A slot machine (American English), poker machine (Australian English), or fruit machine (British English) is a certain type of casino game. Traditional slot machines are coin-operated machines with three or more reels, which spin when a lever on the side of the machine is pulled. The machines include a currency detector that validates the coin or money inserted to play. (The slot machine is also known informally as a one-armed bandit because of its traditional appearance and its ability to leave the gamer penniless.) The machine typically pays off based on patterns of symbols visible on the front of the machine when it stops. Modern computer technology has resulted in many variations on the slot machine concept. Today, slot machines are the most popular gambling method in casinos and constitute about 70% of the average casino's income.