Great Job. I viewed this just because I like seeing what people on HN are working on. Then 1 hour later, I realized that the music was still playing and I was in a state of flow with the work I was doing. This surprised me because I don't normally enjoy this type of music.

Definitely put "slow", "medium" categories on there. Also, maybe filter out the songs that do those jarring breakbeats since those break the state of flow.