Portal 2 Explained

Portal 2
Developer:Valve
Publisher:Valve
Series:Portal
Engine:Source
Genre:Puzzle-platform
Modes:Single-player, multiplayer
Director:Joshua Weier
Producer:Gabe Newell
Composer:Mike Morasky

Portal 2 is a 2011 puzzle-platform game developed by Valve for Windows, Mac OS X, Linux, PlayStation 3, and Xbox 360. The digital PC version is distributed online by Valve's Steam service, while all retail editions were distributed by Electronic Arts. A port for the Nintendo Switch was included as part of Portal: Companion Collection.

Like the original Portal (2007), players solve puzzles by placing portals and teleporting between them. Portal 2 adds features including tractor beams, lasers, light bridges, and paint-like gels that alter player movement or allow portals to be placed on any surface. In the single-player campaign, players control Chell, who navigates the dilapidated Aperture Science Enrichment Center during its reconstruction by the supercomputer GLaDOS (Ellen McLain); new characters include robot Wheatley (Stephen Merchant) and Aperture founder Cave Johnson (J. K. Simmons). In the new cooperative mode, players solve puzzles together as robots Atlas and P-Body (both voiced by Dee Bradley Baker). Jonathan Coulton and the National produced songs for the game.

Valve announced Portal 2 in March 2010, and promoted it with alternate reality games including the Potato Sack, a collaboration with several independent game developers. After release, Valve released downloadable content and a simplified map editor to allow players to create and share levels.

Portal 2 received critical acclaim for its gameplay, balanced learning curve, pacing, dark humor, writing, and acting. Like its predecessor, it has been described as one of the greatest video games ever made by numerous publications and critics.

Gameplay

Portal 2 is a first-person perspective puzzle game. The player takes the role of Chell in the single-player campaign, as one of two robotsAtlas and P-Bodyin the cooperative campaign, or as a simplistic humanoid icon in community-developed puzzles. Characters can withstand limited damage but will die after sustained injury. The goal of both campaigns is to explore the Aperture Science Laboratory—a complicated, malleable mechanized maze. While some parts of the game takes place in modular test chambers with clearly defined entrances and exits, other parts occur in behind-the-scenes areas where the objective is less clear.

The initial tutorials guide the player through movement controls and interactions with their environment, and in the case of the cooperative campaign, interactions with the other player. Gameplay revolves around the use of the Aperture Science Handheld Portal Device, which can create a pair of two portals on suitable surfaces through which the player or objects can pass through. Characters can use these portals to move between rooms or to "fling" objects or themselves across a distance.[1] [2]

Additional game elements not featured in the original Portal include Thermal Discouragement Beams (lasers), Excursion Funnels (tractor beams), and Hard Light Bridges, all of which can be transmitted through portals.[3] [4] Aerial Faith Plates catapult the player and objects through the air. The player must disable sentient, lethal turrets or avoid their line of sight. The Weighted Storage Cube has been redesigned, and there are new types: Redirection Cubes, which have prismatic lenses that redirect laser beams, spherical Edgeless Safety Cubes, an antique version of the Weighted Storage Cube used in the underground levels, and a cube-turret hybrid created by Wheatley after taking control of Aperture. The heart-decorated Weighted Companion Cube reappears briefly.[5] Early demonstrations included Pneumatic Diversity Vents, shown to transport objects and transfer suction power through portals, but these do not appear in the final game.[6] [7] [8] The typical objective of a test chamber or level is to use the portal gun and provided gameplay elements to open a locked exit door and progress to the next chamber.

Paint-like gels (which are dispensed from pipes and can be transported through portals) impart certain properties to surfaces or objects coated with them. Players can use orange Propulsion Gel to cross surfaces more quickly, blue Repulsion Gel to bounce from a surface,[9] and white Conversion Gel to allow surfaces to accept portals.[10] Only one type of gel can affect a certain surface at a time. Some surfaces, such as grilles, cannot be coated with a gel. Water can block or wash away gels, returning the surface or object to its normal state.

In the cooperative campaign, two players can use the same console with a split screen, or can use a separate computer or console; Windows, Mac OS X, and PlayStation 3 users can play with each other regardless of platform.[11] [12] Both player-characters are robots equipped with independent portal guns, a portal pair placed by either player is usable by both. Most chambers lack strict structure, and require players to use both sets of portals for laser or funnel redirection, launches, and other maneuvers.[13] The game provides voice communication between players, and online players can temporarily enter a split-screen view to help coordinate actions.[14] Players can "ping" to draw the other player's attention to walls or objects, start countdown timers for synchronized actions, and perform joint gestures such as waving or hugging. The game tracks which chambers each player has completed and allows players to replay chambers they have completed with new partners.

Portal 2s lead writer Erik Wolpaw estimates each campaign to be about six hours long.[15] Portal 2 contains in-game commentary from the game developers, writers, and artists. The commentary, which is unlocked per completed chapter, appears on node icons scattered through the chambers.[16] According to Valve, each of the single-player and cooperative campaigns is 2 to 2.5 times as long as the campaign in Portal, with the overall game five times as long.[17]

Plot

See also: List of Portal characters.

Backstory

The Portal series shares a fictional universe with the Half-Life series. The events in Portal take place between the first and second Half-Life games,[18] while most of Portal 2 is set "a long time after" the events in Portal.[19]

Before Portal, Aperture Science conducted experiments to determine whether human subjects could safely navigate dangerous "test chambers", until the artificial intelligence GLaDOS, governing the laboratory, killed its employees. At the end of the first Portal, the protagonist Chell destroys GLaDOS and momentarily escapes the facility, but is dragged back inside by an unseen figure later identified by writer Erik Wolpaw as the "Party Escort Bot".[20] A promotional comic shows estranged Aperture Science employee Doug Rattmann, who used graffiti to guide the player in Portal, placing Chell into suspended animation to save her life, until the beginning of Portal 2.

Single-player campaign

In the Aperture Science Enrichment Center, player-character Chell wakes in a stasis chamber resembling a motel room. The complex has become dilapidated after what appears to be millennia of decay. Wheatley (Stephen Merchant), a personality core, guides her through old test chambers from the first game in an attempt to escape the facility after its reserve power is depleted.[21] [22] They accidentally reactivate the dormant GLaDOS (Ellen McLain) while attempting to restore power to the escape pods; she separates Chell from Wheatley and begins rebuilding the facility.[23] [24]

GLaDOS subjects Chell to new tests until Wheatley helps her escape again. They sabotage Aperture's production of turrets and neurotoxin to prevent GLaDOS from killing them, then confront GLaDOS and perform a core transfer; replacing her with Wheatley as the laboratory's controller. Wheatley, immediately driven mad with power, installs GLaDOS on a potato battery. GLaDOS tells Chell that Wheatley was designed as an "intelligence dampening sphere" to deliberately produce illogical thoughts and hamper her own intelligence.[25] Infuriated, Wheatley inadvertently destroys the lift to the surface with Chell and GLaDOS inside, causing them to fall to the facility's abandoned lowest levels.

Chell retrieves the potato battery and they form a reluctant partnership to stop Wheatley before his incompetence destroys the facility. Ascending through laboratories built in the 20th century, they discover audio recordings by eccentric Aperture Science founder Cave Johnson (J. K. Simmons).[26] The recordings reveal how Aperture slowly lost money and prestige throughout the decades, as its pool of test subjects was altered from "astronauts, war heroes, and Olympians" in the 1950s, to homeless people in the 1970s, and Aperture's own employees in the 1980s. In 1981, Johnson became mortally ill after ingesting Moon dust used to manufacture portal-conductive surfaces. His last request was for the mind of his assistant Caroline (McLain) to be transferred—by force, if necessary—to an advanced computer designed to store a human consciousness, which he had previously commissioned to save himself, creating GLaDOS. GLaDOS is troubled by the discovery that she is Caroline.[27]

Chell and GLaDOS return to Aperture's higher levels, where they discover Wheatley's utter incompetence has brought the Aperture facility on the verge of catastrophic failure. Wheatley, after discovering Chell and GLaDOS had returned, decides to keep them alive as test subjects because the "franken-turret" cubes he created were ineffective at solving tests. GLaDOS later reveals that her body came built-in with a euphoric response to test completion that becomes less effective over time. Throughout the following chambers, Wheatley becomes increasingly frustrated with its dwindling effects.[28]

Wheatley reveals that he has a "surprise" for Chell and GLaDOS, later tricking them into a death trap. He reveals that he had discovered the two robots from the Cooperative Testing Initiative, the game's cooperative campaign, making Chell no longer useful to him. She manages to escape from the trap right before its activation. The game's final levels are spent escaping from Wheatley's numerous attempts to kill them.

In the game's boss fight and ending, Chell confronts Wheatley and attaches corrupted personality cores (Nolan North)[29] to force another core exchange and restore GLaDOS to authority. However, Wheatley demolishes the button necessary to initiate the transfer. As the facility crumbles, Chell places a portal on the Moon; she and Wheatley begin to be pulled into the vacuum of space. GLaDOS, having reasserted control over the facility, rescues Chell and abandons Wheatley to outer space.[30] [31] When Chell awakens, GLaDOS claims to have learned of humanity from the remnants of Caroline, but deletes Caroline's personality.[32] Deciding that Chell is not worth the trouble of killing, GLaDOS frees her from the facility.

Cooperative campaign

The cooperative story is chronologically set after the events of the single player campaign, but players are not required to play them in order.[33] Player characters ATLAS and P-Body are bipedal robots constructed by GLaDOS. In the first four 'sets' of levels, the robots are sent on ventures into the depths of the Aperture facilities to recover and upload data disks. After completion of each mission, the robots self-destruct and are reassembled to complete the next.

At first, GLaDOS is excited about her non-human test subjects, but later becomes dissatisfied because the two robots cannot truly die, and at one point also gets uncomfortable with their close partnership.[34] At the end of the story, the robots gain entry to "the Vault", a storage facility of thousands of humans placed in stasis. GLaDOS thanks the robots for their acquisition of new test subjects, and promptly destroys the robots.

"Peer Review" DLC campaign

The robots are reactivated by GLaDOS one week after the original co-op campaign, during which GLaDOS has already wiped out all of the found test subjects after attempting to turn them into "killing machines". The robots are sent to find a saboteur that has taken control of a prototype central core and is causing problems in the facility. The saboteur is revealed to be a bird pecking at the console's keyboard, which sends GLaDOS into a panic when she recognizes it as the one who tried to eat her during her time as a potato battery. The robots manage to shoo away the bird, earning a rare compliment from GLaDOS before she notices eggs in its nest. Instead of having them smashed, GLaDOS has the eggs taken to her chamber so that she can raise the baby birds to be her killing machines.

Development

After the success of Portal, Valve decided to make Portal 2 a standalone product, partly because of pressure from other developers within Valve who wanted to work on a Portal product.[35] Work began almost immediately after the release of Portal.[36] Valve committed more resources to Portal 2s development than they had for the first game; Portal had a team of seven or eight people, but Portal 2 had a team of 30 or 40.[37] The initial team of four was expanded as subgroups formed to devise game mechanics and to plot the story. Participants in internal review processes were inspired by what they saw to join the project. According to Erik Wolpaw, some Portal 2 developers worked on the Left 4 Dead games to help them meet milestones, but returned to Portal 2, "with extra people in tow."[38] Kim Swift, Portals designer, left Valve for Airtight Games halfway through Portal 2s development.[39]

Project manager Erik Johnson said Valve's goal for Portal 2 was to find a way to "re-surprise" players, which he considered a "pretty terrifying" prospect. In March 2011, one month before the game's release, Valve president Gabe Newell called Portal 2 "the best game we've ever done".[40] After Portal 2s release, Geoff Keighley wrote that according to Newell, "Portal 2 will probably be Valve's last game with an isolated single-player experience". Keighley later stated that the use of the word "probably" suggests that "this could change."[41] Newell said that Valve is not "giving up on single-player", but intends to include more social features on top of the single player experience, akin to the cooperative mode in Portal 2.[42]

Design

Initially, Valve planned to exclude portals from Portal 2. For five months, they focused on a gameplay mechanic called "F-Stop"; Valve did not discuss the specifics of the idea, as they planned to potentially reuse it in the future.[43] [44] In 2020, developer LunchHouse Software revealed they were using Valve's F-Stop code in their upcoming game Exposure. The mechanic was based on an "Aperture Camera", with which users could take photos of objects, store the object in a camera, and then replace it while rotating or scaling it.[45] [46] Valve's F-Stop game was set in the 1980s, and would not have featured Chell or GLaDOS; instead, it followed a new test subject involved in a conflict within Aperture after Johnson, in an attempt to reach immortality, uploaded himself into an artificial intelligence and took control of a robot army. Though the playtesters liked F-Stop, they expressed disappointment at the omission of portals. Based on the playtesting feedback, Newell directed the team to reconsider direction around October 2008.

Valve did not aim to make Portal 2 more difficult than Portal, but instead to produce "a game where you think your way through particular parts of the level, and feel really smart when you solve it". To allow players to learn the game rules incrementally, Valve designed two basic types of test chamber: one, which Valve called "checklisting", provides a safe environment for the player to experiment with a new concept, while the other combines elements in new ways to force the player to think laterally.

Test chambers began as isometric drawings on whiteboard. The developers ran a sanity check before crafting simple levels with the Hammer Editor, Valve's level construction tool. Iterative playtesting ensured the solutions were neither too obvious nor too difficult; playtesters sometimes discovered alternative solutions, which the team removed if they were considered too easy.[47]

Valve aimed to teach new players the portal mechanics while still entertaining experienced players. To this end, they streamlined some elements; for example, the moving energy balls of Portal were replaced with lasers, which provide immediate feedback. To evoke a sense of nostalgia and time having passed between the games, Valve included test chambers from the original Portal; they used higher-resolution textures supported by the improved game engine, and applied decay, collapse and overgrowth effects.[48]

The middle section of the single-player campaign takes place in large spaces where few portals can be placed, forcing players to find creative ways to cross. The architecture in these sections was inspired by photographs of industrial complexes such as CERN, NASA, and the abandoned Soviet space program.[49] When Wheatley controls the Aperture facility, the designers "had a blast" creating deranged chambers reflecting Wheatley's stupidity.[50] As solving constant puzzles would tire players, the designers inserted occasional "experiences" to provide respite and advance the plot.[51]

The Repulsion (jumping) and Propulsion (running) gels in Portal 2 originated in . Valve hired the Tag creators to develop the idea further and later decided to include it in Portal 2. Journalists have likened Tag to Narbacular Drop, the DigiPen student project whose mechanics became Portal.[52] [53] [54] As the third Tag gel, which allows the character to walk on any surface regardless of gravity, gave playtesters motion sickness, it was replaced by Conversion gel, which integrates with the portal mechanic.[55] The gels give the player more control over the environment, which increased the challenge for the puzzle designers. The gels are rendered using fluid dynamics routines specially developed at Valve by the former Tag Team. Rendering techniques developed for Left 4 Dead 2 were used to render pools of liquid; Portal 2 combines "flowing" surface maps to mimic the motion of water with "debris flow" maps and random noise to create realistic, real-time rendering of water effects.[56]

Cooperative mode

The cooperative mode originated from players' requests and from anecdotes of players working together on the same computer or console to solve the game's puzzles. Wolpaw likened this to players working together on the same computer to solve point-and-click adventure games.[57] The cooperative campaign was also inspired by Valve's Left 4 Dead cooperative games, in which players enjoyed discussing their personal experiences with the game when they had finished playing it.

