I was going to come in here and give this level a boost as well. I played it earlier today as soon as I saw that Kiavik had turned out something new, and since then it's been all over the streams.
RagnarokX already explained the central trick to this above (and I'm very much looking forward to what he had planned for it himself, once he releases it), but the mechanic really couldn't have received a better, splashier debut than in a level like this. It's
exceptional at introducing the mechanic, signalling puzzle solutions and positional information to the player, and giving you a reason to go back and study it all over again. And then there's that one jaw-dropper near the end that is, no question about it, my favourite single moment in three weeks of playing SMM2. You'll know it when you see it.
Offscreen trickery with the scroll-stop camera lock is something you can expect to come up more often now that's out in the wild, but this level specifically is the rare Mario Maker creation that is an instant classic, sure to be a reference point for design for a long time to come.
If you want to see another fascinating take on offscreen play with the camera lock, I also recommend giving this one a spin: Invisible in the Enchanted Well (FLF-J3H-Y7G). It's another mechanically easy-going puzzle level, very simple to navigate once you understand the gimmick, and at the moment it has very few plays.
