Doom (1993 video game)

"DOOM" redirects here. For other uses, see Doom (disambiguation).

Doom
Cover art by Don Ivan Punchatz
Developer(s)	Id Software Nerve Software (XBLA)
Publisher(s)	Id Software GT Interactive (Windows, Mac, Saturn) Activision (GBA, XBLA) Atari (Jaguar) Bethesda Softworks (XBLA) Sega (32X) Valve Corporation (Steam) Williams Entertainment (SNES, PSX) Ocean Software (PAL SNES) Imagineer (SFC)
Designer(s)	Sandy Petersen John Romero Shawn Green Tom Hall
Programmer(s)	John Carmack John Romero
Artist(s)	Adrian Carmack Kevin Cloud
Writer(s)	Tom Hall
Composer(s)	Bobby Prince
Series	Doom
Engine	Id Tech 1 Reality (SNES)
Platform(s)	MS-DOS ...more
Release	December 10, 1993 DOS & MAC Sega 32X Atari Jaguar SNES PlayStation 3DO Windows Sega Saturn Game Boy Advance Xbox Live Arcade (Activision) Xbox Live Arcade (Bethesda)
Genre(s)	First-person shooter
Mode(s)	Single-player, multiplayer

Doom (typeset as DOOM in official documents) is a 1993 science fiction horror-themed first-person shooter (FPS) video game by id Software. It is considered one of the most significant and influential titles in the video game industry, for having ushered in the popularity of the first-person shooter genre. The original game is divided into three nine-level episodes and distributed via shareware and mail order. The Ultimate Doom, an updated release of the original game featuring a fourth episode, was released in 1995 and sold at retail.

In Doom, players assume the role of an unnamed space marine, who became popularly known as "Doomguy", fighting his way through hordes of invading demons from Hell. With one third of the game, nine levels, distributed as shareware, Doom was played by an estimated 10 million people within two years of its release, popularizing the mode of gameplay and spawning a gaming subculture. In addition to popularizing the FPS genre, it pioneered immersive 3D graphics, networked multiplayer gaming, and support for customized additions and modifications via packaged files in a data archive known as "WADs". As a sign of its effect on the industry, first-person shooter games from the genre's boom in the 1990s, helped in no small part by the game's release, became known simply as "Doom clones". Its graphic violence, as well as satanic imagery, made Doom the subject of controversy.

The Doom franchise was later continued with the follow-up Doom II: Hell on Earth (1994) and numerous mission packs, including Master Levels for Doom II (1995), and Final Doom (1996). Originally released for PC DOS, the games have later been ported to numerous other platforms. Once the game's source code was released in 1997, it spawned even more adaptations, as fans further ported the code to countless devices. The series started to lose mainstream appeal as the technology of the Doom game engine was surpassed in the mid-1990s, although fans have continued making WADs, speedruns, and modifications to the original. The franchise again received popular attention in 2004 with the release of Doom 3, a retelling of the original game using new technology, and an associated 2005 Doom motion picture. Doom 4 was announced as in production in 2008 and was later retitled simply as Doom.

Plot

Doom, a science fiction/horror themed video game, has a background which is given in the game's instruction manual; the rest of the story is advanced with short messages displayed between each section of the game (called episodes), the action as the player character progresses through the levels, and some visual cues.

The player takes the role of an unnamed space marine ("Doomguy") who has been punitively posted to Mars after assaulting his commanding officer, who ordered his unit to fire on civilians. The Martian space marine base acts as security for the Union Aerospace Corporation, a multi-planetary conglomerate, which is performing secret experiments with teleportation by creating gateways between the two moons of Mars, Phobos and Deimos. Mars is considered by space marines to be the dullest assignment imaginable. This all changes when the UAC experiments go horribly wrong. Computer systems on Phobos malfunction, Deimos disappears entirely, and "something fragging evil" starts pouring out of the gateway, killing or possessing all UAC personnel.

