Stack 21 is a clever twist on Blackjack. It is played with a deck which is basically two standard decks of cards with some interesting variations on suits and the four Jokers thrown in. To start, each player is dealt four cards which form the basis for four stacks. The goal is to have each stack sum to 21 points. Any stack which sums to greater than 21 points is immediately tossed out. Any stack that sums to less is still in play. Only stacks that sum to 21 score. When all stacks have either scored or blown, the round is over. - BoardGameGeek