The game of Set is played with a deck of eighty-one cards, each having the following four characteristics:
. Symbol: diamonds, ovals, or squiggles
. Count: 1, 2, or 3 symbols
. Color: red, green, or purple
. Shading: outlined, filled, or striped
The cards are shuffled and a tableau of twelve cards is laid out. Players then attempt to be the first to identify "sets" which exist in the tableau. Sets are removed as they are identified and new cards are dealt in their place. Play continues in this manner until all cards have been used. The winner is the player with the most sets.
A set is a collection of three cards in which each characteristic is either the same on all three cards or different on all three cards. For example, the cards shown below form a set.
To see how the cards above form a set, take each characteristic in turn. First, each card has different symbol: the first card has squiggles, the second diamonds, and the third ovals. Second, each card has the same count of symbols, three. Third each card has a different color, and finally, each card has a different shading. Thus, each characteristic is either the same on all three cards or different on all three cards, satisfying the requirement for a set.
Consider the following example of three cards which do not form a set.
Again, take each characteristic in turn. Each card has a different symbol, each card has a different count of symbols, and each card is the same color. So far this satisfies the requirements for a set. When the shading characteristic is considered, however, two cards are filled and one card is striped. Thus, the shading on all three cards is neither all the same nor all different, and so these cards do not form a set.