Id software pioneered the shareware model in 1990 with Commander Keen, six years before they used it in Quake.
In fact, Keen, Keen 4, Wolfenstein 3D, and Doom all used a three-episode shareware structure where the first episode was free and the rest were considered the "full version."
Doom 2 did not use this structure because Doom itself was a good enough advertisement for it. id then used it again in Quake, but fully broke from it with Quake 2, which just had a demo with a few levels.
Technically correct, but the specific Apogee model of shareware (one free episode, two or more commercial episodes) was much more successful than the original model of distributing everything for free and politely asking people to pay for it; it was pioneered by Id's publisher Apogee.
Not Id, but Apogee, pioneered "the Apogee model" of shareware with the Kroz trilogy in 1987. Apogee published Id's Commander Keen and Wolfenstein games.
As a new player who tried these games... they don't hold up. I'm sorry, but without the nostalgia, it just isn't fun. Technically impressive? Yes. But not fun.
Personally, I don't think any of id's pre-DOOM games hold up well. But that could just be me...
Id software pioneered the shareware model in 1990 with Commander Keen, six years before they used it in Quake.
In fact, Keen, Keen 4, Wolfenstein 3D, and Doom all used a three-episode shareware structure where the first episode was free and the rest were considered the "full version."
Doom 2 did not use this structure because Doom itself was a good enough advertisement for it. id then used it again in Quake, but fully broke from it with Quake 2, which just had a demo with a few levels.