# Portal
**Portal** is a 2007 first-person puzzle-platform video game developed and published by Valve, in which the player solves physical puzzles by creating pairs of connected portals that teleport the player character and objects through space.[1](https://store.steampowered.com/app/400/Portal/) It was released on October 10, 2007, and grew out of *Narbacular Drop*, a student project from [DigiPen Institute of Technology](https://www.edgepedia.org/digipen-institute-of-technology) whose development team Valve hired to rebuild the concept on its [Source](https://www.edgepedia.org/source-game-engine) engine.[1](https://store.steampowered.com/app/400/Portal/) • [2](https://www.digipen.edu/showcase/student-games/narbacular-drop) The game was acclaimed on release, named Game of the Year 2007 at the [Game Developers Choice Awards](https://www.edgepedia.org/game-developers-choice-awards), and spawned a sequel, *Portal 2*, in 2011.[3](https://ttabvue.uspto.gov/ttabvue/ttabvue-92054935-CAN-1.pdf) • [4](https://www.gamespot.com/articles/portal-2-sells-4-million-report/1100-6375689/)
| Key fact | Detail |
|---|---|
| Release | October 10, 2007; developed and published by Valve[1](https://store.steampowered.com/app/400/Portal/) |
| Origin | *Narbacular Drop*, a 2005 DigiPen student game; Valve founder Gabe Newell hired the entire student team after a demo[2](https://www.digipen.edu/showcase/student-games/narbacular-drop) |
| Development | Roughly two years and four months, with no more than ten people; the Game Developer postmortem lists 8 full-time developers[5](https://arkaevren.com/en/games/portal/2007/production-story/) • [6](https://www.gamedeveloper.com/design/thinking-with-portals-creating-valve-s-new-ip) |
| Original packaging | Sold within *The Orange Box* alongside Half-Life 2, its two episodes, and Team Fortress 2[7](https://www.gamespot.com/articles/portal-sells-nearly-4-million/1100-6309201/) |
| Reception | Metacritic score of 90 ("Universal Acclaim") from 27 critic reviews; named Game of the Year 2007, Best Game Design, and Innovation Award at the 2008 Game Developers Conference[8](https://www.metacritic.com/game/portal/critic-reviews/?platform=pc) • [3](https://ttabvue.uspto.gov/ttabvue/ttabvue-92054935-CAN-1.pdf) |
| Sales | Nearly 4 million units excluding Steam sales, as confirmed by Valve in April 2011[7](https://www.gamespot.com/articles/portal-sells-nearly-4-million/1100-6309201/) |
| Sequel | *Portal 2* (2011), which sold 4 million copies[4](https://www.gamespot.com/articles/portal-2-sells-4-million-report/1100-6375689/) |
## Gameplay and setting
The player controls Chell, a silent protagonist navigating the test chambers of the Aperture Science Enrichment Center.[9](https://erikdemaine.org/papers/Portal_FUN2018/paper.pdf) The central tool is the Aperture Science Handheld Portal Device, the portal gun, which places one orange and one blue portal on suitable surfaces; entering one portal transports the player or an object to the other, and momentum is retained through the transit, so flinging the character at speed becomes a core technique.[9](https://erikdemaine.org/papers/Portal_FUN2018/paper.pdf) • [10](https://www.youtube.com/watch?v=Ml8ufaU5xEg) Portals can only be placed on certain surfaces, white concrete walls, while black metallic surfaces reject them, a restriction that structures the game's puzzles.[11](https://www.pcgamer.com/games/puzzle/portal-sicko-beats-the-game-with-switched-wall-textures-so-no-surface-is-where-its-meant-to-be-creating-a-whole-new-puzzling-challenge-in-the-process/)
The game's antagonist and narrator is GLaDOS, the Genetic Lifeform and Disk Operating System, an artificial intelligence voiced by [Ellen McLain](https://www.edgepedia.org/ellen-mclain) who guides, taunts, and menaces the player through the chambers, promising cake as a reward.[10](https://www.youtube.com/watch?v=Ml8ufaU5xEg) The end credits song "Still Alive," written by [Jonathan Coulton](https://www.edgepedia.org/jonathan-coulton), became one of the game's most recognizable elements.[10](https://www.youtube.com/watch?v=Ml8ufaU5xEg)
