In GZDoom the monster count is 22 at the start of the map.
Maybe other source ports don't count Lost Souls in the total or something like that?
Interesting map! It's sort of exploratory even if there's really only a path to follow. I like how you teleport to zones with a different "feeling" to get each one the keys.
It's not completely clear to me why the exterior is damaging, but the rad suits at the doors make it pretty clear even before you step out and take damage for the first time. XD
Not specially hard, but the dark corridor with the spectre opening in front of you and the lost souls attacking from behind can actually surprise you. XD
However, it has 22 enemies surpasing the limit of 20.
And one of them is out of the map, making impossible 100% kills!
Maybe the 100% vanilla compatible restriction shouldn't count at this point?
I'm finding more maps that can't be completed in Chocolate and I don't feel good rating the "respect to restriction" part badly in all of them. xD
This was hard! XD
It took me a while to figure out what to do in the poison area with the cyberdemon, and I got killed a lot in the process, so I had to save to avoid repeating the first half of the level until I found the correct way.
The secrets were fun to find. In the last one I was: "Oh, a Sigil reference!". XD
And the "disco room" with the archviles at the end was awesome looking.
EDIT: Hmmm, looks like it's not vanilla complatible, I can't play it in Chocolate Doom.
The architecture and aesthetics are really impresive. Amazing that it was made in such a short time!
I had to play with IDDQD just to see the map, though. Evading groups of archviles coming for all directions for such a long time is way too much for me. xD
However, when I tried playing it in Chocolate Doom to test if it was vanilla, it didn't work at all, it made me weirdly noclip through the first red door. o_o
It's actually in Boom format, right?