“It was like playing with dolls,” says the video-game designer and 3-D graphics creator John Carmack, thinking back to the computer entertainments before Call of Duty, Halo, Doom and all the other “first-person-shooter” games. “In a typical game of that time, your character was maybe 16-by-16 pixels in an overhead view. Maybe it did some cute things that made you smile. But you were still controlling a tiny little thing on the screen.”

That era ended in November 1991, when Carmack and his colleagues at id Software put out a program called Catacomb 3-D. In many ways, it wasn’t that new or different: “You ran around, you shot things at monsters, you picked up health and bonus items, you got to the end of the level and went to the next one with a different layout,” Carmack said. But for Catacomb 3-D, they swapped the standard bird’s-eye view for one in which the player saw only what his character might see — slime-soaked walls to his left and right, beasties up ahead.

That shift changed the way that people played. “It was more powerful than I expected,” Carmack said. “We’d watch people creeping around a corner, turning with the arrow keys, and then a door would open, and there would be a big troll right there, and people would scream. They would literally fall out of their chair or jump away from the keyboard. It was a reaction that we’d never seen in any other form of video-gaming.” Still, Catacomb 3-D was not widely distributed. The following year, id Software put out a free demo version of a similar game, Wolfenstein 3-D, in which players fought off Nazi mutants and a cyborg Hitler. The marketing scheme worked perfectly. Wolfenstein became a hit, and the “F.P.S.” genre has been popular ever since.

The first-person shooters from id Software built on two traditions in game design. The continuous action came from early flight simulators, in which players drifted slowly through a 3-D world. The maze-and-monster setting came from “dungeon crawls,” which had players step their way through wire-frame corridors, one keystroke at a time. The simulators and the dungeon crawls each employed first-person views, but neither had the fast-paced, run-and-shoot aesthetic of Catacomb or Wolfenstein.