This is a restricted sliding block puzzle and its difficulty is extreme. Juno believes that most human beings cannot solve the puzzle without the aid of a computer. As he vaguely remember, Juno himself needed around two weeks to find one of the solutions, and the solution that he found requires more steps than the minimum movements needed to reach the goal.
Each sliding piece has grooves on two sides and one of the grooves goes halfway along the edge. A pin is set on the opposite side of the half-length groove. The tray also has grooves on two sides on the inside. These features give diabolically balanced restriction to the movement of the sliding pieces and makes the puzzle extremely difficult.
The object of the puzzle is to change the color and direction of the arrow. It requires more than 100 moves to reach the goal and there are lots of dead ends. There are nine challenges in total which can be played by changing the start and goal positions of the spacer (blank) piece. Most of these challenges require shorter moves compared to the initial problem on the first and the second image but it doesn't mean the challenge is easier. You will have no idea whether you are getting closer to the goal or not.
Juno originally designed this puzzle in 1995. He made only two of them using very basic tools. Now, we have lots of machinery and can produce hundreds of puzzles in less time. The major parts of the pieces are milled out by a CNC router, then glued, sanded, and polished. The concave on the top of the pieces make it easy to slide them. Although it is an old design, we believe a very limited number of the puzzles was available in the past because of the difficulty of mass production.
The tray features an uncommon step-shaped joint. This shape gives more gluing area to the joints and contributes to the durability of the tray, but the main reason why Juno chose this joint was just because he wanted to try making it. He also picked seven-layer bamboo plywood for the base of the tray. It has a very smooth surface and is very suitable for sliding block puzzles.
Size: 120 mm x 120 mm x 26 mm (without base)
Number of pieces: 10 (Includes blank piece and tray)
Material: Anegre, Jarrah, American Black Walnut, Bamboo plywood and Stainless pin
Designer: Junichi Yananose (Juno)
Origin: Made in Australia