Looking back, I am surprised id Software ever made it, because the shareware levels from Wolf3D, DooM and Quake were not only some of the best of the games, the shareware campaign for each of those were long enough to keep you busy for hours. Also, Quake shareware discs included the whole game locked behind a simple CD key that got cracked almost immediately. But it's crazy to think that people went through the trouble of mail ordering the games, not pirating them from people who already did, or just continue to play the shareware levels that were some of the best. Plus, there are tons of secrets to find in them!
that's a very interesting fact about Quake... I played the shareware version before buying the full game.
I fiddled a lot with those games. In Doom, in fact, I discovered a newbie hack which I think no one ever discovered. I didnt have internet at the time so I never shared it. I was fascinated by the code of games and used Notepad for Windows 95 to open the WAD files -and others-, just out of curiosity.
Doom 1 and Doom 2 official original WAD files started with the word IWAD. However, the shareware WAD began with PWAD. I changed the P with a I using Notepad,
and for whatever reason that didnt corrupt the file at all.
What I found is that you could play the entire game using the shareware exe of Doom by changing a letter.
Back into Quake, I can't remember the shareware version well, 'cos I got the full version after playing the demo, but imho, most levels of Quake are some of the best levels ever made in a game, imo.
Especially those with old castles when the knight with an axe appear.
also Hexen and Heretic followed the same shareware formula of Doom, but for whatever reason those gave me motion sickness.
Regarding level design, I always enjoyed DooM 1's first episode the best, but over the years I think DooM 2 might be the better designed game. Although, Toxin Refinery is still my favorite single player map. All the time I spent with the automap open trying to find the secrets...
that level was soooooo good that the map I made myself usind DoomEd -or a similar map editor for Doom- and was most proud of is a map I made modifying that level in particular.
I remember filling the map with explosive barrels and lots of pinkies, hordes of enemies..., I created a whole new level within that level, using my very limited skills when my english was so so and couldnt understand all the options the editor gave me.