The notes are mapped to the function keys because you're meant to hold the keyboard like a guitar similar to Frets on Fire. However, I did not include a lefty flip mode, so that would be quite cumbersome if you were a lefty. If you are, I apologize, but I completely didn't think about that when I was making the game.
As for the art, it's mainly a heap of programmer art slapped together. The entire game was made in 2 days, and the art was the least of my concerns, especially since I have almost no artistic talent. I wanted to do the project by myself and with only original assets as a personal challenge.
The music should be playing, and if it's not I don't its a fault with the game. When I tested the game, it never failed to play the music. Unless the Mac and Linux builds somehow handle audio files differently and don't play the music, I don't think its an error with the game.
Note alignment is pretty rough, and it was one of the last things I did. It's a poorly done job that was mostly repeated guess work while half-awake. Going back to it, some notes are pretty far off from the musical cues. I would like to do an automated beatmapping system with MIDIs if I have the time to do so. I did not have enough time to do that for the jam though.
If you're using the original bugged build of the game, the game would decrease your health every time you strum regardless of whether or not you hit notes. If you installed this game before January 20th at about 5 PM EST, then you probably have the bugged build still. Besides that build, there aren't any particular issues with visual note timings. In fact, the visual timings are quite lenient and let you hit notes that are a bit off.