While the single player campaign in Portal 2 is designed to avoid frustrating the player, the cooperative levels focus on coordination and communication, and Valve recognizes they are much more difficult than the single-player puzzles. Valve did not include timed puzzles in the single-player campaigns in Portal and Portal 2, but found that their inclusion in the cooperative mode is effective and gives players a positive feeling after they successfully plan and execute difficult maneuvers.

Each puzzle chamber in the cooperative mode requires actions from both players. As soon as a playtester discovered a way to complete a puzzle with one set of portals, the level was sent back to the designers for further work. With few exceptions, Valve designed the chambers so that both players would remain in sight of each other to promote communication and cooperation. Some of the puzzle chambers were designed asymmetrically; one player would manipulate portals and controls to allow the other player to cross the room, emphasizing that the two characters, while working together, are separate entities. The designers soon realized that the ability to tag surfaces with instructional icons for one's partner was a necessary element, since they found this to be more effective for cooperation than simple, verbal instructions.

Valve considered a competitive mode. According to Wolpaw, the mode was similar to the video game Speedball;[58] one team would try to transport a ball from one side of the playing field to the other using portals, while the other team would attempt to stop them with their own use of portals. Matches would commence with this objective in mind, but quickly descended into chaos. Valve realized that people enjoyed solving puzzles with portals more and therefore they focused on the cooperative mode.[59]

Writing

Wolpaw and ex-National Lampoon writer Jay Pinkerton wrote the single-player story, while Left 4 Dead writer Chet Faliszek wrote GLaDOS's lines for the cooperative campaign.[60] The game has 13,000 lines of dialogue.[61] The writers felt they needed to create a larger story for a stand-alone title, and wanted the game to "feel relatively intimate", and avoided adding too many new characters. They considered expanding the "sterility and dryness" of Portal and adding more comedy to the script. Wolpaw said that while some developers have been moving towards art games, no one had made a comedic video game. The game's story development was tightly coordinated with the gameplay development and testing.[62]

The developers initially envisioned a prequel set in the 1950s, long before GLaDOS took over the Aperture Science facility, with events set in motion when Aperture CEO Cave Johnson is put into a computer, only to realize it was a mistake. Johnson would have led an army of robots, which would battle against the player to rise to power within Aperture. In June 2008, based on information from a casting call website and leaked script samples, Kotaku reported that Valve was seeking voice actors to play Johnson, named him as an AI and identified the game as a prequel.[63] [64] Valve attributed this leak to an "overeager agent". Following negative playtester feedback about the omission of Chell and GLaDOS, Portal 2 was re-conceived as a sequel. The team returned to the idea of exploring parts of the facility from Aperture's early days, and reincorporated Johnson through a series of recordings.

The writers originally conceived several premature joke game endings if the player performed certain actions, but these required too much development effort for little payback and were scrapped. One of these joke endings was triggered by shooting a portal onto the moon's surface, after which the player's character would die from asphyxiation over a closing song, but the idea of creating a portal on the moon was incorporated into the game's final ending. The writers planned that Chell would say a single word during the ending, but this was not considered funny enough.[65] In an early version of the script, Chell finds a lost "tribe" of turrets looking for their leader, a huge "Animal King" turret which can be seen in in-game videos of the retail product. As a reward, the Animal King would have married Chell to a turret, which would have followed Chell around the game without visible movement.[66] The cooperative campaign was planned to feature a more detailed storyline, in which GLaDOS would send two robots to discover human artifacts, such as a comic based on a pastiche of Garfield. The writers hoped to use this idea to make the robots human-like for testing purposes, but recognized that unlike the captive audience of the single-player campaign, the two players in cooperative mode may simply talk over the story, and thus the story was condensed into very basic elements.

Wolpaw said that while many story elements of Portal are revisited in Portal 2, he avoided some of the memes—such as the frequently repeated "the cake is a lie". He said, "if you thought you were sick of the memes, I was sick of it way ahead of you".[67] Wolpaw "couldn't resist putting in just one" cake joke. The writers did not try to predict or write new memes, and Wolpaw said, "you can't really plan for [dialogue to become a meme] because if you do it probably seems weird and forced".[68] Portal 2 produced its own memes, including a space-obsessed personality core.[69] Valve later created a Space Core modification for the game (see below), and the Space Core also appeared as a laser-based engraving on a panel manufactured by NASA for the International Space Station.[70]

The writers saw Aperture Science itself as a character. It is depicted as a "living, breathing place", and "a science company that's gone mad with science."[71] In the Lab Rat comic, the facility is described as a "beautiful and terrible" place, "a metastasized amalgam of add-ons, additions and appropriations. Building itself out of itself."[72]

Richard McCormick of PlayStation 3 Magazine identified several elements of Portal 2s story that reference the myth of Prometheus; McCormick wrote that GLaDOS is a personification of Prometheus, who grants knowledge to humanity—in the form of the portal gun—and is then punished by being bound to a rock, pecked at by birds, and is cast into the pits of Tartarus. McCormick also likens Wheatley to Prometheus' foolish brother Epimetheus. Within the game, a turret makes reference to the Prometheus myth, the word "Tartarus" is visible on the supporting columns in the depths of Aperture Science, and a portrait of Cave and Caroline also shows Aeschylus, the presumed author of Prometheus Bound.[73] Journalists and players have also found connections between Portal 2 and Half-Life 2. As an easter egg, a hidden area in Portal 2 contains the empty dry dock of Aperture Science's cargo ship, the Borealis, which is found during to have been stranded in the Arctic as a result of a teleportation experiment.[74]

Character design

Though Portal 2 introduced some new characters, the writers wanted to maintain the one-on-one relationships between each character and the player-character. Valve explored the possibility of introducing a new protagonist for Portal 2. The playtesters accepted playing as a different character for the first part of the game, but they became disoriented when GLaDOS did not recognize them. The writers returned to using Chell, the protagonist of Portal.[75] Valve artists experimented with Chell's attire, and considered changing her (ambiguous) nationality.[76] They returned to the orange "dehumanizing" jumpsuit from Portal with the top tied around Chell's waist to enhance her freedom of movement and help her "stand out more as an individual".[77] PSM3 called the new look "controversially sexy". As in the first game, Chell's facial appearance is based on that of voice actress Alésia Glidewell.[78] Chell continues her role as a silent observer, as the straight man in response to the insanity around her and refuses to give her antagonists any satisfaction.[79]

As part of her character arc, the plot moves GLaDOS from her anger with Chell for her actions in Portal, which Wolpaw said "was going to get old pretty quick", to an internal struggle. The reuse of McLain's voice led to the creation of a backstory and subplot about GLaDOS's creation. The writers panicked when they realized that their plans to have Chell and GLaDOS play off each other would only work if both players spoke. To remedy this, they created the Caroline subplot to give GLaDOS an external situation to deal with and to drive the story during the middle act of the game.[80]

The writers considered introducing about six personality cores stored in portable spheres,[81] whose main function would be story advancement. They planned cores based on Morgan Freeman's character Red from The Shawshank Redemption[82] and Quint from Jaws, among others. Ultimately they decided to concentrate on a single core, Wheatley, recycling three of the rejected cores in the final boss fight.[83] Karen Prell, a veteran performer for the Muppets, led the animation team for Wheatley and the other personality cores.

Pictures of Cave Johnson, based on the face of lead animator Bill Fletcher, appear throughout Portal 2. Though comparisons have been made between Johnson and Andrew Ryan, the wealthy industrialist who created the fictional underwater city of Rapture in BioShock, Wolpaw says the writers did not consider this character while creating Johnson.[84] The two robotic characters provide some amusing death scenes in the cooperative mode, such as struggling while being crushed by a lowering ceiling.[85] The artists thought the look of the robots would help tell the story, and the fact that they are holding hands emphasizes the cooperative mode. "Expressive noises" and mannerisms are used in place of distinguishable dialogue, and the robotic characters were designed as a double-act, similar to Laurel and Hardy.[86]

Voice cast

GLaDOS returns from Portal as a major character and the game's antagonist, and is voiced by Ellen McLain.[87] The writers found that they needed another character to play off Johnson, but did not want to hire another voice actor. Having already recruited McLain to play GLaDOS, they asked her to provide the voice for Caroline, Cave Johnson's assistant. Wheatley is voiced by Stephen Merchant; early demonstrations at trade shows used the voice of Valve animator Richard Lord.[88] [89] The writers wrote Wheatley's lines with Merchant in mind, citing his unique "vocal silhouette" and his ability to ad lib in a "frantic" manner. They had assumed that Merchant would be unavailable and contacted The IT Crowds writer Graham Linehan to try to get Richard Ayoade, but then discovered that Merchant was interested. Merchant spent around sixteen hours recording lines and was given freedom to improvise.

J. K. Simmons voices Cave Johnson, Aperture Science's founder and CEO.[90] Simmons's selection helped to solidify the character's development. The robots' voices were provided by Dee Bradley Baker, who had performed similar robotic voices for the Star Wars: The Clone Wars media.[91]

In the cooperative campaign, a separate story involves two robotic characters and GLaDOS. The designers initially planned to use Chell and a new human character called "Mel". GLaDOS' dialogue would play off the humans' "image issues", and this aspect was retained after the designers switched to using robots. GLaDOS seems troubled by the robots' cooperation, and tries to aggravate their relationship through psychological tactics, such as praising one robot over the other.[92] Valve initially considered having GLaDOS deliver separate lines to each player, but they found this to be a significant effort for minimal benefit. The writers also tried adding lines for GLaDOS that would encourage the players to compete against each other for rewards, such as meaningless points, but playtesters did not respond well. Faliszek said that in cooperative games, it can be difficult to deliver key dialogue or in-game events to players, who may not be looking in the right direction at the right time. Instead, using their experience from previous games, Faliszek and Wolpaw kept the story and key comedic lines short, and repeated them frequently.[93]

Music

See main article: Music of Portal 2.

Portal 2 contains both scored and procedurally generated music created by Valve's composer, Mike Morasky,[94] and two songs; "Want You Gone" recorded by Jonathan Coulton, used on the final credits of the single-player mode,[95] and "Exile Vilify" by the National, used in the background of one of the Rat Man's dens.[96] [97] The full soundtrack "Songs to Test By", containing most of the songs in the game, was released as three free downloads between May and September 2011,[98] and later in October 2012 as a retail Collector's Edition, including the soundtrack from Portal.[99]

Release

Announcement

In January 2008, Valve spokesman Doug Lombardi told Eurogamer, "There'll be more Portal, for sure",[100] and Portal designer Kim Swift confirmed that work on Portal 2 would begin the following month.[101] Swift said that a multiplayer mode in Portal was "technically possible",[102] but that it was "less fun than you'd think."[103]

Portal 2 was officially announced on March 5, 2010, via Game Informer. Events during the preceding week foreshadowed the announcement. On March 1, Valve released a patch for Portal that included a new achievement, "Transmission Received", requiring the player to manipulate in-game radios. This revealed new sound effects that became part of an alternate reality game (ARG).[104] Some of the new effects were of Morse code strings that suggested GLaDOS was rebooting, while others could be decoded as SSTV images from grainy Aperture Science videos. The images included hints to a BBS phone number that, when accessed, provided a large number of ASCII-based images relating to Portal and segments of Aperture Science documents.[105] Many of these ASCII pictures were later published in the Game Informer reveal of the title. New ASCII images continued to appear on the BBS after the official announcement. Background on the ARG is embedded in additional SSTV images found in a hidden room in Portal 2.[106] Valve's Adam Foster came up with the idea for the ARG, tying it to the Game Informer reveal, and he provided his own home phone line to run the BBS software on, as Valve's offices at the time were too modern to support the protocol. Foster estimates the ARG cost less than $100 to run.[107] [108]

A second Portal patch released on March 3 altered the game's ending sequence to show Chell being pulled back into the Aperture facility.[109] Gaming journalists speculated that an announcement of Portal 2 was imminent.[110] [111] On March 5, Game Informer announced Portal 2s official release on the cover of its April issue.[112] During the following week, Gabe Newell's speech accepting the Pioneer Award at the Game Developers Conference 2010 ended with a fake blue screen of death appearing on a screen behind him with a message purported to be from GLaDOS which hinted of further Portal 2 news at the upcoming E3 2010.[113] Two weeks before the E3, game journalists received a cryptic e-mail, worded as a press release from Aperture Science, hinting that the presentation on Portal 2 would be replaced with "a surprise" jointly hosted by Aperture Science and Valve. This prompted speculation that the surprise would be the announcement of ,[114] but Valve confirmed that it would be about Portal 2.[115] The surprise was the announcement of Portal 2 on PlayStation 3.[116]

Marketing and release

The March 2010 announcement said that Portal 2 would be released in late 2010.[117] [118] In August 2010, Valve postponed the release to February 2011, with a Steam release date of February 9,[119] to allow it to complete changes to the game's dialogue, to fill and connect about sixty test chambers, and to finish refinements to the gel gameplay mechanic. Valve announced a further delay in November 2010 and gave a release dates through retail channels in the week of April 18, 2011: April 20 in North America and April 22 in Europe and Australia.[120] Wolpaw stated that this eight-week delay was used to expand the game's content before reaching an internal milestone called a "content lock", after which no further content could be added. The remaining development work involved debugging. Newell allowed the delay considering the added benefits of the new content, because he thought the company would not lose any commercial opportunities because of it. On February 18, 2011, Newell confirmed that Valve had completed the development work on Portal 2 and that they were "waiting for final approvals and to get the discs manufactured".[121] Portal 2 was the first Valve product simultaneously released for Windows and Mac OS X computers through the Steam platform.[122] Retail copies for all platforms were distributed by Electronic Arts.[123]

On April 1, 2011, Valve released another alternate reality game called the Potato Sack.[124] Players tried to solve the multi-tiered puzzle, coordinating efforts through web sites and chat rooms. Some journalists believed the game denoted the release of Portal 2 on April 15, 2011, instead of the target release date of April 19, 2011.[125] [126] [127] [128] On April 15, the players discovered "GLaDOS@Home", a distributed computing spoof that encouraged participants to play the games to unlock Portal 2 early.[129] [130] Once the puzzles were solved, Portal 2 was unlocked on April 18 at around 21:30 PST, roughly ten hours before its planned release at 7:00 PST on the next day.[131] [132]

Valve created a series of television commercials to promote Portal 2. Valve had worked with advertising agencies in the past, but Lombardi found the advertisements created had shown little ingenuity. Valve's Doug Lombardi had been disappointed by "Copycat treatments. Cliché treatments. Treatments that reveal the agency wasn't listening in the initial meeting."[133] Using viewer feedback, Valve tailored the ad content until they were satisfied with the results. The ads took eight weeks to complete. Valve also developed online promotional videos featuring J. K. Simmons narrating as Cave Johnson, to promote new elements of Portal 2s gameplay. These videos were part of a larger effort described by Newell as a "documentary-style investment opportunity" for Portal 2.[134] An earlier video released on February 14, 2011, promoted the cooperative aspect of Portal 2 as a St. Valentine's gift and "lit up our preorders, our buzz, all the metrics that are used and collected by publishers and retailers". Lombardi said the videos "dwarfed the demos and interviews we did". Valve also offered Portal 2-themed merchandise, such as posters, drinking glasses, and T-shirts.[135]

