Finished the game! I already thought the mechanics were really clever once I started the game and the B-sides twist was fantastic!
I think some sections that require to fast fall or crouch would have been nice since it seemed like the down button wasn't used at all? Also once I realized the player could press buttons too I was able to "cheese" past a few of the levels haha. I think one small improvement for red-green color blindness and even for those who aren't would be to add labels on the buttons that are arrows pointing in the direction they correspond to.
The mechanic and the B-sides actually reminded me a bit of this really cool AGDQ run where two players play Super Mario World together and control switches between them every 1/2 second: