Jacques Mattheij didn't expect to buy two tons of Lego bricks. But that's what happened after an evening of bidding -- or rather, overbidding -- on bulk lots of used bricks on eBay. His plan was to resell the bricks at a profit. But he won more than expected, and by morning, he owned more than 2 million pieces. Now he needed to sort them to get the best price.

If you've ever spent too long looking for the one Lego brick you desperately need, you understand exactly why a machine this large and complex was completely worth the effort. Anyone who grew up with Lego will remember buying and building individual sets, only to see their collection morph into an unruly, unsorted mass over time. Sorting through a vast array of bricks to find a particular piece has long been the bane of many a Lego enthusiast but now one canny constructor has developed a system that uses artificial intelligence to sort through large quantities automatically. Jacques Mattheij observed that there was plenty of money to be made selling Lego on the second-hand market and plenty of eBay listings for bricks in bulk. With that in mind, he began prototyping a rather amazing machine that could classify Lego by shape and color.

How I Built an AI to Sort 2 Tons of Lego Pieces For many years as a child, I did nothing but play with Lego. Eventually I had children of my own, who had a nice Lego collection themselves, but nothing you'd need machinery to sort. That changed after a trip to Legoland in Denmark. I noticed adults at the park buying Lego in vast quantities, despite its high price. Even second-hand Lego isn't cheap, sold as it is by the part on specialized websites, or by the boxed set and in bulk on eBay.

You see, Mattheij decided he wanted in on the profitable cottage industry of online Lego reselling, and after placing a bunch of bids for the colorful little blocks on eBay, he came into possession of 2 tons (4,400 pounds) of Lego -- enough to fill his entire garage. As Mattheij explains in his blog post, resellers can make up to €40 ($45) per kilogram for Lego sets, and rare parts and Lego Technic can fetch up to €100 ($112) per kg. If you really want to rake in the cash, however, you have to go through the exhaustive process of manually sorting through your bulk Lego before selling it in smaller groupings online. Instead of spending an eternity sifting through his own, intimidatingly large collection, Mattheij set to work on building an automated Lego sorter powered by a neural network that could classify the little building blocks. In case you were wondering, Lego comes in more than 38,000 shapes and over 100 shades of color, which amounts to a lot of sorting even with the aid of AI.

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. 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.