John Romero broke his own rules!
Here are John Romero's level design rules :
-always changing floor height when I wanted to change floor textures
-using special border textures between different wall segments and doorways
-being strict about texture alignment
-conscious use of contrast everywhere in a level between light and dark areas, cramped and open areas
-making sure that if a player could see outside that they should be able to somehow get there
-being strict about designing several secret areas on every level
-making my levels flow so the player will revisit areas several times so they will better understand the 3D space of the level
-creating easily recognizable landmarks in several places for easier navigation
These are just what I could find in E1M3 alone, there are plenty more.
No support texture between the brown and grey textures in the secret exit room secret.
No support texture between the computer texture and the hexagons.
Misalignment at the raising stairs room, the other side has one too.
Misalignment at the doorway, the other side has one too.
Above the computer panels is a misalignment in the yellow key room, the other secret has one too.
Misalignment in the central pool room, the other side has one too.
An inaccessible outside area with some ammo behind the yellow door.
Following those rules must be hard, especially using DoomED where there was no visual inspection possible and basically relying on what you know and the values of height and alignment.
Yeah, I know, even though DoomED lets the mapper edit the map and see changes on the fly while still ingame, the fact that the only available resolution was 320x200 makes it hard to tell what's a misalignment, and Romero had to work with a deadline.
What a fucking amateur