Roulette is a casino game in which bets are placed on the outcome of a spin of a wheel. Players place their bets by placing chips on a betting table, the exact location of each chip indicating the type and amount of the bet. Each bet has a different odds of winning. The game originated in France and was popularized throughout Europe. The roulette wheel is a circular disk with divisions marked red and black and, on American tables, an extra green division numbered 0. The object of the game is to predict where the ball will land in one of the compartments of the wheel.
A player can make a bet on a single number, various groupings of numbers, whether they are odd or even, the color red or black or if they are high (19-36) or low (1-18). The odds for a particular bet depend on how many other bets are placed on that same spin. Each roulette table has a minimum and maximum stake per bet. When a bet is made, the croupier puts a marker (called a dolly) on the winning number on the layout and removes all losing bets. The croupier then pays all winning bets.
The origins of roulette are disputed, with fanciful stories including that it was invented in the 17th century by French physicist Blaise Pascal as part of his quest for a perpetual motion machine. By the 1800s, it had reached its modern form and became a staple in casinos and gambling dens across Europe.
During the 18th century, the game made its way to America where it was heavily modified due to rampant cheating by both operators and gamblers. The wheel was moved from the base to the top of the table to prevent devices being hidden in it and the betting grid was simplified. This led to the American-style game that is now played in most casinos.
The American-style game has a few additional symmetries compared to the European-style wheel. The first is that there are no high red numbers or low black numbers in the wheel between the zero and the row of 12 numbers. The other symmetry is that the 0-3-0 pattern in the center of the wheel contains no numbers 13-18.