How stuff works: Pazaak

Pazaak, an ancient game dating back to Old Republic times, was a popular card game in which the goal was to reach 20 without going over, or at least come closer to it than the opponent. The player with the nearest sum to the number 20 won the round, and the player who won three rounds won the match. If in one round the scores of the two players were equal, the round was not counted at all.