This is taking a lot of inspiration from Doom, but the actual raycasting engine is more like Doom's predecessors, the most well-known of which is probably Wolfenstein 3D: perpendicular walls, constant floor and ceiling height. Wolf3D didn't have textured floors and ceilings because of performance reasons, but several other similar games had them. Doom and IIRC Duke Nukem as well used a BSP engine which was much more flexible (walls could intersect at any angle, variable floor and ceiling heights), although the levels were still "flat" (you couldn't have several "stories" inside a level, e.g. you couldn't design a bridge that you could walk over and under).

For some reason I irrationally like the posterization effect that's created when something is darkened to almost zero.

Really cool. It's also something LLM's are ridiculously bad at, so you kinda have to do it properly.

I respect the amount of work that goes into projects like this; I can't wait to be able to play it.

As a fellow 3d-engine-with-foolishly-unreasonable-constraints developer, I love the detail in the explanations here and seeing the process you went through.

It'd be more interesting if you made a similar looking game using modern APIs imo