Google says its modular smartphone Project Ara won’t be quite as modular as planned. Several key components will be non-replaceable, including the screen and memory.

The original plan for Ara — or at least the concept Google initially explored — was that literally every part of the handset could be replaced, Lego style. Google has now concluded that the technical challenges involved aren’t worthwhile given how few people, at least among Ara’s likely users, will be interested in changing and upgrading these key components.

Instead the processor, the RAM, the on-board storage and the screen will all be fixed. The handset will then have six slots for adding or replacing from a range of 30 or so modules. Examples include a secondary e-ink display and a higher-resolution camera, though Google also hopes third parties will develop creative modules such as a glucose monitor for diabetic users.

The phone will have the ability to combine multiple installations of the same module in an appropriate manner, such as using two speakers to increase the maximum volume. There’ll also be some ’empty’ modules which fit a slot if you don’t like the visual effect of unused space.

A Wired report details a demo which shows the concept itself is already working. It’s a truly plug-and-play system, with a tester being able to add a camera module and immediately take a shot.

Securing the module in place is done electronically and controlled by software, so it’s possible to release a module through a touchscreen command or even voice control. It’s also possible to password-protect a module such as a data storage unit to stop it from being removed.

While the technology does sound impressive, it will require a change in marketing focus. Originally the sales pitch was that the phone would never become obsolete thanks to the ability to easily upgrade key components. Now it seems Google will instead have to stress the potential for itself and other developers to come up with creative accessory modules, in effect taking the same approach to hardware as already happens with apps.