The only things I'd improve are the basic gameplay. For some reason running half-into a wall greatly increases friction, both horizontally and vertically, which meant that jumping into a wall immediately made you "stick" to the wall and lose your vertical speed, which was annoying. Walking into a wall was also considerably slower than I'd expect because of that, so I had to walk away from walls, but that meant that on the tightropes of the level with the difficult puzzle I kept falling off. It didn't hurt my experience that much (still 4 stars), but it's something to consider.