You swipe the power button, and the seemingly regular device magically expands from 6.7 inches all the way to a 7.4-inch tablet. (You swipe the power button down, or simply squeeze the phone to make it return to normal.) Oppo is currently working on adding the option to stop the "expansion" at any point in between, to accommodate any video size or simple preference.
As one might expect, Oppo's expanding screen does show a tiny crease from where it bends back behind the phone, but with the screen light on, it seems unnoticeable, without visible scratches from the mechanism's motion (bear in mind that this device has yet to see any serious use). The sound from the motor mechanism is also barely audible, according to BBC.
Unfortunately for all the phone enthusiasts out there, this is still only a concept phone and will not be out for sale anytime soon. There is also no selfie camera on this version of the device.
Although there has been talk amongst other companies, such as LG and TCL, about such a "roll-out" technology, Oppo is the first to show us a functional device that uses it—and has applied for lots of patents for it.