Doom is a 1993 first-person shooter developed 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.
Doom is divided into three episodes: "Knee-Deep in the Dead", "The Shores of Hell", and "Inferno". A fourth episode, "Thy Flesh Consumed", was added in an expanded version of the game, The Ultimate Doom. The game itself contains very few plot elements, with the minimal story instead given in the instruction manual and short text segues between episodes.
In "Knee-Deep in the Dead", he fights through the high-tech military bases, power plants, computer centers and geological anomalies on Phobos. It ends with the player character entering the teleporter leading to Deimos. In "The Shores of Hell" he fights through installations on Deimos, similar to those on Phobos, but warped and distorted from the demon invasion and interwoven with beastly architecture.
After defeating the titanic Cyberdemon, the marine discovers the vanished moon is floating above Hell. "Inferno" begins with the marine fighting his way through Hell ultimately defeating the Spider Mastermind that planned the invasion.
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 a subject of controversy.
Doom is a first-person shooter presented with early 3D graphics. The player controls an unnamed space marine—later termed the Doomguy—through a series of levels set in military bases on the moons of Mars and in Hell. To finish a level, the player must traverse through the area to reach a marked exit room.
Levels are grouped together into named episodes, with the final level focusing on a boss fight with a particularly difficult enemy. While the levels are presented in a 3D perspective, the enemies and objects are instead 2D sprites presented from several set viewing angles.