One really interesting genre is ‘maps made from memory’. Some people have re-created the original Doom and Doom II maps entirely from memory, without looking at the originals.

When you play through them, everything has a weird, surreal quality. Almost everything is how you yourself would remember it (if you’ve played the originals hundreds of times like us Doom geeks…), but distorted and not quite right. Corridors are longers, doors wider, rooms don’t quite feel right, some walls aren’t the right colors, etc.