Doom

Doom is the game that started it all. It was first released on December 10, 1993, when a shareware copy was uploaded to an FTP server at the University of Wisconsin.

History and development
The development of Doom began in 1992, with John Carmack writing the new game engine while the rest of id Software was finishing Spear of Destiny (the sequel to Wolfenstein 3D). When the full design phase began in late 1992, the main thematic influences were the movies Aliens and Evil Dead II. The title of the game was chosen by John Carmack:
 * There is a scene in "The Color of Money" where Tom Cruse [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 Cruse 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 specifications 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 a simpler design primarily advocated by John Carmack, resulting in Hall's eventually being forced to resign from id Software. Most of the final level designs are those of John Romero and Sandy Petersen. The graphics, by Adrian Carmack, Kevin Cloud, and Gregor Punchatz, were created in various ways: although much was drawn or painted, several of the monsters were digitized from sculptures in clay or latex, and some of the weapons are modeled on toy guns from Toys "Я" Us. A heavy metal/ambient soundtrack was supplied by Bobby Prince.

Doom's primary distinguishing characteristic at the time of its release was its "3-D" graphics, then unparalleled by other real-time-rendered games running on consumer-level hardware. Several new features improved on those of Wolfenstein 3D:
 * Altitude differences (all floors/ceilings in Wolfenstein 3D are at the same height).
 * Non-perpendicular walls (all walls in Wolfenstein 3D run along a rectangular grid).
 * Full texture mapping of all surfaces.
 * Varying light levels (all areas in Wolfenstein 3D have identical lighting). This not only made each map's structure more visually authentic, but contributed to its atmosphere and gameplay by using darkness to frighten or confuse the player.
 * A less static architecture than in Wolfenstein 3D: platforms can move up or down, floors can be lifted sequentially to form staircases, and bridges can rise or lower.
 * A stereo sound system, which makes it possible to roughly tell the direction and distance of a sound's origin. The player is kept on guard by the grunting and snarling of monsters, and receives occasional clues to the locations of secret areas by hearing hidden doors open remotely. (Monsters can also become aware of the player's presence as he fires a weapon.)

id's programmers had to make use of several tricks for these features to run smoothly on 1993-vintage home computers. Most significantly, Doom levels are not truly three-dimensional: they are internally represented on a two-dimensional plane, with height differences added separately (a similar trick is still used by many games to create huge outdoor environments).

Story
Doom has a simple plot; its background is given in the instruction manual, and the in-game story advances mainly through short messages displayed between the game's episodes.

The player takes the role of a nameless space marine, "one of Earth's toughest, hardened in combat and trained for action", who has been incarcerated on 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 which is performing secret experiments on interdimensional travel. Suddenly, something goes wrong and creatures from Hell swarm out of the teleportation gates. A defensive response from base security fails to halt the invasion, and the bases are quickly overrun by demons; all personnel are killed or turned into zombies. A UAC detachment from Mars travels to Phobos to investigate the incident, but radio contact soon ceases and only one human is left alive &mdash; the player, whose task is to escape the carnage in one piece.

Gameplay
Doom is a first-person shooter with a science fiction/horror theme. The objective of each level is simply to locate the exit room that leads to the next area (invitingly labeled with a red EXIT sign), while surviving all hazards along the way. Among the obstacles are monsters, pits of radioactive waste, ceilings that descend to crush the player, and locked doors for which a keycard or remote switch need to be located. The levels are sometimes labyrinthine (the automap is a crucial aid in navigating them), and feature plenty of hidden rooms that hold powerups as a reward for players who explore thoroughly.

Doom's weapon arsenal was highly distinctive in 1993 and eventually became prototypical for first-person shooters. The player starts out armed only with a pistol, and brass-knuckled fists in case his ammunition runs out, but larger weapons can be picked up: a chainsaw, a shotgun, a chaingun, a rocket launcher, a plasma gun, and the immensely powerful BFG 9000. There is a wide array of additional powerups, such as a backpack that increases the player's ammunition-carrying capacity, armor, medical supplies to heal injuries, and strange alien artifacts which can turn the player invisible or boost his health beyond its normal maximum.

The enemy monsters are Doom's central gameplay element. There are 10 types of monster, including possessed humans as well as demons of different strength, ranging from weak but ubiquitous imps and red, floating cacodemons to the bosses, which tend to survive multiple strikes even from the player's strongest weapons. The monsters generally exhibit very simple AI, and in most cases must seek to overwhelm the player by outnumbering him (though this can sometimes backfire due to monster infighting).

Aside from the single-player game mode, Doom features two multiplayer modes usable over a network: co-operative mode, in which two to four players team up against the legions of Hell, and deathmatch mode, in which two to four players fight each other.

