The deck consists of 81 unique cards that vary in four features across three possibilities for each kind of feature: number of shapes (one, two, or three), shape (rectangle, squiggle, oval), shading (solid, dotted, or open), and color (red, green, or purple).[1] Each possible combination of features (e.g. a card with three dotted green rectangles) appears as a card precisely once in the deck. In the game, certain combinations of three cards are said to make up a SET. For each one of the four cat