Limbo is a puzzle-platform video game with horror elements developed by independent studio Playdead and originally published by Microsoft Game Studios for the Xbox 360. The game was released in July 2010 on Xbox Live Arcade, and it has since been ported by Playdead to several other systems, including the PlayStation 3, Linux, Android and Microsoft Windows. Limbo is a 2D side-scroller, incorporating a physics system that governs environmental objects and the player character. The player guides an unnamed boy through dangerous environments and traps as he searches for his sister. The developer built the game's puzzles expecting the player to fail before finding the correct solution. Playdead called the style of play "trial and death" and used gruesome imagery for the boy's deaths to steer the player from unworkable solutions.

The game is presented in monochromatic tones, using lighting, film grain effects and minimal ambient sounds to create an eerie atmosphere often associated with the horror genre. Journalists praised the dark presentation, describing the work as comparable to film noir and German Expressionism. Based on its aesthetics, reviewers classified Limbo as an example of video games as an art form.

Limbo received critical acclaim, but its minimal story polarised critics; some critics found the open-ended work to have deeper meaning that tied well with the game's mechanics, while others believed the lack of a significant plot and abrupt ending detracted from the game. A common point of criticism from reviewers was that the high cost of the game relative to its short length might deter players from purchasing the title, but some reviews proposed that Limbo had an ideal length. The game has been listed among the greatest games of all time.

Limbo was the third-highest selling game on the Xbox Live Arcade service in 2010, generating around $7.5 million in revenue. It won several awards from industry groups after its release, and was named as one of the top games for 2010 by several publications. Playdead's next title, Inside, was released in 2016 and revisited many of the same themes presented in Limbo.

Gameplay

The player controls the boy throughout the game. As is typical of most two-dimensional platform games, the boy can run left or right, jump, climb onto short ledges or up and down ladders and ropes, and push or pull objects. Limbo is presented through dark, greyscale graphics and with minimalist ambient sounds, creating an eerie, haunting environment. The dark visuals also serve to conceal numerous lethal surprises, including such environmental and physical hazards as deadly bear traps on the forest floor, or lethal monsters hiding in the shadows. Among the hazards are glowing worms, which attach themselves to the boy's head and force him to travel in only one direction until they are killed.

The game's second half features mechanical puzzles and traps using machinery, electromagnets, and gravity. Many of these traps are not apparent until triggered, often killing the boy. The player is able to restart at the last encountered checkpoint, with no limits placed on how many times this can occur. Some traps can be avoided and used later in the game; one bear trap is used to clamp onto an animal's carcass, hung from the end of a rope, tearing the carcass off the rope and allowing the branch and rope to retract upwards and allow the boy to climb onto a ledge otherwise out of reach. As the player will likely encounter numerous deaths before they solve each puzzle and complete the game, the developers call Limbo a "trial and death" game. Some deaths are animated with images of the boy's dismemberment or beheading, although an optional gore filter on the Xbox 360 blacks out the screen instead of showing these deaths (although audio is still played), as well as removing or replacing hanging/dead children. Game achievements (optional in-game goals) include finding hidden insect eggs and completing the game with five or fewer deaths.

Plot The primary character in Limbo is a nameless boy in search of his sister, who awakens in the middle of a forest on the "edge of hell" (the game's title is taken from the Latin limbus, meaning "edge"), where he encounters a humongous spider who tries to kill him. After using a trap to cut off the sharp points on half of the spider's legs, it retreats further into the forest, and the boy is allowed to pass. However, he is later caught in webs and spun into a cocoon. Shortly after freeing himself, he encounters a colony of other boys who actively try to kill him with traps, and later poison darts; they later fall victim to their very own final traps, after the boy finally manages to kill the spider after a short chase. At one point during his journey, he encounters a female character, who he thinks might be his sister, but is prevented from reaching her. The forest eventually gives way to a crumbling city environment, followed by industrial and flooded environments. On completion of the final puzzle, the boy is thrown through a pane of glass and back into the forest area from the beginning. After he wakes up, he walks a short distance until he again encounters the girl, who, upon his approach, stands up startled. At this point, the screen cuts to black, abruptly ending the game.

