Polybius is an urban legend and arcade game rumored to have been released to the public for a brief period in the early 1980s. The only purported evidence of the game's existence are a screen shot of the title screen and a black and white photograph of the cabinet. The cabinet design is said to be largely featureless; a black cabinet body with only the Polybius title on the header of the bezel. Its controls supposedly consist of only a joystick and a single button. The title screen image contains a copyright date of 1981 to the company "Sinneslöschen, Inc." Translated from German, "Sinneslöschen" means "sensory-extinguishing."
According to the legend, Polybius is said to be extremely addictive, and those that played the game experienced severe, traumatic mental effects. Depending on the version of the legend told, such effects include amnesia, blackouts, memory loss, nausea, epileptic fits, migraines, headaches, night terrors, and even suicide. Additionally, the game was supposedly monitored by black-clad government agents that visited the locations where the cabinets were set up.
One possible explanation for the origin of the legend is that it was inspired by an early test version of Tempest
with graphics that easily triggered seizures in people with epilepsy.