The story behind this thing is that I had this pair of hexagonal shaped gluing jigs that I was using to help me align Pennyhedron puzzles pieces. I was using these jigs so often that they had found themselves a sort of place of honor sitting on the back corner of my table saw workbench. I got in the habit of stacking a set of 6 octahedral blocks inside of these jigs just because I thought it looked cool, and it gave the jigs a visual sense of purpose to be containing a rhombic dodecahedron.

One day when I was busy working at the table saw making cuts on some other project, I looked over and noticed that the 6 octahedral blocks had been slowly vibrating themselves out of position while the saw was running, and so that anal retentive part of me got in the habit of flushing them back up every so often over the course of many long workdays. One day as I was flushing up the faces of the blocks, I stopped to ponder how it was that each block was able to vibrate out of position in the first place, and yet still the whole structure remained relatively intact and stable.

I could tell that there was something special happening there, so I stopped the saw and spent some further time analyzing how the combination of the surfaces of the gluing jigs plus the surfaces of the 6 blocks themselves worked together to keep the motion of each block constrained. Further brainstorming ensued, leading up to the Barcode Burr interlock prototype.

After having spent time doing analysis of the Barcode Burr geometry inspiration, I came up with this design for a puzzle piece shape which was based on my idea of having the core octahedral blocks each having an arm extending around to the other side of the core cluster in order to hold the cluster in position. These arms replaced the need for the hexagonal gluing jig base and cap components that were keeping things together in that previous inspiration.

Overall, I was extremely pleased to have come up with what seemed to me at the time (and in the 20 years since, has proven to be true) a totally new and exciting form of interlocking geometry which not only has the novel property that each piece is freely able to move along a diagonal axis of the underlying cubic structure, but also that each piece is that same shape and that the structure itself holds together and maintains its properties even when multiple pieces have been removed! Big celebration time!

Although those traits I just mentioned are very special, the overall appearance of the assembled structure left something to be desired from an aesthetic standpoint, so I spent some time with scrap blocks of geometry and masking tape, experimenting with how I could augment/truncate this piece shape into something that had a more appealing external shape once assembled; this led up to the Barcode Burr piece geometry prototype.

Building off the work that I did with the Barcode Burr interlock prototype, I came up with this modified pieces shape by augmenting some blocks in certain places to fill gaps, and truncating surfaces in other places in order to turn the previous spiky abstract appearance into that cubic aesthetic that we all know and love.

Whereas the previous prototype was easy to disassemble because those spiky corners gave the user something to grab onto and pull out, the cubic nature of these truncated pieces is such that it's tricky to actually get a grip on individual pieces once the whole structure is assembled. In order to facilitate easier physical manipulation, I extended the long triangular "arm" part of each piece so that it projects all of the way through the other side of the puzzle and thus gives the user something to push against, and used a contrasting color of wood in order to help give visual indication of where to push.

Once again, this was a big moment to celebrate for me because now this new piece shape that I came up with not only has all the cool interlocking properties that the previous prototype did, but also it's much more aesthetically pleasing to touch and interact with, plus from an intellectual viewpoint it is exciting that the shape is a space filling solid now, too.

I quickly realized that the truly neat thing about this new form of interlocking geometry was that it would allow for high-level solution sequences because the pieces can move one at a time rather than necessarily in groups of three, like is the case with most every other puzzle based on the rhombic dodecahedron. Truth be told, my desire to develop a high-level RD puzzle design is why I went down this road of geometric exploration in the first place, so it was not long at all after completing the woodwork on this prototype that I went to town on it with a pencil (at first) and eventually a pen, as I came up with patterns of pins and grooves that I could cut into the pieces in order to turn this into something truly exceptional. I wanted to have as many moves as possible, so just went with the standard "binary progression" of piece movements because it seemed classy and fun.