DOOM 3

Doom 3 is a story-driven action game played from a first-person perspective with occasional cutscenes in a third-person perspective. As with previous Doom games, the main objective is to successfully pass through its levels, defeating a variety of enemy characters intent on killing the player's character. Doom 3's more story-centered approach, however, means that the player often encounters friendly non-player characters, who provide key plot information, objectives and inventory items. The game incorporates ten weapons for the players use to survive, including conventional firearms such as a submachine gun, shotgun and grenades, experimental plasma weaponry, and the powerful BFG 9000 and chainsaw weapons of the Doom franchise.

Enemies come in multiple forms and with different abilities and tactics, but fall into two broad categories of either zombies or demons. Zombies are humans possessed by demonic forces, who attack the player's character using their hands and melee weapons or a variety of firearms, while demons are creatures from Hell, most of which attack using claws and spines, or by summoning fireballs. The corpses of demons are reduced to ashes after death, leaving no trace of their body behind.

Doom 3 is set on the planet Mars in the year 2145. According to the game's backstory, the Union Aerospace Corporation (UAC) has grown to become the largest corporate entity in existence with near-unlimited funds and has set up a research facility on Mars. At this base, the UAC are able to conduct research into several scientific areas, including advanced weapons development, biological research, space exploration and teleportation, outside of legal and moral boundaries. As the player progresses through the game, they learn that the employees on the base are unsettled due to a large number of incidents involving hearing voices, unexplained sightings and increasing cases of paranoia and insanity, often leading to fatal accidents with the facility's machinery. Rumors regarding the nature of experiments in the UAC's Delta Labs division are especially prevalent among the base's employees.

Much of Doom 3's story and dialogue were written by author Matthew J. Costello.

In June 2000, id Software's game engine designer John Carmack, posted an internal company plan announcing a remake of Doom using next generation technology. This plan revealed controversy had been growing within id Software over remaking Doom. Kevin Cloud and Adrian Carmack, two of id Software's owners, were always strongly opposed to remaking Doom, believing that id was going back to the same formulas and properties too often. However, after the positive reception to Return to Castle Wolfenstein and the latest improvements in rendering technology, most of the employees agreed that a remake was the right idea and presented the two owners with an ultimatum: allow them to remake Doom or fire them.

After the reasonably amicable confrontation (although artist Paul Steed, one of the instigators, was fired in retaliation), the agreement to work on Doom 3 was made. id Software began development on Doom 3 in late 2000, immediately after finishing Quake III: Team Arena. The game was made by 20 to 22 people. The game's development budget was $10 million.

Doom 3 received a favorable reception from critics, with the PC version of the game holding an 87 percent score and an 88 percent score at the review compilation sites Metacritic and GameRankings respectively. Much praise was given to the quality of Doom 3's graphics and presentation; GameSpot described the game's environments as "convincingly lifelike, densely atmospheric, and surprisingly expansive", while PC Gamer UK described the graphics and non-player character modeling and animation as simply "flawless", stating that Doom 3 signaled the return of the Doom franchise to the forefront of the computer and video game industry, eleven years after the release of the original Doom. IGN's Dan Adams noted that the game's presentation comprised a remarkably high proportion of the game, stating that "without the atmosphere, Doom 3 is a plain shooter that hearkens back to those of the '90s." In addition, several reviewers praised id Software for making the game still look surprisingly good even on lower graphics levels.

A number of reviewers also praised the attention paid to the game's premise and setting; GameSpot's Greg Kasavin described getting "the impression that Doom 3 takes place in a fully realized world" while IGN noted that "the UAC base also has a very worn and lived-in feel that adds to the realism." Eurogamer in particular pointed out that the game's opening sequence "feels like a fitting tribute to the excellent ideas" of Valve's genre-defining Half-Life.

In early 2008, a new series of Doom novels by Matthew J. Costello were published, an author who had worked on the story and scripts for Doom 3 and Resurrection of Evil; previous Doom novels had expanded the storyline of the original two Doom games. The series of books aims to novelize the story of Doom 3, with the first installment, Worlds on Fire, published on February 26, 2008. The second book in the series, Maelstrom, was released in March 2009.

The game engine for Doom 3, id Tech 4, has been licensed out for the use of other developers, such as in Human Head Studios' Prey, Raven Software's Quake 4, Splash Damage's Enemy Territory: Quake Wars, Raven Software's Wolfenstein, and Splash Damage's Brink; however id Tech 4 has not been widely licensed compared to Epic Games' Unreal Engine. On November 22, 2011, the source code of the engine was released under the GNU GPL-3.0-or-later, but the game's artwork content still remains under the EULA. A later source code drop also included the changes made for the BFG Edition, allowing the re-release to potentially be ported to other previously unsupported platforms such as Linux and OS X, and such a port was eventually released.