Roullete, or roulette, is a casino game where players place bets on which red or black numbered compartment of a spinning, dishlike device called a wheel of fortune a small ball will come to rest in. The game emerged in the late 18th century and became popular in European casinos. Bets are made against the house and can be placed on a single number, various groupings of numbers (such as odd-even, first or second dozen) or colors, whether they are high (19-36) or low (1-18), and more.
The roulette wheel consists of a solid wooden disk slightly convex in shape with metal separators around its rim, which are arranged in thirty-six alternating red and black compartments. On European-style wheels a 37th compartment painted green carries the sign of 0, while on American-style wheels two additional green compartments are marked 0 and 00. The whole wheel is attached to a spindle in the center.
When a player makes a bet, the croupier puts the ball into the wheel and spins it until it slows down just before it is about to land. When the wheel stops, winners are rewarded according to their betting odds. Outside bets pay off at higher odds than those on individual numbers.
A variety of systems have been devised to beat the maths, some easy and some complicated. A simple search on Google will return millions of such systems—some well described, others not so. The mathematical analysis of the game, however, suggests that no system can convert a fair game into a profitable enterprise.