Start with the three puzzle pieces of two jockeys and two weary-looking mules. Rearrange the pieces so that the mules miraculously break into a frenzied gallop. Use your mouse to drag the pieces and double click to rotate them. The mules do not overlap. There is a clever, but not deceptive solution to this puzzle.
If you can't find the solution, click or scroll down for an explanation.
This ambiguous "Trick-Mules Puzzle" is solved by the realization that the mules can have two different orientations. Here the same lines and contours have two interpretations, one horizontal and one vertical.
Over the years advertising has been based on this puzzle. The earliest version of the puzzle used two dogs and appeared in "The Magician's Own Book," published in 1857. In 1872 Sam Loyd, the great American puzzlist, adapted the concept, and produced "The Trick Mules Puzzle."
The idea of two figures which have four parts that are interchangeable dates back to the Middle Ages. The concept was popular in other cultures as well, as is this 17th-century Persian design.