Nine easy pieces - shapes made of 2, 3, 4 and 5 equilateral triangles joined - fill the encircled pattern and form a large variety of shapes outside the ring, too. For the toughest challenge, have no two of the same color share sides. A computer search by Bill Cutler proved only 2 solutions meet this condition - out of the 15,140 different ways to fill the circle! We had posed this question as a contest for the International Puzzle Party in 1997, and Bill's findings won the prize. All acrylic, five-color mix in a 5.5" tray. For 1 or 2 players, ages 6 to adult.