Insanely good! Simple but really well executed My highscore is 762.2k with a full combo, aside from maybe the first note.
As a bit of feedback, it would be good if there was a count-in at the start of the song on each loop, since it's really disorienting when the thing changes directions, or right after you exit the starting menu. Might also be good to have a small animation, like a color flash, when a note changes, so that it doesn't come as such a surprise when they start changing. I'll also echo someone else and say that color-coding the arrows would help the readability. I think the difficulty is just right for a game jam game though, and the song is pleasant. Good stuff.