A very good game, great graphics. I didn't have any big problems with the game, but I noticed a few aspects:
1) The rhythm concept is incredibly cool, but also very difficult to achieve. I tried to synchronize myself as well as I can, but if you don't hit the beat right, you lose a bullet and there's also the problem that you might be surrounded by enemies at that moment and they won't wait for you until you shoot.
2) On that piano panel, I no longer understood what I had to do, because I didn't manage to pass...