The puzzle in question is The Melting Tile, which also happens to have been the IPP37 Exchange Puzzle of puzzle/puzzle books collector Yee Dian Lee of Malaysia. I would imagine most puzzlers would have heard of the famous Melting Block puzzle designed by Tom O’Beirne, which has seen different variants made by different puzzle craftsmen over the years. The Melting Block is a 3D packing puzzle that requires a puzzler to fit a ninth block into a box which already contains 8 other block pieces (of varying shapes) with no internal spaces/voids. Sounds impossible right? Yes and No. Bill Cutler describes it as such:

The Melting Block is more of a paradox then a puzzle. The eight pieces fit together easily to form a rectangular block 57 x 87 x 132. This fits into the box with a little room all around, but looks to the casual observer to fill up the box completely. When the ninth piece is added to the group, the pieces can be rearranged to make a 58 x 88 x 133 rectangular solid. (This second construction is a little more difficult). This is a great puzzle to show to “non-puzzle people” and is one of my favorites.

Goh Pit Khiam applied this same principle and came up instead with a 2D version the goal is to remove 7 pieces that fills a tray completely, rearrange them and fit in an 8th red piece…and completely fill up the tray again…again seemingly impossible. Quite a design feat I might add, and burr tools is not something you can use here for this sort of design.

When Oscar came to Singapore and we had an informal second Singapore Puzzle Party, Oscar played with The Melting Tile and managed to solve it over dinner. I decided to give my copy of this Exchange Puzzle a try, but (fortunately or unfortunately) with the benefit of knowing the hint for solving such a puzzle…which Oscar alluded to during his solve.

With a hint or not, this is one of those puzzles which can be solved with some persistence. Given the fact that it has only 7+1 red piece to fit into a squarish tray, it is not such an impossible task as one would imagine. Both solving and un-solving and placing the pieces back to where they belong doesprovide some degree of challenge, easy for some, difficult for others.  But notwithstanding, a nice puzzle to confound non-puzzlers and even puzzlers alike. I love it when people give that look of bewilderment on their faces when they see the small red piece fit inside the tray with the rest…”gosh, how’s that possible?”

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Unlike the IPPs with hundreds in attendance and a planned 3-day agenda and side tours, our little SPP was just a small gathering over dinner with just 8 of us, including Oskar! David Ang of Cubewerkz came with his gang of twisty enthusiasts and speed-cubers (all students by the way – Bin Jie,, Seung Ha, Ryan Peh and Daryl Tan) plus the two of us from the non-twisty domain, Goh Pit Khiam and myself. As you might imagine, given such a small group, the number of puzzles that went around were rather few. I showed off to Oskar some of my recent designs and prototypes such as my Handkerzzle, L(8)tice-2, Micro-Hex and a 2014 design but recently reproduced-Ball In Cylinder #2.  David brought a number of twisties he was currently selling on his new site and Pit Khiam took out a couple of his own designs and also displayed his Android platform digital puzzles. Oskar had a number of goodies in his bag, mainly his 3D printed and incredible looking gear mechanisms and twistie-style puzzles. All in all, it was a pleasant evening of catching up with Oskar and the rest of the gang  and a chance to handle some of Oskar’s newest toys!

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My CrossFit puzzle was inspired by two puzzles. First, it was Goh Pit Khiam’s Number Blocks which appeared at IPP35 in Ottawa, Canada. That puzzle had four pieces which danced in and out of a tray with an overhang which made it into an interlocking packing puzzle, which requires a certain number of moves in proper sequence to solve. Not quite your usual 2D style packing puzzle. The second puzzle is Tom Jolly’s Square Dance which has 9 pieces and has a level 1.8.5.3.4 solution.

I was looking to design something that was somewhere in between the two and for the sake of achieving a symmetrical shape, settled in the end for a “cross” shape. And you need to fit 5 odd-shaped pieces into the tray… hence the name CrossFit (which is also the name of a type of high intensity gym workout). Designing wasn’t the problem and my basic design was very kindly scaled up by fellow puzzler Stanislav Knot of the Czech Republic.

I asked Tom Lensch (who had produced copies of my IPP36 Design Competition entry “Magiq #8”) to cut a prototype for me. I was hoping to enter the CrossFit for the IPP37 Nob Yoshigahara Puzzle Design Competition. Tom kindly agreed to do so, but said he couldn’t do so in time for the competition. And while he was very busy with making puzzles for IPP37, he still managed to produce a single prototype copy and passed it to me at IPP37 in Paris. As you can see from the photos, Tom did a great job making the puzzle, even for a prototype.

The goal of CrossFit was to re-arrange a scrambled set of digits into the correct order. To assemble the pieces to the solved state requires 21 moves with a level 1.2.10.5.3 solution. On paper it seems to be a nice challenge of slightly above moderate difficulty. And Tom himself found it pretty difficult to solve too. However, when Tom passed it to Gary Foshee (designer of Lunatic Lock and Open Transparent Lock), Gary shifted the pieces here and there and solved it under 10 minutes. So maybe it wasn’t as challenging as I had hoped. Well, I will see if I can improve the design to a level where I think its good enough for the design competition. Meanwhile CrossFit will remain a nice well-crafted prototype.

Micro Hex

Again here I was inspired by someone else’s design…that of Wil Strijbos! No need to mention the many (metal) puzzles he is well-known for. Just google Wil Strijbos and you can his puzzles and (even get his contact details, I am told). The puzzle of inspiration was his Heavy Metal Triangle Puzzle. Wil’s was a 3-piece puzzle which forms a triangular shape. I was hoping to produce a 6-piece puzzle to form hexagon shape. After much effort with Burr Tools, I managed to come up with a unique solution design for what I thought could work quite well. All 6 pieces were identical and nicey formed the hex version of Wil Strijbos’ Triangle Puzzle. And it required a minimum of 8 moves to remove the 1st piece.

I sent my design to Steve Nicholls who does a lot of 3D printing work including puzzles of course. He has been a great help in 3D printing several other puzzle prototypes for me in the past and his work is very good. He 3D prints all his puzzles for exchange at IPP. In the meantime, I also scouted around for a CNC fabricator that could CNC mill my Micro Hex. There were a several vendors who could do the job but all were prohibitively expensive when it came to just making a single copy. I also contacted and told Wil of my design and asked if he would like to get his fabricator (who had manufactured the Triangle Puzzle) to make my Micro Hex. To my surprise, Wil told me that a long time ago, he had already produced a Hex-shaped metal version with 6 pieces!..but just not as many moves to solve as mine…oh well!

Like Tom, Steve was also busty preparing for IPP but did manage to pass me a yellowish 3D printed copy of Micro Hex in Paris as well as another Hexagon shaped design I called Hexagonal Shift. Steve did comment that Micro Hex did have piece(s) that could rotate during play. Now this is dreaded because rotation means a solver can short cut a move to solve the puzzle in an unintended way by twisting or rotating a piece out of the puzzle easily. I tested out the puzzle myself and found that indeed I could rotate some pieces but only with a bit of force. On hindsight, it was a blessing in disguise that I didn’t proceed with any expensive CNC machining given the rotation problem. As of this writing, Steve will try to make adjustments to the height of the puzzle in the hopes of eliminating any rotational moves. Let see what he comes up with.

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If you are familiar with Goh’s work, you may have come across several other (physically) similar looking puzzles in the “blocks” family such as his Arrow Blocks, Stumbling Blocks, Road Blocks and Check Box. But don’t be mistaken; while they look alike, each of them are different in their own right in terms of design and solutions and all providing good challenges.

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