Release and sales
The shareware format of the initial release encouraged players to distribute Doom as widely as possible; by 1995, it was estimated to have been installed on more than 10 million computers. Although most users did not purchase the registered version, over one million copies have been sold, and this popularity helped the sales of later games in the Doom series which were not released as shareware.

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 FPS with a deathmatch mode (MIDI Maze, on the Atari ST, had one in 1987), but it was the first to use Ethernet connections, and the combination of violence and gore with fighting friends made deathmatching in Doom particularly attractive. Due to its widespread distribution, Doom became the game that introduced deathmatching to a large audience (as well as introducing the term "deathmatch").

An important feature of the Doom engine is a modular approach that allows game content to be replaced by custom patch files, known as PWADs. Wolfenstein 3D had not been designed this way, but fans had nevertheless figured out how to create their own levels for it, and id Software decided to push this phenomenon further. The first level editors appeared in early 1994, followed over the next few years by additional tools which allow most aspects of the game to be edited. Although the majority of PWADs contain one or several custom levels of essentially the same style as the original game, others implement new monsters and other resources, and heavily alter the gameplay; various popular movies, television series, and other brands from popular culture have been turned into Doom maps by fans (although this has led to copyright disputes), including Aliens, Star Wars, The X-Files, The Simpsons, and Batman. In 1994 and 1995, PWADs were primarily available online over bulletin board systems or sold in collections on compact discs (sometimes bundled with editing guidebooks) in computer shops; FTP servers later became the primary distribution method. Tens of thousands of PWADs (at least) have been created in total; the FTP archive at Doomworld.com alone contains over 13,000 files.

Negative reaction
In a press release dated January 1, 1993, id Software wrote 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 inconvenience at workplaces, occupying the time of employees and clogging computer networks with traffic caused by deathmatches. Intel and Carnegie Mellon University, among many other organizations, reportedly formed policies specifically disallowing Doom-playing during work hours.

Doom was (and remains) a controversial product due to its high levels of violence, gore, and Satanic imagery. It has been repeatedly criticized by Christian organizations for its diabolic undertones, and prompted fears that virtual reality technology, then in its earliest forms, could be used to simulate extremely realistic killing; in 1994, this led to unsuccessful attempts by Washington state senator Phil Talmadge to introduce compulsory licensing of VR use. The game again made national headlines in 1999, when it was linked to the Columbine High School Massacre.

Legacy
Doom is widely regarded as one of the most important titles in gaming history. In the wake of its immense popularity, dozens of new first-person shooter titles appeared, which were more often referred to as "Doom clones" than "first-person shooters". id Software went on to release a sequel, Doom II, followed by the officially licensed expansion packs Ultimate Doom, Master Levels for Doom II, and Final Doom. Doom itself was eventually ported to several dozen other operating systems and consoles.

Doom has also appeared in several other media, including a comic book, four novels, and a film released in October 2005. The game's development and impact on popular culture is the subject of the book Masters of Doom by David Kushner.

Devoted players have spent years creating speedruns, competing for the quickest completion times and sharing knowledge about routes through the levels and how to exploit engine bugs as shortcuts. Achievements include the completion of both Doom and Doom II on the Ultra-Violence difficulty setting in less than 30 minutes each. In addition, a few players have also managed to complete Doom II in a single run on the Nightmare! difficulty setting (level designer John Romero has characterized the idea of such a run with the statement "it's just gotta be impossible!"). Movies of most of these runs are available from the Compet-N database.

Although the popularity of the Doom games decreased following the publication of Quake (1996), the series has retained a strong fan base that continues playing competitively and creating new PWADs (the Doomworld FTP archive still receives a few to a dozen new PWADs each week), and Doom-related news is still tracked at various community websites. Interest in Doom was renewed in 1997, when the source code for the engine was released; fans then began porting the game to various operating systems, even to previously unsupported platforms such as the Sega Dreamcast and the iPod, and adding new features which allow PWADs to alter the gameplay more radically (such as OpenGL rendering and scripting). There are well over 50 distinct source ports, some of which remain under active development.

Episodes

 * Knee-Deep in the Dead
 * The Shores of Hell
 * Inferno
 * Thy Flesh Consumed (added in Ultimate Doom)

Weapons

 * Fists
 * Chainsaw
 * Pistol
 * Shotgun
 * Chaingun
 * Rocket launcher
 * Plasma gun
 * BFG 9000

Monsters

 * Baron of Hell
 * Cacodemon
 * Cyberdemon
 * Demon
 * Former Human
 * Former Human Sergeant
 * Imp
 * Lost Soul
 * Spectre
 * Spider Mastermind