Rock-paper-scissors didn’t arrive in the U.S. until the 20th century, but it’s one of the oldest games used for making decisions in human existence, even if its history is muddled with legends and exaggerations put forth by Internet historians and Redditors (for example, the reason why the game is sometimes called “Rochambeau” is fiercely debated).

The earliest known references to finger-flashing games are a tomb-wall painting at the Beni Hasan burial site in Middle Egypt (dated to around 2000 B.C.E.) and centuries later on a scroll from Japan. Versions of rock-paper-scissors can be found in cultures around the world, but outside of North America it remains most ubiquitous in Asia. In Japan, the game is called jan-ken or jankenpon, and uses the same rock-paper-scissors finger positions, though a variation features a tiger, a village chief, and the village chief’s mother (who beats the chief). In Indonesia, the game is earwig-man-elephant, where the earwig overcomes the elephant by crawling up his trunk and eating his brain.

But whatever the interpretation, the game is pervasive, combining everyday utility with basic human psychology. People tend to think that it’s a random (and thus fair) way of making trivial decisions, but the game’s simple structure still allows for an element of strategy, making it an unlikely but fitting subject for a worldwide competition. While your best chance of winning would be to choose your moves completely at random, humans are naturally terrible at behaving randomly. Well-trained players who think of the game as a psychologically driven battle can use this fact and other influencers to increase their chances of winning.

Ironically, children are actually the most difficult to play against because they’re the most random in their choices, while adults who who are inclined to overthink their moves tend to be more predictable, Simmons says. More skilled players use gambits, which are pre-decided sets of three throws that help reduce the chance that you give away your next move. The Great Eight Gambits, the most common strategies employed, have names like “Bureaucrat” (for three papers used in a row) and “Fistful o’ Dollars” (for rock, paper, paper). “It’s about choice and the power of suggestion,” Simmons says. “The game itself almost disappears and it becomes this rarified force of will between two competitors when they both know what they’re doing.”

The Walker brothers’ website was partially inspired by the game’s psychological and game-theoretical underpinnings—which have now spawned legitimate research studies and many Internet articles proclaiming to teach you How to Always Win at Rock-Paper-Scissors. In a time when the Internet was first beginning to give people’s secret passions a platform, the brothers managed to hit a nerve and inspire a subculture. By the time the brothers threw their first “world championship” at a pub in Toronto in 2002, there was a line of people two blocks long in the middle of a snowstorm, determined to try their luck in the formal elimination contest or the seedy “street competition.”