Perplex City was an alternate reality game created by the London-based developer Mind Candy under the direction of the lead producer and designer, Adrian Hon, that ran from April 2005 to February 2007. The first "season" of the game had players looking for "The Receda Cube" (referred to as "the Cube"), a priceless scientific and spiritual artifact to the people of a fictional metropolis known as "Perplex City", which had been stolen and buried somewhere on Earth.

The game offered a cash prize of £100,000 (approximately $130,000 or €115,000) to the person who found the cube. The Cube was found by Andy Darley of Middlesex, UK in a wooded area in Northamptonshire, UK on February 2, 2007.

Mind Candy sold foil packs of puzzle cards to fund the game. Each card featured a different puzzle, and although the cards provided additional story lore, it was possible to participate in the ARG without purchasing them. According to Mind Candy, the first wave of cards for the new game season, called Perplex City Stories, were to be released on March 1, 2007. In June 2007, they announced that the second season was on indefinite hold.