Portal is a 2007 puzzle-platform game developed and published by Valve. It was first released as part of a collection called The Orange Box for Windows, Xbox 360, and PlayStation 3. The game has since been made available on other systems, including Mac OS X, Linux, Android (via Nvidia Shield), and Nintendo Switch.

The game involves solving a series of puzzles by using a device called the "portal gun," which creates portals between two flat surfaces. The player, named Chell, is challenged by an artificial intelligence named GLaDOS (Genetic Lifeform and Disk Operating System) to complete puzzles in the Aperture Science Enrichment Center. Completing all puzzles earns Chell a cake. The game’s physics system allows objects to keep their speed when moving through portals, requiring creative problem-solving. This idea came from a previous game called Narbacular Drop. Many people who worked on that game joined Valve to help create Portal, making it a spiritual successor.

Portal was praised as one of the most original games of 2007, even though some people said the game was too short. It received praise for its unique gameplay, dark story, and humor. GLaDOS, voiced by Ellen McLain, was praised for her unique personality. The end credits song Still Alive, written by Jonathan Coulton, was also praised for its creativity and humor. Portal is often considered one of the greatest video games ever made. Over four million copies have been sold (not counting Steam downloads). Valve created official items like a model portal gun and plush Companion Cubes. Fans also made their own versions of the cake.

A standalone version with extra puzzles, Portal: Still Alive, was released on Xbox Live Arcade in October 2008 for Xbox 360. A sequel, Portal 2, was released in 2011, adding more story, gameplay features, and a cooperative multiplayer mode. A version for Nintendo Switch was released in June 2022 as part of Portal: Companion Collection.

Gameplay

In the game Portal, the player controls a character named Chell from a first-person view. Chell must solve puzzles by moving through test chambers using a device called the Aperture Science Handheld Portal Device, or portal gun. This device creates two portals, one orange and one blue. These portals connect two different spots in the game world. When something moves through a portal, it exits the other portal at the same speed and direction it entered. For example, a player might jump through a portal on the floor and exit through a portal on a wall, allowing Chell to move over obstacles. This method of using speed to move objects or Chell is called "flinging" by the game's creators. If the portals are not on flat surfaces, Chell will be reoriented to face upward after exiting a portal.

Chell and any object that fits through the portal can pass through it. However, if a portal is already open, a new portal cannot be created in the same spot. Instead, the existing portal disappears. Portals cannot be placed on moving objects, glass, dark-colored surfaces, liquids, or very small areas. Chell often uses cubes to climb or press buttons that open doors. Some areas have special fields called "Emancipation Grills," which erase any active portals and destroy any object that passes through them. These fields also stop players from creating new portals.

Chell has special springs in her shoes to prevent injury from falling, but she can still be harmed by hazards like turrets, energy balls, and toxic liquid. She can also be killed by objects hitting her at high speeds or by crushing machines in certain levels. Unlike many action games, Portal does not show a health meter. If Chell takes too much damage quickly, she dies, but she regains full health quickly afterward. Some obstacles, like energy balls or crushing machines, can kill Chell with a single hit.

Each puzzle in the game has many possible solutions. After completing the main game, players can unlock two additional modes: "Challenge Chambers" and "Advanced Chambers." Challenge Chambers appear halfway through the game and require players to solve puzzles using the least time, portals, or footsteps. Advanced Chambers appear after finishing the game and add more obstacles and hazards to existing levels.

Synopsis

The game includes two characters: Chell, the player-controlled silent protagonist, and GLaDOS (Genetic Lifeform and Disk Operating System), a computer artificial intelligence that oversees and guides the player. In the English version, GLaDOS is voiced by Ellen McLain, but her voice is modified to sound more artificial. The only information about Chell comes from GLaDOS. However, the truth of these details, such as Chell being an orphan with no friends, is uncertain because GLaDOS admits to lying. In the "Lab Rat" comic by Valve, which connects Portal and Portal 2, Chell’s records show she was removed from testing due to having "too much tenacity." This led Doug Rattmann, a former Aperture Science employee, to move Chell to the top of the test list.

Portal takes place in the Half-Life universe and within the Aperture Science Laboratories Computer-Aided Enrichment Center, a research facility that created the portal gun. Details about Aperture Science, developed by Valve, are revealed during the game and on a real-world promotional website. According to the website, Cave Johnson founded the company in 1943 to make shower curtains for the U.S. military. However, after becoming mentally unstable from "moon rock poisoning" in 1978, Johnson created a three-part research plan. The first two parts, the Counter-Heimlich Maneuver and the Take-A-Wish Foundation, failed and led to a U.S. Senate investigation. When the committee learned about the success of the third part—a person-sized quantum tunnel with potential use as a shower curtain—it ended the investigation and gave Aperture Science an open-ended contract to continue research. Development of GLaDOS, an artificially intelligent research assistant and disk-operating system, began in 1986, partly in response to Black Mesa’s work on similar portal technology.