Additional and downloadable content

Portal 2 includes bonus content, including four promotional videos, a Lab Rat comic, and an interactive trailer for the 2011 film Super 8, constructed with the Source game engine.[136] A feature called "Robot Enrichment" allows players to customize the cooperative campaign characters with new gestures and cosmetic items such as hats or flags. These can be earned in-game, traded with other players, or bought through microtransactions at the in-game store.[137]

Valve planned to produce downloadable content for Portal 2, beginning with "Peer Review", released on October 4, 2011.[138] [139] [140] [141] The content, which is free regardless of platform, includes a new cooperative campaign which extends the game's story. A week from the end of the cooperative campaign, GLaDOS prepares Atlas and P-Body to deal with an intruder within Aperture Science—the bird that had previously abducted her as a potato.[142] The content also adds a "challenge mode" similar to that in Portal—players try to complete specific chambers with the shortest time or fewest portals used, both which are tracked on overall and friends leaderboards. The challenge modes are available for both single-player and cooperative modes.[143] [144]

According to Faliszek, user-generated content for Portal 2 would be available on all platforms, but because of software dependencies, the necessary modding tools would only be available for Windows.[145] Valve released beta versions of the modding tools on May 10, 2011,[146] and supported a competition held by the community mapping website "Thinking with Portals" in May 2011, providing prizes for the most-selected maps.[147] The "Perpetual Testing Initiative", a free title update for the Windows and Mac versions, was released on May 8, 2012, and includes a new level editor and a means of obtaining and sharing user-created levels through the Steam Workshop.[148] [149] In November 2011, GTTV host Geoff Keighley said that Valve was developing a simplified level editing tool to allow novice editors to assemble test chambers without learning how to use the modified Valve Hammer Editor, and an in-game system to distribute user-created levels via the Steam Workshop.[150] This mapping system entered beta testing in March 2012.[151] [152] Within a few days of release, the Perpetual Testing Initiative add-on had been used to create 35,000 maps, with 1.3 million downloads of these maps through Steam.[153] Within a month, more than 150,000 user-created maps were available. The first release of the Perpetual Testing Initiative was limited to single-player maps, but a patch released in August 2012 enabled users to create new levels for cooperative play.[154]

, Valve supports fan reuse of Portal 2 content, offering selected assets and assistance. The Windows release of Bastion includes a weapon inspired by Portal 2s Conversion Gel and turrets; its developer Supergiant Games received writing assistance from Erik Wolpaw and McLain voiced new lines for the turrets.[155] An add-on scenario for Hidden Path Entertainment's tower defense game incorporates GLaDOS as an antagonist using new dialogue from McLain and assets from Portal 2.[156] Wolpaw and McLain also helped to create additional lines for GLaDOS for a custom single-player map commissioned by Gary Hudston, which he used to propose marriage to his fiancée, Stephanie.[157] [158] For a patch for Bethesda's that incorporated support for Steam Workshop content, Valve developed a free add-on module that introduced the Space Core as a non-player character that follows the player around.[159] Valve collaborated with Zen Studios to create a Portal 2-themed pinball table, among other Valve-themed tables, for their games Pinball FX 2 and Zen Pinball.[160] A Portal 2-themed set is available for Lego Dimensions by Warner Bros. Entertainment and Traveller's Tales; the game features additional stories written by Traveller's Tales with Valve's blessing set after the events of Portal 2, with Ellen McLain, Stephen Merchant and J.K. Simmons reprising their respective voice roles, as well as a new GLaDOS credits song written by Jonathan Coulton and performed by McLain.[161]

The Xbox 360 version was added to the backwards compatibility feature for the Xbox One in June 2016.[162] Alongside Portal, Portal 2 was released on the Nintendo Switch on June 28, 2022, as part of Portal: Companion Collection, developed by Valve and Nvidia Lightspeed Studios.[163] [164]

Use in education

Teach with Portals

Valve announced "Teach with Portals" and "Steam for Schools" in June 2012, initiatives that offered Portal 2 and Portal 2 Puzzle Maker for education. The educational version was free but only contained the single-player campaign and Puzzle Maker, and was only available for "Steam for Schools" users.[165]

Several critics wrote that Portal 2 excels in teaching the player to solve puzzles; in a review for the New York Times, Seth Schiesel wrote, "Somewhere out there an innovative, dynamic high school physics teacher will use Portal 2 as the linchpin of an entire series of lessons and will immediately become the most important science teacher those lucky students have ever had." Mathematics and science teachers wrote e-mails to Valve to tell them how they had included Portal in their classroom lessons as part of a project to promote the "gamification of learning".[166] Portal developers Joshua Weier and Yasser Malaika led a team within Valve to explore ways of using Portal 2 for education. This led to the development of Puzzle Maker, a level editor for Portal 2 players, built from the professional tools used to develop the game. Weier and Malaika did not want to design curricula themselves, but wanted to provide educators with tools for creating lesson plans. Hammer, the only tool freely available before the release of the built-in level editor in 2012, was difficult for educators to learn and understand. To address this, Valve gave Puzzle Maker an easy-to-learn interface and the ability to share puzzles and lesson plans. The tools were developed with a mathematics teacher and her students.[167] This formed the basis of a new "Steam for Schools" initiative launched in June 2012, under which educators could acquire Portal 2 and the Puzzle Maker software free of charge for classroom use through its "Teach with Portals" program.[168] In November 2012, Valve estimated that over 2,500 educators were using the "Teach with Portals" software within their lesson plans.

Research

In 2016, a study demonstrated that the Portal 2 Puzzle Maker can be used as a measure of fluid intelligence, similar to the (BOMAT).[169] Referred to as the Portal 2 Test Battery, the participants of the study completed a series of test chambers that progressively became harder.

Some studies have been conducted to determine if video games can have a significant impact on cognitive and non-cognitive skills.[170] [171] Through multiple pretests and post tests, a 2014 study has shown that Portal 2 can improve problem solving skills, spatial skills, and persistence for a designated task. The participants of this study did not need to have previous gaming experience. Another study done in 2017 found that commercial video games, like Portal 2, can also increase communication, adaptability and resourcefulness.

Hardware support

Razer Hydra

Sixense developed a version of Portal 2 to support the Razer Hydra motion controller for PC that allows enhanced control of some game elements.[172] Ten extra single-player levels are available as downloadable content for this version.[173] Writer Chet Faliszek said Sixense developers spent nine months to a year in-house at Valve preparing the native version.[174] A limited edition of the Razer Hydra comes bundled with a copy of Portal 2 for PC.[175]

PlayStation 3

The announcement that Portal 2 would be available on PlayStation 3 came as a surprise to the industry because Gabe Newell had criticized that console in the past, citing difficulties in the port of The Orange Box.[176] The move toward the PlayStation 3 was a result of growing frustration with Microsoft's policies for Xbox 360 content, including the difficulty of releasing patches and new content. Newell saw Sony's publication model as more open, allowing Steam-like features to be used on the console. Portal 2 was the first PlayStation 3 game to support a subset of features from Steamworks, including automatic updates, downloadable content, and community support.[177] The game supports cross-platform play between the PlayStation 3, Windows, and OS X versions.[178]

The Steam overlay shows the player's friends on both Steam and the PlayStation Network, with achievements rewarded for both Steam and PlayStation Network Trophies.[179] Players can unlock the game on Steam for Windows and OS X for no additional charge. The integration of Steamworks on the PlayStation 3 allows Valve to collect data about problems that arise after shipping and push appropriate updates. Valve has stated they do not plan on integrating other PlayStation 3 features, such as 3D television or PlayStation Move support.[180] [181] In June 2012, Valve announced that the PlayStation 3 version would be patched later that year to include support for the PlayStation Move motion controller, and to add the additional content that was previously provided with the Hydra, under the name Portal 2 In Motion.[182] The patch was released in early November 2012.[183] A free co-op add-on for the Portal 2 In Motion content was added in June 2013.[184] Valve said that despite additional support for PlayStation 3 over Xbox 360, the core game is the same on both platforms.[185]

SteamOS and Linux

As of February 2014, SteamOS, Valve's own Linux-based operating system, supports Portal 2 and its predecessor, as do most modern Debian-based Linux distributions on its services via the Steam client. Released as a Beta in early 2014 for Linux distributions, it holds all of the same traits as the other versions, retaining cross-platform play, split screen and fully native controller support.

Reception

Critical response

Portal 2 was a strong favorite of gaming journalists during closed-door previews at the E3 2010 convention. The Game Critics Awards, selected by journalists and critics, awarded Portal 2 the title of Best PC Game and Best Action/Adventure Game,[186] and nominated the game for Best of Show and Best Console Game.[187] IGN named Portal 2 as its Best of E3 for PC, Xbox 360, and PlayStation 3 systems and Best Puzzle Game, and nominated it for Best Overall Game.[188] GameSpy named Portal 2 the Best Overall Game and Best Puzzle Game of E3.[189] Portal 2 won the 2010 Spike Video Game Award for "Most Anticipated Game for 2011".[190]

Portal 2 received universal acclaim upon release.[191] [192] Several reviewers identified Portal 2 as an early contender for "Game of the Year",[193] [194] [195] [196] while others called it one of the best games of all time.[197] [198] [199] [200] Upon release, the game was widely considered to be as good as or better than the original. Eurogamers Oli Welsh said that the game avoids the normal pitfalls that developers introduce in sequels, stating that "Portal is perfect. Portal 2 is not. It's something better than that." Gus Mastrapa of The A.V. Club wrote that with Portal 2, Valve had alleviated any doubts that "Portal could be expanded into a big, narrative experience with all the bells and whistles of a mainstream gaming hit".[201] IGNs Charles Onyett wrote that the sequel "makes the original look like the prototype it was" by expanding the game in gameplay and story.[202]

Most reviewers praised the writing and voice acting in the game.[203] [204] [205] Dan Stapleton of PC Gamer was able to predict many of the plot twists within Portal 2 story but "still looked forward to witnessing exactly how the characters would react"; he praised the development of the characters, as "their charm makes what would otherwise be an empty and lifeless world feel boisterous and alive".[206] The characters were well received.[207] [208] Onyett wrote that Merchant's "obvious enthusiasm for the role benefits the game" and that the "consistently clever writing perfectly complements the onscreen action". Game Informer Adam Biessener considered Johnson to be an even better character than GLaDOS, and praised the game's "pitch-perfect delivery" and "brilliant comedic timing".[209] In contrast, Peter Bright of Ars Technica wrote that compared to the loneliness and despair he felt while playing the first game, the characters, Wheatley and GLaDOS, lost some of this feeling and "the inane babble served only to disrupt the mood".[210]

Portal 2s additional gameplay elements, like light bridges, lasers, and the gels, were praised as appropriate additions to the game. Reviewers were pleased with the difficulty of the puzzles throughout the game, which appeared visually complicated at first but had uncomplicated solutions.[211] [212] [213] [214] Times Evan Narcisse said that he feared the addition of new gameplay elements would "dilute the purity of the experience, but everything's still executed with Valve's high level of charm and panache." Tom Hoggins of The Telegraph praised the manner with which these elements were introduced through a "brilliant learning curve of direction, rather than instruction", and considered it a "design ethos that is supremely generous, but dealt with marvellous economy". Chris Kohler of Wired wrote that the game's puzzles "never require excessively complicated solutions", and that much of the puzzle solving is "filled with moments that will have you slapping your forehead and thinking, 'Oh my God, I'm such an idiotwhy didn't I see that before?.[215] Stapleton was not as pleased with the gel additions as with the other new mechanics, calling it "difficult to control". He felt that they have "only a couple of uses at most". Bright felt that Portal 2 was easier than its predecessor, in part that he felt much of the game was effectively tutorials for the new gameplay additions, requiring "careful use of the tools provided", leaving him with the impression that "the game was on rails".

The cooperative puzzle solving aspect was highlighted as a valuable addition to the game. Welsh called the cooperative mode "one of the most satisfying and genuinely collaborative gaming experiences you can have with a friend". Onyett wrote, "Valve knows how a good co-operative mode requires a game design that doesn't simply encourage but requires you to work together. In Portal 2, communication is vital to success". Several reviewers praised the non-verbal cues that players could initiate to work with their partners. Portal 2 was praised for the amount of detail in its design, sound, and music. Nelson credited the "sheer amount of detail" put into the game's world, and wrote, "it all feels very real and natural with brief moments where you're simply sucked into this world". Onyett was impressed with the amount of visual details and capabilities Valve achieved from their Source game engine and that the added details and animations of the levels "consistently serv[ed] not only to entertain the eye but to expand our understanding of the game's characters". Hoggins wrote that the game's world reacted to the player-character Chell's presence "in a startlingly organic way", and praised Valve's design as "an achievement of world-building that compares favourably with BioShock underwater city of Rapture".

