“A variant of four-ball is the East Asian game yotsudama (四つ球, Japanese for ‘four balls’), or sagu (사구, Korean for ‘four balls’).
“The game is played with two red object balls, one white cue ball and one yellow cue ball (or sometimes both cue balls are white, one having a red spot). Each of the two players is assigned a white or yellow cue ball; whether the opponent can use it as an object ball is a difference between the Japanese and Korean versions.
“A point is scored when the shooter caroms on two balls. A carom on only one ball results in no points, and ends the shooter’s inning.”