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How Ernö Rubik Created the Rubik's Cube

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This story originally appeared in the August 2014 issue of mental_floss magazine. Subscribe to our print edition here, and our iPad edition here.

The Rubik's Cube's 40-year history is full of twists—quintillions and quintillions of them.

By Noah Davis

At 29, Ernö Rubik was too old to be playing with blocks. But the Hungarian professor of architecture couldn’t help himself: He was fascinated with shapes and spent much of his free time building and perfecting 3-D models. In 1974, a particular project had him stumped. For months, he’d been working on a block made of smaller cubes that could move without causing the whole structure to fall apart. So far, each attempt had failed. The evidence was strewn all over the two-bedroom apartment he shared with his mother.

One spring day, a frustrated Rubik left the apartment and wandered the streets of Budapest. He followed a gentle bend in the Danube River, a path he had walked countless times before. At one point, he stopped to listen to the water lapping ashore and looked down at the polished round pebbles that lined the riverbank. Suddenly, his heart started racing.

The solution was right at his feet: If individual blocks hinged on a rounded core, they could move freely while maintaining the shape of a cube. Rubik raced home and created a prototype held together with paper clips and rubber bands—a structure consisting of 21 smaller cubelets, adhered to a rounded interlocking mechanism. “It was very emotional,” the inventor told CNN in 2012. And that was long before he realized the device’s potential to torment millions of people the world over while making him incredibly rich.

Rubik’s solution was really “only a starting point,” he later remembered. Having marked each side with different colored stickers, he gave the block a few twists and watched it devolve into a chaotic collage. “After only a few turns, the colors became mixed,” he wrote in an unpublished memoir. “It was tremendously satisfying to watch this color parade.” Before long, Rubik decided to reset his cube. “[It was] like after a nice walk when you have seen many lovely sights you decide to go home; after a while I decided it was time to go home.”

It took Rubik a month of trial and error to find that way home. When he finally returned the cube to its original pattern, he showed it off to—who else?—his mother. “I remember how proudly I demonstrated [it] to her when I found the solution,” Rubik told Discover in 1986, “and how happy she was in the hope that from then on I would not work so hard on it." But solving the cube hardly curbed his obsession. He soon showed the toy to his students, thinking it would be a handy aid for teaching math lessons on group theory and spatial relationships. That’s when Rubik realized his brainchild might have a wider audience.

Bringing the cube to market was not going to be easy. Hungary was locked behind the Iron Curtain, where imports and exports were tightly controlled. And in any case, a puzzle with 43,252,003,274,489,856,000 possible wrong moves was a hard sell. But, as a man inspired by challenges, Rubik wanted to try. In 1977, he agreed to let a Hungarian toy-making collective produce the cube. The effort was a disappointment. The Magic Cube came out clunky, and half of the 10,000-piece order was prematurely canceled.

A year later, a Magic Cube was sitting on a café table outside Budapest. It caught the attention of Tior Laczi, a Hungarian businessman living in Austria who had a soft spot for math. He bought it off the waiter for about $1. There was nothing like it on the toy market, he knew, and he thought he could popularize it. But first, he wanted to meet the mind behind the block. When he did, he was underwhelmed. “When [he] first walked into the room, I felt like giving him some money,” Laczi told Discover. “He looked like a beggar. He was terribly dressed, and he had a cheap Hungarian cigarette hanging out of his mouth. But I knew I had a genius on my hands. I told him we could sell millions.” Rubik agreed to let him try.

Laczi started shopping the cube around at international toy fairs. In 1979, he bumped into British toy expert Tom Kremer at a fair in Nuremberg. Like Laczi, Kremer saw the design’s international potential. Luckily, Kremer had friends in high places. He pulled some strings and invited the bigwigs at Ideal Toy Corp.—the same company that banked on the teddy bear craze in the 1900s—to Budapest. After five days of tense negotiations, Ideal ordered one million cubes.

Rebranded as the Rubik’s Cube, the block was an outlier toy, elegant in its simplicity. It didn’t shoot, flash, whistle, or wet its diapers; it wasn’t cute or fuzzy. Ideal’s marketing campaign played to the user’s intelligence. Solving the cube required brains and focus. “Sure, Sir Isaac Newton unraveled the mysteries of gravity, but could he have unraveled the mysteries of the Rubik’s Cube?” the TV commercial voice-over teased. Consumers were alerted to the toy’s addictive nature. “Warning: Once you get your hands on a Rubik’s Cube, you may never be able to put it down.” In essence, it was the perfect puzzle: a language-less object that makes intuitive sense despite being maddeningly difficult to solve. In a business where games didn’t necessarily require intelligence, it relied on precisely that—plus patience and persistence. In return, it offered a meditative occupation for the hands and brain. And untold satisfaction when order, at last, was restored.

Soon, adults and kids alike became obsessed. More than 100 million cubes were sold in a little more than a year, turning Rubik into Hungary’s first self-made millionaire. In 1980, it won the prestigious German Game of the Year award and similar accolades in France, Britain, and the United States. Books covering the cube simultaneously held the first, second, and fourth spots on the New York Times paperback best-seller list. “It’s hard to overestimate what a phenomenon it was,” says Paul Hoffman, who oversees a traveling museum exhibit celebrating the toy’s 40th anniversary. Today, with 350 million official cubes sold and at least one billion knockoffs in circulation, it’s the best selling toy on the planet.

While his creation became a cultural icon, Rubik himself kept developing puzzles and Rubik-themed products. He never matched the smashing success of his first invention, but to him, that doesn’t matter. “For me, the most enjoyable part is the puzzle, the process of solving, not the solution,” he told CNN. In 1990, he became president of the Hungarian Academy of Engineering, where he created the International Rubik Foundation to support young engineers and industrial designers. Now 70, Rubik says his greatest joy comes from watching his creation inspire others. “I’m wondering how people are so creative, and how many things were born out of and inspired by the cube.” And this many years later, the famously reserved inventor still feels “very emotional” about the twists and turns that have brought him—and his toy—a long way from the banks of the Danube.

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iStock // Ekaterina Minaeva
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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May 23, 2017
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