U & U Hanayama cast Metal Brain Teaser Puzzle (Level 4)Two U-shaped bolts and four nuts - this looks like a combination of spare parts but looks are deceiving. This puzzle comes with a deviously hidden trick. The key to unlocking these parts is to look carefully at each part first. The theme is complexity. It was designed by Kyoo Wong. U & U was puzzle of the year at IPP 2014 in London, U.K.