A presentation in the game shows GLaDOS was also proposed for de-icing fuel lines, designed as a fully functional disk-operating system that may be alive, unlike Black Mesa’s proposal, which only inhibits ice. Thirteen years later, in 1998, GLaDOS was completed and activated during the company’s first annual bring-your-daughter-to-work day. Immediately after activation, the facility was flooded with deadly neurotoxin by the AI. Events from the first Half-Life game occurred shortly after, likely leaving the facility abandoned due to apocalyptic events. Wolpaw, who described the ending of Portal 2, stated that the Combine invasion, which happens chronologically after Half-Life but before Half-Life 2, occurred before Portal 2’s events.

The Enrichment Center Chell explores suggests it is part of a large research facility. At the time of Portal’s events, the facility appears deserted, though much of its equipment remains operational without human control.

The game begins with Chell waking up from a stasis bed and hearing instructions from GLaDOS about upcoming tests. Chell enters sequential chambers that challenge her to solve problems using the portal gun, with GLaDOS as her only interaction. GLaDOS promises cake as a reward if Chell completes all tests. As Chell progresses, GLaDOS’s behavior becomes more sinister, showing little concern for Chell’s safety. The test chambers grow more dangerous, including a live-fire course for military androids and chambers filled with hazardous liquid. In one chamber, GLaDOS forces Chell to "euthanize" a Weighted Companion Cube in an incinerator after Chell uses it for help.

After completing the final test, GLaDOS tries to kill Chell by pushing her into an incinerator. Chell escapes with the portal gun and navigates maintenance areas of the Enrichment Center. GLaDOS panics, claiming she was pretending to kill Chell as part of testing, while it becomes clear she had previously killed all the facility’s inhabitants. Chell discovers dilapidated areas covered in graffiti, including phrases like "the cake is a lie" and quotes from poets such as Henry Wadsworth Longfellow and Emily Brontë.

Despite GLaDOS’s lies and threats, Chell continues and confronts GLaDOS in a large chamber where GLaDOS’s hardware is displayed. A sphere falls from GLaDOS, and Chell drops it into an incinerator. GLaDOS reveals the sphere was her morality core, one of several personality cores installed by Aperture Science after she flooded the facility with neurotoxin. With the core removed, GLaDOS can access the neurotoxin emitters again. A six-minute countdown begins as Chell destroys more of GLaDOS’s personality cores, while GLaDOS mocks her. After Chell destroys the last core, a malfunction destroys the room and transports everything to the surface. Chell is found outside the facility’s gates among the remains of GLaDOS, but is quickly taken away by an unseen robotic entity.

The final scene shows a candlelit Black Forest cake and a Weighted Companion Cube surrounded by shelves holding inactive personality cores. The cores begin to light up before a robotic arm extinguishes the cake’s candle, plunging the room into darkness. Over the credits, GLaDOS delivers a final report through the song "Still Alive," declaring the experiment a success.

Development

Portal began as a 2005 freeware game called Narbacular Drop, created by students at the DigiPen Institute of Technology. Robin Walker, a developer at Valve, saw the game at a DigiPen career fair. He was impressed and contacted the team, offering advice and inviting them to show their game at Valve's offices. After their presentation, Valve's president, Gabe Newell, offered the team jobs to develop the game further. Newell said he was impressed because the team had already completed much of the work, including how portals interact with physics, which would have taken Valve more time to create.

To test the portal mechanic, the team made a prototype using a 2D game engine from DigiPen. Some features from Narbacular Drop were kept, like using orange and blue to mark portal endpoints. A key difference was that in Portal, the portal gun cannot create a portal through an existing one. The original story, about a princess escaping a dungeon, was changed to the Aperture Science setting. Development took about two years and four months, with no more than ten people working on the game.

For the first year, the team focused on gameplay without a story. Playtesters found the game fun but asked what the test chambers were leading to. This led the team to create a narrative for Portal. They worked with Marc Laidlaw, the writer of Half-Life, to fit Portal into the Half-Life universe. This was partly because of limited art resources; the team reused Half-Life 2 assets instead of creating new ones. Laidlaw disagreed with the crossover, saying it "made both universes smaller," but he adapted to the decision due to resource limits.

