Bluffing, to a science. Stacks is a 15-card, 3-4 player bluffing game where the stakes are high and they keep raising. Overview Play cards each turn to increase the point value of your Stack. Make a bid that matches the value of all the cards in your Stack. Keep raising the Bid each turn to stay in the round. Get caught lying, and your opponent takes everything. Beware the dastardly -10 card, or use it yourself to catch your opponents by surprise. Each round of Stacks is about a minute long, from dealing the cards to scoring the points. Play a few rounds at lunch or a few hundred.