Half-Life, often abbreviated as HL or HL1, is a sci-fi first-person shooter computer game developed by Valve Software, first released by Sierra Studios on November 19, 1998. Designed for PCs running Microsoft Windows, the game uses a heavily modified version of the Quake engine, called GoldSrc.

In Half-Life, players assume the role of Dr. Gordon Freeman, a recently graduated theoretical physicist who must fight his way out of an underground research facility whose teleportation experimentations have gone terribly wrong. The game was the first first-person shooter with a story told entirely in-game in real time, without the use of cutscenes. On its release, critics hailed its overall presentation and numerous scripted sequences, and it won over 50 Game of the Year awards in 1998-9. Its gameplay influenced first-person shooters for years to come, and has since been regarded as one of the greatest games of all time.

With over eight million copies sold since, Half-Life is the best-selling PC first-person shooter to date. The Half-Life franchise – expansions such as Half-Life: Opposing Force; standalone Half-Life: Blue Shift; mods such as Counter-Strike, Team Fortress Classic, Deathmatch Classic, Ricochet, and Day of Defeat; and its sequel Half-Life 2 – has seen over 15 million sales.

The game was also released for the PlayStation 2 on November 15, 2001. A Sega Dreamcast port was made, but was cancelled just 2 weeks before release. The fully-playable Dreamcast version has since been released onto the Internet.[10]

The titles of Half-Life and its expansion packs are all named after scientific terms. Half-Life itself is a reference to the half life of a quantity, the amount of time required for the quantity to decay to half of its initial value. Opposing Force is a reference to Newton’s third law of motion, while Blue Shift refers to the blue shifting of the frequency of radiation caused by the Doppler effect.


  • 1 Plot
    • 1.1 Storyline
  • 2 Gameplay
    • 2.1 Characters and creatures
    • 2.2 Weapons
  • 3 Development
    • 3.1 Ports
      • 3.1.1 Dreamcast version
      • 3.1.2 Macintosh version
    • 3.2 Later developments
  • 4 Reception
    • 4.1 Products
  • 5 Expansions
    • 5.1 Third-Party Mods
  • 6 Soundtrack
  • 7 See also
  • 8 References
  • 9 External links


Most of the game is set in a remote desert area of New Mexico in a facility known as the Black Mesa Research Facility, a fictional complex that bears many similarities to both the Los Alamos National Laboratory and Area 51, during May or December (as seen on calendars in the game) of 200X, meaning it takes place sometime between the years 2000 and 2009. The game’s protagonist is the theoretical physicist Gordon Freeman, a survivor of an experiment that goes horribly wrong when an unexpected “resonance cascade” (a completely fictitious phenomenon; see also constructive interference and prompt critical) rips dimensional seams, devastating the facility. Aliens from another world – known as Xen – subsequently enter the facility through these dimensional seams (an event known as the “Black Mesa Incident”).

As Freeman tries to make his way out of the ruined facility to find help for the injured, he soon discovers that he is caught between two sides: the hostile aliens and the Hazardous Environment Combat Unit, a United States Marine Corps Special Forces division dispatched to cover up the incident by eliminating the aliens, as well as Dr. Freeman and the other surviving Black Mesa personnel. Throughout the game, a mysterious figure known (but not actually referred to in-game) as the “G-Man” regularly appears, apparently monitoring Freeman’s progress. Ultimately, Freeman uses the co-operation of surviving scientists and security officers to work his way towards the mysterious “Lambda Complex” of Black Mesa (signified with the Greek “λ” character), where a team of survivors teleport him to the alien world Xen to kill the Nihilanth, the creature keeping Xen’s side of the dimensional rift open.

The game’s plot was originally inspired by the video games Doom and Quake, both personal computer games produced by id Software, Stephen King’s short story/novella The Mist, and an episode of The Outer Limits called “The Borderland.” It was later developed by Valve’s in-house writer and author, Marc Laidlaw, who wrote the books Dad’s Nuke and The 37th Mandala.



The “resonance cascade”, as witnessed by Gordon Freeman.

Half-Life begins with a long expository sequence that situates the player in the game’s environment prior to serious action or gameplay. The player-controlled character, Dr. Gordon Freeman, starts his day riding a tram deep into the heart of the Black Mesa Facility, where most of the game is set, on his way to the Anomalous Materials Lab to begin work. The tram ride gives players a perspective of the facility, setting the mood and serving as a vehicle for some comic relief moments. The ride also marks the first appearance of the G-Man, first shown as a strange man in a blue suit watching Gordon from another tram. When Gordon Freeman arrives at the Anomalous Materials Lab, a front desk security guard informs him that a system crash occurred shortly before he arrived, which has complicated communications between the Black Mesa scientists. The player must then acquire his Hazardous Environment suit before proceeding to the test chamber.

