Sets, Planets, and Comets

Set is an enjoyable—even addictive—card game that challenges players to identify

certain visual patterns. A mathematically rich game, it provides ample opportunity for

students and teachers to ponder combinatorial, algebraic, and geometric questions. Part

of Set’s appeal is that once the fundamentals of the game are understood, it is nearly

impossible to resist investigating its structure, whatever one’s background. We con-

centrate on the geometry, introducing interesting objects we call planets and comets,

which lead to an elegant variation on the game.