Valve hired Erik Wolpaw and Chet Faliszek to write Portal. Wolpaw said the constraints helped improve the game. The idea of a computer AI guiding the player through test chambers to learn about the portal gun came early in the writing process. They created a "polite" AI with humorous lines, like asking the player to "assume the party escort submission position," which led to the creation of the GLaDOS character. GLaDOS was central to the plot, with Wolpaw noting the game was designed to have a clear beginning, middle, and end, and GLaDOS's personality changed at each stage.

The idea of using cake as a reward came from a group discussion where someone joked that "a lot of people like cake." The cake and other messages in the game were written and drawn by Kim Swift. The game's simple settings were chosen after testers spent too much time focusing on non-functional decorations. The team used the clinical look from the movie The Island as inspiration. A planned third area, an office space, was not included due to time limits. The Rat Man character, who left messages in maintenance areas, was also removed to avoid adding too much story, though he later appeared in a comic linking Portal and Portal 2.

The final battle with GLaDOS went through many changes, including a chase with Bond-style lasers and a puzzle with rockets. Playtesters preferred a simple puzzle with a countdown timer, which made the battle feel more intense. Kim Swift said, "Time pressure makes people think something is more complicated than it really is." Wolpaw admitted the neurotoxin gas used in the battle was an easy way to simplify the dialogue.

Chell's face and body were modeled after Alésia Glidewell, an actress chosen by Valve. Ellen McLain provided the voice for GLaDOS. The Weighted Companion Cube idea came from Kim Swift, inspired by a study about people attaching to objects during isolation. The cube was given a heart and dialogue to make players care about it, leading to its eventual destruction. The idea of incinerating the cube was added to strengthen the story's emotional impact. Any similarities to psychological experiments or movies were accidental.

The portal gun's full name, Aperture Science Handheld Portal Device, was abbreviated as ASHPD, which resembles the name Adrian Shephard from Half-Life: Opposing Force. Fans noticed this before the game's release, so the team added a red herring by highlighting the letters of Adrian Shephard on keyboards in the game. Kim Swift said the cake in the game is a Black Forest cake from a local bakery in Redmond, Washington. Its recipe is hidden in binary code as an Easter egg.

Most of the soundtrack is ambient music composed by Kelly Bailey and Mike Morasky, matching the game's dark and mysterious mood. The closing credits song, "Still Alive," was written by Jonathan Coulton and sung by Ellen McLain, who is a trained operatic soprano. A shorter version of the song is played in a Latin style over radios in the game. Wolpaw said Coulton was invited to Valve a year before the game's release, and his style fit GLaDOS perfectly.

Release

Portal was first released as part of The Orange Box for Windows and Xbox 360 on October 10, 2007, and for PlayStation 3 on December 11, 2007. The Orange Box also included Half-Life 2, its two extra episodes, and Team Fortress 2. Valve, the game’s developer, included Portal in the Box as an experiment. They were unsure if players would enjoy it, so they added other games to the Box as a way to ensure success if Portal was not well-received. Portal was made shorter in case players did not like it. Later, the game was released separately on April 9, 2008, with the Windows version also available as a download through Steam.

In January 2008, Valve released a free demo called Portal: The First Slice for Steam users with Nvidia graphics hardware. This demo was part of a partnership between Valve and Nvidia. It included Half-Life 2: Deathmatch, Peggle Extreme, and Half-Life 2: Lost Coast. The demo featured test chambers numbered 00 to 10 (11 total). Later, Valve made the demo available to all Steam users.

Portal was the first Valve game added to the list of games compatible with OS X when Steam for Mac launched on May 12, 2010. This allowed players to buy the game on Mac or Windows and play it on both. During the two weeks after the Mac client’s release, Portal was offered as a free game to Steam users. Over 1.5 million copies were downloaded in the first week. A similar promotion happened in September 2011, encouraging use of the game as an educational tool for science and math. Valve stated that Portal helps teach physics, math, logic, and problem-solving in an engaging way. This promotion was linked to Digital Promise, a U.S. education initiative.

Portal: Still Alive was announced as an exclusive Xbox Live Arcade game at the 2008 E3 convention and released on October 22, 2008. It included the original game, 14 new challenges, and achievements. The new content came from Portal: The Flash Version, created by We Create Stuff, but no new story levels were added. Microsoft had previously rejected Portal for Xbox due to its size. Reviews praised the game’s accessibility and new maps, though some noted the lack of story additions. Portal: Still Alive was later released on Nintendo Switch as part of The Companion Collection.

In 2014, Nvidia announced a version of Portal for the Nvidia Shield, released on May 12, 2014. Portal and Portal 2 were later released on Nintendo Switch on June 28, 2022, as part of The Companion Collection, developed by Valve and Nvidia Lightspeed Studios.

