STACKS is a set collection game built around collecting sets of red, blue, and green cards. The cards may be in a central array on the table, in front of a player, or in a player's hand. On their turn a player will either play 1 card from their hand or the top card of the deck to the central array. Alternatively, they can play a set of cards (one of each type) to the central array. Depending upon the adjacencies of colors and certain card effects, the card which was played may have its effect triggered or the player may be forced to acquire cards. The game will end when the deck runs out of cards. Then, each player scores points for cards left in their hand and cards in front of them. Any sets of cards (one of each type) in front of them can be combined into a single card. The player with the fewest points wins.