Some reviewers said that the second act of the game, taking place in the less-structured portion of the old Aperture facilities, may be confusing to some players. Young wrote that in the second act, the game "cranks up the difficulty level at a speed that may dishearten casual gamers", and said that particularly when traveling between chambers, he had "absolutely no idea where I was supposed to head next". Kohler wrote that while the player can explore the abandoned areas of Aperture, "none of it ever does anythingit's just a lot of sterile, duplicated, non-interactive environments". Watters wrote that the loading time between the game's levels, in contrast to earlier Valve games, are "long enough to make you take notice and wish they were shorter". Watters also said that it was unfortunate that the game lacks "stand-alone test chambers and leaderboards ... but even so, Portal 2 is not light on content" without these. Welsh said that the attempt to recapture the spirit of the song "Still Alive" at the end credits of Portal 2 "was a mistake". Video game critic Ben "Yahtzee" Croshaw wrote in his Extra Punctuation column that, while Portal 2 was a "very good game", it unnecessarily retconned portions of the original game's story, and did not really further the game's concept. However, this criticism was directed solely at the campaign, and he stated that he found the game's co-op to be "much more appealing and much more within the spirit of the original".[216]

On April 20, 2011, it was reported that customers had launched a protest against perceived shortcomings of Portal 2.[217] [218] Users complained that the game was too shortsome saying that it is only four hours long, about the existence of paid, downloadable content for some versions at launch, and that the Windows and OS X versions were ports of the console version. Other journalists countered that the quality of the graphics on the Windows and Mac versions did not suggest a simple console port. Stephen Totilo of Kotaku wrote that the game lasted nine hours and that the downloadable content consisted purely of cosmetic add-ons.[219] Some journalists said that the minimal impact of The Potato Sack alternative reality game on the early release of Portal 2 may be influencing the user scores.[220] [221]

Awards

Portal 2 won the title of "Ultimate Game of the Year" at the 2011 Golden Joystick Awards,[222] and ranked second place on Time's "Top 10 Video Games of 2011".[223] Gamasutra, IGN, Eurogamer, Kotaku, the Associated Press, and The Mirror listed Portal 2 as their top video game of 2011.[224] [225] [226] [227] [228] [229] The game received twelve nominations including "Game of the Year" for the 2011 Spike Video Game Awards, where it was the most-nominated title,[230] and won for "Best PC Game", "Best Male Performance" for Stephen Merchant, "Best Female Performance" for Ellen McLain, "Best Downloadable Content", and "Best Multiplayer Game".[231] The title was nominated for five Game Developers Choice Awards for 2012, including "Game of the Year",[232] and won in the "Best Narrative", "Best Audio" and "Best Game Design" categories.[233] It was nominated for ten Interactive Achievement Awards from the Academy of Interactive Arts & Sciences, including "Game of the Year"; it was ultimately awarded with outstanding achievements in "Connectivity", "Original Music Composition", and "Character Performance" for Wheatley.[234] [235] Portal 2 was nominated for six BAFTA Video Games Award categories,[236] and won for "Best Game", "Best Story" and "Best Design".[237] The Game Audio Network Guild awarded the game for "Best Dialog", "Best Interactive Score", and "Best Original Vocal – Pop" (for "Want You Gone").[238] In the inaugural New York Videogame Critics Circle Awards, Portal 2 was given the top honors for best writing and best acting.[239] The Perpetual Testing Initiative add-on was awarded the 2012 Golden Joystick for "Best Use of DLC".[240] Portal 2 was nominated for the 2016 Steam Awards by the Steam community[241] and won the award for “Villain Most In Need Of A Hug”.[242]

Awards and nominations for Portal 2
Year Award Category Result
2010Game Critics AwardsBest PC Game[243]
Best Action/Adventure Game
2011Golden Joystick AwardsUltimate Game of the Year
Spike Video Game AwardsGame of the Year[244]
Best Xbox 360 Game
Best PC Game
Best Multiplayer
Best Song in a Game ("Exile Vilify")
Best Song in a Game ("Want You Gone")
Best Original Score
Best Performance by a Human Male (Stephen Merchant)
Best Performance by a Human Female (Ellen McLain)
Character of the Year (Wheatley)
Best DLC (Peer Review)
16th Satellite AwardsOutstanding Action/Adventure Game[245]
2012Game Developers Choice AwardsGame of the Year
Best Narrative
Best Audio
Best Game Design
Innovation
15th Annual Interactive Achievement AwardsGame of the Year[246]
Outstanding Achievement in Game Direction
Outstanding Achievement in Gameplay Engineering
Outstanding Achievement in Art Direction
Outstanding Achievement in Connectivity
Adventure Game of the Year
Outstanding Innovation in Gaming
Outstanding Achievement in Original Music Composition
Outstanding Achievement in Character Performance (Wheatley)
Outstanding Achievement in Story
Game Audio Network Guild AwardsBest Interactive Score
Best Original Vocal Song – Pop ("Want You Gone")
Best Dialog
8th British Academy Games AwardsBest Game
Design
Action
Performer (Stephen Merchant)
Story
GAME Award of 2011
Golden Joystick AwardsDLC of the Year (Perpetual Testing Initiative)[247]

Sales

Based on sales data from Amazon.com, Portal 2 was the best-selling game in the United States in the first week of its release,[248] but was overtaken by Mortal Kombat in its second week.[249] According to NPD Group, Portal 2 was the second-best selling game in the U.S. in April 2011,[250] at 637,000 copies, and the fourth-best selling in May.[251] However, NPD does not include sales on Valve's Steam platform.[252] Portal 2 was the best selling game in the U.K. in the first week of its release, the first number-one for a Valve game.[253] It retained the top spot during its second week.[254]

Portal 2 was released a few days before the PlayStation Network outage. Gamasutra analyst Matt Matthews said that, based on NPD Group data, the outage "did not seriously affect retail sales of software",[255] but some developers did report drops in sales.[256] ShopToNews analyst Joe Anderson expected that the effect of the outage on UK sales of Portal 2 would be mild.[257] On June 22, Newell announced that Portal 2 had sold 3 million copies.[258], Electronic Arts stated that more than 2 million copies of Portal 2 have been sold by retailers worldwide.[259] In an August 2011 interview, Newell stated that "Portal 2 did better on the PC than it did on the consoles".[260] Upon release of the Perpetual Testing Initiative in May 2012, Newell stated that Portal 2 had shipped more than 4 million units, with the personal computer versions outselling the console versions. Overall, Portal and Portal 2 had together shipped more than 8 million units.[261]

Mods

See also: List of Source mods. In addition to player-created levels, there have been complete mods of Portal 2 created by users. Several notable mods are self-contained playable campaigns in their own right, and have earned critical praise.[262]

Portal Stories: Mel

See main article: Portal Stories: Mel. Portal Stories: Mel is a single-player mod of Portal 2 developed by Prism Studios, a group made up of eight fans of the Portal series. The mod was released on June 25, 2015, for Windows, OS X and Linux systems, available freely to people that own Portal 2 on Steam.[263]

Aperture Tag: The Paint Gun Testing Initiative

See main article: Aperture Tag: The Paint Gun Testing Initiative. Aperture Tag: The Paint Gun Testing Initiative is a single-player modification of Portal 2 developed by "The Aperture Tag Team" released in 2014. The mod replaces the portal gun with a gun that can shoot the various gels (mimicking how Tag: the Power of Paint worked) to otherwise various portal-based puzzles.[264]

Thinking with Time Machine

See main article: Thinking with Time Machine. Thinking with Time Machine is a single player mod for Portal 2 created by Ruslan Rybka and released in 2014, which gives the player the ability to record actions that can be played back by a duplicate of the player-character, including the use of a second set of portals.[265] [266]

Portal Reloaded

See main article: Portal Reloaded. Portal Reloaded is a single-player mod for Portal 2 created by Jannis Brinkmann and was released on April 19, 2021, exactly 10 years after the release of Portal 2.[267] The mod gives players the ability to fire a third portal, the "time portal", to travel between the present and future versions of each test chamber.[268]

Portal Revolution

See main article: Portal Revolution. Portal Revolution is a single-player mod for Portal 2 developed by Second Face Software, released on January 6, 2024.[269]

