The Unholy Trinity

An example of how not to make a map. Lots of ugly rooms filled with same types of enemies. The blue key room in particular has about ten hell knights and barons trapped on pillars, and you have only a super shotgun to fight them; thankfully, what _would_ have been a mind-numbingly boring fight is skippable because the blue key is right there for you to take. Errors large and small abound, such as the pass-through metal bars or the clumsy approach to detailing and shading.
New music, in the form of a bad-sounding midi which barely has any rhythm.

Finished within 4 minutes or so A 2016 re-release of a 1994 level. The text file warns: "Bad, really bad 1994 quality", and is right; there's nothing whatsoever interesting about this level -- you enter one flat room after another and shoot at haphazardly spread out monsters. There is an "invisible teleporter" gimmick which, however, I have barely noticed in my playthrough. The exit isn't even hidden or locked in any way, and can be easily stumbled into accidentally. There's nothing to say.

The map feels very linear throughout, with you basically doing one thing in each room and moving on to the next. The rooms are very varied though, and there is actually something pleasant to uncovering the successive areas. There are some puzzles, one of which involves illusionary walls, with a zombie shooting at you from "nowhere" being the only hint; this is a clever puzzle but it could ruin the map if the player accidentally kills the zombie early and gets stuck. The spiderdemon hall near the end contains what is either a glitch or a really annoying "trick": columns that seem safe at first, but actually don't shield you from the spider's gunfire at all.   Almost finished, ~20 minutes; died to the spiderdemon.

(MAP03 review only)   Finished, ~20 minutes Yet another map which drops the ball in terms of difficulty. Health is provided in extreme abundance, and even when heftier enemies show up, their attacks are easy to dodge in the huge arenas (even the cyberdemon/spiderdemon fight at the end provides such ample cover that you need almost to be _trying_ to die -- as, uh, has happened to me). I've once read that, with the advent of modern source ports which streamlined mouse aiming, older Doom levels suddenly became very easy; this would explain why so many of these mid-90's maps feel so strangely unchallenging...
The area beyond the yellow key door offers a more interesting fight, what with the corridor filled with lost souls. However, the map quickly loses momentum after that, wasting the player's time with the pointless room of six teleporters, which all turn out to lead to identical closets with medikits. Turns out, that room is just a red herring; the real way to progress is to open a door indistinguishable from a wall. Annoyingly, having to hump the walls to find the hidden door happens several times throughout the map.
Powerups are scattered haphazardly, including a pointless invulnerability sphere, numerous invisibility spheres despite the total lack of hitscanner enemies (this is another 90's thing, it seems; did the people back then _really_ think invisibility spheres helped against projectile-throwing demons?), and a light-amplification visor despite a lack of dark areas where it'd be useful.
The map topology is as basic as it gets: a small starting room with four doors, one initially open and three locked with keys, each door leading to a totally separate area housing the key to the next door over. Each area is distinct visually, although there's a lot of simplistic-looking, overly large rooms. There's fairly little interconnection between individual rooms within each area; mostly you just progress from room to room, and things like windows are rare. The map suffers from "symmetry syndrome", where the mapper goes out of his way to make every room symmetrical, without thinking if it improves the room or not (example: in the red door area, there's a side room housing an irritating slow-moving lift, not worth visiting except to get 100% kills... and this side room of course gets dutifully duplicated on the other side of the area).
There is custom music in the form of a rock midi, not particularly well-made, but not overly grating either.

Played for 13 minutes before dying. Did not enjoy this one; the caves ("catacombs" according to the text file?) section being unmapped AND full of samey corridors AND full of "mystery meat" switches was obnoxious. Likewise did not enjoy the "nested squares" section at the start, with ugly gray walls. Only visual highlight I've seen during my playthrough were rooms with water pools. Could not find a way to access yellow key, or do much of anything in the nukage area except dying, although it was satisfying to risk the run across nukage in hopes of finding a radsuit--and subsequently find one. 
Slightly interesting is how enemies roam the interconnected caves and can surprise you from unexpected directions, but this only happened to me once or twice. 
The revenant was placed uselessly and could be taken out too easily with hit-and-run tactics. 
Too generous with health (soulsphere) and weaponry (room in caves). 
The entrance to caves, with a long corridor which has to be entered from a demon-infested pool, was a briefly tense moment, but not sure if the demons chasing after me from the pool could enter the cave area; would have made for an even tenser experience.