There is no professional agreement on which puzzles are the most difficult, although general recognition is given to various puzzles as being mind-bendingly hard, or even impossible.
Imagine being able to put something together, that hardly anyone on the planet could undo, never mind reassemble. Some great puzzle makers out there have spent their lives trying to do just that.
Ball in a Cage (Balls Out)
"I design puzzles, I do not solve the puzzles, I am a very bad puzzle solver. The Phoenix puzzle gave me the greatest thrill when I was designing." - Alfons Eyckmans (Designer of Muff & Supernova) in Conversation with SiamMandalay
While there are some unsettling takes on the famous Rubrics Cube, including what many enthusiasts have said is the hardest of them all, The Sudoku Cube, arguably the trickiest puzzles out there take more than measured twists of the wrist.
Interlocking puzzles, often referred to as Burr puzzles, which were thought to be introduced to the western world as early as the 18th century (though could have been a part of traditional Chinese game culture before that) are often recognized as the most perplexing of physical puzzles.
The burr puzzle is usually made out of wood, and contains a number of interlocking pieces. In the past each puzzle had a generic name, but over the years manufactures have been putting their own names on an original take on the burr.
To give you an idea of how difficult a burr can be, often the entire structure must be put together before one main interlocking piece will secure the shape. Sometimes non-linear movements are required to put the puzzles together, while some of harder puzzles take a number of moves before you can even dissemble the structure.
The Puzzle Makers making it difficult
The Millennium 13 piece burr, designed by Donald Osselaer in 2012, is thought to be almost unassailable in its stubbornness not be solved. In a blog Osselaer wrote, “I believe this will be my final puzzle when it comes to ‘hugeness’. Firstly because there is little point in making puzzles that no human would ever want to solve, and secondly because the computers of today can hardly even grasp this hugeness.”
Burrtools is a computer program that helps you solve the puzzle, but as the maker said, and as others who have attempted to use the program to solve the puzzle, the software is not much help. The level of difficulty is often based on how many ‘right’ moves it takes to put the puzzle together. In the case of the Millennium, it’s 521 right moves. Just so you can compare, one of the same designer’s easier puzzles takes 11 right moves, and even those puzzles are by no means easy to a novice.
"The puzzle "Muff" is a puzzle with surprises, but the puzzle "Confucius 3" seems to me, one of the most difficult puzzles." - Alfons Eyckmans
Bill Cutler, a renowned American mathematician and later burr puzzle maker, created some baffling 6 piece burrs, not the hardest, but tricky for their time.
One of these was Bill's Baffling Burr, a puzzle with which five moves are required just to unlock the first piece from the finished puzzled. Since Cutler released this very difficult puzzle more difficult variations of the 6 piece burr were created.
One of these was the Six of Diamonds, a puzzle designed by Stewart Cofflin in 1998. The puzzle was so hard because none of the pieces were identical, although they looked like they were.
Edward Hordern, who was one of the world's leading authorities on interlocking puzzles once famously said that the Six of Diamonds was one of the hardest puzzles he had ever come across.
18-piece Supernova created by Jack Krijne and Alfons Eyckmans. As with most confounding puzzles the only way to complete them, unless you use a program, is usually to disassemble the puzzle before you put it back together, carefully taking notes as to how you will assemble it. The problem with the Supernova is that it takes 166 moves just to get the first piece out! Alfons Eyckmans also created The Muff, which although takes a meager 93 moves to unlock the puzzle, is thought to be just as hard, or even harder.
Alfons and Jack have formed a formidable puzzle making partnership, pushing the boundaries of complexity and design. Their burr puzzle designs evolved one after the other culminating in The Supernova.
"It took me nearly two years to design "the Baroness" level 152, Jack continued to work with the puzzle and designed the puzzle "Exelsior" level 156. I am going further and got after +/- 1 day designed the puzzle "Supernova" level 166. Jack and I have decided that the puzzle "Supernova" was been established by our joint effort."
The Supernova is known as a 6x6x6 puzzle, with 18 pieces in total. As you can see in this video here, these puzzles are referred to as the “mother-load of nasty puzzles”, and for most folks are frankly impossible to solve without instructions or tutorials.
The puzzles in the video are not the hardest, but you might get an idea of how complex 18-piece burrs can be.