of them on the table. Of the other pyramid traditions of Continental Europe, only Russian pyramid survives. Snooker, originally known as snooker's pool, can be considered a member of this family. Rotation games Rotation games require players to make legal contact with the lowest numbered ball on the table or a foul is called. The earliest rotation game, originally known as 61, started off as a variant of fifteen-ball pool during the mid-nineteenth century. The name "rotation" came from how the balls were placed around the table in its unracked offshoot Chicago. 61 has spawned many variations of its own such as American rotation, nine-ball, ten-ball, and Kelly pool. Of these, nine-ball is the most popular and the predominant professional game with ten-ball as the second-most prominent. There are many local and regional tours and tournaments that are contested with nine-ball. The World Pool-Billiard Association (WPA) publishes the world standardized rules. The European professional circuit has instituted rules changes to make it more difficult to achieve a legal break shot. The largest nine-ball tournaments are the US Open Nine-ball Championship and the WPA World Nine-ball Championship for men and women. A hotly contested event is the annual Mosconi Cup, which pits invitational European and U.S. teams against each other in one-on-one and nine-ball matches over a period of several days. The Mosconi Cup games are played under the more stringent European rules, as of 2007. Straight pool Also known as 14.1 continuous, this game originated as a slight modification of continuous pool, another offshoot of fifteen-ball pool. The shooter may attempt to shoot at any object ball on the table. The goal is to reach a set number of points determined by agreement before the game. One point is scored for each object ball pocketed where no is made. A typical game might require a player to score 100 points to win. In professional competition, straight pool is usually played to 125 points. Straight pool is a game, meaning the player must indicate the intended object ball and pocket on every shot. Eight-ball The most commonly played pool game is eight-ball, which appeared at the beginning of the twentieth century. It is often thought of as synonymous with "pool". The game has numerous variations, mostly regional. It is the second most played professional pool game, after nine-ball, and for the last several decades ahead of straight pool. The goal of