## Development
Portal's path to Valve was unusual. Seven DigiPen students created *Narbacular Drop* as their senior project, a 3D puzzle game in which Princess "No-Knees" escapes a sentient dungeon using two interconnected portals she can place on walls, ceilings, and floors.[2](https://www.digipen.edu/showcase/student-games/narbacular-drop) • [6](https://www.gamedeveloper.com/design/thinking-with-portals-creating-valve-s-new-ip) At DigiPen's career fair, Valve representatives saw the game and invited the team to demonstrate it at Valve's offices, where [Gabe Newell](https://www.edgepedia.org/gabe-newell) was sitting in the audience; about fifteen minutes into the demo he offered the entire team jobs on the spot to remake the game on the Source engine.[2](https://www.digipen.edu/showcase/student-games/narbacular-drop) • [6](https://www.gamedeveloper.com/design/thinking-with-portals-creating-valve-s-new-ip) The team, including producer Kim Swift, began work on [Portal](https://www.edgepedia.org/portal-video-game) in July 2005.[6](https://www.gamedeveloper.com/design/thinking-with-portals-creating-valve-s-new-ip)
**Playtesting and story.** The team adopted Valve's practice of near-continuous playtesting, bringing in a new player every week and observing them from beginning to end, which let them build a smooth difficulty ramp by splitting concepts that confused testers into separate sections.[6](https://www.gamedeveloper.com/design/thinking-with-portals-creating-valve-s-new-ip) Because the team lacked the staffing to animate human characters, the story had to be told without visible characters; writer Erik Wolpaw's recorded text-to-speech announcements for the game's first room became the narrative voice of GLaDOS, and the facility was tied to Aperture Science, the fictional rival of Half-Life's Black Mesa.[6](https://www.gamedeveloper.com/design/thinking-with-portals-creating-valve-s-new-ip)
**Technical work.** [Porting](https://www.edgepedia.org/porting) the portal mechanic into Source required a custom portal system rather than a simple teleport: the physics code had to treat a portal as a temporary hole connecting geometry in different parts of the map, and the team solved problems such as objects straddling a portal and self-collision, level-of-detail calculations measured through portals, and stencil-buffer rendering that allowed deeply recursive portal views.[6](https://www.gamedeveloper.com/design/thinking-with-portals-creating-valve-s-new-ip)
## Release and reception
Valve packaged Portal inside *The Orange Box* (2007) with [Half-Life 2](https://www.edgepedia.org/half-life-2), its episodes, and [Team Fortress 2](https://www.edgepedia.org/team-fortress-2), a decision the team credited with exposing an experimental, short, story-driven puzzle game to a much wider audience than a standalone release could have reached.[6](https://www.gamedeveloper.com/design/thinking-with-portals-creating-valve-s-new-ip) Critics rated it highly: Metacritic recorded a score of 90 from 27 reviews, all positive, and PC Gamer UK called it "a magnificent puzzle game" in which players "almost never get stuck."[8](https://www.metacritic.com/game/portal/critic-reviews/?platform=pc) At the 2008 [Game Developers Conference](https://www.edgepedia.org/game-developers-conference) it was named Game of the Year 2007 and won Best Game Design and the Innovation Award.[3](https://ttabvue.uspto.gov/ttabvue/ttabvue-92054935-CAN-1.pdf)
By April 2011 Valve confirmed the original Portal had sold nearly 4 million units worldwide excluding Steam sales.[7](https://www.gamespot.com/articles/portal-sells-nearly-4-million/1100-6309201/) The game's popularity produced official merchandise such as plush Companion Cubes and fan recreations of the cake and portal gun.[10](https://www.youtube.com/watch?v=Ml8ufaU5xEg)
