Originally, slot machines were designed to be easy to operate. A player inserts cash or, in the case of “ticket-in, ticket-out” machines, a paper ticket with a barcode, and then activates the machine by pushing a lever or button. The machine then displays symbols and, if they match, awards credits based on the paytable. The symbols vary from game to game, but classic symbols include stylized lucky sevens and fruit. Most slot games have a theme, with the symbols and bonus features typically aligned with that theme.
Modern variations on the slot machine offer more complicated gameplay and greater levels of sophistication, increasing both the skill level required to play and the entertainment value. Some of these games have multiple reels and multiple paylines, allowing players to choose how many lines they want to play. Video slots can also encourage players to use a feature called “sync up” to maximize their chances of winning by linking a specific set of symbols across several reels.
While some slot machines look like the mechanical models of decades ago, they’re actually driven by a computer that determines every outcome based on the results of previous pulls and other factors. The computers are programmed to achieve a certain payback percentage — on the Las Vegas strip, this is about 92%, according to research firm ReelMetrics. The computer algorithms are weighted to ensure that they remain pseudo-random. However, even when the weightings are removed, they’re still random enough to prevent anyone from predicting their outcome with any accuracy.