Perplex City is an Alternate Reality Game by Mind Candy which ran for over two years starting in April 2005. The titular metropolis exists in another dimension with connections to Earth and has slightly better technology and a society based around puzzles. One of their major artifacts, the Receda Cube, was stolen and hidden somewhere on Earth. Lacking the ability to send people to retrieve it, the citizens of the Perplex City Academy formed a team to recruit people from Earth to find and return the Cube.
Perplex City may be the ARG which has appeared in the most forms of media during its run. The primary connection between the city and Earth was via puzzle cards, which were sold in randomized packs. The cards had clues hidden on them, as well as a code to enter online to earn points for solving the actual puzzle. There was also the obligatory website, which had (in addition to basic information) a number of hidden URLs and live online events. The game also appeared in newspapers, on television and radio, on multiple telephone lines for players to call, at a live concert and on a music CD.
The prize for finding the cube was £100,000, awarded to a player in February 2007. Additionally, players could earn leitmarks (which took the form of small rubber pins and icons on a player's profile) for solving a certain number of cards or for other achievements.
A second season, which was to involve players assisting one of the characters solve a murder mystery, was repeatedly delayed, and then cancelled when much of the development staff resigned. Perplex City was repurposed as a general puzzle-solving website, We Love Puzzles, and Mind Candy is, at the time of this writing, selling cell phone charms with an MMORPG attached.
This alternate-reality game provides examples of:
- Aborted Arc: Season 2/Violet Underground was aborted in June 2007 and never finished.
- All There in the Manual: As to be expected, you had to go over a horde of different media to get the whole story, some of which wasn't revealed until after the first season ended.
- Block Puzzle: #148 Serious Scientific Sokoban involves pushing a crate through a room Sokoban-style.
- Calvinball: #140 Mornington Crescent is based on a game of the infamous Mornington Crescent. The aim is to determine the winning move based on the moves previously played (the rules are, of course, not provided).
- Classic Cheat Code: #181 Down, A, B, Up, Up, Right was a card about identifying their sources.
- Darker and Edgier: The back of Season 2 cards indicated cracks in the veneer of the city's exterior. One of the more thought-provoking ones included the implication that it was essentially a world of those with Asperger's, and those that didn't were ostracized similar to what some with Asperger's experience in Real Life.
- Everything's Better with Penguins: Season 2 #070 Penguin Sums is a math puzzle involving penguins.
- Fox-Chicken-Grain Puzzle: #087 Bar Crossing is one, framed as a problem of getting two drunk people and a cocktail to another room.
- Last Lousy Point: Three cards from the first season remained unsolved years after the season ended. Luckily, they're not required to complete the game.
- #251, The Thirteenth Labour, required a bruteforce decryption of a string of 352 characters. This was eventually cracked in February 2010, but the solution has not been shared.
- #256, Billion to One, required players to locate a man based on a single photograph and the name "Satoshi". This was achieved in December 2020, using a facial recognition image search tool released earlier that year (the intended method was based on the "six degrees of separation" theory).
- #238, Riemann, requires a solution of the Riemann Hypothesis, a mathematical challenge that hasn't been solved in over a hundred years of existence. The card even mentions the $1,000,000 prize being offered for solving the problem.
- MacGuffin: The Receda Cube, being the ultimate target of the first season.
- Match-Three Game: Season 2 #099 Countered requires the player to clear a board with a sequence of Bejeweled-style moves.
- Mondegreen: One of the cards is actually about identifying misheard phrases and lyrics
- Monty Hall Problem: #174 Jaunty Paul is a direct statement of the problem.
- 1000 Origami Cranes: #155 Sadako Sasaki references one of the most famous real-life examples.
- 3 + 5 = 4: #057 Volume requires the solver to obtain 400 mL of water given two cups of capacity 300 mL and 500 mL.