Originally conceived as Project Andromeda, running an evolution of Windows 10 Mobile, the relative failure of UWP (Universal Windows Platform) apps caused a rethink. This resulted in the Surface Duo, running Android, which was launched in 2020.
The Duo had two Gorilla Glass displays, hinged with cams to fold shut completely or open completely to 360 degrees, forming a more traditional phone form factor, if wide.
Android itself was adapted with a Microsoft launcher that split the UI (user interface) according to the two displays, with applications either running side by side or ‘spanned’ by dragging them (via the navigation bar) into the centre hinge area.
Launching with Android 10, this was updated through 2022 to Android 12L and the myriad early bugs were fixed along the way. At the time of writing, it’s in its last year of security updates, finishing in Autumn 2023.
The Duo wasn’t marketed outside the enthusiast and business world, mainly because, with no NFC and only a single selfie camera, it was unlikely to appeal to consumers. It was succeeded by the Duo 2
, which added a triple camera and NFC.