On his way to the test chamber, Gordon receives a briefing from a group of scientists. Before entering the test chamber, his co-workers inform him that his job is to push a “specimen” into the scanning beam for analysis. As soon as he does so, a fictional time-space catastrophe called a “resonance cascade” occurs. This event opens a portal between Earth and a bizarre world called Xen. During this, Freeman is briefly teleported there and at one point sees alien life forms known as Bullsquids and Vortigaunts.

Back in Black Mesa, Gordon exits the test chamber and sees that most of the scientists he had spoken to minutes before are dead. After finding some survivors, he discovers that there are no means to communicate with the world outside Black Mesa. Scientists then implore Gordon to make his way to the surface to get help. Black Mesa has suffered massive structural damage, and to make matters worse, aliens from Xen begin randomly teleporting all around them. Some are shown to be “wild” alien animals who attack the player because they are unfamiliar with their new surroundings and feel compelled to defend themselves. Others, such as the Vortigaunts, are depicted as more intelligent and attack Gordon with a clear intent to kill. The player can also occasionally glimpse the G-Man, who watches from out-of-reach places and always disappears before Gordon can get to him.

As the player progresses through the game, he runs into scientists who inform him that human soldiers are on the way to the base to rescue them. However, once Gordon encounters the soldiers, he discovers that the Hazardous Environment Combat Unit, which has taken control of Black Mesa, is not just killing the aliens, but is also killing everyone connected to Black Mesa. After fighting the soldiers and eventually reaching the surface of the complex, Gordon is informed by scientists that the secretive Lambda Team may have the means to solve the problems brought on by the cascade. Gordon must then reach the Lambda Complex at the other end of the facility to assist them.

Gordon Freeman is subsequently faced with several tasks, such as killing a giant, rapidly growing tentacle creature, riding across the facility on a railway system in order to reach a satellite rocket that must be launched in order to reverse the resonance cascade, and fighting a group of mysterious Black Ops, before being captured by Marines and dumped in a garbage compactor. Gordon escapes without being crushed and makes his way to an older, secret part of the Facility where he discovers an extensive collection of specimens collected from Xen long before the resonance cascade.

Gordon again reaches the surface, which has become a war zone. The Vortigaunts, along with Alien Grunts and a giant monstrosity, have begun fighting the Marines, who are beginning to lose. They’ve called in reinforcements, but it isn’t enough to turn the tide. Gordon must scale cliffs and navigate bombed out buildings while avoiding both sides. Finally, Gordon reaches relative safety underground.

The Marines begin to evacuate Black Mesa and airstrikes begin. At one point, the player must use the military equipment to call an air strike to re-enter the base. Gordon navigates underground water channels and tries to avoid scores of alien soldiers as they pick off remaining Marine stragglers. After much struggle, Gordon finally reaches the Lambda Complex, which is revealed to be the location where they developed the teleportation technology that allowed scientists to travel to Xen in the first place. Gordon reaches the handful of surviving personnel, who have holed themselves up in a small stronghold, and discovers that, unfortunately, the satellite he launched was not able to reverse the effects of the resonance cascade because an immensely powerful being on the other side of the rift is keeping the portal between the worlds open. Gordon must kill this being to prevent the Xen aliens from taking over completely. The scientists activate the teleporter and Gordon is relocated to Xen.

Freeman on Xen.

Freeman on Xen.

On the strange border world, Gordon encounters many of the aliens that had been brought into Black Mesa, as well as the remains of HEV-wearing researchers that came before him. The player engages in one of the few boss-style battles against Gonarch, a giant headcrab with a huge egg sac. After fighting his way through an alien camp, Gordon arrives at a huge alien factory complex, which engineers and builds the Alien Grunt soldiers. After fighting his way through mysterious, levitating creatures, he finds a giant portal and enters it.