Responding to a frantic distress call from the overrun scientists, the Martian marine unit is quickly sent by ship from Mars to Phobos to investigate, where the player character is left to guard the perimeter with only a pistol while the rest of the group proceeds inside. The marine hears assorted radio messages, gunfire, and screams, followed by silence: "Seems your buddies are dead." The player cannot navigate the ship off of Phobos alone and sees that the only way out is to fight through the Phobos complex.

As the last man standing, the player character's mission is to fight through the entire onslaught of demonic enemies by himself in order to keep them from attacking Earth. Knee-Deep in the Dead, the first episode and the only one in the shareware version, is set in 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, only to be overwhelmed by monsters.

In the second episode, The Shores of Hell, the marine has successfully teleported to Deimos. He fights his way 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 truth about the vanished moon: it is floating above Hell.

The third episode, called Inferno, begins after the marine climbs off Deimos to the surface. The marine fights his way through Hell and defeats the Spider Mastermind that planned the invasion. Then the marine finds a hidden doorway back to Earth opens for the hero, who has "proven too tough for Hell to contain". However, a burning city and a rabbit's head impaled on a stake (named in The Ultimate Doom as the marine's pet rabbit, Daisy) show that the demons have invaded Earth, setting the stage for Hell on Earth. The sequel retcons the events of Doom as an alien invasion of the Mars moon bases.

In The Ultimate Doom expansion, in the fourth episode Thy Flesh Consumed, it tells that the marine fought valiantly against the hordes of demons that the Spider Mastermind sent through that hidden doorway but ultimately the forces of Hell prevailed in the invasion of Earth. The locales of Thy Flesh Consumed are varied, including a mix of high-tech bases and demonic temples, though the atmosphere appears to be Earth.

Gameplay

"Episode I: Knee-Deep in the Dead" takes place in the research, industrial and military facilities on the surface of Phobos. In the screenshot, the player armed with a chainsaw confronts a basic zombie marine on a bridge over a chemical waste storage

Being a first-person shooter, Doom is experienced through the eyes of the main character. This character is not named throughout the game. The game's designer, John Romero, has pointed out that this is so the player feels more involved in the game: "There was never a name for the DOOM marine because it's supposed to be you." At its core, the gameplay is similar to classic shooter games, presenting the player with the challenge of surviving while shooting every enemy in sight, but with its pseudo-3D first-person perspective giving environments a spatial representation that has a major effect on the level design and gameplay experience.

In order for the game to be completed, the marine must fight through Phobos, Deimos, and then Hell itself, each presented as an episode containing eight distinct levels, along with an optional ninth hidden level for each one. The Ultimate Doom, the retail store version of the game, adds a fourth episode, Thy Flesh Consumed. Set between the end of Doom and before Doom II and featuring the first contribution of Tim Willits to the Doom franchise, the fourth episode was designed for expert Doom players seeking a major challenge (being considerably more difficult than the original episodes).

The objective of each level is simply to locate the exit room that leads to the next area, marked with an exit sign and/or a special kind of door, while surviving all hazards on the way. Among the obstacles are demonic monsters, pits of toxic or radioactive slime, ceilings that lower and crush anything below them, and locked doors which require a keycard, skull-shaped key device, or a remote switch to be located. The levels are sometimes labyrinthine and feature plenty of items such as additional ammo, health increases and other "power-ups" along the way, as well as the occasional secret areas which are not immediately obvious as a reward for players who explore more carefully. To ease navigation through the levels, a full screen automap is available and shows the areas explored to that point. Many versions of Doom (and its sequels) include secret levels which are accessed by the player discovering alternate exits, often hidden behind secret doors, hidden passageways, or in areas which are difficult to reach. Despite carrying masses of high-tech weaponry, the main character can still run at blistering speeds.

Doom is notable for the weapons arsenal available to the marine, which became prototypical for first-person shooters. The player character starts armed only with a pistol, and fists in case the ammunition runs out, but larger weapons can be picked up: these are a chainsaw, a shotgun, a chaingun, a rocket launcher, a plasma rifle, and finally the immensely powerful BFG 9000. There is a wide array of power-ups, such as a backpack that increases the player character's ammunition-carrying capacity, armor, first aid kits to restore health, the berserk pack which both restores health and causes the player's punching attack to deal enormous damage, supernatural blue orbs (named soul spheres in the manuals) that boost the player character's health up to a maximum of 200%, nightvision, computer maps (which show every area of the level), partial invisibility, and protective suits that allow the player to survive in toxic acids.

The enemy monsters in Doom make up the central gameplay element. The player character faces them in large numbers, with the number generally increased when the higher of the game's five difficulty levels is chosen when starting a new game. There are 10 types of monsters, including possessed undead humans as well as demons, all which vary in many ways. The monsters have very simple behavior, consisting of either walking toward their opponent, or attacking by throwing fireballs, biting, and scratching. They will fight each other if one monster is accidentally harmed by another (though most monsters are not harmed by the ranged attacks of their own kind).

Aside from the single player game mode, Doom features two multiplayer modes playable over a network: "cooperative", in which two to four players team up, and "deathmatch", in which two to four players play against each other. Online multiplayer was eventually made available through the DWANGO service.

Development

Main article: Development of Doom

The development of Doom started in 1992, when John D. Carmack developed a new 3D game engine, the Doom engine, while the rest of the id Software team finished the Wolfenstein 3D prequel, Spear of Destiny. When the game design phase began in late 1992, the main thematic influences were the science fiction action film Aliens and the horror film Evil Dead II. The title of the game was picked by John Carmack: "There is a scene in The Color of Money where Tom Cruise [sic] shows up at a pool hall with a custom pool cue in a case. 'What do you have in there?' asks someone. 'Doom.' replied Cruise with a cocky grin. That, and the resulting carnage, was how I viewed us springing the game on the industry."

Designer Tom Hall wrote an elaborate design document called the Doom Bible, according to which the game would feature a detailed storyline, multiple player characters, and a number of interactive features. However, many of his ideas were discarded during development in favor of simpler design primarily advocated by John Carmack, resulting in Hall in the end being forced to resign due to not contributing effectively in the direction the rest of the team was going. Most of the level design that ended up in the final game is that of John Romero and Sandy Petersen. The graphics, by Adrian Carmack, Kevin Cloud and Gregor Punchatz, were modelled in various ways: although much was drawn or painted, several of the monsters were built from sculptures in clay or latex, and some of the weapons are toy guns from Toys "R" Us. A heavy metal-ambient soundtrack was supplied by Bobby Prince.

Engine technology

Main article: Doom engine

Doom's primary distinguishing feature at the time of its release was its relatively realistic 3D graphics. The advance from id Software's previous game Wolfenstein 3D was enabled by several new features in the Doom engine, including height differences (all rooms in Wolfenstein 3D have the same height), non-perpendicular walls (all walls in Wolfenstein 3D run along a rectangular grid), full texture mapping of all surfaces (in Wolfenstein 3D, floors and ceilings are flat colors) and varying light levels and custom palettes (all areas in Wolfenstein 3D are fully lit at the same brightness). The latter contributed to Doom's visual authenticity, atmosphere and gameplay, as the use of darkness to frighten or confuse the player was nearly unheard of in games released prior to Doom; palette modifications were used to enhance effects such as the berserk power which tints the player's vision red.

In contrast to the static levels of Wolfenstein 3D, those in Doom are highly dynamic: platforms can lower and rise, floors can rise sequentially to form staircases, and bridges can rise and fall. The lifelike environment was enhanced further by the stereo sound system, which made it possible to roughly determine the direction and distance of a sound effect. The player is kept on guard by the grunts and growls of monsters, and receives occasional clues to finding secret areas in the form of sounds of hidden doors opening remotely. As in Wolfenstein 3D, enemies can also become aware of the player's presence by hearing distant gunshots.

John Carmack had to make use of several tricks for these features to run smoothly on home computers of 1993. Most significantly, the Doom engine and levels are not truly three-dimensional; they are internally represented on a single plane, with height differences stored separately as displacements. (A similar trick is still used by many games to create huge outdoor environments.) This allows a two point perspective projection, with several design limitations: for example, it is not possible for the Doom engine to render one room over another. However, thanks to its two-dimensional property, the environment can be rendered very quickly, using a binary space partitioning method in conjunction with raycasting. Another benefit was the clarity of the automap, as that could be rendered with 2D vectors without any risk of overlapping. Additionally, the BSP tree technology created by Bruce Naylor was used.

Another important feature of the Doom engine is its modular data files, which allow most of the game's content to be replaced by loading custom WAD files. Wolfenstein 3D was not designed to be expandable, but fans had nevertheless figured out how to create their own levels for it, and Doom was designed to further extend the possibilities. The ability to create custom scenarios contributed significantly to the game's popularity (see the section on WADs, below).

Release

To promote Windows 95, Bill Gates, aware of the video game's popularity, showcased a video presentation while digitally superimposed into Doom

The development of Doom was surrounded by much anticipation. The large number of posts in Internet newsgroups about Doom led to the SPISPOPD joke, to which a nod was given in the game in the form of a cheat code. In addition to news, rumors and screenshots, unauthorized leaked alpha versions also circulated online. Many years later these alpha versions were sanctioned by id Software because of historical interest; they reveal how the game progressed from its early design stages. The first public version of Doom was uploaded to Software Creations BBS and an FTP server at the University of Wisconsin–Madison on December 10, 1993.

Doom was released as shareware, with people encouraged to distribute it further. Although most users did not purchase the registered version, over one million copies have been sold, and the popularity helped the sales of later games in the Doom series that were not released as shareware. In 1995, The Ultimate Doom (version 1.9, including Episode IV) was released, making this the first time that Doom was sold commercially in stores.

In a press release dated January 1, 1993, id Software had written that they expected Doom to be "the number one cause of decreased productivity in businesses around the world." This prediction came true at least in part: Doom became a major problem at workplaces, both occupying the time of employees and clogging computer networks with traffic caused by deathmatches. Intel, Lotus Development and Carnegie Mellon University are among many organizations reported to form policies specifically disallowing Doom-playing during work hours. At the Microsoft campus, Doom was by one account equal to a "religious phenomenon".

In late 1995, Doom was estimated to be installed on more computers worldwide than Microsoft's new operating system Windows 95, despite million-dollar advertising campaigns for the latter. The game's popularity prompted Bill Gates to briefly consider buying id Software, and led Microsoft to develop a Windows 95 port of Doom to promote the operating system as a gaming platform. One such presentation to promote Windows 95 had Bill Gates digitally superimposed into the game. The 1995 release of Microsoft Excel 95 included a Doom-esque secret level as an Easter egg containing portraits of the programmers among other things.

The game was made available on Steam on August 3, 2007, running on the DOSBox DOS emulator.

Expansions and Ports

Main article: Official versions of Doom

The popularity of Doom led to the development of expansion packs and alternate versions based on the same game engine, including The Ultimate Doom (1995), Final Doom (1996), and Doom 64 (1997). Doom became a "killer app" that all capable consoles and operating systems were expected to have, and versions of Doom have subsequently been released for the following systems: DOS, Microsoft Windows, Linux, Amiga, Apple Macintosh, SNES, Sega 32X, Sony PlayStation, Game Boy Advance, iOS, Symbian OS, RISC OS, Atari Jaguar, Sega Saturn, Nintendo 64, Tapwave Zodiac, 3DO, Xbox, and Xbox Live Arcade. Some of these were bestsellers even many years after initial release. In 2013, a version of Doom was ported to the Commodore VIC-20, a vintage 1980 introductory home computer having only 3,583 bytes of BASIC RAM, an 8 bit 6502A processor with rudimentary graphics, no sprites and just 8 colors.

WADs

Main article: Doom WAD

The ability for others to create custom levels and otherwise modify the game, in the form of custom WAD files (short for "Where's All the Data?"), turned out to be a particularly popular aspect of Doom. Gaining the first large mod-making community, Doom affected the culture surrounding first-person shooters, and also the industry. Several future professional game designers started their careers making Doom WADs as a hobby, among them Tim Willits, who later became the lead designer at id Software.

The first level editors appeared in early 1994, and additional tools have been created that allow most aspects of the game to be edited. Although the majority of WADs contain one or several custom levels mostly in the style of the original game, others implement new monsters and other resources, and heavily alter the gameplay; several popular movies, television series, other video games and other brands from popular culture have been turned into Doom WADs by fans, including Aliens, Star Wars, The X-Files, Teenage Mutant Ninja Turtles,The Simpsons, South Park, Sailor Moon, Dragon Ball Z, Red Faction, The Thing, Pokémon, Batman and Sonic the Hedgehog. Some works, like the Theme Doom Patch, combined enemies from several films, such as Aliens, Predator and The Terminator. Some add-on files were also made that changed the sounds made by the various characters and weapons.

Around 1994 and 1995, WADs were primarily distributed online over bulletin board systems or sold in collections on compact discs in computer shops, sometimes bundled with editing guide books. FTP servers became the primary method in later years. A few WADs have been released commercially, including the Master Levels for Doom II, which was released in 1995 along with Maximum Doom, a CD containing 1,830 WADs that had been downloaded from the Internet. Several thousand WADs have been created in total: the idgames FTP archive contains over 13,000 files, and this represents only a fraction of the complete output of Doom fans. Third party programs were also written to handle the loading of various WADs, since the game is a DOS game and all commands had to be entered on the command line to run. A typical launcher would allow the player to select which files to load from a menu, making it much easier to start. In 1995, WizardWorks Software released the D!Zone pack featuring hundreds of levels for Doom and Doom II. D!Zone was reviewed in Dragon by Jay & Dee; Jay gave the pack 1 out of 5 stars, while Dee gave the pack 1½ stars.

Reception

Reception

Review score

Publication	Score
Allgame

Doom was widely praised in the gaming press and is broadly considered to be one of the most important and influential titles in gaming history. In 1996, Computer Gaming World ranked it as the fifth best video game of all time. In 2001, Doom was voted the number one game of all time in a poll among over 100 game developers and journalists conducted by GameSpy. In 2003, IGN ranked it as the 44th top video game of all time and also called it "the breakthrough game of 1993", adding: "Its arsenal of powerful guns (namely the shotgun and BFG), intense level of gore and perfect balance of adrenaline-soaked action and exploration kept this gamer riveted for years." PC Gamer proclaimed Doom the most influential game of all time in its ten-year anniversary issue in April 2004. In 2004, readers of Retro Gamer voted Doom as the ninth top retro game, with the editors commenting: "Only a handful of games can claim that they’ve changed the gaming world, and Doom is perhaps the most qualified of them all." In 2005, IGN ranked it as the 39th top game. On March 12, 2007, The New York Times reported that Doom was named to a list of the ten most important video games of all time, the so called game canon. The Library of Congress took up this video game preservation proposal and began with the games from this list. In 2009, GameTrailers ranked Doom as number one "breakthrough PC game". That same year, Game Informer put Doom sixth on their list of the games of all time, stating that it gave "the genre the kick start it needed to rule the gaming landscape two decades later." Game Informer staff also put it sixth on their 2001 list of the 100 best games ever. In 2012, Time named it one of the 100 greatest video games of all time as "it established the look and feel of later shooters as surely as Xerox PARC established the rules of the virtual desktop," adding that "its impact also owes a lot to the gonzo horror sensibility of its designers, including John Romero, who showed a bracing lack of restraint in their deployment of gore and Satanic iconography." Including Doom on the list of the greatest games of all time, GameSpot wrote that "despite its numerous appearances in other formats and on other media, longtime fans will forever remember the original 1993 release of Doom as the beginning of a true revolution in action gaming."

