Since its 2007 launch, the iPhone has had the same basic design: a flat, rigid rectangle.

Now, Apple is folding on that form factor.

Apple debuted the new foldable iPhone Duo on Tuesday at its annual September hardware event, marking the biggest design change in the device’s history.

John Ternus, Apple’s CEO, critiqued other foldables that “feel like two phones awkwardly stuck together.” The company wanted a larger display, one that is “as natural and intuitive as an iPad,” he said.

The device has two displays: the closed front and the full-sized open screen. When opened, the phone can also have two displays on each side of the hinge.

It’s 50%…