In a vast cave, Gordon finally confronts the Nihilanth, the creature who was maintaining the rift, and destroys it. As the creature dies, it explodes in a giant green blast that overpowers Gordon’s senses. After awakening, Gordon’s movement is restricted as he is confronted by the G-Man. Both are transported to various locales around Xen, while the G-Man praises the player’s actions in the border world. The G-Man explains that his “employers”, believing that Gordon has “limitless potential”, have authorized him to offer Freeman a job. The final teleportation takes the player to the original tram car, which appears to be flying through space. If the player refuses the job offer, the G-Man teleports him to a location in front of a considerable number of alien enemies, stating, “No regrets, Mr. Freeman,” as the screen fades out. If the player accepts, by stepping into a portal, he finds himself floating in nothingness and hears the G-Man’s voice one last time: “Wisely done, Mr. Freeman. I will see you up ahead.”


In this scene, the player must bypass a dam and reservoir guarded by an Apache helicopter, a group of soldiers, and a cannon emplacement. This shot shows the original MP5 sub-machine gun, rather than the High Definition Pack's M4 Carbine replacement.

In this scene, the player must bypass a dam and reservoir guarded by an Apache helicopter, a group of soldiers, and a cannon emplacement. This shot shows the original MP5 sub-machine gun, rather than the High Definition Pack’s M4 Carbine replacement.

Half-Life, a first-person shooter, requires the player to perform two kinds of tasks: combat and puzzle solving. Unlike its peers at the time, Half-Life utilized scripted sequences, which range from small events, such as an alien ramming down a door, to major plot points. While most contemporary first-person shooters relied on cut scene intermissions to detail their plotlines, Half-Life‘s story is put forth entirely through scripted sequences, keeping the player in the game at all times. In line with this, the player rarely loses the ability to control Gordon, who never speaks and is never actually seen in the game. Half-Life has no “levels”, opting instead for a continuous world divided by short load times to minimize interruptions in gameplay. That said, the game can clearly be split up into distinct “chapters”, the titles of which will flash up on the screen at the start of each one.

The game regularly integrates puzzles, such as navigating a maze of conveyor belts. Some puzzles involve using the environment to kill an enemy. There are few “bosses” in the conventional sense, where the player defeats a superior opponent by direct confrontation. Instead, such monsters occasionally define chapters, and the player is generally expected to use the terrain, rather than firepower, to kill the “boss”. Late in the game, the player receives a “long jump module” for their HEV suit, which increases the horizontal distance and speed of jumps, by crouching before jumping. This is used for platformer-style jumping puzzles in the later portion of the game.

Characters and creatures

For the most part the player battles through the game alone, but is occasionally assisted by non-player characters; specifically security guards and scientists who fight alongside the player, assist in reaching new areas and impart relevant plot information.

A wide array of enemies populate the game including alien lifeforms such as headcrabs, bullsquids, headcrab zombies and Vortigaunts. The player also faces human opponents, in particular HECU Marines and black ops assassins who are dispatched to contain the alien threat and silence all witnesses.


Half-Life has a large array of weapons the player can use, including the trademark crowbar for mêlée fighting, the conventional firearms of the Glock 17 pistol, SPAS-12 shotgun, MP-5 submachine gun with grenade launcher, .357 Magnum revolver, and rocket launcher as well as unconventional weapons ranging from a crossbow to alien weapons such as Snarks – small, voracious, explosive alien insectoids – to experimental weapons including the Gluon gun and Gauss gun.

With the installation of the High Definition Pack, the weapons’ appearances are substantially updated, mainly due to a larger number of polygons in the models. Although their appearances have changed, they perform exactly the same as their original counterparts in terms of gameplay. The Glock 17 and MP5 are replaced by the Beretta 92FS and M4A1 as well.


Half-Life was the first product of Kirkland, Washington-based developer Valve Software, which was founded in 1996 by former Microsoft employees Mike Harrington and Gabe Newell. They settled on a concept for a horror-themed 3D action game, and licensed the Quake engine from id Software. Valve eventually modified the engine a great deal, notably adding skeletal animation and Direct3D support; a developer stated in a PC Accelerator magazine preview that seventy percent of the engine code was rewritten. The company had difficulties finding a publisher at first, many believing their project “too ambitious” for a studio headed by newcomers to the video game industry. However, Sierra On-Line had been very interested in making a 3D action game, especially one based on the Quake engine, and so signed them for a one-game deal.

The original code name for Half-Life was Quiver, after the Arrowhead military base from Stephen King’s novella The Mist, which served as early inspiration for the game. Gabe Newell explained that the name Half-Life was chosen because it was evocative of the theme, not clichéd, and had a corresponding visual symbol: the Greek letter λ (lower-case lambda), which represents the decay constant in the half-life equation.

