I swear I remember posting a screenshot of this level I was working on at the time with the caption "Bats in Tubes and an Imp", but I can't find the phrase anywhere. Maybe the thread's gone or maybe I'm just crazy.
Anyway, I had this level "Hexxis" I was working on, and over the years I've sporadically messed with it, and added to it. But honestly I've always been more interested in the (G)ZDoom engine as a technical playground than in its gameplay. My interests skew towards aesthetics, technicals, special effects, and general engine pushing, so I never really added much gameplay to "Hexxis" beyond the very bare-bones. I kinda don't really even like shooter gameplay that much, so I don't enjoy the idea of designing enemy encounters and test playing them ad nauseum. But I did do a lot of what I enjoy in "Hexxis", so there's a bunch of effects and weird things from over the years.
Some effects it contains:
Spoiler:At this point I've been fiddling with it for ~20 years or whatever, so I figure I should just let whoever might remember it at least see it. I kind of just want to be done with it.
It is completable, in that there's a beginning, a flow of progression of some description, and an exit.
Here's the zip file.
It's got "Hexxis" and a couple other bonus things I was also working on over the years. I'll let the chips fall where they may.