Go is a board game involving two players that originated in ancient China more than 2,500 years ago. It was considered one of the four essential arts of a cultured Chinese scholar in antiquity. Its earliest written reference dates back to the Confucian Analects. There is significant strategy and philosophy involved in the game, and the number of possible games is vast, despite its relatively simple rules. The two players alternately place black and white playing pieces, called "stones", on the vacant intersections of a board with a 19x19 grid of lines. Beginners often play on smaller 9×9 and 13×13 boards, and archaeological evidence shows that game was played in earlier centuries on a board with a 17×17 grid. By the time the game had spread to Korea and Japan in about the 5th and 7th centuries AD respectively, however, boards with a 19×19 grid had become standard. The objective of the game—as the translation of its name implies—is to have surrounded a larger total area of the board with one's stones than the opponent by the end of the game, although this result typically involves many more intricacies than simply using surrounding areas directly.