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.