Cast Quartet, designed by Mine Uyematsu, is one of the most intricate puzzles in the Hanayama Cast series. Inspired by mathematical and geometric principles, the puzzle features four interlocked rings that must be separated and reassembled. Though the design may appear simple, its complexity lies in the multiple solutions and tricky manoeuvres required to solve it. With a difficulty rating of 10/10 ( and 6/6 stars) the Cast Quartet is considered one of the more challenging puzzles in the Huzzle series, highly regarded by experienced puzzlers for its elegant design and demanding solution.