The first public appearances of Half-Life came in early 1997; it was a hit at Electronic Entertainment Expo that year, where they primarily demonstrated the animation system and artificial intelligence. Valve Software hired science fiction author Marc Laidlaw in August 1997 to work on the game’s characters and level design. Half-Life was originally planned to be shipped in late 1997, to compete with Quake II, but was postponed when Valve decided the game needed significant revision.

In a 2003 Making Of… feature in Edge, Newell discusses the team’s early difficulties with level design. In desperation, a single level was assembled including every weapon, enemy, scripted event and level design quirk that the designers had come up with so far. This single level inspired the studio to press on with the game. As a result, the studio completely reworked the game’s artificial intelligence and levels in the year leading up to its release. At E3 1998 it was given Game Critics Awards for “Best PC Game” and “Best Action Game”. The release date was delayed several times in 1998 before the game was finally released in November of that year.


Half-Life was ported to the PlayStation 2 by Gearbox Software and released in 2001. This version of the game had a significant overhaul in terms of both character models, weapons, and more advanced and extended levels and general map geometry (see Half-Life High Definition Pack for a model-comparison). Despite the increased level of detail, the style of some of the models (most noticeably the human grunts) is also noticeably altered, meaning that whether they actually look better or not is subject to opinion. Also added in is a head-to-head play and a co-op expansion called Half-Life: Decay that allowed players to play as the two female scientists Dr. Cross and Dr. Green at Black Mesa.

Versions for the Sega Dreamcast and Apple Macintosh were essentially completed, but never commercially released. The Dreamcast edition was eventually leaked onto the internet.

Dreamcast version

Gearbox Software was slated to release a port to the Sega Dreamcast under contract by Valve and their then publisher Sierra On-Line near the end of 2000. At the ECTS 2000, a build of the game was playable on the publisher’s stand, and developers Randy Pitchford and Brian Martel were in attendance to show it off and give interviews to the press. However, despite only being weeks from going gold, it was never commercially released; Sierra announced that Half-Life on Dreamcast was cancelled “due to changing market conditions” onset by third-party abandonment of the Dreamcast. That year Sierra On-Line showed a PlayStation 2 port at E3 2001. This version was released in North America in late October of the same year, followed by a European release just a month later. Around the same time, Half-Life: Blue Shift, which was intended to be a Dreamcast-exclusive side story, was released on PC as the second Half-life Expansion Pack.

Although it has never officially been released, the Dreamcast version was leaked onto the Internet, and was proven to be fully playable; it contains the full versions of Half-Life and Blue Shift, both with an early version of the High Definition Pack, but has a somewhat inconsistent framerate and lengthier load times when the player moves from area to area. Also, there are some saving problems; the number of blocks required to save on a VMU increases rapidly as the player reaches the end of a level, then drops at the start of the next. While the game allows the user to remove files to increase space, sometimes it still isn’t enough.

Macintosh version

Though more or less complete and ready for mass production, the Macintosh port of Half-Life was scrapped because of incompatibility with the Windows PC version’s multiplayer mode. The developers also stated that mods for PC Half-Life would not be compatible with the Mac port. Additionally, concerns over the task load associated with providing technical support on more than one end platform at once may have contributed to the demise of Half-Life for Macintosh.

Later developments


Half-Life 2 and Half-Life: Source

The sequel, Half-Life 2, was merely a rumor until it was finally revealed at E3 in May 2003, which ignited a firestorm of hype surrounding the game. The player again takes the role of Gordon Freeman, this time several years after the Black Mesa incident in the dystopic Eastern European “City 17” where he must fight as part of a rebellion against an alien regime. After a series of controversies and delays Half-Life 2 was released on November 16, 2004.

To experience firsthand the processes mod-makers would have to go through with the new engine, Valve ported Half-Life (dubbed Half-Life: Source) and Counter-Strike to their new Source engine. Half-Life: Source is a straight port, lacking any new content or the Blue Shift High Definition pack. However, it does take advantage of vertex and pixel shaders for more realistic water effects, as well as Half-Life 2’s realistic physics engine. They also added several other features from Half-Life 2, including improved dynamic lightmaps, vertex maps, and a shadowmap system with cleaner, higher resolution, specular texture and normal maps, as well as utilization of the render-to-texture soft shadows found in Half-Life 2′s Source engine, along with 3D skybox replacements in place of the old 16-bit color bitmap skies. Also redesigned was the crossbow that will pin its targets to a nearby wall if they’re close enough. The Half-Life port possesses many of the Source engine’s graphical strengths as well control weaknesses that have been noted in the Source engine. Half-Life: Source is available with special editions of Half-Life 2.

