Hi, I’m Carlos Moreno Serrano, sprocket314 on the Mechanical Puzzle Discord (MPD), MakerWorld and Instagram.
For my 40th birthday my wife had the genius idea of giving me my first 3D printer. I took a liking to CAD design and learned how to use Fusion 360. Over the years, I designed a number of functional prints but puzzles quickly took over: I published my first puzzle design in November 2025, and in March this year I started collecting puzzles too. It has been an incredible first year. This blog is where I’ll write about the puzzles I design, the ones I love, and the friends I’ve made along the way.
How I got into puzzles#
I have always liked puzzles. Growing up I got my hands on the mass-produced classics like the Tower of Hanoi, the Chinese Rings and some simple burrs like the barrel or the sphere (at this stage, burrs were my least favourite, but how things change over time…).
While in university, I came across Livewire, a legendary wire puzzle company. I LOVED their wire puzzles. I got almost the entire collection over the years. I was so sad when they stopped doing business.
Then, when trying to complete my Livewire collection, I came across this “secret” online auction for puzzles, the Haubrich Puzzle Auction. That is when I learned of Wil Strijbos’s Lotus puzzle and Kagen Sound’s Lotus boxes. I contacted both designers to see if they had any copies left. After a few years, I got a response from Wil and from Kagen Sound. I was in luck! However, the price for their puzzles sounded excessive for the amount of disposable income I had at the time. How wrong I was! If I could talk to my past self, I would have jumped at the opportunity.
Fast forward to March 2026. I suddenly remembered Wil’s Lotus puzzle and I decided to look for it. I came across a blog post from Zen Puzzler about Wil’s Tube It In and a new version, Tube It In 2, that is much harder, designed by William Hu and, more importantly, 3D-printed. So I decided to comment on the blog post and see if there is a way to get the STL files for it. Zen told me to ask William directly at the MPD and gave me the link to the Mechanical Puzzle Discord server, and the rest is history. I went crazy after that: I caught the puzzle bug and my wallet would never be the same again.
My first year of designs#
The first puzzle I designed, in November 2025, was a complete set of the 25 notchable burr pieces, with a case, inspired by dambin’s set of the 14 most common pieces. In February 2026 came Onigiri +2, my take on Teddy Sakamoto’s Onigiri, with seven ball bearings instead of five. The chaps from the MPD recommended that I ask Teddy for his blessing and I did. Luckily, Teddy was super friendly and instantly gave me his blessing. He even told me that his design was also inspired by Marbles Cage from Dr. Volker Latussek. We exchanged emails and I took the bold move of asking to meet him in person because I was to spend a month in Tokyo over the summer and he said yes!
From March on, month by month, in the order I designed them. Every linked design except Pallet is free to print on my MakerWorld profile.
- March. Pyramidst, a packing puzzle, and Hard Drive: stack four discs inside the frame in the right order, with every magnet the right way round.
- April. Qubits, a kit for prototyping TICs (Turning Interlocking Cubes), because TICs are hard to prototype any other way (although lately, software is getting better at this and I know of some designers that have successfully managed to design TICs with code).
- May. Boxy, a reusable modular box that turns Qubits into endless restricted packing puzzles, and a 9-piece board burr set: 15 pieces that build 21 board burrs of increasing difficulty.
- June. Slider, a sliding puzzle, and quoob, a maze cube.
- July. The Bull, my first kumiki (more about it below), and my first 2D kumiki; Otsukare, CMS82 and Rhythm, sequential puzzle boxes; DualMaze 1 and two more plate mazes.
- August. The Frankenburr: Bill Cutler’s burr No. 305, where every stick is itself a recursive interlocking puzzle. Allard reviewed it, and gave it its name, on Puzzling Times. Also the Goat, Macaque and Blue Jay kumiki, and the Fish trophy, a 2D kumiki.
- September. Pallet and Pallet Double Stack, sliding puzzles where you move the forklifts and pallets until the pallets are in order, 1 to 4: 130 challenges between the two sets, from easy to difficult. They are produced and sold by NothingYet Designs. The Bullseye Burr, nicknamed “The Monstrosity”: 9 pieces, level 171 and 344 moves, yet surprisingly logical to solve. Also Dracula; Borg Drive and Fidget Box; the Skull, Fox and Moose kumiki; and Niagara Balls.
