From 1994 on, the mapping community started to evolve and people have been very productive with doing their own maps - a lot of map CD-ROMs from this era proof that id software's decision to make Doom modable was a very good choice and responsible for the ongoing success of the game. Still it took about 4 more years for me to discover the possibilites when I bought one of these (it was called "Boom - Levels und Addons") in our local computer store - fun fact: Doom was on the index in Germany, addon discs were not.