Google sold most of Motorola Mobility to Lenovo for $2.9 billion earlier this year, but it kept one small part of the phone manufacturer. Motorola's Advanced Technology and Projects group had been working on Project Ara when it was incorporated by Google — an ambitious plan for a modular smartphone that could retail for around $50, comprised of parts that users could purchase and swap in and out at their leisure. Now Phonebloks — a company that previously worked with Motorola to create a concept for a modular smartphone — has shown off how Project Ara is progressing in a video tour of Google's offices.

We see an early version of what Motorola called Project Ara's "endo" — its endoskeleton — into which modules are slotted into a silver frame and locked into place using magnets. Those magnets are electro-permanent, meaning phone components can be secured or unlocked with an app: a design decision that means Project Ara phones won't need a covering or outer case.

Also shown off is an app that will enable people to plan a possible Project Ara phone ahead of purchase, and manufacturing partner 3D Systems' early designs for the casing of Ara's modules. The designs on show suggest users will eventually be able to customize their phones with textured effects, bright colors, or pictures of cats wearing goggles. The video is likely aiming to stoke interest in Project Ara a week before the first Ara Developers Conference, to be held online and in Mountain View, California, on April 15th and 16th.