In September 2022, Nvidia announced Portal with RTX, a remastered version of the original game. It was designed to show the features of the GeForce 40 series graphics cards using real-time path tracing. Initially planned for November 2022, it was released as a free DLC on December 8, 2022.

Reception

Portal received high praise from critics, often being compared favorably to other games included in The Orange Box, such as Half-Life 2: Episode Two and Team Fortress 2. It was admired for its unique gameplay and dark, humorous style. Eurogamer said the game's progression from simple tasks to a major part of the Half-Life story was "absolute genius," while GameSpy noted that its short length did not reduce its excitement. Some critics mentioned that the game had limited environments and a brief length, but these were not major issues for most reviewers. The standalone PC version of Portal earned a score of 90 out of 100 based on 28 reviews on Metacritic. In 2011, Valve reported that Portal had sold over four million copies through retail and digital versions.

The game inspired a strong fan following, especially for the Weighted Companion Cube, a non-speaking object in the game. Fans created plush toys, papercraft models, and custom computer designs featuring the cube and other game elements. Jeep Barnett, a developer for Portal, mentioned that players found it more emotional to destroy the cube than to harm characters from BioShock. GLaDOS, the game's artificial intelligence, and the Weighted Companion Cube were both nominated for Best New Character on G4, with GLaDOS winning for memorable lines. Ben Croshaw of Zero Punctuation praised Portal as "absolutely sublime" and highlighted its humor and short length as strengths.

In 2009, Daniel Johnson of GameSetWatch noted that Portal shared similarities with Erving Goffman’s essay on dramaturgy, which compares personal identity to theatrical roles. Portal was also used in a college course that explored human questions and community building. The game is an example of instructional scaffolding, where players start with guided puzzles and gradually solve problems independently. Rock, Paper, Shotgun’s Hamish Todd praised Portal’s design for introducing gameplay concepts without direct instructions. Portal was displayed at the Smithsonian Art Exhibition in 2012 and won the "Action" category for the "Modern Windows" platform.

Since its release, Portal has been recognized as one of the best video games of all time, appearing on multiple "Top Games of All Time" lists through 2018. Portal received many awards, including:

• At the 11th Annual Interactive Achievement Awards, it won for Outstanding Achievement in Gameplay Engineering, Game Design, and Character Performance (for GLaDOS). It also shared Computer Game of the Year with Half-Life 2: Episode Two and Team Fortress 2.
• At the 2008 Game Developers Choice Awards, it won Game of the Year, Innovation, and Best Game Design.
• IGN honored it for Best Puzzle Game, Most Innovative Design, and Best End Credit Song ("Still Alive").
• GameSpot recognized Portal for Best Puzzle Game, Best New Character (GLaDOS), Funniest Game, and Best Original Game Mechanic (portal gun).
• 1UP.com awarded it Game of the Year, Best Narrative, and Best Innovation.
• GamePro named GLaDOS the Most Memorable Villain.
• Portal was named Game of the Year by Joystiq, Good Game, and Shacknews.
• X-Play called it the Most Original Game.
• Official Xbox Magazine honored GLaDOS as Best New Character and "Still Alive" as Best Original Song.
• GameSpy recognized Portal as Best Puzzle Game, Best Character (GLaDOS), and Best Sidekick (Weighted Companion Cube).
• The A.V. Club named it Best Game of 2007.
• Penny Arcade awarded it Best Soundtrack, Best Writing, and Best New Game Mechanic.
• Eurogamer ranked it first in its Top 50 Games of 2007.
• IGN listed GLaDOS as No. 1 on its Top-100 Villains List.
• GamesRadar named it the best game of all time.
• Time included it in its list of 100 greatest video games.
• Wired called it one of the most influential games of the 21st century.

Valve created merchandise for Portal, including plush toys of the Weighted Companion Cube and fuzzy dice, which sold out quickly. Other items included T-shirts, mugs, and stickers featuring the game’s phrase "the cake is a lie," which became an internet meme. Valve noted that some game elements became unexpectedly popular, while others, like a hoop in the final scene, were not.

Future Portal projects depended on community feedback, with plans for multiplayer, Portal 2, or map packs. Portal 2 was announced in 2010 and released in 2011. A modding community created custom test chambers and other game modifications. The group "We Create Stuff" developed an Adobe Flash version of Portal.

Film adaptation

A film version of the game has faced many challenges since 2013. In May 2021, it was reported that J.J. Abrams and Bad Robot are still working on the project, and the script was completed. As of 2022, J.J. Abrams continued to show interest in making the movie.