Half-Life Source has been criticised for not fully utilizing many of the features of the Source engine found in Half-Life 2, as it still uses textures and models from the original game. Due to this, a third-party mod remake called Black Mesa is also under development. Day of Defeat: Source was released on September 26, 2005.

On June 10, 2005, Valve announced through their Steam update news service an upcoming port of Half-Life Deathmatch, the multiplayer portion of the original game, much in the same fashion as the earlier released Half-Life: Source. No exact release date was given, simply the words “In the coming weeks…” On July 2, 2006, Half-Life Deathmatch: Source was released.

On June 1, 2006 Half-Life 2: Episode One was released. It is part of a three episode trilogy, of which the second episode is scheduled to be released in fall 2007.



Half-Life’s public reception was overwhelmingly positive in terms of reviews, acclaim and sales. As of 2007 over 8 million copies of the game have been sold, making it the best-selling first person shooter of all time.

Half-Life was critically acclaimed, earning an overall score of 96% on review collection website Metacritic.. IGN described it as “a tour de force in game design, the definitive single player game in a first person shooter.” Gamespot claimed that it was the “closest thing to a revolutionary step the genre has ever taken”. Gamespot inducted Half-Life into their “Greatest Game of All Time” list in May 2007.


The popularity of the Half-Life Series has led way to an array of side products and collectibles. Valve offers Half-Life-related products such as a plush vortigaunt, plush headcrab, posters, clothing and mousepads.


Two expansion packs by outside developer Gearbox Software have been released for the PC version: Half-Life: Opposing Force (1999) and Half-Life: Blue Shift (2001). The former, often shortened to OpFor or OP4, returns the player to Black Mesa during the events of Half-Life’s storyline, but this time from the perspective of one of the soldiers in the Hazardous Environment Combat Unit sent to cover up evidence of the incident. It introduced several new weapons (notably the M249 SAW LMG and a Barnacle grappling gun), new non-player characters, both friendly and hostile (Otis the security guard and the “Race X” aliens, respectively) and new, previously unseen areas of the facility. The expansion is shorter than Half-Life, having 11 chapters to the original’s 19.

The player takes control of Barney Calhoun in Blue Shift.

The player takes control of Barney Calhoun in Blue Shift.

Blue Shift returns the player to HL’s Black Mesa timeline once more, this time as one of the facility’s security guards. (This expansion was originally developed as a bonus mission for the canceled Dreamcast version.) Blue Shift came with an optional High Definition Pack that could update the look of Half-Life, Opposing Force, and the new Blue Shift content. In particular, the models’ polygon count and texture resolutions were increased. However, the style of some of the models (most noticeably the human grunts) was noticeably altered, meaning that whether they actually look better or not is subject to opinion. Some changes were also made to the in-game sounds, most notably the shotgun. Blue Shift had relatively little new content compared to Opposing Force: aside from a few models (jacket-less scientists and security guards, Otis, and Dr. Rosenberg) all content was already present in the original Half-Life.

Half-Life: Decay was another expansion by Gearbox, released only as an extra with the PlayStation 2 version of Half-Life. The add-on featured cooperative gameplay in which two players could solve puzzles or fight against the many foes in the Half-Life universe.

In 2000, a compilation pack titled the Half-Life: Platinum Collection was released, including (with their respective manuals):

  • Half-Life
  • Counter-Strike
  • Team Fortress Classic
  • Half-Life: Opposing Force

In 2002, the pack was re-released under the new titles Half-Life Platinum Pack[44] and Half-Life: Generations. These new iterations also included the Half-Life: Blue Shift expansion pack.

In 2005, Half-Life 1: Anthology was released, containing Steam-only versions of the following games on a single DVD:

  • Half-Life
  • Half-Life: Opposing Force
  • Half-Life: Blue Shift
  • Team Fortress Classic

Third-Party Mods

See main article List of Half-Life mods

From its release in 1998, Half-Life saw fervent support from independent game developers, due in no small part to support and encouragement from Valve Software. Worldcraft, the level-design tool used during the game’s development, was included with the game software. Printed materials accompanying the game indicated Worldcraft’s eventual release as a retail product, but these plans never materialised. Valve also released a software development kit, enabling developers to modify the game and create mods. Both tools were significantly updated with the release of the version patch. Many supporting tools (including texture editors, model editors, and rival level editors like the multiple engine editor QuArK) were either created or updated to work with Half-Life.

