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Perplex City was a long-term alternate reality game (ARG) presented by Mind Candy, a London-based development team. The first "season" of the game had players looking for "The Receda Cube" (referred to simply as "The Cube"), a priceless scientific and spiritual artifact to the people of a fictional metropolis known as "Perplex City", that had been stolen and buried somewhere on Earth. The game offered a real-life £100,000 reward (approx. $130,000 or €115,000) to whoever found it. Like most alternate reality games, the story of Perplex City is told through blogs, puzzles, and other various media.
According to Mind Candy, the first wave of cards for the new game season, called Perplex City Stories, would be released on March 1, 2007. However, in June 2007, they released an announcement which declared that the second season was on indefinite hold.
Perplex City is a massive fictitious metropolis that has an unknown number of connections to Earth. It has a near-future feel to it, with advanced mobile technology, neuro-enhancing pharmaceuticals and kilometer-high skyscrapers. There is also a slightly more Utopian element to city life than commonly found on Earth. The most important characteristic of the city's culture is the importance they place on puzzles and other mental pursuits. Their leading competitive event, the Academy Games, is primarily a competition of intellectual skill rather than physical strength. In fact, nearly every part of their culture touches upon the cryptic and mind.
Their religions fall loosely around a mythology of building, construction and technology, none of which are explicitly theistic. The Cube is, in all cases, a sacred and holy object, and rightfully so. It possesses a range of unusual properties which many believe to be of a supernatural origin.
Citizens of Perplex City
Key figures in city life include Sente Kiteway, Master of The Academy (The academy being an advanced learning institution in the city) and former custodian of the Cube. His two daughters, Scarlett and Violet, communicate regularly with the people of Earth through their blogs. Pietro Salk, an investigative reporter for leading newspaper The Sentinel, produced many leads before he was unceremoniously killed off for getting too close to the truth. The team at the Academy tasked with returning the Cube (and ostensibly authors of the puzzle cards) are also frequently in touch, and Kurt McAllister is an important ally to players on Earth.
An artifact called the Receda Cube (pronounced /Reh-kay-duh/) is stolen from the Perplex City Academy and makes its way to Earth. A Cube Retrieval Team (CRT) is formed to search for the Cube. Because citizens of Perplex City are unable to travel to Earth, the Master of Perplex City Academy, Sente Kiteway, asks for help in finding the Cube from the citizens of Earth, offering to share any leads or clues that he or the CRT may get.
Clues to the location of the Cube are periodically left by the person who stole it, known only as Combed Thunderclap. It is discovered that an organization called the Third Power and a Cube-worshipping cult called the Reconstructionists are also looking for the Cube. While the people of Earth are left to search for the Cube on Earth, various citizens of Perplex City, particularly Kurt McAllister and Sente’s two daughters, Scarlett and Violet, attempt to find additional clues in Perplex City and to discover the identity of Combed Thunderclap. The former three discover the lab in which the Cube was made. They find that the Cube was built by Sente and can be used as a weapon and a teleporter. The Cube is finally found by the people of Earth in Northamptonshire, England; they also determine that it was Violet who stole the Cube and hid it on Earth, in an effort to keep it out of the hands of the Third Power.
Mind Candy sells a series of collectible puzzle cards. They are sold in booster packs, with each pack containing six random cards from the total possible 256 cards. Cards are divided into sets and subsets of varying rarity and difficulty.
Unlike CCGs such as Magic: The Gathering or Pokémon, though, the cards are not designed for competitive player-versus-player "combat". Instead, each card depicts a different puzzle, with the rarer cards also featuring more complex riddles. Cards are marked with unique identifiers which can then be entered onto the Perplex City website, earning points and a place on a leaderboard. Many cards contain hidden features, such as ultraviolet or heat-sensitive inks, and they cover a broad range of themes from pop-culture trivia to cryptography and logic brainteasers.
Each card is a member of a four-card set. If all four cards are solved by a player, they receive double points for each card in the set.
- Riemann (S1, Card #238) apparently asks players to prove the Riemann hypothesis. However, the Perplex City web site could not possibly have validated such a proof, so it is likely that this was not the actual solution. This is currently the only remaining unsolved card.
- Billion to One (S1, Card #256) features the face of a man, with a caption in Japanese that reads 私を見つけなさい, which translates to "Find Me." His image has been spread to social networking sites, in attempts to locate and make contact with this person. The card was solved in December of 2020 when the man in question was found.  He explained that the original idea had been that he would ask the actual puzzle question for the card to whoever found him, but since he had forgotten the question, the puzzle author later posted a recording of the question on Soundcloud: it was "Who died after giving birth to flames?", with the answer Izanami.
