I had a nice little time with it. Pretty good for the timeframe of a jam.
Some of the combinations in level 2 were a bit uncomfortable to press; I have a laptop with up and down being the size of one key total, so this may be a contributing factor. This is a relatively minor issue.
Also, the notes aren't really following the song so much so as they're following the tempo, but this is understandable.
Maybe some small sound effects/a soundtest in the menu; I thought my sound wasn't working until I started a song.
Overall though, it was a nice little game. I had some fun with it, and it's clear that effort went into this.