Half-Life’s code has been released and is being used as a base for many multiplayer mods such as the immensely popular Counter-Strike. Other popular multiplayer mods include Team Fortress Classic (TFC), Day of Defeat, Deathmatch Classic (DMC), Action Half-Life, Firearms, Science and Industry, The Specialists, and Natural Selection. TFC and DMC were developed in-house at Valve Software. Counter-Strike, Day of Defeat, and others that began life as the work of independent developers (self-termed “modders”), later on received aid from Valve. There was even a free team-based multiplayer mod called Underworld Bloodline created to promote the Sony Pictures movie Underworld.

Numerous single player mods have also been created, like USS Darkstar  (1999, a futuristic action-adventure onboard a zoological research spaceship), The Xeno Project 1 and 2 (1999-2005, a two-part mod starting in Xen and again including spaceships), Edge of Darkness  (2000, which features some unused Half-Life models), Half-Life: Absolute Redemption (2000, which brings back Gordon Freeman for four additional episodes and another encounter with the G-Man), They Hunger (2000-2001, a survival horror total conversion trilogy involving zombies), and Poke646  (2001, a follow-up to the original Half-Life story with improved graphics).

Some Half-Life modifications eventually landed on retail shelves. Counter-Strike was the most successful, unexpectedly becoming the biggest selling online game to date and having been released in five different editions: as a standalone product (2000), as part of the Platinum Collection (2000), as an Xbox version (2003) as the single player spin-off, Counter-Strike: Condition Zero (2004), and the newest addition, Counter-Strike: Source, which runs on Half-Life 2′s Source engine. Team Fortress Classic, Day of Defeat and Gunman Chronicles (2000, a futuristic Western movie-style total conversion with emphasis on its single player mode) were also released as stand-alone products.


Half-Life’s soundtrack was composed by Kelly Bailey.

  • 1. “Adrenaline Horror” – 02:09
  • 2. “Vague Voices” (Black Mesa Inbound) – 02:11
  • 3. “Klaxon Beat” – 01:00
  • 4. “Space Ocean” (Echoes of a Resonance Cascade) – 01:36
  • 5. “Cavern Ambiance” (Zero Point Energy Field) – 01:39
  • 6. “Apprehensive Short” – 00:23
  • 7. “Bass String Short” – 00:06
  • 8. “Hurricane Strings” (Neutrino Trap) – 01:33
  • 9. “Diabolical Adrenaline Guitar” (Lambda Core) – 01:44
  • 10. “Valve Theme [Long Version]” (Hazardous Environments) – 01:22
  • 11. “Nepal Monastery” – 02:08
  • 12. “Alien Shock” (Biozeminade Fragment) – 00:36
  • 13. “Sirens in the Distance” (Triple Entanglement) – 01:12
  • 14. “Nuclear Mission Jam” (Something Secret Steers Us) – 02:00
  • 15. “Scared Confusion Short” – 00:16
  • 16. “Drums and Riffs” (Tau-9) – 02:03
  • 17. “Hard Technology Rock” – 01:40
  • 18. “Steam in the Pipes” (Negative Pressure) – 01:55
  • 19. “Electric Guitar Ambiance” (Escape Array) – 01:24
  • 20. “Dimensionless Deepness” (Dirac Shore) – 01:24
  • 21. “Military Precision” – 01:20
  • 22. “Jungle Drums” – 01:49
  • 23. “Traveling Through Limbo” (Singularity) – 01:17
  • 24. “Credits / Closing Theme” (Tracking Device) – 01:39
  • 25. “Threatening Short” (Xen Relay) – 00:37
  • 26. “Dark Piano Short” – 00:17
  • 27. “Sharp Fear Short” – 00:08

(Note: Most of the tracks were re-titled and carried over to the Half-Life 2 original soundtrack; the names in parentheses are the revised titles used in the Half-Life 2 OST. Tracks 2, 12, 13, and 24 were remixed for the sequel.)

The tracks “Dark Piano Short” and “Sharp Fear Short” are later used in various forms of media, including the popular reality television show Fear Factor and Power Rangers: S.P.D