Kiefer-161 features hundreds of species and cultural blocs living side-by-side, and the lingua franca they’ve settled on is long strings of flags- vexils, as they’re called locally, telling the world who you are, what you believe in, what you’d like to buy or sell, or what emergency is going down.
(Of course, this is only the barest 101; there are hundreds of flags, all kinds of subtleties in the order and method of flying them, and even dialects of flag syntax.)