Blackjack has many rule variations. Since the 1960s, blackjack has been a high-profile target of advantage players, particularly card counters, who track the profile of cards that have been dealt and adapt their wagers and playing strategies accordingly. At a casino blackjack table, the dealer faces five to seven playing positions from behind a semicircular table. Between one and eight standard 52-card decks are shuffled together. At the beginning of each round, up to three players can place their bets in the “betting box” at each position in play.
The players' object is to win money by creating card totals that turn out to be higher than the dealer's hand but do not exceed 21 ("busting"/"breaking"), or alternatively by allowing the dealer to take additional cards until he/she busts. On their turn, players must choose whether to "hit" (take a card), "stand" (end their turn), "double" (double wager, take a single card and finish), "split" (if the two cards have the same value, separate them to make two hands) or "surrender" (give up a half-bet and retire from the game). Number cards count as their natural value; the jack, queen, and king (also known as "face cards" or "pictures") count as 10; aces are valued as either 1 or 11 according to the player's choice. If the hand value exceeds 21 points, it busts, and all bets on it are immediately forfeit.