External links

Notes and References

  1. Web site: Portal 2 influenced by Left 4 Dead – Valve . . February 11, 2011 . February 11, 2011 . live . https://web.archive.org/web/20110213144938/http://www.computerandvideogames.com/288474/news/portal-2-influenced-by-left-4-dead-valve/ . February 13, 2011.
  2. News: Portal 2 developer interview: Chet Falisek and Erik Wolpaw . . March 4, 2011 . March 4, 2011 . David . Brown . live . https://web.archive.org/web/20110309212313/http://www.telegraph.co.uk/technology/video-games/8359173/Portal-2-developer-interview-Chet-Falisek-and-Erik-Wolpaw.html . March 9, 2011.
  3. Web site: Two more Portal 2 E3 gameplay videos . Mike . Jackson . June 29, 2010 . July 1, 2010 . Computer and Video Games.
  4. Web site: Portal 2 Multiplayer Preview . Arthur . Gies . September 6, 2010 . September 6, 2010 . IGN . January 25, 2012 . dead . https://web.archive.org/web/20120125084337/http://xbox360.ign.com/articles/111/1118382p1.html.
  5. Web site: 12 new high-res Portal 2 screenshots confirm Companion Cube comeback . Tom . Senior . February 28, 2011 . March 1, 2011 . . November 24, 2011 . https://web.archive.org/web/20111124175600/http://www.pcgamer.com/2011/03/01/12-new-high-res-portal-2-screenshots-confirm-companion-cube-comeback.
  6. Web site: Portal 2 E3 Demo Videos Part 4 and Part 5 Incite Anger . Xas . de Matos . June 30, 2010 . July 1, 2010 . . live . https://web.archive.org/web/20110614155855/http://www.shacknews.com/article/64559/portal-2-e3-demo-videos . June 14, 2011.
  7. Book: Keighley, Geoff . B004XMZZKQ . The Final Hours of Portal 2 . 2011. Also available as iPad or Steam application.
  8. Web site: Behold Some Amazing 'Portal 2' Cube Tricks . Russ . Frushtick . April 29, 2011 . April 29, 2011 . MTV . dead . https://web.archive.org/web/20110501011034/http://multiplayerblog.mtv.com/2011/04/29/behold-some-amazing-portal-2-cube-tricks/ . May 1, 2011.
  9. Web site: Portal 2 E3 demo: final parts 6 and 7 out now . Stephany . Nunneley . July 1, 2010 . July 1, 2010 . . live . https://web.archive.org/web/20100704114551/http://www.vg247.com/2010/07/01/portal-2-e3-demo-final-parts-6-7-out-now/ . July 4, 2010.
  10. News: Portal 2 Review . April 19, 2011 . April 19, 2011 . . Tom . Hoggins . live . https://web.archive.org/web/20110419151249/http://www.telegraph.co.uk/technology/video-games/8458871/Portal-2-review.html . April 19, 2011.
  11. Web site: Portal 2 update adds Big Picture split-screen . Brenna . Hillier . November 21, 2012 . November 21, 2012 . . live . https://web.archive.org/web/20121128191017/http://www.vg247.com/2012/11/21/portal-2-update-adds-big-picture-split-screen/ . November 28, 2012.
  12. Gonzalez . Annette . March 5, 2010 . Portal 2 For Two . dead . . https://web.archive.org/web/20100307064210/http://gameinformer.com/b/news/archive/2010/03/05/Portal-2-For-Two.aspx . March 7, 2010 . March 5, 2010.
  13. News: 'Portal 2': A closer look at co-operative play . Brett . Molina . April 19, 2011 . April 20, 2011 . . https://web.archive.org/web/20110426065822/http://content.usatoday.com/communities/gamehunters/post/2011/04/portal-2-a-closer-look-at-cooperative-play/1 . April 26, 2011 . live.
  14. Web site: E3 2010: Portal 2 Preview . Damien . Hatfield . June 16, 2010 . June 16, 2010 . IGN . live . https://web.archive.org/web/20100618200728/http://ps3.ign.com/articles/109/1098375p1.html . June 18, 2010.
  15. Web site: Interview: Valve on their insane Portal 2 ideas . Tom . Francis . . September 10, 2010 . September 10, 2010 . live . https://web.archive.org/web/20120426004729/http://www.pcgamer.com/2010/09/10/interview-valve-on-their-insane-portal-2-ideas/ . April 26, 2012.
  16. Web site: Rewarding The Players: Valve On Portal 2 . Brandon . Sheffield . November 8, 2010 . November 10, 2010 . . dead . https://web.archive.org/web/20101110010451/http://www.gamasutra.com/view/feature/6198/rewarding_the_players_valve_on_.php . November 10, 2010.
  17. Web site: Dear Valve, 'Portal 2' better be awesome. But no pressure. . Winda . Benedetti . September 8, 2010 . September 8, 2010 . . dead . https://web.archive.org/web/20100910233151/http://technolog.msnbc.msn.com/_news/2010/09/08/5068274-dear-valve-portal-2-better-be-awesome-but-no-pressure . September 10, 2010.
  18. Web site: Valve Plans To Bridge Portal And Portal 2 With A Surprise, Keep Gordon Freeman Out Of It . Stephan . Totilo . March 11, 2011 . March 11, 2011 . Kotaku . live . https://web.archive.org/web/20121018082803/http://kotaku.com/5781121/valve-plans-to-bridge-portal-and-portal-2-with-a-surprise-keep-gordon-freeman-out-of-it . October 18, 2012.
  19. Web site: How Valve Opened Up Portal 2: Interview . Wesley . Yin-Poole . March 14, 2011 . July 25, 2011 . Eurogamer . live . https://web.archive.org/web/20121016002502/http://www.eurogamer.net/articles/2011-03-10-portal-2-how-valve-opened-up-portal-2 . October 16, 2012.
  20. Web site: Q&A with Portal 2 writers Erik Wolpaw and Jay Pinkerton . Matt . Braga . April 19, 2011 . April 20, 2011 . . live . https://archive.today/20130104035703/http://arts.nationalpost.com/2011/04/19/qa-with-portal-2-writers-erik-wolpaw-and-jay-pinkerton/ . January 4, 2013.
  21. Web site: Jumping into Portal 2 . Charles . Onyett . January 14, 2011 . January 14, 2011 . IGN . live . https://web.archive.org/web/20110117112822/http://uk.xbox360.ign.com/articles/114/1144048p1.html . January 17, 2011.
  22. Web site: The Very Beginning Of 'Portal 2' Revealed . Russ . Frushtick . February 17, 2011 . February 17, 2011 . MTV . dead . https://web.archive.org/web/20110221043628/http://multiplayerblog.mtv.com/2011/02/17/portal-2 . February 21, 2011.
  23. Web site: Portal 2 given story, British friend, deeper gameplay . Ben . Kuchera . June 16, 2010 . June 16, 2010 . Ars Technica . live . https://web.archive.org/web/20100619071515/http://arstechnica.com/gaming/news/2010/06/portal-2-given-story-british-friend-deeper-game-play.ars . June 19, 2010.
  24. News: E3 2010: Portal 2 preview . Keith . Stewart . June 18, 2010 . June 21, 2010 . . live . https://web.archive.org/web/20131203195038/http://www.theguardian.com/technology/gamesblog/2010/jun/18/e3-2010-portal-2 . December 3, 2013.
  25. News: Top five GLaDOS insults in Portal 2 . Chad . Sapieha . April 20, 2011 . April 20, 2011 . . live . https://web.archive.org/web/20110423032735/http://www.theglobeandmail.com/news/technology/video-games/controller-freak/top-five-glados-insults-in-portal-2/article1992165/ . April 23, 2011.
  26. Web site: Portal 2 releases – Unreview, uninterview, unstudiovisit . Justin . Krantzl . April 19, 2011 . April 20, 2011 . . live . https://web.archive.org/web/20110420083843/http://www.vg247.com/2011/04/19/portal-2-releases-unreview-uninterview-unstudiovisit/ . April 20, 2011.
  27. Portal 2 . . Valve . April 19, 2011 . . Chapter 7: The Reunion.
  28. [Valve Corporation|Valve]
  29. Web site: Plunkett . Luke . May 2, 2011 . Proof That Nolan North Is In Too Many Damn Video Games . live . https://web.archive.org/web/20120217032120/http://www.kotaku.com.au/2011/05/proof-that-nolan-north-is-in-too-many-damn-video-games/ . February 17, 2012 . May 14, 2011 . Kotaku.
  30. Web site: Curtis . Tom . March 8, 2012 . GDC 2012: Portal 2: Making a sequel to a 'perfect' game . live . https://web.archive.org/web/20160924052953/http://www.gamasutra.com/view/news/164930/GDC_2012_Portal_2_Making_a_sequel_to_a_perfect_game.php . September 24, 2016 . March 8, 2012 . Gamasutra.
  31. Portal 2. Valve. Valve. April 19, 2011. PC/Mac/PlayStation 3/Xbox 360. Chapter 9: The Part Where He Kills You.
  32. Web site: Funny People: Erik Wolpaw, Portal 2 head writer . Anthony John . Agnello . July 10, 2012 . July 10, 2012 . . live . https://web.archive.org/web/20120713003918/http://gameological.com/2012/07/interview-erik-wolpaw-portal-2-head-writer/ . July 13, 2012.
  33. Web site: Valve drop Portal 2 co-op details . March 31, 2011 . March 31, 2011 . . https://web.archive.org/web/20110405132119/http://www.computerandvideogames.com/296191/news/valve-drop-portal-2-co-op-details/ . April 5, 2011.
  34. Portal 2 . . Valve . April 19, 2011 . PC/Mac/PlayStation 3/Xbox 360.
  35. Web site: Video: Making Portal 2, the sequel to a game that didn't need one . . July 17, 2012 . July 17, 2012 . live . https://web.archive.org/web/20120720012931/http://www.gamasutra.com/view/news/173723/Video_Making_Portal_2_the_sequel_to_a_game_that_didnt_need_one.php . July 20, 2012.
  36. Web site: Synthesizing Portal 2 . Chris . Remo . September 20, 2010 . September 20, 2010 . . dead . https://web.archive.org/web/20120119070426/http://www.gamasutra.com/view/feature/6141/synthesizing_portal_2.php . January 19, 2012.
  37. Web site: Portal 2: A Student Video Game Project, All Grown Up . Travis . Larchuk . April 19, 2011 . June 18, 2011 . . live . https://web.archive.org/web/20110625113250/http://www.npr.org/2011/04/19/135511250/portal-2-a-student-video-game-project-all-grown-up?ps=cprs . June 25, 2011.
  38. Web site: Valve on Portal 2 . May 10, 2011 . May 11, 2011 . . Rob . Crossley . dead . https://web.archive.org/web/20110516222025/http://www.develop-online.net/features/1189/VALVE-ON-PORTAL-2 . May 16, 2011.
  39. Web site: Portal Designer Kim Swift Leaves Valve For Dark Void Dev . Remo . Chris . December 7, 2009 . . July 9, 2010 . dead . https://web.archive.org/web/20100510011636/http://www.gamasutra.com/view/news/26404/Portal_Designer_Kim_Swift_Leaves_Valve_For_Dark_Void_Dev.php . May 10, 2010.
  40. Web site: Gabe Newell: Portal 2 is "The Best Game We've Ever Done" . Matt . Leone . March 11, 2010 . March 12, 2010 . . dead . https://web.archive.org/web/20120203185706/http://www.1up.com/news/gabe-newell-portal-2-game . February 3, 2012.
  41. Web site: The Final Hours of Portal 2 blog is live . Geoff . Keighley . June 18, 2011 . live . https://web.archive.org/web/20110529183746/http://thefinalhoursofportal2.com/blog/finalhours/welcometotheblog/ . May 29, 2011.
  42. Web site: Valve's not "giving up on single-player at all," plans to add more social features to titles . . May 7, 2011 . Stephany . Nunneley . live . https://web.archive.org/web/20140420030651/http://www.vg247.com/2011/05/07/valves-not-giving-up-on-single-player-at-all-plans-to-add-more-social-features-to-titles/ . April 20, 2014.
  43. Web site: Portal 2 Wasn't Going to Include Portals, According To New iPad App . Stephen . Tolito . April 21, 2011 . May 6, 2011 . Kotaku . live . https://web.archive.org/web/20101106085901/http://kotaku.com/#!5794465/portal-2-wasnt-going-to-include-portals-according-to-new-ipad-app . November 6, 2010.
  44. Web site: Valve's Wolpaw Offers Behind-The-Scenes Peek Into Portal 2 . Alexander . Leigh . May 6, 2011 . . https://web.archive.org/web/20110508191011/http://www.gamasutra.com/view/news/34406/Valves_Wolpaw_Offers_BehindTheScenes_Peek_Into_Portal_2.php . May 8, 2011 . live . May 6, 2011.
  45. Web site: F-Stop, the secret mechanic of Valve's unreleased Portal prequel, has finally been revealed . Craig . Pearson . January 2, 2020 . January 2, 2019 . . January 2, 2020 . https://web.archive.org/web/20200102145849/https://www.rockpapershotgun.com/2020/01/02/f-stop-the-secret-mechanic-of-valves-unreleased-portal-prequel-has-finally-been-revealed/ . live .
  46. Web site: A New Documentary Series is Exploring Valve's Original Pitch for Portal 2 . Mathew . Olsen . January 2, 2020 . January 2, 2020 . . January 2, 2020 . https://web.archive.org/web/20200102194904/https://www.usgamer.net/articles/a-new-documentary-series-is-exploring-valves-original-pitch-for-portal-2 . live .
  47. Thinking With Portals: Making a Portal 2 Test Chamber . . March 17, 2010 . March 17, 2010 . Ben . Reeves . dead . https://web.archive.org/web/20111223151107/http://www.gameinformer.com/b/features/archive/2010/03/17/thinking-with-portals-making-a-test-chamber.aspx . December 23, 2011.
  48. Portal 2 . Valve . April 19, 2011 . Windows . Chapter 1 . Intro 4 developer commentary . Mike Morasky and Kelly Thornton.
  49. News: Specially Level With Me, Adam Foster – Part Two . Robert . Yang . December 6, 2012 . December 6, 2012 . . dead . https://web.archive.org/web/20121209012108/http://www.rockpapershotgun.com/2012/12/06/specially-level-with-me-adam-foster-part-two/ . December 9, 2012.
  50. News: Valve On Portal 2: Spoiler Interview Part One . John . Walker . April 27, 2011 . April 27, 2011 . . live . https://web.archive.org/web/20110429232357/http://www.rockpapershotgun.com/2011/04/27/valve-on-portal-2-spoiler-interview-part-one/ . April 29, 2011.
  51. News: Valve on Portal 2: Spoiler Interview Part Two . John . Walker . April 28, 2011 . April 28, 2011 . . live . https://web.archive.org/web/20110430003650/http://www.rockpapershotgun.com/2011/04/28/valve-on-portal-2-spoiler-interview-part-two/ . April 30, 2011.
  52. Web site: Valve Hires DigiPen Team; Seemingly for Portal 2 . Brian . Leahy . March 8, 2010 . March 8, 2010 . . live . https://web.archive.org/web/20110518161744/http://www.shacknews.com/article/62689/valve-hires-digipen-team-seemingly . May 18, 2011.
  53. From Narbacular Drop To Portal . Dan . Ryckert . March 8, 2010 . March 8, 2010 . . dead . https://web.archive.org/web/20100310204433/http://gameinformer.com/b/features/archive/2010/03/08/narbacular-drop.aspx . March 10, 2010.
  54. Web site: E3 2010: Portal 2 Preview . Jake . Gaskill . June 18, 2010 . June 19, 2010 . . dead . https://archive.today/20120707160044/http://e3.g4tv.com/games/xbox-360/63787/portal-2/articles/71011/E3-2010-Portal-2-Preview/ . July 7, 2012.
  55. News: Five things you didn't know about 'Portal 2' . Marc . Saltzmann . April 14, 2011 . April 14, 2011 . . https://archive.today/20130105064249/http://content.usatoday.com/communities/gamehunters/post/2011/04/five-things-you-didnt-know-about-portal-2/1 . January 5, 2013 . live.
  56. Water Flow in Portal 2 . Alex . Vlachos . July 28, 2010 . August 10, 2010 . SigGraph 2010 . dead . https://web.archive.org/web/20100820182322/http://www.valvesoftware.com/publications/2010/siggraph2010_vlachos_waterflow.pdf . August 20, 2010.
  57. News: Portal 2: A Look at the Hotly Anticipated Videogame . Kao . Ryan . September 4, 2010 . . September 4, 2010 . https://web.archive.org/web/20100906103452/http://blogs.wsj.com/speakeasy/2010/09/04/portal-2-a-look-at-the-hotly-anticipated-videogame/ . September 6, 2010 . live.
  58. Web site: The Portal 2 that never was . Welsh . Oli . . March 8, 2012 . October 8, 2013 . live . https://web.archive.org/web/20130928160750/http://www.eurogamer.net/articles/2012-03-08-the-portal-2-that-never-was . September 28, 2013.
  59. Web site: Valve Cut Portal 2 Competitive Multiplayer . Steve . Watts . August 26, 2010 . August 26, 2010 . . dead . https://web.archive.org/web/20120518085218/http://www.1up.com/news/valve-cut-portal-2-competitive . May 18, 2012.
  60. News: Portal 2: "Let's make Caddyshack" . . April 25, 2011 . April 25, 2011 . Oli . Welch . Eurogamer.net . live . https://web.archive.org/web/20110428041701/http://www.eurogamer.net/articles/2011-04-24-portal-2-lets-make-caddyshack-interview . April 28, 2011.
