Texas Hold ’em (or Hold’em, Holdem) is the most popular poker variant played in casinos in the United States. Hold ’em’s simplicity and popularity has inspired a wide variety of strategy books which provide recommendations for proper play. Popularity of the game surged in the 2000s due to exposure on TV, on the Internet, and in popular literature. During this time, Hold ’em replaced all other forms of poker as the most common game in U.S. casinos. The no-limit betting form is used in the widely televised main event of the World Series of Poker (WSOP) and the World Poker Tour (WPT).