I'm gonna take a moment to think out loud aboutTHE THIRD DIMENSION
3-4 accessible layers (plus the hash walls and the void) would be alright for most situations. Any more and it gets difficult to differentiate between layers from a top-down perspective, any less and there's really no point to having them in the first place.
Right now there are three accessible layers, this being the bottom one. You're on the edge of the void, and your vision is very limited. The rule of thumb is that you can only see what you can step on. The tiles on your level are, of course, visible. Only the ledges of the layer right above are also visible.
Climb up on the middle layer, and things get less dark. The middle layer tends to form trenches with the current map generation. It's not as messy as it was before, but I'm still going to need to even things out based on the amount of neighbours.
And the top layer. Only the solid walls block your view now. The visibility can jump quite a bit from the previous layer, so there could be a fourth one between the top and middle layers. That, or the top layer should at least be rarer than the middle one.
I like the compromise that your "memory" records the characters but not the heightmap. That way you can quickly review what's accessible and what's not, but you're not overloaded with information about places you can't even see. It's probably too dark for some screens, but I can't light it up too much or it'll get in the way. Another solution would be to use a lighter color for the background and a darker one for the characters.
Otherwise the palette is usable, if a bit bland. It's got just a hint of red/brown. I think the tone could change more between the accessible layers to help create the illusion ofTHE THIRD DIMENSION