Yep, Windows 8 had a mobile/tablet version.

I also mentioned in another comment that they could simply do the same thing as with the Deck, have it start with a handheld/controller friendly UI (hmmm where could Microsoft’s Xbox division find that?) and give the option to switch to regular old Windows to do desktop stuff. It’s not as if playing on the desktop without a mouse and keyboard attached to the Deck is a fun experience either!