  61. News: 13,000 Lines of Chat in Portal 2 . Alec . Meer . January 14, 2011 . January 14, 2011 . . live . https://web.archive.org/web/20110116034314/http://www.rockpapershotgun.com/2011/01/14/13000-lines-of-chat-in-portal-2/ . January 16, 2011.
  62. Web site: Interview: Portal 2 project lead Joshua Weier and writer Erik Wolpaw . Xav . de Matos . March 21, 2011 . March 21, 2011 . . live . https://web.archive.org/web/20110323094549/http://www.shacknews.com/article/67873/interview-portal-2-project-lead . March 23, 2011.
  63. Web site: Casting call reveals Portal 2 details . Kotaku . July 18, 2008 . Luke . Plunkett . June 10, 2008 . live . https://web.archive.org/web/20080624084216/http://kotaku.com/5014851/rumor-casting-call-reveals-portal-2-details . June 24, 2008.
  64. Web site: More details on Portal 2's bad guy . Kotaku . July 18, 2008 . Luke . Plunkett . June 10, 2008 . live . https://web.archive.org/web/20080624084305/http://kotaku.com/5015122/more-details-on-portal-2s-bad-guy . June 24, 2008.
  65. Web site: The Portal 2 that never was . Oli . Welsh . March 8, 2012 . March 8, 2012 . . live . https://web.archive.org/web/20120310152808/http://www.eurogamer.net/articles/2012-03-08-the-portal-2-that-never-was . March 10, 2012.
  66. Chell Almost Married A Turret In Portal 2 . . Tim . Turi . September 1, 2012 . September 6, 2012 . dead . https://web.archive.org/web/20120905034907/http://www.gameinformer.com/b/news/archive/2012/09/01/chell-almost-married-a-turret-in-portal-2.aspx . September 5, 2012.
  67. Web site: Portal 2's Wolpaw: 'I Do Not Want To Resurrect A Three-Year-Old Meme' . Chris . Remo . June 18, 2010 . June 18, 2010 . . dead . https://web.archive.org/web/20100620021958/http://www.gamasutra.com/view/news/29015/Portal_2s_Wolpaw_I_Do_Not_Want_To_Resurrect_A_ThreeYearOld_Meme.php . June 20, 2010.
  68. Web site: Portal 2's Writer Didn't Try to Reinvent the Cake . Susan . Arendt . March 14, 2011 . March 14, 2011 . . live . https://web.archive.org/web/20110316031421/http://www.escapistmagazine.com/news/view/108449-PAX-East-2011-Portal-2s-Writer-Didnt-Try-to-Reinvent-the-Cake . March 16, 2011.
  69. Web site: Impressions: Skyrim's Portal 2 Mod . Nathan . Grayson . February 7, 2012 . February 7, 2012 . . live . https://web.archive.org/web/20120209085434/http://pc.gamespy.com/pc/elder-scrolls-v/1218191p1.html . February 9, 2012.
  70. Web site: NASA launches Portal 2 character into orbit . . July 22, 2012 . July 22, 2012 . Tom . Phillips . live . https://web.archive.org/web/20120725020417/http://www.eurogamer.net/articles/2012-07-23-nasa-to-fire-portal-2-character-into-orbit . July 25, 2012.
  71. Web site: Portal 2: Test Subjects . Dan . Griliopoulos . March 28, 2011 . March 28, 2011 . IGN . dead . https://web.archive.org/web/20110829095625/http://pc.ign.com/articles/115/1157988p1.html . August 29, 2011.
  72. Web site: Portal 2: Lab Rat – Part 1 . Joey . Esposito . April 8, 2011 . April 11, 2011 . . live . https://web.archive.org/web/20110410020811/http://comics.ign.com/articles/116/1160605p1.html . April 10, 2011.
  73. Web site: 10 incredible Portal 2 secrets you might have missed . Richard . McCormick . July 17, 2011 . July 17, 2011 . . live . https://web.archive.org/web/20110720003634/http://www.computerandvideogames.com/311288/portal-2-10-incredible-secrets-you-might-have-missed/?cid=OTC-RSS&attr=CVG-General-RSS . July 20, 2011.
  74. Web site: Portal 2 Easter Egg Video: Finding Borealis . Stephen . Johnson . April 20, 2011 . April 20, 2011 . . dead . https://web.archive.org/web/20121017171904/http://www.g4tv.com/thefeed/blog/post/712006/portal-2-easter-egg-video-finding-borealis/ . October 17, 2012.
  75. Web site: Wolpaw: Players Don't Care About Portal's Chell . Brenna . Hillier . March 14, 2011 . June 20, 2011 . VG24/7 . live . https://web.archive.org/web/20110717195941/http://www.vg247.com/2011/03/14/wolpaw-players-dont-care-about-portals-chell/ . July 17, 2011.
  76. Redesigning Portal: Valve's Artist Speaks . Ben . Reeves . March 22, 2010 . March 22, 2010 . . dead . https://archive.today/20130102205349/http://www.gameinformer.com/b/news/archive/2010/03/22/redesigning-chell-valve-s-artist-speaks.aspx . January 2, 2013.
  77. Web site: The New Look For Portal 2's Heroine Explained . Michael . McWheator . February 23, 2011 . February 23, 2011 . Kotaku . live . https://web.archive.org/web/20110708224535/http://kotaku.com/5767246/the-new-look-for-portal-2s-heroine-explained . July 8, 2011.
  78. Web site: Meet the real-life Chell from Portal 2 . . March 29, 2011 . April 20, 2011 . live . https://web.archive.org/web/20110405131959/http://www.computerandvideogames.com/295904/blog/meet-the-real-life-chell-from-portal-2/ . April 5, 2011.
  79. Web site: Valve: Portal's Chell is Silent Because It's Funnier . Tom . Goldman . May 7, 2011 . May 22, 2011 . . live . https://web.archive.org/web/20110511090046/http://www.escapistmagazine.com/news/view/109845-Valve-Portals-Chell-is-Silent-Because-Its-Funnier . May 11, 2011.
  80. Web site: Writing Valve's silent protagonists . Brendan . Sinclair . October 12, 2011 . October 12, 2011 . . live . https://web.archive.org/web/20131104131011/http://www.gamespot.com/articles/writing-valves-silent-protagonists/1100-6339609/ . November 4, 2013.
  81. Portal 2 . Valve . April 19, 2011 . Windows . Chapter 3 . Bridge the Gap developer commentary . Doug Word.
  82. Web site: 'So, Here's Something Pretentious!' – Anecdotes and Thoughts from Erik Wolpaw's Portal 2 Discussion at the NYU Game Center . Alex . Navarro . . May 6, 2011 . May 6, 2011 . live . https://web.archive.org/web/20110509031911/http://www.giantbomb.com/news/so-heres-something-pretentious-anecdotes-and-thoughts-from-erik-wolpaws-portal-2-discussion-at-the-nyu-game-center/3148/ . May 9, 2011.
  83. Web site: Being Nathan Drake – Interview . Johnny . Minkley . May 9, 2011 . May 9, 2011 . . live . https://web.archive.org/web/20110512135717/http://www.eurogamer.net/articles/2011-05-09-being-nathan-drake-interview . May 12, 2011.
  84. Web site: Erik Wolpaw on Portal 2's ending: "the (spoiler) is probably lurking out there somewhere" . Rich . Stanton . April 26, 2011 . April 26, 2011 . . live . https://web.archive.org/web/20110430071821/http://www.pcgamer.com/2011/04/26/erik-wolpaw-on-portal-2s-ending-the-spoiler-is-probably-lurking-out-there-somewhere . April 30, 2011.
  85. Web site: Preview: Portal 2 (co-op) . Christopher . Grant . June 21, 2010 . June 21, 2010 . . dead . https://web.archive.org/web/20120118040431/http://www.joystiq.com/2010/06/21/preview-portal-2-co-op/ . January 18, 2012.
  86. Web site: Portal 2 Hands-on . Christian . Donlan . February 4, 2011 . February 4, 2011 . . live . https://web.archive.org/web/20110207012708/http://www.eurogamer.net/articles/2011-02-04-portal-2-hands-on . February 7, 2011.
  87. News: GLaDOS, the greatest video game villain of all time, is back for more cake and chaos in Portal 2 . . February 21, 2011 . March 23, 2011 . Andrew . Ramadge . live . https://web.archive.org/web/20110403112053/http://www.news.com.au/technology/gaming/glados-the-greatest-video-game-villain-of-all-time-back-for-cake-and-chaos-in-portal-2/story-e6frfrt9-1226010080569 . April 3, 2011.
  88. Portal 2 Gains a Talkative Companion . . Gus . Mastrapa . June 16, 2010 . June 16, 2010 . live . https://web.archive.org/web/20100618224204/http://www.wired.com/gamelife/2010/06/portal-2-wheatley/ . June 18, 2010.
  89. Portal 2 Has A Release Date And A New Voice Actor . Phil . Kollar . August 18, 2010 . August 18, 2010 . . dead . https://web.archive.org/web/20120531080748/http://www.gameinformer.com/b/news/archive/2010/08/18/portal-2-has-a-release-date.aspx . May 31, 2012.
  90. Web site: PAX: Portal 2 Nabs J. K. Simmons . Greg . Miller . March 11, 2011 . March 11, 2011 . IGN . live . https://web.archive.org/web/20110314200146/http://ps3.ign.com/articles/115/1155074p1.html . March 14, 2011.
  91. Book: Portal 2: Collector's Edition Guide . . 2011 . 978-3-86993-038-1.
  92. Web site: PAX Prime 2010: Portal 2 Co-Op Hands-On Impressions . Stephen . Johnson . September 3, 2010 . September 3, 2010 . . live . https://web.archive.org/web/20120115024905/http://www.g4tv.com/games/xbox-360/63787/portal-2/articles/72045/PAX-Prime-2010-Portal-2-Co-Op-Hands-On-Impressions/ . January 15, 2012.
  93. Web site: Portal 2 preview . Emanuel . Maiberg . January 21, 2011 . January 21, 2011 . . https://web.archive.org/web/20111203004615/http://www.gamepro.com/article/previews/217934/portal-2-preview/ . dead . December 3, 2011.
  94. Web site: FAQs About the Portal 2 Song . Jonathan . Coulton . April 29, 2011 . May 20, 2011 . jonathancoulton.net . live . https://web.archive.org/web/20110505014446/http://www.jonathancoulton.com/2011/04/29/faqs-about-the-portal-2-song/ . May 5, 2011.
  95. Web site: Portal 2 Ending Song: Want You Gone by Jonathan Coulton Video and Lyrics . Dana . Vinson . April 20, 2011 . April 21, 2011 . . live . https://web.archive.org/web/20121017092218/http://www.g4tv.com/thefeed/blog/post/712014/portal-2-ending-song-want-you-gone-by-jonathan-coulton-video-and-lyrics/ . October 17, 2012.
  96. News: The National To Provide Song For Portal 2 . John . Walker . March 11, 2011 . March 11, 2011 . . live . https://web.archive.org/web/20120512090835/http://www.rockpapershotgun.com/2011/03/11/the-national-to-provide-song-for-portal-2/ . May 12, 2012.
  97. Web site: The National Release "Exile Vilify" off Portal 2 Soundtrack . Nathan . Spicer . April 19, 2011 . April 19, 2011 . . live . https://web.archive.org/web/20110424044748/http://www.pastemagazine.com/articles/2011/04/the-national-release-exile-vilify-off-portal-2-sou.html . April 24, 2011.
  98. Web site: Valve offers Portal 2 soundtrack for free . May 25, 2011 . May 25, 2011 . . Fred . Dutton . live . https://web.archive.org/web/20110528150855/http://www.eurogamer.net/articles/2011-05-25-valve-offers-portal-2-soundtrack-for-free . May 28, 2011.
  99. Web site: Portal 2: Songs To Test By (Collector's Edition) due next month . Jeffrey . Matulef . September 25, 2012 . December 23, 2012 . . live . https://web.archive.org/web/20130102185636/http://www.eurogamer.net/articles/2012-09-25-portal-2-songs-to-test-by-collectors-edition-due-next-month . January 2, 2013.
  100. Web site: More Portal for sure – Valve . January 30, 2008 . Purchese, Rob . January 31, 2008 . . live . https://web.archive.org/web/20120802035558/http://www.eurogamer.net/articles/more-portal-for-sure-valve . August 2, 2012.
  101. Portal . Face Time . . February 21, 2008 . June 26, 2011 . dead . https://web.archive.org/web/20121017131242/https://www.g4tv.com/videos/20385/face-time-portal/ . October 17, 2012.
  102. Valve Releases the Pressure . GT.TV with Geoff Keighley . . March 1, 2008 . June 26, 2011 . December 31, 2010 . https://web.archive.org/web/20101231000714/http://www.gametrailers.com/episode/gametrailers-tv/10%26ch%3D2%26sd%3D1?ep=10&ch=2&sd=1 . live.
  103. Web site: GDC 08: Portal Creators on Writing, Multiplayer, Government Interrogation Techniques . Shacknews . February 23, 2008 . February 23, 2008 . Chris . Faylor . live . https://web.archive.org/web/20110424104647/http://www.shacknews.com/article/51474/gdc-08-portal-creators-on . April 24, 2011.
  104. Web site: Anatomy of an Alternate-Reality Game . April 26, 2010 . May 13, 2010 . . Alex . Wawro . live . https://web.archive.org/web/20100501031529/http://www.pcworld.com/article/195026/anatomy_of_an_alternatereality_game.html . May 1, 2010.
  105. Web site: Portal Patch Adds Morse Code, Achievement – Portal 2 Speculation Begins (Updated) . Alice . O'Connor . Brian . Leahy . March 1, 2010 . March 2, 2010 . . live . https://web.archive.org/web/20120924092002/http://www.shacknews.com/article/62575/portal-patch-adds-morse-code . September 24, 2012.
  106. Web site: Portal 2 Easter egg: Valve never meta-ARG it didn't like . JC . Fletcher . April 20, 2011 . April 20, 2011 . Joystiq . dead . https://web.archive.org/web/20110423032325/http://www.joystiq.com/2011/04/19/portal-2-easter-egg-valve-never-meta-arg-it-didnt-like/ . April 23, 2011.
  107. Web site: The first anyone had seen publicly of Portal 2 was relayed over this modem from 1987 from my kitchen . Robert . Purchase . June 7, 2013 . June 7, 2013 . . live . https://web.archive.org/web/20130610172809/http://www.eurogamer.net/articles/2013-06-04-the-first-anyone-had-seen-publicly-of-portal-2-was-relayed-over-this-modem-from-1987-from-my-kitchen . June 10, 2013.
  108. Web site: Alternate Reality Game puzzle design . Adam . Foster . . June 18, 2013 . June 18, 2013 . live . https://web.archive.org/web/20130701161614/http://www.gamasutra.com/blogs/AdamFoster/20130617/194321/ . July 1, 2013.
  109. Web site: Portal Mystery Deepens with Second Update . Chris . Faylor . March 3, 2010 . March 3, 2010 . . live . https://web.archive.org/web/20110320032144/http://www.shacknews.com/article/62622/valve-changes-portals-ending-in . March 20, 2011.
  110. Geeky Clues Suggest Portal Sequel Is Coming . . Gus . Mastrapa . March 2, 2010 . March 2, 2010 . live . https://web.archive.org/web/20100303235223/http://www.wired.com/gamelife/2010/03/portal-viral/ . March 3, 2010.
  111. Web site: Rumor: Valve To Make Portal 2 Announcement During GDC 2010 . . March 3, 2010 . March 3, 2010 . Jake . Gaskill . live . https://web.archive.org/web/20121017172010/http://www.g4tv.com/thefeed/blog/post/702963/rumor-valve-to-make-portal-2-announcement-during-gdc-2010/ . October 17, 2012.
  112. Web site: Portal 2 is official, first image inside . March 5, 2010 . March 5, 2010 . Andrew . Webster . live . https://web.archive.org/web/20100307124459/http://arstechnica.com/gaming/news/2010/03/portal-2-is-official-first-image-inside.ars . March 7, 2010.
  113. Web site: Portal 2 Hijacks Blue Screen of Death At GDC Awards . Luke . Plunkett . March 11, 2010 . March 12, 2010 . Kotaku . live . https://web.archive.org/web/20100314003729/http://kotaku.com/5491651/portal-2-hijacks-blue-screen-of-death-at-gdc-awards . March 14, 2010.
  114. Web site: E3 Portal 2 event replaced by "surprise" . Robert . Purchase . June 2, 2010 . June 2, 2010 . . live . https://web.archive.org/web/20100605022850/http://www.eurogamer.net/articles/e3-portal-2-event-replaced-by-surprise . June 5, 2010.
  115. Web site: Valve Delays Portal 2, Confirms E3 Surprise Is 'PORTAL-2-THEMED-FOR-GOD'S SAKE' . . June 9, 2010 . June 9, 2010 . Chris . Faylor . live . https://web.archive.org/web/20110409164713/http://www.shacknews.com/article/64185/valve-delays-portal-2-confirms . April 9, 2011.
  116. Web site: Valve's E3 surprise is... oh. Portal 2 on PS3 . Tom . Francis . PC Gamer . June 15, 2010 . June 26, 2011 . live . https://web.archive.org/web/20110426215821/http://www.pcgamer.com/2010/06/15/valves-e3-surprise-is-oh-portal-2-on-ps3/ . April 26, 2011.
  117. Portal 2 . Meagan . VanBurkleo . April 2010 . 50–62 . Game Informer.
  118. Web site: Portal 2 due out this Christmas . Bramwell . Tom . March 5, 2010 . . March 5, 2010 . live . https://web.archive.org/web/20100307050922/http://www.eurogamer.net/articles/portal-2-due-out-this-christmas . March 7, 2010.
