IN THE LEGO MOVIE, an epiphany transforms Emmet, the everyman hero, into a master builder. Seeing Lego part numbers superimposed on every brick in his universe, he realizes that, for the first time, he can build incredible designs from his imagination, with no instructions.

This scene triggered my own epiphany. I realized what sets master builders apart: They dive deep. They can name every piece of what they’re building. Suddenly, it seemed inevitable. That database must actually exist. Ninety seconds of web searching later, I found Rebrickable.

Using a list of Lego sets you own, Rebrickable can generate a list of other sets you can build (including brilliant hobbyist designs), with links to instructions. This list is ranked by the percentage of pieces already in your possession—the entire galaxy of Lego creations gets sifted to mirror your brick collection. If you’ve bought Star Wars sets, you can see that you only need 14 additional gray, white, or burgundy bricks to build a Star Wars ARC-170 starfighter, pod racer, or troop transporter.

J.C. Herz About @jcherz is the author of Learning to Breathe Fire.

Then, with one click, you can export that list of missing pieces to several online vendors who will assemble the order and mail it to your house for a few bucks plus postage. Browsing the virtual aisles of BrickOwl, a global aggregator of brick merchants, is a kid-in-a-candy-store experience. A rotor assembly: Add to cart! Robot legs! Yes! Lego minifigure falcon wings? Never knew they existed, awesome! You can easily import these orders back into Rebrickable, so the next time you hit What Can I Build? the list of possible designs is resifted to reflect the addition of those new pieces.

This is when the insanity begins. Because when you have customized project recommendations and a just-in-time sourcing system, you realize you need inventory control. Otherwise, it’ll take 10 minutes to find the piece you need, and that’s no fun.

As a kid, I didn’t spend that much time with Lego. But as a parent, I’m one of those people who can spend ridiculous money at the Container Store. I like to categorize things, then see all the things, in well-organized containers, displayed to reflect a well-thought-out taxonomy of form and function. Neatness isn’t the payoff. The pleasure lies in creating a system of classification: What is the right way to formulate categories? When do categories fork into subcategories? Is there a sequence that makes better sense?

I bought four clear plastic storage boxes with adjustable compartments and went on a brick-sorting bender. An undifferentiated sea of bricks became intuitive inventories—Minifig Pieces, Technic Pieces, Car & Truck Parts, and the Container of Slopes, Headlights, Textured Bricks, and Smooth Tiles. It was a blast.

As it turns out, the dream parent-child combo for Lego isn’t father-son. It’s a little boy who loves to build new things and a mom who loves being able to put her finger on any one of 68 part types in less than 20 seconds.

“I need a 2 by 1 slope,” the little boy says.

“A standard slope or an inverted slope?”

“Inverted.”

“Got it. Here ya go.”

Watching my 5-year-old download instructions and build cars, trucks, and space vehicles, tweak them, and substitute parts, I’ve realized there’s an important step between just following instructions and being able to improvise. The scaffold to expertise is having lots of instructions but not having all the pieces. If you don’t have a piece that’ll attach to the bottom of a small brick to hold a wheel underneath, you can’t build a motorcycle. When a kid pores over half a dozen downloaded instructions for motor­cycles and makes that determination, he has figured out something about the design process, something that helps him to improvise and later to build without instructions.

This is how people learn to cook. It’s how they learn to code. They start with ingredients, techniques, pieces. When they want to do something different, they find recipes, references, ways of going about it. They learn what is essential and what can be substituted or left out. They develop knowledge about how the pieces combine. They invest themselves in the activity. Lego, for its part, has officially blessed Rebrickable, because Lego appears to grasp this: Kids who download new instructions every day spend more time with their bricks and get excited about Lego robotics camp. Deep inquiry nurtures focus. Intention.

What I’ve learned from Rebrickable is the importance of intention, and how it defines a person’s online experience. Without intention, it’s easy to waste hours on social media and feel empty or leached out. With intention, online media doesn’t keep you in the shallows. It takes you deeper into whatever you want to learn. It brings you closer to the more expert version of yourself. Whatever your intention is, that is the special piece that unlocks all the rest.

I know that sounds like a cat poster. But it’s true.