## Sequel and later releases
*Portal 2* was released in April 2011, adding new gameplay mechanics and a cooperative multiplayer mode, and sold 4 million copies.[4](https://www.gamespot.com/articles/portal-2-sells-4-million-report/1100-6375689/) • [10](https://www.youtube.com/watch?v=Ml8ufaU5xEg) Both games later came to [Nintendo Switch](https://www.edgepedia.org/nintendo-switch) as the *Portal: Companion Collection*, released June 28, 2022.[12](https://www.nintendo.com/en-gb/Games/Nintendo-Switch-download-software/Portal-Companion-Collection-2168991.html) In December 2022, NVIDIA Lightspeed Studios released *Portal with RTX*, a free downloadable content package for existing Portal owners that rebuilt the game's graphics with full ray tracing and NVIDIA DLSS.[13](https://www.nvidia.com/en-us/geforce/news/gfecnt/202212/portal-rtx-available-december-8/)
## Analysis and legacy
Portal's central mechanic has been studied formally. Erik D. Demaine of MIT CSAIL and colleagues classified the computational complexity of generalized Portal, proving [NP-hardness](https://www.edgepedia.org/np-hardness), PSPACE-completeness, or pseudo-polynomiality depending on which game mechanics are allowed; their turret-based proof also generalizes to show NP-hardness of many other 3D games, including Half-Life 2, Doom, and [Grand Theft Auto](https://www.edgepedia.org/grand-theft-auto).[9](https://erikdemaine.org/papers/Portal_FUN2018/paper.pdf) The game's design, which introduces the portal mechanic gradually and restricts portal placement to specific surfaces, has been widely cited as a model of puzzle-game teaching, and its humor and GLaDOS are frequently referenced in internet culture.[11](https://www.pcgamer.com/games/puzzle/portal-sicko-beats-the-game-with-switched-wall-textures-so-no-surface-is-where-its-meant-to-be-creating-a-whole-new-puzzling-challenge-in-the-process/) • [14](https://repository.nwu.ac.za/bitstreams/c5da3fe3-9374-47e6-a16c-11aeaa14bd2b/download)
## References
1. [Portal on Steam, Valve Corporation](https://store.steampowered.com/app/400/Portal/)
2. [Narbacular Drop, DigiPen Institute of Technology](https://www.digipen.edu/showcase/student-games/narbacular-drop)
3. [Valve answer brief, USPTO Trademark Trial and Appeal Board proceeding 92054935](https://ttabvue.uspto.gov/ttabvue/ttabvue-92054935-CAN-1.pdf)
4. [Portal 2 sells 4 million – Report, GameSpot](https://www.gamespot.com/articles/portal-2-sells-4-million-report/1100-6375689/)
5. [20 Facts From the Development of Portal, Arka Evren](https://arkaevren.com/en/games/portal/2007/production-story/)
6. [Thinking With Portals: Creating Valve's New IP, by Kim Swift et al., Game Developer](https://www.gamedeveloper.com/design/thinking-with-portals-creating-valve-s-new-ip)
7. [Portal sells nearly 4 million, GameSpot](https://www.gamespot.com/articles/portal-sells-nearly-4-million/1100-6309201/)
8. [Portal critic reviews, Metacritic](https://www.metacritic.com/game/portal/critic-reviews/?platform=pc)
9. [The Computational Complexity of Portal and Other 3D Video Games, Demaine, Lockhart, and Lynch, FUN 2018](https://erikdemaine.org/papers/Portal_FUN2018/paper.pdf)
10. [Portal ~Full Gameplay~, YouTube description](https://www.youtube.com/watch?v=Ml8ufaU5xEg)
11. [Portal sicko beats the game with 'switched' wall textures, PC Gamer](https://www.pcgamer.com/games/puzzle/portal-sicko-beats-the-game-with-switched-wall-textures-so-no-surface-is-where-its-meant-to-be-creating-a-whole-new-puzzling-challenge-in-the-process/)
12. [Portal: Companion Collection, Nintendo](https://www.nintendo.com/en-gb/Games/Nintendo-Switch-download-software/Portal-Companion-Collection-2168991.html)
13. [Portal with RTX available December 8, NVIDIA](https://www.nvidia.com/en-us/geforce/news/gfecnt/202212/portal-rtx-available-december-8/)
14. [Thesis section 3.5.4.3 Portal games, North-West University repository](https://repository.nwu.ac.za/bitstreams/c5da3fe3-9374-47e6-a16c-11aeaa14bd2b/download)
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*Topic: Encyclopedia › Sports, games, and recreation › Video games and digital play › Games and gameplay › Individual game titles › Individual PC and computer-platform game titles*
*Initially written Sep 17, 2026 · Reviewed: Sep 17, 2026; Sep 30, 2026; Oct 21, 2026 · Edited: Sep 30, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
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