Maximum Carnage!

On oddball from 1995, which makes it pretty normal actually.

Certain facets of this quickly hit me as unusual. The gameplay, even though it's largely insubstantial tussling with weaker monsters, has pretty good flow and kinetics for the time; coasting down the hallways feels buttery smooth. It's also a "non-linear" map where the exit is randomly off to the side in a secret-like alcove (very obvious, don't worry), so you can leave after engaging only a third of the already scant 31 monsters. And the look -- which is actually pretty and cohesive for something made in the days of DEU and EdMap -- stood out as a mix between a MyHouse wad and Entryway. It doesn't have obvious homages like the pointy staircase, but there are remnants of it in the (free) rocket launcher alcove, and one room with off-kilter 64x64 columns, and the general way areas are connected.

Then I read the text file and got all my answers: this is a DM map outfitted for singleplayer (more thoughtfully than most SP adaptations), and it also is trying to lightly ape Entryway. 

A fun little old vignette and mystery to boot.