Put a flip in it!

I stopped trying to be clever and just started rendering sectors from back to front using a breadth-first queue. Even though this overdraws more pixels, it ends up being faster than using portals to clip geometry, especially when there are things like stairs or plinths.

Oh boy, this looks lovely. And nice optimizations, sometimes we need to try to find out what the best approach is ^^

ahah welcome to the dark side ;)
indeed pico8 ‘gpu’ is usually faster than lua!