I don’t think Sandy did much game design on Doom though. He was mainly a level designer who came in late in the project to finish the levels started by Tom Hall, who had left id software, and to grind out levels for the third episode. By the time Sandy joined id software, Doom (the engine and game mechanics) was already pretty much the game it was going to be.

I should also say that the maps he made for Doom and Doom 2 are by far my least favorite in the game.