit. One thing that could have made this feel better would be some visual or auditory feedback when you hit the notes correctly, like maybe a screen shake for correct hits or some bad sound if you miss?
Overall fun game though!