Thanks, Lucinda! I'd already looked at some older tutorial levels but I don't learn well like that; I have to just... do stuff and analyse the results. Anyway, I'm getting there, I think. And this level doesn't require advanced shifting/warping, anyway, thankfully.
Added in some more warps today, visually improved some screens, and built three or so new ones, bringing the total of new screens since the "resurrection" up to 10, so the screen count now is... whatever it was before I stopped in 2013 (539, if I didn't miscount then?) plus 10. So, possibly, the next one will be 550?! Wheeeee!!!
Biggest roadblock today is that I discovered one of the tilesets I used back then has "no use! FU" written at the bottom. I *think* it's one I probably had permission for despite this, because I usually respect people's wishes and wouldn't even start working with a tileset if the creator forbade it so clearly; it may also have been part of a set of tilesets released in bulk by the creator a while after they released their levels. But, I don't *remember*, which means I may have been using it without permission purely by error? Because of course mistakes happen. And I don't remember who made it, and I don't remember asking for permission. So I'm really uncertain about that tileset now. Unfortunately I've already used it in an entire area. There's other tilesets that do something similar, so I could probably replace it with one of those if necessary, but, ugh.
Mostly this has made me aware that I really need to check *all* the tilesets I've used in this level so far (the second part, anyway; for the first part, permission was definitely acquired for all tilesets that didn't already come with a blanket permission), and it seems to kind of border on the impossible to really find out what the permission situation was back then, for a lot of my tileset collection from 10 years ago. :-/