At the time Bart Simpson found the arcade game Triangle Wars at Captain's Blip's Zapateria, Polybius was located on its right side and had a mark informing it was property of the US government. No further information is given about the gameplay or anything else.
Behind the Laughter
It is a reference to the legendary Polybius arcade game, which supposedly existed in Portland, Oregon in 1981 and provoked several negative symptoms on its players, such as extreme addiction, amnesia, night terror, horrible nightmares or even propensity to suicide and was supposedly filled with subliminal messages. According to the legend, Polybius existed for approximately one month, in very limited quantities to only a few arcades, while men-in-black (suspected to be government agents) routinely altered its configuration. In some versions of the myth, the game is said to have been created by the U.S. Government which is why "Property of U.S. Government" is printed on the front of the machine.