Actually, I hated it because I spent ten minutes stuck in a room because I couldn't find which wall was the hidden supernarrow stairs that shared the same texture as every other wall. 
@sanspoint Probably because it was their one shred of originality because most of it was right-angled corridors with little else going for it.
...I think it predicted the modern FPS there. 
@Jo @sanspoint did it.. did it have chest high walls? 
@polychrome @Jo @sanspoint the doom engine can't do that, can it?
@monorail @polychrome @sanspoint Doom and Doom II do them all the time, as they're just a sector like everything else on the map.
Just don't expect them to be effective cover, though.
@Jo @monorail @polychrome @sanspoint I'm pretty sure walls can provide some cover though, especially when the enemies are below you
@noiob @Jo @monorail @sanspoint though if I remember correctly it -can- stop moving projectiles like missiles or fireballs 
possibly also Lost Soul attacks.
@polychrome @noiob @monorail @sanspoint Sometimes, yeah, because unguided projectiles go for player position at the time of launch.. It's the friggin' hitscanners that get the better of the walls, for the most part.
@noiob @monorail @polychrome @sanspoint I did say "effective", tbh. 
@noiob @Jo @monorail @sanspoint doom doesn't take height into account when calculating bullet raycasts.
It's actually a 2D shooter game with "3D" visuals.