Doom (stylized as DOOM or DooM in other media) is a 1993 first-person shooter developed and published by id Software for MS-DOS. Players assume the role of a space marine, popularly known as "Doomguy", fighting his way through hordes of invading demons from Hell. The first episode, comprising nine levels, was distributed freely as shareware and played by an estimated 15–20 million people within two years; the full game, with two further episodes, was sold via mail order. An updated version with an additional episode, Ultimate Doom, was released in 1995 and sold at retail.
Along with its predecessor Wolfenstein 3D, Doom helped define the FPS genre and inspired numerous similar games, known as "Doom clones". It is one of the most significant games in video game history, and is frequently cited as one of the greatest games of all time. It pioneered online distribution and technologies including 3D graphics, networked multiplayer gaming, and support for customized modifications via packaged files (WADs). Its graphic violence and hellish imagery also made it the subject of controversy, however.
Doom has been ported to numerous platforms. The Doom franchise continued with Doom II: Hell on Earth (1994) and expansion packs including Master Levels for Doom II (1995). The source code was released in 1997, inspiring further adaptations. Id returned to the franchise with Doom 3 (2004), a horror-focused retelling using the id Tech 4 engine, followed by a 2005 Doom film. A 2016 reboot also titled Doom, powered by id Tech 6, returned to the fast-paced action of the first games.
Source: https://en.m.wikipedia.org/wiki/Doom_(1993_video_game)