When Google sold its struggling Motorola Mobility division to Lenovo, it didn't sell off the entire thing: Google kept the good stuff. One of the things Google held on to was the futuristic, modular smartphone program, Project Ara, which the company just released new details about.

Project Ara, which began as a viral video concept called Phonebloks and was taken up by Motorola's Advanced Technology and Projects group -- which is kind of like a Google [X] for mobile -- is an initiative to create a fully customizable modular smartphone that's manufactured by a high-speed 3D printing production platform.

It's like a smartphone made of high-tech legos, or the Moto X's customizability taken to the next level. You have a base plate that serves as the body of the phone, and various functions can be added as a hardware blok, depending on what your individual needs are. So, for example, if you love photography but don't care about gaming, you can buy a nice, more expensive, camera sensor blok but save money on a cheap processing blok and screen.

Google recently announced that it was moving forward with Project Ara, publicizing that the basic system might be sold to consumers for as little as $50.

Now Google, through the Phonebloks YouTube channel, has released an update on its progress.

The promotional video is mostly a non-technical introduction to the concept and the team behind Project Ara, but there are some interesting new details to be found there as well. For one, we get to see the prototype Endo -- the base plate upon which hardware blocks will be attached -- and how they will attach them.

This is probably the coolest bit of the video, about half way through, where we see the team demonstrating the electro-permanent magnetic attachment system. The engineers can take a hardware blok and slide it into place, after which they're locked in place by electromagnetism. And apparently the system stays firm even when the Endo isn't powered on.

The electromagnetic lock can be controlled by apps, the user interface of which we get a brief peak at as well. (If only all electronic components could work this way, tinkerers could avoid the frustration of broken plastic clips and regluing things back together!)

We also get a peak at what looks to be three possible different sizes for Project Ara phones -- a mini, regular, and phablet version (featuring 2x5, 3x6, and 4x7 grids for bloks, respectively) -- which shows up on the screen for just a second while Google designer Daniel McCloskey gabs about the aesthetics of modular bloks.

The video is frustratingly brief and cursory about Project Ara's features, but you won't have to wait long for more details. The Project Ara Developers Conference begins this April 15 at the Googleplex, where undoubtedly we'll find out more about the super futuristic smartphone project.