Neat platformer and cool implementation of using the background of the level to indicate the timing of the beats. My first attempt was around 16:38, and it was fairly difficult mainly due to the controls and a couple of tight timings. I can't quite describe the problem, but I think it's mainly the walljump's stickiness when you try to jump while holding against the wall resulting in a tiny and awkward jump. I personally like the speed boost you get from jumping; it makes the movement feel more unique, and spamming it to move faster makes me feel like a speedrunner. The 3-color ones were fun levels and I really like them, though one minor suggestion would be to speed up the fading for faster tempos so that it's not as visually confusing.
This was a fun platformer, and I think you did well in capturing the feel of the B-side levels.