One level for any limit removing ports. PrBoom-Plus or (G)ZDoom are recommended.
This level is improved version of my map for speedmap contest on iddqd(point)ru on which all competitors were limited with four hours and with common theme. I hope all players who liked my "Generator of Evil" will like this level too.
If this level is too hard for you, then you can watch in-wad demo1 by Nikolay "Heretic" Kamnev. Compatible port like prboom-plus is needed in this case.
Do not play this level in the current vanilla PrBoom (up to 2.4.8 for now), because of all existing versions of PrBoom are buggy on levels with big open areas - precision problems. Use PrBoom-Plus instead of classic PrBoom.
The latest Eternity release (3.33.33) also can't handle this map correctly - the same precision problems.