Hello. I feel like this is divided into levels 0-3 and a fanmade level known as the intermission.
If there is carpet you are in level 0.
If there is tiled floor, you are in level 1.
If there is a wooden floor in every neighbouring room, you are in the intermission.
If there are tiny halls with pipes, you are in level 2.
If there are brick or tiled walls, you are in level 3.
Is this correct?