- October. The Luban Burr: level 49, 99 moves, and the whole challenge is getting that first piece out. Also the two-step kumiki Cube 8, Cube 11 and Fox, and Cube 10; EQ Wallet; Window, a flat Bullseye; Tethered Kumiki; and the Kumiki Racing Set.
- November. Plotter, so far.
I’ll write about every design without a link in future posts, one month at a time.
How I design#
I design with BurrTools, OpenSCAD and Claude Code, and that is how I make sure every puzzle has a unique solution. A big portion of my puzzles draw on mathematical research papers. My kumiki, for example, build on Peng Song, Chi-Wing Fu and Daniel Cohen-Or’s Recursive Interlocking Puzzles (SIGGRAPH Asia 2012): the pieces come out in one order only, and whatever is left stays locked together until the last piece.
Before I design anything, I check whether it has been done. For burrs that means puzzlewillbeplayed.com, Ishino Keiichiro’s extraordinary index of interlocking puzzles. I built myself a way to search it by what the pieces actually are, and with his kind permission it is now open to everyone as the Burr Atlas.
The people#
The best part of this year has been the people. The puzzling community has welcomed me with open arms. From Mr. Mark, sending me a large number of puzzles made from Lego, to Chris Klarmann, who I now meet every time I fly out to my company’s HQ. Let’s go over a few puzzle meet-ups.
Japan#
This summer I spent a whole month in Japan, from mid-July to mid-August.
In Tokyo I arranged a puzzle designers’ meet-up at Torito, and solving puzzles with three of my favourite designers, Teddy Sakamoto, Akaki Kuumeri and Frédéric Boucher, was a dream come true. We all shared our new puzzles and prototypes and had a fantastic time. Afterwards Teddy, Akaki and I went for tonkatsu at Yodobashi Camera in Akiba.
Back at Torito on a family visit, I gave Meiko-san, the owner, my first ever kumiki puzzle: the Bull. It had to be a bull, since torito means “little bull” in Spanish. Meiko-san asked me to solve it for her, and then put it on display on a shelf in the shop.
I also went to the annual karakuri exhibition at Mitsukoshi Ginza, where I met Kikuchi-san, a famous karakuri puzzle designer. On another day at the same event I met Tsuburai-san, who was kind enough to give me a copy of his P&P box.
While I was there, The Geek and The Friki interviewed me about puzzles: Un episodio sin guion: IA, puzles y la vida en Japón. It’s in Spanish only.
More puzzle friends#
In September I went to the Midlands Puzzle Party, where Kevin Sadler, famous for his blog Puzzle Mad, tried all of my kumiki puzzles and some of my other designs.
On 20th October I had a lovely night of pizza and puzzles with the famous designer William Hu and Rémy, a Canadian puzzle enthusiast.
Whenever work takes me to my company’s HQ, I meet up with my very dear friend Chris Klarmann, a fellow puzzler, and we swap puzzles. This time some of my colleagues joined us and we managed a few hours of puzzling together.
Come to SEPP#
Almost exactly a year after I started collecting, I’m organising and hosting the first South East Puzzle Party:
- Saturday 13 March 2027, 10am to 5pm
- Bisley Scout & Guide HQ, School Close, Bisley, Woking GU24 9EG
- £10 entry, including an exclusive SEPP puzzle to take home
- Burrs, puzzle boxes, interlocking, disentanglement and packing puzzles
Please RSVP to southeastpuzzleparty@gmail.com so we can estimate numbers. Payment details come with the RSVP reply.
What’s next#
Next on Next Piece: a series going through my designs month by month, in the order I made them, until I catch up with the present. Along the way, I’ll write about puzzles I love and explain more about the Burr Atlas.
New posts arrive in the RSS feed and on Instagram. Thanks for reading, and see you on 21st November at the Midlands Puzzle Party (MPP) hosted by Allard.