I think the difficulty is backward, with course 3 being the easiest, and course 1 being the hardest.
The only level I didn't really like was level 3 of course 1. I think there should be a pogo platform you can land on when you go through the hole, or no high tele after that hole, or something. Other than that, everything else felt good.
The tele doors don't work for solly on c1, so the map is unbeatable for solly rn