The game was ported to numerous console gaming platforms both domestically and abroad where it maintained its popularity, receiving generally favorable critical reception.

Controversies

Doom's level of graphic violence made the game highly controversial. In the screenshot, effects of a rocket hitting a group of enemies

Doom was notorious for its high levels of graphic violence and satanic imagery, which generated controversy from a broad range of groups. Yahoo! Games listed it as one of the top ten most controversial games of all time. It was criticized by religious organizations for its diabolic undertones and was dubbed a "mass murder simulator" by critic and Killology Research Group founder David Grossman. Doom prompted fears that the then-emerging virtual reality technology could be used to simulate extremely realistic killing.

The game again sparked controversy throughout a period of school shootings in the United States when it was found that Eric Harris and Dylan Klebold, who committed the Columbine High School massacre in 1999, were avid players of the game. While planning for the massacre, Harris said that the killing would be "like playing Doom", and "it'll be like the LA riots, the Oklahoma bombing, WWII, Vietnam, Duke Nukem and Doom all mixed together", and that his shotgun was "straight out of the game". A rumor spread afterwards that Harris had designed a Doom level that looked like the high school, populated with representations of Harris's classmates and teachers, and that Harris practiced for his role in the shootings by playing the level over and over. Although Harris did design Doom levels, none of them were based on Columbine High School.

While Doom and other violent video games have been blamed for nationally covered school shootings, 2008 research featured by Greater Good Science Center shows that the two are not closely related. Harvard medical school researchers Cheryl Olson and Lawrence Kutner found that violent video games did not correlate to school shootings. The U.S. Secret Service and Department of Education analyzed 37 incidents of school violence and sought to develop a profile of school shooters, they discovered that the most common traits among shooters were that they were male and had histories of depression and attempted suicide. While many of the killers—like the vast majority of young teenage boys—did play video games, this study did not find a relationship between game play and school shootings. In fact, only one eighth of the shooters showed any special interest in violent video games; far less than the number of shooters who seemed attracted to books and movies with violent content.

Excess Intranet/LAN usage

When Doom came out, complaints soon started from Internet node managers about excess load on their servers caused by Doom inter-player communication packages, and to some server managers' antivirus software was added an "Antidoom" package that blocked Doom-related packages and sent a Doom "end this game" code to any Doom players detected.

Legacy

Doom franchise

Main article: Doom (series)

Doom has appeared in several forms in addition to video games, including a Doom comic book, four novels by Dafydd Ab Hugh and Brad Linaweaver (loosely based on events and locations in the games), a Doom board game and a live-action film starring Karl Urban and The Rock released in 2005. The game's development and impact on popular culture is also the subject of the book Masters of Doom by David Kushner.

The Doom series remained dormant between 1996 and 2000, when Doom 3 was announced. A retelling of the original Doom using entirely new graphics technology, Doom 3 was hyped to provide as large a leap in realism and interactivity as the original game and helped renew interest in the franchise when it was released in 2004. After the Doom 4 project development was scrapped in 2013, id's Tim Willits said that the next game in the Doom series was still the team's focus, but it has not been confirmed to be titled Doom 4. It was renamed to simply Doom in 2014.

Clones

Main article: First-person shooter

The phrase "Doom clone" was initially popular to describe the style of gameplay in Doom-like games, but after 1996 was gradually replaced by "first-person shooter". By 1998 the phrase "first-person shooter" had firmly superseded "Doom clone".

