Gambling involves wagering something of value on a random event with the intent of winning a prize, fundamentally requiring consideration, risk, and a potential reward. Its origins trace back to the Paleolithic era, with six-sided dice appearing in Mesopotamia by 3000 BCE, playing cards emerging in 9th-century China, and the world's first known casino, the Ridotto, opening in Venice in 1638. The popular U.S. card game Poker evolved from the 17th-century Persian game As-Nas, highlighting the activity's long, diverse history. This significant global commercial activity was valued at an estimated $335 billion in 2009, though the term "gaming" is often used to refer to legal gambling, a distinction not universally observed. Historically, gambling has been a major recreational pursuit subject to varying levels of regulation, from widespread outlawing in the early 20th-century U.S. to the opening of regulated casinos in Singapore in 2010 to promote responsible play.