Mahjong is a tile-based game for three to four players. Though regional variations may exclude certain tiles or add unique ones, it is typically played with a set of 144 tiles based on Chinese characters and symbols. Players hold one of four "wind" positions referred to as the East, South, West, and North. Once each player draws a hand of thirteen tiles, in clockwise order beginning with the "prevailing wind," each player draws a tile, then discards that tile or another from their hand. Players may call to use another player's discarded tile under certain conditions. The object of each round is to complete and score a legal hand using a drawn tile or another player's discarded tile to form four melds and a pair (eye.) Players may also score with special hands that do not follow the typical pattern. Players hold a persistent score across rounds until the game ends.