Perpetual Testing Initiative
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 robots—ATLAS and P-Body—in 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.
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. 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 appears briefly. 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. 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, and white Conversion Gel to allow surfaces to accept portals. 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. 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. The game provides voice communication between players, and online players can temporarily enter a split-screen view to help coordinate actions. 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 2's lead writer Erik Wolpaw estimates each campaign to be about six hours long. 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. 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.
Synopsis
Setting
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, while most of Portal 2 is set "a long time after" the events in Portal.
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". 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.
Plot
Single-player
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. 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.
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. 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). 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.
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.
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) 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. When Chell awakens, GLaDOS claims to have learned of humanity from the remnants of Caroline, but deletes Caroline's personality. Deciding that Chell is not worth the trouble of killing, GLaDOS frees her from the facility.
Co-op
The cooperative story is chronologically set after the events of the single-player campaign, but players are not required to play them in order. 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. 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
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. Work began almost immediately after the release of Portal. Valve committed more resources to Portal 2's 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. 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." Kim Swift, Portal's designer, left Valve for Airtight Games halfway through Portal 2's development.
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". After Portal 2's 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." 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.
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. 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. 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.
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.
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. When Wheatley controls the Aperture facility, the designers "had a blast" creating deranged chambers reflecting Wheatley's stupidity. As solving constant puzzles would tire players, the designers inserted occasional "experiences" to provide respite and advance the plot.
The Repulsion (jumping) and Propulsion (running) gels in Portal 2 originated in Tag: The Power of Paint. 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. 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. 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.
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. 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; 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.
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. The game has 13,000 lines of dialogue. 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.
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. 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. 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. 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". 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". Portal 2 produced its own memes, including a space-obsessed personality core. Valve later created a Space Core modification for the game The Elder Scrolls V: Skyrim (see below), and the Space Core also appeared as a laser-based engraving on a panel manufactured by NASA for the International Space Station.
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." 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."
Richard McCormick of PlayStation 3 Magazine identified several elements of Portal 2's 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. 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 Half-Life 2: Episode Two to have been stranded in the Arctic as a result of a teleportation experiment.
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. Valve artists experimented with Chell's attire, and considered changing her (ambiguous) nationality. 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". 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. 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.
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.
The writers considered introducing about six personality cores stored in portable spheres, whose main function would be story advancement. They planned cores based on Morgan Freeman's character Red from The Shawshank Redemption 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. 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. The two robotic characters provide some amusing death scenes in the cooperative mode, such as struggling while being crushed by a lowering ceiling. 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.
