Polybius is a great urban legend that got its start in Portland. There’s lots of fodder thrown around about it, but The Polybius Conspiracy is a seemingly real investigation on the subject. They even have a lot of interviews from local people – but it turns out to be COMPLETELY FALSE and their main character was an actor. Yet none of that was disclosed and is yet another reason you should be very weary of documentaries as information sources (most evidence shows you should NOT be putting faith in them more than opinion pieces).
This is also a good video about the game.