Development

According to Playdead co-founder Dino Patti and lead designer Jeppe Carlsen, Playdead's game director, Arnt Jensen, conceived Limbo around 2004. At that time, as a concept artist at IO Interactive, Jensen became dissatisfied with the increasingly corporate nature of the company. He had sketched a "mood image" of a "secret place" to get ideas, and the result, similar to the backgrounds of the final game, inspired Jensen to expand on it. Jensen initially tried on his own to program the game in Visual Basic around 2004, but found he needed more help and proceeded to create an art style trailer by 2006. He had only intended to use the trailer as a means to recruit a programmer to help him, but the video attracted substantial interest in the project from across the Internet, eventually leading him to meet with Patti, who was also dissatisfied with his job. Their collaboration led to the founding of Playdead. Although Patti helped in the first few months with programming, he realised that the project was much larger than the two of them could handle, and Patti developed the business around the game's expanded development.

Initial development was funded personally by Jensen and Patti, along with Danish government grants, including funding from the Nordic Game Program, while large investors were sought later in the development cycle. Jensen and Patti did not want to commit to major publishers, preferring to retain full creative control in developing the title. Jensen originally planned to release Limbo as a free Microsoft Windows title, but by this point, Jensen and Patti decided to make the game a retail title.

Playdead chose to ignore outside advice from investors and critics during development, such as to add multiplayer play and adjustable difficulty levels, and to extend the game's length. According to Patti, Playdead felt these changes would break the integrity of Jensen's original vision. Patti also felt that the investors "tried to control the company with no usable knowledge or respect", citing that after Microsoft raised concerns about the death of the boy, "one of the investors suggested we make him appear older by giving him a moustache." Numerous iterations of the game took place during a -year development cycle, including changes Jensen had demanded to polish the title, some elements being added two months prior to the game's release. Patti stated that they "trashed 70%" of the content they had developed, due to it not fitting in well with the context of the game. The core development team size was about 8 developers, expanding to 16 at various stages with freelancers. Playdead developed the design tools for Limbo in Visual Studio; Patti commented they would likely seek third-party applications for their next project given the challenges in creating their own technology. Patti later revealed they had opted to use the Unity engine for their next project, citing the development of their custom engine for Limbo as a "double product, doing both engine and game", and that their Limbo engine is limited to monochromatic visuals.

Story, art and music direction From the game's inception, Jensen set out three goals for the final Limbo product. The first goal was to create a specific mood and art style. Jensen wanted to create an aesthetic for the game without resorting to highly detailed three-dimensional models, and instead directed the art towards a minimalistic style to allow the development to focus its attention on the gameplay. Jensen's second goal was to only require two additional controls—jumping and grabbing—outside of the normal left-and-right movement controls, to keep the game easy to play. Finally, the finished game was to present no tutorial text to the player, requiring players to learn the game's mechanics on their own. The game was purposely developed to avoid revealing details of its content; the only tagline the company provided was, "Uncertain of his sister's fate, a boy enters Limbo." This was chosen so that players could interpret the game's meaning for themselves.

Some aspects of Limbo bore out from Jensen's own past, such as the forest areas that were similar to forests around the farm where he grew up, and the spider coming from Jensen's arachnophobia. Jensen drew inspiration from film genres, including works of film noir, to set the art style of the game; the team's graphic artist, Morten Bramsen, is credited with recreating that art style. Much of the game's flow was storyboarded very early in development, such as the boy's encounters with spiders and mind-controlling worms, as well as the overall transition from a forest to a city, then to an abstract environment. As development progressed, some of the original ideas became too difficult for the small team to complete. The storyline also changed; originally, the spider sequences were to be present near the end of the game, but were later moved to the first part. In retrospect, Jensen was aware that the first half of the game contained more scripted events and encounters, while the second half of the game was lonelier and puzzle-heavy; Jensen attributed this to his lack of oversight during the latter stages of development. Jensen purposely left the game with an open ending though with a specific interpretation only he knew, though noted after the game's release that some players, posting in forum boards, had suggested resolutions that were "scary close" to his ideas.