The player assumes the role of a space marine, later unofficially referred to as Doomguy, fighting through hordes of undead humans and invading demons.

The game begins on the moons of Mars and finishes in hell, with the player traversing each level to find its exit or defeat its final boss.

While the environment is shown in a 3D perspective, the enemies and objects are instead 2D sprites rendered at fixed angles, a technique sometimes referred to as 2.5D graphics or billboarding.

[2] In the single-player campaign mode, the player controls an unnamed space marine—later unofficially termed "Doomguy"—through military bases on the moons of Mars and in hell.

The player can find weapons and ammunition throughout the levels or can collect them from dead enemies, including a pistol, a shotgun, a chainsaw, a plasma rifle, and the BFG 9000.

The player also encounters pits of toxic waste, ceilings that lower and crush objects, and locked doors requiring a collectable keycard or a remote switch.

[6] Power-ups include health or armor points, a mapping computer, partial invisibility, a radiation suit against toxic waste, invulnerability, or a super-strong melee berserker status.

[12] In the future, an unnamed marine is posted to a dead-end assignment on Mars after assaulting a superior officer who ordered his unit to fire on civilians.

The Union Aerospace Corporation, which operates radioactive waste facilities there, allows the military to conduct secret teleportation experiments that turn deadly.

John Carmack conceived a game about using technology to fight demons, inspired by a Dungeons & Dragons campaign the team played.

[24] They moved operations to a dark office building, naming it "Suite 666" while drawing inspiration from the noises they heard from a neighboring dental practice.

Rather than a deep story, he wanted to focus on technological innovation, dropping the levels and episodes of Wolfenstein in favor of a fast, continuous world.

[22] However, the team then realized that Carmack's vision for a seamless world would be impossible given the hardware limitations, and Hall was forced to rework the design document once again.

[6][26] He was also upset with how much he was having to fight with John Carmack to get what he saw as obvious gameplay improvements, such as flying enemies, and began to spend less time at work.

[31][32] Petersen later recalled that John Carmack and Romero wanted to hire other artists instead, but Cloud and Adrian disagreed, saying that a designer was required to help build a cohesive gameplay experience.

[30] After the multiplayer component was coded, the development team began playing four-player games, which Romero termed "deathmatch", and Cloud named the act of killing other players "fragging".

[32][40] Prince believed that ambient music would be more appropriate and produced numerous tracks in both styles in hope of convincing the team, and Romero incorporated both.

Prince created the sound effects based on short descriptions or concept art of a monster or weapon and adjusted them to match the completed animations.

Instead, he gave software retailers the option to sell copies of the first Doom episode at any price, in hopes of motivating customers to buy the full game directly from id.

Id began receiving calls from people interested in the game or angry that it had missed its planned release date, as anticipation built over the year.

At midnight on December 10, 1993, after working for 30 straight hours testing, the development team at id uploaded the first episode to the internet, letting interested players distribute it for them.

Although the company estimated that only 1% of shareware downloaders bought the full game, this was enough to generate initial daily revenue of US$100,000, selling in one day what Wolfenstein had sold in one month.

[76][77][78] Reviewers heavily praised the single-player gameplay: Electronic Entertainment called it "a skull-banging, palm-sweating, blood-pounding game", while The Age said it was "a technically superb and thrilling 3D adventure".

[59][97][98] The SNES version, however, was noted for weaker graphics and unresponsive controls, though reviewers such as Computer and Video Games, GamePro, and Next Generation were split on awarding high or middling scores due to these faults.

[148][149][150] As the "first-person shooter" genre label had not yet solidified at the time, Doom was described as a "first person perspective adventure" and "atmospheric 3-D action game".

[165][166][167] Doom was notorious for its high levels of graphic violence and satanic imagery, which generated controversy from a broad range of groups.

[171] Doom again sparked controversy in the United States when it was found that Eric Harris and Dylan Klebold, who committed the Columbine High School massacre on April 20, 1999, were avid players.

John Carmack and Romero had strongly advocated for mod support, overriding other id employees who were concerned about commercial and legal implications.

[178][179] It was followed by "countless" others, including many based on other franchises like Aliens and Star Wars total conversion mods, as well as DeHackEd, a patch editor first released in 1994 by Greg Lewis that allowed editing of the game engine.

[186][187] A sixth episode, Sigil II, was released on the game's 30th anniversary, December 10, 2023, again for €6.66 for a digital copy with a soundtrack by Valient Thorr, as well as physical editions on floppy disk.