I was going around in circles inside the tree kingdom! Perhaps this structure in the trees was not empty of life after all. I began to feel that I was being deliberately led from one blindfall to another by someone opening and then closing off behind me one passageway after another.
This is the kind of old-school dungeoncrawling trick that a Gygax-style DM would use.
One reason it’s hard to pull off in recent-edition D&D is that it works best when PCs are mapping. Otherwise it’s harder to get that dawning realization that the PCs are being shepherded forward; you just come to a point when the PCs say, “We return the way we came,” and the DM says “You can’t.”
I’m in favor of the occasional mapping-based dungeon, although a little goes a long way. It does allow for a different suite of DM tricks.
Opening and closing doors in response to PC movement is one of the few ways monsters can frustrate PCs without getting themselves killed. Good for a mastermind-type villain. Be fair to the PCs though: at worst, the PCs should be shepherded into exciting danger, not trapped in a boring dead-end.