"The idea for this puzzle comes from the 'Horse' puzzle, also available in the Cast Puzzle series. The 'Horse' puzzle was derived from a puzzle attained in California, one that was made with real horseshoes. With the W-U puzzle, the difficulty is ramped up considerably over the original 'Horse' puzzle. I hope your frustration level ramps up, as well. The key word is 'hoof.'"
-Nob Yoshigahara, 1995