  119. Web site: Portal 2 Teleports to Shelves Next February . Gregory . Gay . August 18, 2010 . April 21, 2011 . . live . https://web.archive.org/web/20100821232135/http://www.escapistmagazine.com/news/view/102867-Portal-2-Teleports-to-Shelves-Next-February . August 21, 2010.
  120. Web site: Portal 2 Delayed to 'The Week of April 18' . Xav . de Matos . . November 18, 2010 . November 18, 2010 . live . https://web.archive.org/web/20110307032034/http://www.shacknews.com/article/66536/portal-2-delayed-hits-stores . March 7, 2011.
  121. Web site: Newell: Portal 2 'pretty much' ready for release . February 19, 2011 . February 20, 2011 . . live . https://web.archive.org/web/20110222165443/http://www.computerandvideogames.com/289822/news/newell-portal-2-pretty-much-ready-for-release/ . February 22, 2011.
  122. Web site: Steam Coming to Mac in April, Portal 2 This Fall . . Chris . Faylor . March 8, 2010 . March 8, 2010 . live . https://web.archive.org/web/20120117112859/http://www.shacknews.com/article/62687/steam-coming-to-mac-in . January 17, 2012.
  123. Web site: EA, Valve Confirm Distribution Agreement For Portal 2 . Kris . Graff . December 22, 2010 . December 22, 2010 . . dead . https://web.archive.org/web/20101225133128/http://www.gamasutra.com/view/news/32162/EA_Valve_Confirm_Distribution_Agreement_For_Portal_2.php . December 25, 2010.
  124. Potato Sack Developers Helped Design Portal 2 ARG . . April 20, 2011 . April 20, 2011 . Nathan . Brown . dead . https://web.archive.org/web/20110423010511/http://www.next-gen.biz/news/potato-sack-developers-helped-design-portal-2-arg . April 23, 2011.
  125. Web site: Portal 2 to get early release on Steam? . April 13, 2011 . April 13, 2011 . Tom . Phillips . . live . https://web.archive.org/web/20110417014518/http://www.metro.co.uk/tech/games/860768-portal-2-to-get-early-release-on-steam . April 17, 2011.
  126. Web site: Portal 2 to release early? Potato sack ARG signs point to "yes" . Nathan . Greyson . April 13, 2011 . April 13, 2011 . . live . https://web.archive.org/web/20110416054113/http://www.vg247.com/2011/04/13/portal-2-to-release-early-potato-sack-arg-signs-point-to-yes/ . April 16, 2011.
  127. Web site: Portal 2 levels appear in potato sack games, clues suggest Portal 2 could be released early . Tom . Senior . April 13, 2011 . April 13, 2011 . . live . https://web.archive.org/web/20110416053452/http://www.pcgamer.com/2011/04/13/portal-2-levels-appear-in-potato-sack-games-clues-suggest-portal-2-could-be-released-early . April 16, 2011.
  128. Valve May Release Portal 2 On Friday, Not Tuesday . Chris . Kohler . April 13, 2011 . April 13, 2011 . . live . https://web.archive.org/web/20110416065828/http://www.wired.com/gamelife/2011/04/valve-may-release-portal-2-on-friday-not-tuesday . April 16, 2011.
  129. Web site: Play indie games, help Portal 2 release early . Pete . Davidson . April 15, 2011 . April 15, 2011 . . https://web.archive.org/web/20111203050324/http://www.gamepro.com/article/news/218877/play-indie-games-help-portal-2-release-early/ . dead . December 3, 2011.
  130. Play Steam Games, Launch Portal 2 Early . Jason . Schreier . April 15, 2011 . April 15, 2011 . . live . https://web.archive.org/web/20110418184148/http://www.wired.com/gamelife/2011/04/portal-2-early-launch . April 18, 2011.
  131. Web site: No more potatoes: Portal 2 available right now on Steam . Brenna . Hillier . April 18, 2011 . April 18, 2011 . . live . https://web.archive.org/web/20110420083833/http://www.vg247.com/2011/04/19/portal-2-available-now/ . April 20, 2011.
  132. Web site: Portal 2 unlocked early with potato power . Alice . O'Connor . April 18, 2011 . . April 19, 2021 . April 18, 2021 . https://web.archive.org/web/20210418143313/https://www.shacknews.com/article/68156/portal-2-unlocks-early-with . live .
  133. Web site: Valve's in-house Portal 2 ad the result of "copycat" agency treatments (Update) . Brenna . Hillier . March 17, 2011 . March 17, 2011 . . live . https://web.archive.org/web/20120926025954/http://www.vg247.com/2011/03/17/valves-in-house-portal-2-ads-the-result-of-copycat-agency-treatments/ . September 26, 2012.
  134. News: Trailer Park: 'Portal 2' . Brett . Molina . March 22, 2011 . March 22, 2011 . . https://web.archive.org/web/20110326212019/http://content.usatoday.com/communities/gamehunters/post/2011/03/trailer-park-portal-2-1/1 . March 26, 2011 . live.
  135. Web site: Portal 2 goodies now on sale . Pete . Davidson . April 19, 2011 . April 19, 2011 . . https://web.archive.org/web/20111203050322/http://www.gamepro.com/article/news/218934/portal-2-goodies-now-on-sale/ . dead . December 3, 2011.
  136. News: Portal 2 has hidden interactive Super 8 teaser level . Tom . Senior . April 19, 2011 . April 19, 2011 . . live . https://web.archive.org/web/20110422112527/http://www.pcgamer.com/2011/04/19/portal-2-has-hidden-interactive-super-8-teaser-level/ . April 22, 2011.
  137. Web site: Portal 2 has item store, trading coming soon . Tom . Senior . April 19, 2011 . April 19, 2011 . . live . https://web.archive.org/web/20110429013029/http://www.pcgamer.com/2011/04/19/portal-2-has-item-store-trading-coming-soon . April 29, 2011.
  138. Web site: Portal 2's Creators On Crafting Games Through Experiential Stories . Kevin . Ohannessian . April 27, 2011 . April 27, 2011 . . live . https://web.archive.org/web/20110430132704/http://www.fastcompany.com/1750003/portal-2-valve-eric-wolpaw-jeep-barnett-doug-lombardi . April 30, 2011.
  139. Web site: Portal 2 DLC release date . Fred . Dutton . September 30, 2011 . September 30, 2011 . . live . https://web.archive.org/web/20111002143400/http://www.eurogamer.net/articles/2011-09-30-portal-2-dlc-release-date . October 2, 2011.
  140. Web site: Free Portal 2 DLC out next month . . Fred . Dutton . August 18, 2011 . August 18, 2011 . live . https://web.archive.org/web/20110828193924/http://www.eurogamer.net/articles/2011-08-18-free-portal-2-dlc-out-next-month . August 28, 2011.
  141. Web site: Portal 2 Peer Review DLC is 1.37GB . Robert . Purchase . October 4, 2011 . October 4, 2011 . . live . https://web.archive.org/web/20111005214559/http://www.eurogamer.net/articles/2011-10-04-portal-2-peer-review-dlc-is-1-37gb . October 5, 2011.
  142. Web site: Portal 2 Peer Review DLC: fun, but missing the magic . Peter . Bright . October 9, 2011 . October 11, 2011 . Ars Technica . live . https://web.archive.org/web/20111009222148/http://arstechnica.com/gaming/reviews/2011/10/portal-2-peer-review-fun-but-missing-the-magic.ars . October 9, 2011.
  143. Web site: Valve Offering Free Portal 2 DLC On All Available Platforms This Summer . Kyle . Orland . April 29, 2011 . April 29, 2011 . . live . https://web.archive.org/web/20110501024250/http://www.gamasutra.com/view/news/34403/Valve_Offering_Free_Portal_2_DLC_On_All_Platforms_This_Summer.php . May 1, 2011.
  144. News: Free DLC for 'Portal 2' launching this summer . . April 29, 2011 . April 29, 2011 . Brett . Molina . https://web.archive.org/web/20110504023015/http://content.usatoday.com/communities/gamehunters/post/2011/04/free-dlc-for-portal-2-launching-this-summer/1 . May 4, 2011 . live.
  145. Web site: Portal 2 Mod Levels 'For All Platforms' . NowGamer . January 24, 2001 . June 24, 2011 . live . https://web.archive.org/web/20120120224936/http://www.nowgamer.com/news/919495/portal_2_mod_levels_for_all_platforms.html . January 20, 2012.
  146. Web site: Now You Can Make Your Own Custom Portal 2 Puzzles (I Said NOW!!) . Michael . McWhertor . Kotaku . May 10, 2011 . June 24, 2011 . live . https://web.archive.org/web/20110514142654/http://kotaku.com/5800623/now-you-can-make-your-own-portal-2-puzzles-i-said-now . May 14, 2011.
  147. Web site: Portal 2 mapping contest kicks off . Tom . Senior . May 26, 2011 . October 11, 2011 . . live . https://web.archive.org/web/20110807093335/http://www.pcgamer.com/2011/05/26/portal-2-mapping-contest-kicks-off/ . August 7, 2011.
  148. Web site: 'Portal 2' puzzle creator launches May 8 . . April 26, 2012 . April 26, 2012 . Brett . Molina . https://web.archive.org/web/20120501183927/http://content.usatoday.com/communities/gamehunters/post/2012/04/portal-2-puzzle-creator-launches-may-8/1#.T5mlLatYtSM . May 1, 2012 . live.
  149. Web site: 'Portal 2' gets level creation tools May 8th for PC and Mac . Griffin . McElroy . April 26, 2012 . April 26, 2012 . . live . https://web.archive.org/web/20120427190132/http://www.theverge.com/gaming/2012/4/26/2977445/portal-2-level-creation-steam . April 27, 2012.
  150. Web site: Valve Tinkering With an Excellent Portal 2 Feature That Talks Back . Stephan . Tolito . October 18, 2011 . October 19, 2011 . Kotaku . live . https://web.archive.org/web/20111020121041/http://kotaku.com/5851007/valve-tinkering-with-an-excellent-portal-2-feature-that-talks-back . October 20, 2011.
  151. Web site: Portal 2 Puzzle Creator in internal beta testing now, will use Steam Workshop . Tom . Senior . March 14, 2012 . March 14, 2012 . . live . https://web.archive.org/web/20120316182343/http://www.pcgamer.com/2012/03/14/portal-2-puzzle-creator-in-beta-testing-now-will-use-steam-workshop/ . March 16, 2012.
  152. Web site: Portal 2 Sees Map Editor Next Year . Frank . Cifaldi . October 21, 2011 . October 21, 2011 . . dead . https://web.archive.org/web/20111023191550/http://www.gamasutra.com/view/news/38044/Portal_2_Sees_Map_Editor_Next_Year.php . October 23, 2011.
  153. Portal 2's Perpetual Testing Initiative Off To A Good Start . Matt . Helgeson . May 10, 2012 . May 11, 2012 . . dead . https://web.archive.org/web/20120512040310/http://www.gameinformer.com/b/news/archive/2012/05/10/portal-2-39-s-perpetual-testing-initiative-off-to-a-good-start.aspx . May 12, 2012.
  154. Web site: Valve Announces Documentary Film on Pro Gaming, Portal 2 Co-Op Map Maker . Mike . Sharkley . August 17, 2012 . August 17, 2012 . . February 3, 2013 . https://web.archive.org/web/20130203125658/http://pc.gamespy.com/articles/122/1225780p1.html.
  155. Web site: Bastion on PC? Now you're thinking with portals . August 22, 2011 . August 23, 2011 . Ars Technica . live . https://web.archive.org/web/20110910165003/http://arstechnica.com/gaming/news/2011/08/bastion-on-the-pc-now-youre-thinking-with-portals.ars . September 10, 2011.
  156. Portal's GLaDOS Invades the World of Defense Grid! . . December 2, 2011 . live . https://web.archive.org/web/20120113082616/http://www.gamasutra.com/view/pressreleases/80521/Portalrsquos_GLaDOS_Invades_the_World_of_DefenseGrid.php . January 13, 2012.
  157. Custom 'Portal 2' Video Game Level Built for Marriage Proposal . Evan . Narcisse . August 23, 2011 . August 23, 2011 . . live . https://web.archive.org/web/20110919074825/http://techland.time.com/2011/08/23/custom-portal-2-video-game-level-built-for-marriage-proposal/ . September 19, 2011.
  158. Web site: Behind The Scenes Of The Portal Proposal . Chris . Morris . August 26, 2011 . August 26, 2011 . . dead . https://web.archive.org/web/20110925024514/http://www.gamasutra.com/view/news/36788/Behind_The_Scenes_Of_The_Portal_Proposal.php . September 25, 2011.
  159. Web site: Skyrim gets HD texture pack, Portal 2 Space Sphere . . February 7, 2012 . February 7, 2012 . Alice . O'Conner . live . https://web.archive.org/web/20120208225406/http://www.shacknews.com/article/72350/skyrim-hd-textures-portal-2-dlc . February 8, 2012.
  160. Web site: Portal Pinball: hands-on with Pinball FX2's new Portal themed table . Tom . Marks . May 5, 2015 . May 5, 2015 . . live . https://web.archive.org/web/20150508020103/http://www.pcgamer.com/portal-pinball-hands-on-with-pinball-fx2s-new-portal-themed-table/ . May 8, 2015.
  161. Web site: Portal, Dr. Who, The Simpsons and more confirmed for Lego Dimensions . . Michael . McWhertor . May 10, 2015 . May 10, 2015 . live . https://web.archive.org/web/20150512160424/http://www.polygon.com/2015/5/10/8583417/lego-dimensions-leak-portal-dr-who-jurassic-world-the-simpsons . May 12, 2015.
  162. Web site: Portal 2 and Left 4 Dead receive Xbox One backwards compatibility . Jeffrey . Matulef . June 16, 2016 . June 16, 2016 . . live . https://web.archive.org/web/20160617132927/http://www.eurogamer.net/articles/2016-06-16-portal-2-left-4-dead-receive-xbox-one-backwards-compatibility . June 17, 2016.
  163. Web site: Portal and Portal 2 coming to Nintendo Switch . Nicole . Carpenter . February 9, 2022 . . February 9, 2022 . February 9, 2022 . https://web.archive.org/web/20220209230408/https://www.polygon.com/22926148/portal-and-portal-2-nintendo-switch-release-date-2022 . live .
  164. Web site: Portal and Portal 2 coming to Nintendo Switch . Tom . Phillips . February 9, 2022 . . February 9, 2022 . February 9, 2022 . https://web.archive.org/web/20220209223746/https://www.eurogamer.net/articles/2022-02-09-portal-and-portal-2-coming-to-nintendo-switch . live .
  165. Web site: Valve details Teach with Portals, Steam for Schools educational initiatives . . Dave . Tach . June 30, 2012 . October 25, 2016 . live . https://web.archive.org/web/20161022002418/http://www.polygon.com/gaming/2012/6/20/3101653/valve-teach-with-portal-steam-for-schools-education . October 22, 2016.
  166. Web site: How Portal 2 Developers Became The Best 6th Grade Physics Teachers Ever . Katie . Salen . November 13, 2012 . November 14, 2012 . . live . https://web.archive.org/web/20121116175737/http://www.fastcompany.com/3002872/how-portal-2-developers-became-best-6th-grade-physics-teachers-ever . November 16, 2012.
  167. Web site: Valve helps educators Teach With Portals . Leigh . Alexander . June 20, 2012 . June 20, 2012 . . dead . https://web.archive.org/web/20120622041824/http://gamasutra.com/view/news/172716/Valve_helps_educators_Teach_With_Portals.php . June 22, 2012.
  168. Web site: Valve Gives Away Portal 2 for Free to Teachers with 'Steam for Schools' . Evan . Narcisse . June 20, 2012 . June 20, 2012 . Kotaku . live . https://web.archive.org/web/20120623193304/http://kotaku.com/5919912/valve-gives-away-portal-2-for-free-to-teachers-with-steam-for-schools . June 23, 2012.
  169. Foroughi . Cyrus K. . Serraino . Carolyn . Parasuraman . Raja . Boehm-Davis . Deborah A. . October 2016 . Can we create a measure of fluid intelligence using Puzzle Creator within Portal 2? . Intelligence . 56 . 58–64 . 10.1016/j.intell.2016.02.011. 16707254 .
  170. Shute . Valerie J. . Ventura . Matthew . Ke . Fengfeng . August 2014 . The power of play: The effects of Portal 2 and Lumosity on cognitive and noncognitive skills . Computers & Education . 80 . 58–67 . 10.1016/j.compedu.2014.08.013. 15876432 .
  171. Barr . Matthew . May 2017 . Video games can develop graduate skills in higher education students: A randomised trial . Computers & Education . 113 . 86–97 . 10.1016/j.compedu.2017.05.016 . free.
  172. Web site: Review: The Razer Hydra Savages Portal 2 (In a Good Way!) . GeekBeat.tv . Gord . McLeod . June 24, 2011 . June 24, 2011 . https://web.archive.org/web/20110627025717/http://geekbeat.tv/review-the-razer-hydra-savages-portal-2-in-a-good-way/ . June 27, 2011 . live.
  173. Web site: Portal 2 First DLC Content, Designed Specifically For Razer Hydra Controller . Jillian . Horsey . June 20, 2011 . June 24, 2011 . live . https://web.archive.org/web/20110625140425/http://www.geeky-gadgets.com/portal-2-first-dlc-content-designed-specifically-for-razer-hydra-controller-20-06-2011/ . June 25, 2011.