Out of print cards
Two cards are no longer in circulation. The cards were excluded from wave-three print runs because they did not fit on the print layout. While these problems have been rectified, Mind Candy has no plans to replace or reprint these cards in the future. They are:
- Card #238 (Riemann) - chosen to be excluded due to the complete inability of the card to be solved for the foreseeable future.
- Card #245 (Relativity) - chosen to be excluded more or less at random, but the decision was no doubt influenced by the fact that the problem and solution are quite complex.
The puzzle cards are intended as an introduction to the characters and story of Perplex City itself, and the deeper mysteries of the Cube theft. Clues found on the cards direct players to various websites, blogs, emails, phone calls, and SMS messages, originating from Perplex City. These often feature puzzles of their own, whose solutions lead to further puzzles. Frequently these puzzles require players to co-operate in reaching various goals.
Perplex City has been running since late 2004, much longer than the traditional ARG. Its longevity has allowed for a number of events that simply would not be possible within a two-month traditional lifespan of an ARG. Some examples of this include:
- Players wrote a book to enable a character to become a "published author" and gain access to relevant archives.
- A full-length CD of cryptic techno music was released by a Perplexian musician.
- A banner plane flew across Manchester with a keyword that enabled access to a new area of the game.
- Sixty players attended an in-game event in search for clues, only for one of their own to be revealed as a mole and escape in a black helicopter.
- 220 people participated in the first Perplex City Academy Games in London, a high-tech scavenger hunt across the capital. A month later, a similar event was held in New York.
In late 2006, Mind Candy released Perplex City: The Board Game. Players solve anagrams, logic problems, visual puzzles, and trivia questions to collect a set of colored stones. Players can also challenge one another for their collected stones. To win, the last stone must be collected through challenging another player.
The rules insert maintains an in-universe approach to Perplex City, giving background about its puzzle-loving citizens and a fictional history of the board game.
The Mind Candy cards were first released in select outlets arounds the world, but are increasingly readily available from retailers both on- and offline. On September 7, 2006, Mind Candy announced that GameStop was to begin carrying Perplex City cards in 700 stores in the United States. As of September 26, 2006, some 682,425 cards have been marked as solved on the Perplex City leaderboard, with 45,215 players registered.
In June 2007 Mind Candy announced that it would be putting season 2 of its ARG on hold indefinitely. Mind Candy's focus later moved to the Moshi Monsters franchise and the Perplex City project was abandoned.
The reviewer from the online second volume of Pyramid stated that "The object of the game is, well . . . that depends. The whole game is incremental. At its simplest, the idea is to solve the poser on a card. If you want to become 200,000 very real dollars richer (apparently they can do bank transfers across the dimensional gulf), you need to suck as much information as you can out of as many sources as you can, including the cards, some scattered websites, and even real people (or their cell phones), to unlock where on Earth the Cube has been hidden."
- Alternate reality game
- Masquerade (book)
- Eric Harshbarger, Perplex City puzzle designer
- Andrea Phillips, Perplex City writer & designer
- Naomi Alderman, Perplex City writer
- Digital Treasure Hunt gets Winner, a BBC story.
- "The Perplex City endgame story: The weekend". www.andthenhesaid.com.
- "The Perplex City endgame story: The end". www.andthenhesaid.com.
- Violet Underground Archived 2007-02-16 at the Wayback Machine
- "Find Satoshi". Find Satoshi.
- "billion2one.org: Help Us Find This Man!". September 2, 2006. Archived from the original on 2006-09-02.
- "Find Satoshi". Find Satoshi.
- https://soundcloud.com/user-650898069-942959925/speech-20201230195201540. Missing or empty
- Seaside Press Archived 2006-07-20 at the Wayback Machine, in-game website with a real-life link to purchase the book online.
- "502 Bad Gateway nginx openresty 18.104.22.168". www.heshrecords.com. Archived from the original on September 29, 2007.
- PXC Live Event: A Mole Amongst Thee ARGN, October 30, 2005
- London Live Event Archived 2006-07-03 at the Wayback Machine from Perplex City official site.
- New York PCAG Tournament Archived 2006-06-15 at the Wayback Machine The Scarlett Kite, March 8, 2006
- "PerplexCity: The Boardgame (2006)". BoardGameGeek. Retrieved 20 September 2016.
- Perplex City News Archived 2006-09-01 at the Wayback Machine accessed September 26, 2006
- VCs invest in alternate reality Archived 2006-09-20 at the Wayback Machine ZDNet News: December 6, 2005
- "Pyramid: Pyramid Pick: Perplex City". www.sjgames.com.