Lego's new toy train is a STEM tool for preschoolers

Coding Express is one way to teach your toddler basic programming concepts.

Twenty years ago Lego introduced Mindstorms as a way to engage kids who were becoming more interested in video games and the internet than plastic building blocks. It was successful enough that the kits became a regular sight in robotics classes and competitions. Now the line is on its fourth generation, and it's been joined by other STEM-friendly Lego kits like Boost and Powered Up to bring tech skills to many different types of kids. Now Lego's educational division goes even younger with Coding Express, a set that will teach 3- and 4-year-olds the basics of programming while they construct a world of trains, picnics and wandering deer.

This isn't going to teach your kids popular coding languages like Python or Swift. Coding Express is firmly for the preschool crowd, so the idea here is to just get kids acclimated to concepts like loops and subprograms. It doesn't require a computer or tablet to work, ether. Instead, kids go hands-on with a physical train set, which includes a small engine and tracks that kids put together themselves. To direct the train's actions, kids place colored ovals on the track and a camera on the underside of the engine reads the color. Each shade represents a different command: red is a hard stop, blue toots the train's horn and so on. Kids have to think about what they want the train to do ahead of time, basically constructing a simple program.

A train is just the tip of the iceberg for Coding Express, though. It can be connected to an app, but not to write programs. Instead, it can change what the blocks represent — instead of a train carrying cargo, the pieces can be rearranged to make it look like a hungry caterpillar, with emotions that are controlled by the colored discs. In the app, kids will watch the caterpillar's reactions as it travels on the track, becoming happy or sad based on the discs they place in front of it. More programs can be added later on that will expand the types of emotional and social skills the kids are learning, while still giving them that all-important coding background.

Because it's intended for a younger crowd, Coding Express is built on the larger Duplo blocks that are easier for small hands to manipulate (and harder to swallow). Each kit comes with the engine and plenty of track, but also lots of figures and accessories. The other accessories really help develop a kid's imagination, with adorable details like cake and tea for a picnic, or a deer and a deer-crossing sign. The sets are big enough that six kids can work on one at the same time, which is great for building interpersonal skills as well.

All of these skills are part of the Common Core curriculum, and Coding Express' included lesson plans are all compliant with those educational standards. In fact, the sets aren't intended for the retail market at all. Schools will have to buy them through Lego's educational portal for $200 a set, starting October in the US and China and globally in the spring.

Though Duplo carries an age range of 18 months to 5 years, Coding Express aims just a bit higher, technically starting at age two. But Lego Education is reluctant to push any particular age group for Coding Express. Instead, the company thinks teachers and the kids themselves will decide when they're ready to start, and when they're ready to move on to more-advanced product like Mindstorms.