one of the most important titles in gaming
Doom has a science fiction/horror theme, and a simple plot. The background is only given in the game's manual, and the in-game story is mainly advanced with short messages displayed between the game's episodes.
The player takes the role of a nameless space marine (referred to as "Doomguy" or "The Doomguy" by many fans), "one of Earth's toughest, hardened in combat and trained for action", who has been deported to Mars for assaulting a senior officer when ordered to kill unarmed civilians. He is forced to work for the Union Aerospace Corporation (UAC), a military-industrial conglomerate that is performing secret experiments with teleportation between the moons of Mars, Phobos and Deimos. The Marine may have been forced into a security or unimportant staff position according to the manual, stating "with no action for fifty million miles, your day consisted of suckin' dust and watchin' restricted flicks in the rec room." Suddenly, something goes wrong and creatures from Hell come out of the teleportation gates, or "Gateways". A defensive response from base security fails to halt the invasion, and the bases quickly get overrun by demons; all personnel are killed or turned into zombies. At the same time, Deimos vanishes entirely. A UAC team from Mars is sent to Phobos to investigate the incident, but soon radio contact ceases and only one human is left alive - the player, whose task is to make it out as such
In order to complete the game, the player must fight through three episodes containing nine levels each (see Episodes and levels of Doom). Knee-Deep in the Dead, the first episode and the only one in the shareware version, is set in the high-tech military bases on Phobos. It ends with the player fighting the Barons of Hell and afterwards entering the teleporter leading to Deimos, ending with the player getting overwhelmed by monsters and seemingly killed. In the second episode, Shores of Hell, the player journeys through the Deimos installation, whose areas are interwoven with beastly architecture, warped and distorted by the demonic invasion. After encountering the Cyberdemon, the truth about the vanished moon is discovered: it is floating above Hell. The player climbs down to the surface, and the final episode, Inferno, begins. After destroying the final boss, the Spider Mastermind, a hidden doorway opens for the hero who has "proven too tough for Hell to contain", leading back home to Earth. The expansion pack Ultimate Doom adds a fourth episode, Thy Flesh Consumed, chronicling the marine's return to Earth, in other words his adventures between the first three traditional episodes of Doom and Doom II.
Doom is widely regarded as one of the most important titles in gaming history. It was voted the "#1 game of all time" in a poll among over 100 game developers and journalists conducted by GameSpy in July 2001,[17] and PC Gamer proclaimed Doom the most influential game of all time in its ten-year anniversary issue in April 2004, and named it the second best game of all time a year later (number one was Half-Life). However, several game journalists have also contrasted the relatively simplistic gameplay in Doom unfavorably with more story-oriented first-person shooters such as Half-Life.