This is how BB-8 works, straight from Sphero's co-founder

BB-8 has enamored Star Wars fans since we first saw the little droid in trailers and teasers, and once it was revealed that the droid was actually a practical effect, meaning it wasn't created in a computer, the fans had a good time trying to figure out how it worked.

The $150 version of the toy has since been released — it's amazing, by the way — and Polygon caught up with Adam Wilson, the co-founder and chief scientist at Sphero, to talk about the toy's design.

We were scared that he wouldn't be able to say much, but after launch not many surprises were left. "I mean, I can tell you everything now!" he said with a laugh. "As of today I can just explore all of that. Really it's our Sphero robot ball, a self-balancing, gyro-driven ball inside of there. And on the top of that it has keyed magnets, so one of them is positive and the other is negative."

This means that the head can only connect in one direction, so the robot always knows which way is "forward." The folks at uBreakiFix actually tore their toy apart to get a look at the internal mechanism if you want to see the little droid without its shell. A fair warning for any tinkerers; there doesn't seem to be a way to open BB-8 without destroying the outer shell.

What's interesting is that the arm that supports the head isn't articulated in any way. The entire internal structure of the robot moves when the head moves. "If you want to just spin the head, it's still the same thing, the sphero inside of there is turning," Wilson explained. "When you're spinning the head around, the whole mechanism is spinning around, giving it a new forward."

"It's very tricky because you can't see the mechanism inside," he continued. "We have clear ones for development. It's a complicated physical system for sure."

The $80 version of the toy, which was made by Hasbro, opens much more easily, so you can see a simplified version of the same mechanism.

What's interesting is that this version of the droid came after the movie was finished; The Force Awakens used a variety of practical effects for the movie version of the droid.

"They had already shot the movie and made a prop ... they had shot all the movie with these props but none of them were full working droids," Wilson explained. "They were half-droids with a man and a green screen. They were still physical props but it wasn't a solo act. It couldn't stand on its own."

The idea of a fully functional BB-8 was attractive, however. Sphero was a part of Disney Techstars, an accelerator working with startups, and they had a meeting with Disney CEO Bob Iger where they were shown an image of the droid and asked if it would be possible to make a functional, standalone robot.

"We wanted to try to come lower than $150 actually, but it was a struggle"

"We had already done a lot of stuff like this, with magnets on the head," Wilson said. "We showed him our idea of how that would work, we showed him a magnet head that day." Sphero isn't involved with the creation of the larger versions of the droid you may have seen at events and may come to Disney's theme parks, but according to Wilson those droids may be using some of the ideas that Sphero shared with Disney.

"We wanted to try to come lower than $150 actually, but it was a struggle," he explained. For a while they thought it would even be released at $200, but they wanted to get the features and price to the point where they themselves said they would buy the product and be happy with it.

"We felt that $150 was a pretty good number, and it leaves a little bit of meat on the bone for both Disney and us to make money on this product, because it's really hard to make money on toys," Wilson said. "We also know what the competition is for the same character ... we just felt we had to surpass a certain point. It has to do a lot more than just be an RC toy to be worth that."

The toy doesn't just roll around; it can react to voice commands and learn about its environment. It can even be updated with new features as the movie grows closer. The Sphero team had exacting standards for the details and design of the robot's external shell. All of these things work together creates a toy that's one of the most interesting products on the market, even if you're not particularly interested in Star Wars.

Knowing how it's done is fascinating, but the real magic of the design happens when you see one in action, rolling around and interacting with its environment and the people in it. The Sphero team has made an amazing toy.