A casino is a facility where people can gamble and play games of chance. Casinos are often located in areas where gambling is legal, such as in Nevada or Macau. In the United States, the majority of casinos are located in Las Vegas, although many cities have small casinos as well. Most casinos offer a variety of gambling games, including table games such as blackjack and roulette, slot machines, and poker. In addition, some casinos offer live entertainment and tournaments. Most casino games involve some degree of chance, but some require skill. In games that have a skill element, the house edge is the average profit the casino expects to make from those who gamble. This advantage is computed from the mathematically determined odds of a game, and is expressed as a negative number (for example, the house edge of blackjack). In games where players compete against each other, such as poker, casinos earn money via a commission known as the rake. The casino industry is characterized by its high margins and rapid turnover of customers. A typical customer of a modern casino is an older adult who gambles for fun and not for serious financial gain, but who has a high income. These customers are known as high rollers, and they are a key source of revenue for casinos. In 2005, high rollers made up 23% of all casino gamblers. Because of the large sums of money that are handled within a casino, there is always a temptation for patrons and employees to cheat or steal. To counter this, casinos employ a wide range of security measures. These include security cameras that monitor the entire casino at once, allowing security personnel to spot any suspicious behavior quickly; specialized systems such as “chip tracking” that allow the casino to oversee the exact amount of money wagered on each game minute by minute; and automated systems that control slot machine payouts. In the twentieth century, most European countries changed their laws to permit casinos. These casinos are highly regulated, and they tend to be more luxurious than their American counterparts. They often have a distinctive architectural style, such as the Art Deco-style building at the Monte Carlo resort in Monaco. Most casinos are designed around noise, light, and excitement. The floors and walls are usually bright and sometimes gaudy, and the lighting is often red, which is thought to stimulate gamblers and make them more likely to lose track of time. Casinos also feature a variety of loud, flashing, and humming machines that are used to distract gamblers from the fact that they are losing money. In addition, alcoholic drinks are served to gamblers at the tables and by waiters who circulate the gaming floor.