Doom was influential and dozens of new first-person shooter titles appeared following Doom's release, and they were often referred to as "Doom clones" rather than "first-person shooters". The term "Doom clone" was used to described the style of gameplay in Doom-like games. While the term was initially popular, it was after 1996 gradually replaced by "first-person shooter", around 1998 the phrase "first-person shooter" had firmly superseded "Doom clone". Some of these were certainly "clones"—hastily assembled and quickly forgotten—others explored new grounds of the genre and were highly acclaimed. Many of the games closely imitated features in Doom such as the selection of weapons and cheat codes. Doom's principal rivals were Apogee's Rise of the Triad and Looking Glass Studios' System Shock. The popularity of Star Wars-themed WADs is rumored to have been the factor that prompted LucasArts to create their first-person shooter Dark Forces.

Also, the Doom game engine was licensed by id Software to several other companies as well, who released their own games based on it, including Heretic, Hexen: Beyond Heretic, Strife and HacX. A Doom-based game called Chex Quest was released in 1996 by Ralston Foods as a promotion to increase cereal sales, and the United States Marine Corps released Marine Doom.

When, three years later, 3D Realms released Duke Nukem 3D, a tongue-in-cheek science fiction shooter based on Ken Silverman's technologically similar Build engine, id Software had nearly finished Quake, its next-generation game, which mirrored Doom's success for much of the remainder of the 1990s and significantly reduced interest in its predecessor.

Community

In addition to the thrilling nature of the single-player game, the deathmatch mode was an important factor in the game's popularity. Doom was not the first first-person shooter with a deathmatch mode—Maze War was a multiplayer FPS in 1973, and by 1977 was running over ethernet on Xerox computers. However, the widespread distribution of PC systems and the violence and gore of Doom made deathmatching particularly attractive. Two-player multiplayer was also possible over a phone line by using a modem, or by linking two PCs with a null-modem cable. Due to its widespread distribution, Doom hence became the game that introduced deathmatching to a large audience and was also the first game to use the term "deathmatch".

Although the popularity of the Doom games dropped with the release of more modern first-person shooters, the game had still retained a strong fan base that continues to this day by playing competitively and creating WADs, and Doom-related news is still tracked at multiple websites such as Doomworld. Interest in Doom was renewed in 1997, when the source code for the Doom engine was released (it was also placed under the GNU General Public License in 1999). Fans then began porting the game to various operating systems, even to previously unsupported platforms such as the Dreamcast. As for the PC, over 50 different Doom source ports have been developed. New features such as OpenGL rendering and scripting allow WADs to alter the gameplay more radically.

Devoted players have spent years creating speedruns for Doom, competing for the quickest completion times and sharing knowledge about routes through the levels and how to exploit bugs in the Doom engine for shortcuts. Achievements include the completion of both Doom and Doom II on the difficulty setting "Ultra-Violence" in less than 30 minutes each. In addition, a few players have also managed to complete Doom II in a single run on the difficulty setting "Nightmare!", on which monsters are more aggressive, launch faster projectiles (or, in the case of the Pinky Demon, simply move faster), and respawn roughly 30 seconds after they have been killed (level designer John Romero characterized the idea of such a run as "[just having to be] impossible"). Movies of most of these runs are available from the COMPET-N website.

As of 2008, online co-op and deathmatch play still continued on servers listed through services such as Odamex, Skulltag, ZDaemon and Doom Connector. Some of the source ports used for online play (for example Skulltag) also support additional game modes such as "last man standing", "survival" (co-op) and "invasion" modes. There is also a roguelike game based on Doom, DoomRL. In 2011, a modification for Doom, , was released with the intent of replicating the design style of the original game.

External links

• Ultimate Doom at id Software
• Doom at MobyGames
• Doom (VG) at IMDb
• Doom on Doom Wiki
• Leukart, Hank (1994). "The "Official" Doom FAQ". Archived from the original on 2013-07-31. Retrieved November 15, 2005.