Roulette is primarily a game of luck, as the outcome of each spin is determined by random chance. The layout of the wheel and the distribution of numbers are designed to ensure randomness and make it difficult to predict where the ball will land.

The ball eventually loses momentum, passes through an area of deflectors, and falls onto the wheel and into one of thirty-seven (single-zero, French or European style roulette) or thirty-eight (double-zero, American style roulette) or thirty-nine (triple-zero, "Sands Roulette") colored and numbered pockets on the wheel ...