How many unique sets are there? When three cards form a set, we can also count the number of attributes for which all three cards are the same. In the card game Set, each card features a number of shapes, with four attributes: Number: The number of shapes is 1, 2, or 3. Color: Each shape is red, purple, or green. Shape: Each shape is oval, diamond, or squiggle. Shading: Each shape is hollow, shaded, or solid. There is exactly one card for each possible combination of attributes.
