The Missing Square Puzzle. How can this be? You have two white triangles 13 cm x 5 cm Two yellow pieces of acrylic the same size. Two blue pieces of acrylic the same size. Two red pieces of acrylic the same size. And two green pieces of acrylic the same size. Arranging the pieces as in the photo one triangle fits and the other triangle seems to have a 1 cm square gap. How can this be? Overall dimensions, 160 mm x 140 mm x 6 mm Warning this may hurt your head!!