Love the concept and art. This puzzle was too much for me to solve, though I really enjoyed the ones before it. In terms of controls, as a general note you should never assume that the user knows the conventions, so mentioning to use the arrow keys to move on the first level would have been nice as I was confused for a little bit thinking WASD were it.
I don't know if this is helpful but the solution to the puzzle is to first make the red wall slide down but changing the world direction twice then standing on the yellow button. After this you get off the button and flip everything back so the red wall in on top of the yellow wall while pressing down blue button. The final step is to flip the world just once instead of twice so the red wall can't move and just exit the level.