  174. Web site: Why Portal 2 doesn't support PS Move . Wesley . Yin-Poole . February 25, 2011 . February 25, 2011 . . live . https://web.archive.org/web/20110228181635/http://www.eurogamer.net/articles/2011-02-25-why-portal-2-doesnt-support-ps-move . February 28, 2011.
  175. Web site: CES: Razer Gets Portal 2 Exclusives . Levi . Buchanan . January 8, 2011 . January 8, 2011 . IGN . dead . https://web.archive.org/web/20120114214225/http://pc.ign.com/articles/114/1143181p1.html . January 14, 2012.
  176. Web site: Valve Apologizes For Sony-Bashing, Announces Portal 2 for PS3 . Matt . Peckham . June 15, 2010 . June 15, 2010 . . live . https://web.archive.org/web/20100619071727/http://www.pcworld.com/article/198935/valve_apologizes_for_sonybashing_announces_portal_2_for_ps3.html?tk=hp_blg . June 19, 2010.
  177. Web site: Portal 2, Steamworks PS3-bound in 2011 . . Tor . Thorsen . June 15, 2010 . June 16, 2010 . March 13, 2012 . https://web.archive.org/web/20120313222355/http://e3.gamespot.com/story/6265808/portal-2-steamworks-ps3-bound-in-2011.
  178. Web site: Portal 2 PS3, Steam cross-platform play . Wesley . Yin-Poole . January 18, 2011 . January 18, 2010 . . live . https://web.archive.org/web/20160303221700/http://www.eurogamer.net/articles/2011-01-18-portal-2-ps3-steam-cross-platform-play . March 3, 2016.
  179. Web site: Valve details PS3 Steam support for Portal 2 . . April 13, 2011 . April 13, 2011 . live . https://web.archive.org/web/20110416054453/http://www.computerandvideogames.com/298024/news/valve-details-ps3-steam-support-for-portal-2/ . April 16, 2011.
  180. Web site: Valve 'no plans' for 3D, Move support in Portal 2 . . June 22, 2010 . June 22, 2010 . Tim . Ingham . live . https://web.archive.org/web/20120105185436/http://www.computerandvideogames.com/253007/valve-no-plans-for-3d-move-support-in-portal-2/ . January 5, 2012.
  181. Web site: Portal 2 on PS3 Will Not Feature Move Support (Updated) . Steve . Watts . February 17, 2011 . February 17, 2011 . . live . https://web.archive.org/web/20110404113831/http://www.shacknews.com/article/67555/portal-2-on-ps3-will . April 4, 2011.
  182. Web site: Portal Picks Up a PlayStation Move Controller, Returns to the PS3 With New Levels . Luke . Plunkett . June 5, 2012 . June 5, 2012 . Kotaku . live . https://web.archive.org/web/20120608033319/http://kotaku.com/5915992/portal-picks-up-a-playstation-move-controller-returns-to-the-ps3-with-new-levels . June 8, 2012.
  183. Web site: Portal 2 'In Motion' DLC out in US today, launch trailer . . November 6, 2012 . November 6, 2012 . Mike . Jackson . live . https://web.archive.org/web/20121109085616/http://www.computerandvideogames.com/377130/portal-2-in-motion-dlc-out-in-us-today-launch-trailer/ . November 9, 2012.
  184. Web site: Portal 2's Move-based In Motion DLC gets a free co-op campaign . . June 6, 2013 . June 6, 2013 . Jeffrey . Matulef . live . https://web.archive.org/web/20130609044914/http://www.eurogamer.net/articles/2013-06-06-portal-2s-ps3-dlc-in-motion-gets-a-free-co-op-campaign . June 9, 2013.
  185. Web site: Core Portal 2 game is the same "whether you buy it on PS3 or 360", says Valve . January 22, 2011 . January 24, 2011 . Stephany . Nunneley . . live . https://web.archive.org/web/20120926025822/http://www.vg247.com/2011/01/22/the-core-portal-2-game-is-the-same-whether-you-buy-it-on-ps3-or-360-says-valve/ . September 26, 2012.
  186. Web site: 2010 Winners . . July 6, 2010 . July 6, 2010 . live . https://web.archive.org/web/20120204061915/http://www.gamecriticsawards.com/winners.html . February 4, 2012.
  187. News: E3 2010: Game Critics Awards nominees announced . Mike . Snider . June 29, 2010 . June 30, 2010 . . live . https://web.archive.org/web/20121003040202/http://content.usatoday.com/communities/gamehunters/post/2010/06/e3-2010-game-critics-awards-nominees-announced/1 . October 3, 2012.
  188. Web site: E3 2010: Best of E3 Awards . IGN . June 17, 2010 . June 30, 2010 . dead . https://web.archive.org/web/20120126065957/http://games.ign.com/articles/109/1094418p1.html . January 26, 2012.
  189. Web site: GameSpy's Best of E3 2010 Awards . . June 25, 2010 . June 30, 2010 . live . https://web.archive.org/web/20120323102917/http://www.gamespy.com/articles/110/1102167p1.html . March 23, 2012.
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  200. News: Portal 2 Is A Hole In One . Ryan . Kuo . April 19, 2011 . April 19, 2011 . . live . https://web.archive.org/web/20110425041138/http://blogs.wsj.com/speakeasy/2011/04/19/portal-2-is-a-hole-in-one/ . April 25, 2011.
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  204. News: 'Portal 2' is a dark, humorous joy (and that's no lie) . Larry . Frum . April 19, 2011 . April 19, 2011 . CNN . live . https://web.archive.org/web/20120114154516/http://edition.cnn.com/2011/TECH/gaming.gadgets/04/19/portal.2.review/ . January 14, 2012.
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  208. 'Portal 2' videogame review: Physics is phunny . John . Young . April 20, 2011 . April 20, 2011 . . live . https://web.archive.org/web/20110420141435/http://popwatch.ew.com/2011/04/20/portal-2-review/ . April 20, 2011.
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  219. Web site: The People are Panning Portal2 . April 19, 2011 . Tolito . April 19, 2011 . Kotaku . live . https://web.archive.org/web/20110927182932/http://kotaku.com/5793543/the-people-are-panning-portal-2 . September 27, 2011.
  220. News: Let's Address Some Portal 2 Nonsense . John . Walker . April 19, 2011 . April 19, 2011 . . live . https://web.archive.org/web/20110421034518/http://www.rockpapershotgun.com/2011/04/19/lets-address-some-portal-2-nonsense/ . April 21, 2011.
  221. Web site: Portal 2 Metacritic user score pounded . . April 19, 2011 . April 19, 2011 . Fred . Dutton . live . https://web.archive.org/web/20110425034355/http://www.eurogamer.net/articles/2011-04-19-portal-2-metacritic-user-score-pounded . April 25, 2011.
  222. Web site: Portal 2 voted GOTY at Golden Joysticks . . October 21, 2011 . October 21, 2011 . Matthew . Handrahan . live . https://web.archive.org/web/20111024163848/http://www.gamesindustry.biz/articles/2011-10-21-portal-2-voted-goty-at-golden-joysticks . October 24, 2011.
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  225. IGNs 2011 Game of the Year Video . IGN . January 17, 2012 . January 17, 2012 . live . https://web.archive.org/web/20120120181914/http://www.ign.com/videos/2012/01/17/igns-2011-game-of-the-year-video . January 20, 2012.
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  227. Web site: Portal 2 Takes Kotaku's 2011 Game of the Year Award for Science, You Monster . Mike . Fahey . January 2, 2012 . January 2, 2012 . Kotaku . live . https://web.archive.org/web/20120107183425/http://kotaku.com/5872357/portal-2-takes-kotakus-2011-game-of-the-year-award-for-science-you-monster . January 7, 2012.
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  230. Web site: Portal 2 Leads Spike TV VGA Nominees With 12 Nods . Kyle . Orland . November 16, 2011 . November 16, 2011 . . dead . https://web.archive.org/web/20111119014716/http://www.gamasutra.com/view/news/38603/Portal_2_Leads_Spike_TV_VGA_Nominees_With_12_Nods.php . November 19, 2011.
  231. Skyrim, Portal 2, Arkham City Won Big At VGAs . Jeff . Cork . December 11, 2011 . December 11, 2011 . . dead . https://web.archive.org/web/20120106132343/http://www.gameinformer.com/b/news/archive/2011/12/11/skyrim-portal-2-arkham-city-won-big-at-vgas.aspx . January 6, 2012.
  232. Web site: Portal 2, Skyrim, Bastion lead finalists for 12th annual Game Developers Choice Awards . January 5, 2012 . January 5, 2012 . . live . https://web.archive.org/web/20120108071505/http://www.gamasutra.com/view/news/39507/Portal_2_Skyrim_Bastion_lead_finalists_for_12th_annual_Game_Developers_Choice_Awards.php . January 8, 2012.
  233. Web site: Skyrim wins Game of the Year at GDC Awards . March 8, 2012 . March 8, 2012 . . live . https://web.archive.org/web/20120309185300/http://www.gamasutra.com/view/news/164945/Skyrim_wins_Game_of_the_Year_at_GDC_Awards.php . March 9, 2012.
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  236. Web site: 'Batman,' 'L.A. Noire' lead BAFTA game award nods . Brett . Molina . February 16, 2012 . February 21, 2012 . . https://web.archive.org/web/20120219232220/http://content.usatoday.com/communities/gamehunters/post/2012/02/batman-la-noire-lead-bafta-game-award-nods/1#.T0RCAbEgdSM . February 19, 2012 . live.
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  238. Web site: Battlefield 3, Portal 2, more win big at 10th annual G.A.N.G. Awards . Tom . Curtis . March 14, 2012 . March 14, 2012 . . live . https://web.archive.org/web/20120317172318/http://www.gamasutra.com/view/news/165833/Battlefield_3_Portal_2_more_win_big_at_10th_annual_GANG_Awards.php . March 17, 2012.
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  245. Web site: Satelitte Awards 2011. International Press Academy. November 2, 2022. live. https://web.archive.org/web/20221003162343/https://www.pressacademy.com/award_cat/2011/. October 3, 2022.
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  248. Web site: Saling The World: Portal 2 Leads Cross-Platform Charts Worldwide . Danny . Cowen . April 22, 2011 . June 27, 2011 . . dead . https://web.archive.org/web/20110508225028/http://www.gamasutra.com/view/news/34245/Saling_The_World_Portal_2_Leads_CrossPlatform_Charts_Worldwide.php . May 8, 2011.
  249. Web site: Saling The World: Mortal Kombat Overtakes Portal 2 Stateside . Danny . Cowen . April 29, 2011 . April 29, 2011 . . dead . https://web.archive.org/web/20110430220720/http://www.gamasutra.com/view/news/34356/Saling_The_World_Mortal_Kombat_Overtakes_Portal_2_Stateside.php . April 30, 2011.
  250. Web site: NPD: Mortal Kombat beats Portal 2 in US . Fred . Dutton . May 12, 2011 . June 27, 2011 . . live . https://web.archive.org/web/20110517205317/http://www.eurogamer.net/articles/2011-05-12-npd-mortal-kombat-beats-portal-2-in-us . May 17, 2011.
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  252. Web site: Portal 2 Has Sold More Than 3 Million Copies . Patrick . Klepek . June 22, 2011 . December 16, 2014 . . live . https://web.archive.org/web/20121018222444/http://www.giantbomb.com/news/portal-2-has-sold-more-than-3-million-copies/3412/ . October 18, 2012.
  253. Web site: Portal 2 Scores Valve First Ever Top Spot In UK Sales Charts . Mike . Rose . April 26, 2011 . April 26, 2011 . . dead . https://web.archive.org/web/20110429021926/http://www.gamasutra.com/view/news/34287/Portal_2_Scores_Valve_First_Ever_Top_Spot_In_UK_Sales_Charts.php . April 29, 2011.
  254. Web site: Portal 2 Holds On To Top Spot For Second Week In UK Sales Charts . Mike . Rose . May 3, 2011 . May 3, 2011 . . dead . https://web.archive.org/web/20110506054314/http://www.gamasutra.com/view/news/34468/Portal_2_Holds_On_To_Top_Spot_For_Second_Week_In_UK_Sales_Charts.php . May 6, 2011.
  255. Web site: Analysis: Did The PSN Outage Hurt U.S. PS3 Hardware Sales? . Matt . Matthews . Gamasutra . June 21, 2011 . June 27, 2011 . dead . https://web.archive.org/web/20141011072659/http://www.gamasutra.com/view/news/35290 . October 11, 2014.
  256. Web site: Developers Say PSN Outage Affecting Sales, But Remain Hopeful . Kris . Graft . Gamasutra . April 26, 2001 . June 27, 2011 . dead . https://web.archive.org/web/20110811064726/http://www.gamasutra.com/view/news/34306/Developers_Say_PSN_Outage_Affecting_Sales_But_Remain_Hopeful.php . August 11, 2011.
  257. Web site: Has PSN outage affected Portal 2 PS3 sales? . Joe . Anderson . ShopToNews . April 26, 2011 . June 27, 2011 . May 12, 2012 . https://web.archive.org/web/20120512200042/http://www.shoptonews.net/2011/04/26/has-psn-outage-affected-portal-2-ps3-sales/.
  258. Web site: Newell: Portal 2 Has Sold 3 Million Copies . Kyle . Orland . June 22, 2011 . June 22, 2011 . . dead . https://web.archive.org/web/20110625134506/http://www.gamasutra.com/view/news/35402/Newell_Portal_2_Has_Sold_3_Million_Copies.php . June 25, 2011.
  259. Web site: Crysis 2 racks up three million sales . . July 26, 2011 . July 26, 2011 . Fred . Dutton . live . https://web.archive.org/web/20110807062713/http://www.eurogamer.net/articles/2011-07-26-crysis-2-racks-up-three-million-sales . August 7, 2011.
  260. Web site: The Valve Way: Gabe Newell And Erik Johnson Speak . Christian . Nutt . August 29, 2011 . August 30, 2011 . . dead . https://web.archive.org/web/20110930134908/http://www.gamasutra.com/view/feature/6471/the_valve_way_gabe_newell_and_.php?page=4 . September 30, 2011.
  261. Web site: Portal 2 has sold over 4M copies . Eric . Caoili . May 8, 2012 . May 8, 2012 . . dead . https://web.archive.org/web/20120508191845/http://www.gamasutra.com/view/news/169967/Portal_2_has_sold_over_4M_copies.php . May 8, 2012.
  262. News: Pearson. Craig. December 20, 2021. The best Portal 2 mods. en. Rock, Paper, Shotgun. November 2, 2022. live. https://web.archive.org/web/20221012214749/https://www.rockpapershotgun.com/the-best-portal-2-mods. October 12, 2022.
  263. Fan Made Portal 2 Mod Looks Good Enough To Be From Valve . Kyle . Hillard . January 31, 2015 . May 10, 2015 . . dead . https://web.archive.org/web/20150702043017/http://www.gameinformer.com/b/news/archive/2015/01/31/fan-made-portal-2-mod-looks-good-enough-to-be-from-valve.aspx . July 2, 2015.
  264. Web site: Portal 2 mod Aperture Tag releases on Steam, for a price . Phil . Savage . July 16, 2014 . May 27, 2019 . PC Gamer. live. https://web.archive.org/web/20221030025011/https://www.pcgamer.com/portal-2-mod-aperture-tag-releases-on-steam-for-a-price/. October 30, 2022.
  265. Web site: Portal 2 mod Thinking With Time Machine now available on Steam . April 22, 2014 . May 27, 2019 . Phil . Savage . PC Gamer. live. https://web.archive.org/web/20221030025024/https://www.pcgamer.com/portal-2-mod-thinking-with-time-machine-now-available-on-steam/. October 30, 2022.
  266. This Portal 2 Mod Lets You Play Against Yourself . Bo . Moore . April 28, 2014 . May 27, 2019 . Wired. live. https://web.archive.org/web/20221030025025/https://www.wired.com/2014/04/thinking-with-time-machine/. October 30, 2022.
  267. Web site: Portal Reloaded mod adds a third portal that lets you travel through time . April 20, 2021 . Mollie. Taylor. PC Gamer. live. https://web.archive.org/web/20220818080508/https://www.pcgamer.com/portal-reloaded-mod-adds-a-third-portal-that-lets-you-travel-through-time/. August 18, 2022.
  268. Web site: Macgregor . Jody . Portal Reloaded adds a third portal and the fourth dimension . November 4, 2020. November 2, 2022 . . en-US. live. https://web.archive.org/web/20211006221058/https://www.pcgamer.com/portal-reloaded-adds-a-third-portal-and-the-fourth-dimension/. October 6, 2021.
  269. Web site: Serin . Kaan . Portal 2's game-sized prequel mod squeezes in 40 new puzzles, fully-voiced original characters, and an 8-hour story . GamesRadar . January 6, 2024 . January 6, 2024.

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