Not only is Apple going foldable with its new iPhone Duo, its user interface is going vertical too.

The iOS 27 operating system for the iPhone Duo takes advantage of the foldable smartphone’s new form factor with user interface changes designed for the phone’s larger display. That meant turning parts of the iPhone’s longtime UI on its head.

The home screen dock that has been positioned horizontally and at the bottom of every operating system since the first iPhone has now been moved to the side, as have other controls.

The change not only maximizes screen space, but it puts major controls closer to the user’s thumb, helpful for a phone that folds out longer than it is tall. The controls stay in the same location whether the phone is open or closed.

Apple said Wednesday at the iPhone Duo’s unveiling that it had to adjust every app’s layout and reconsider long-standing iPhone design principles because of the new vertical UI.

The status bar, for example, which displays Wi-Fi, cell signal, and battery life, was redesigned from a standard horizontal display showing these three icons next to each other into a more compact graphic that puts the information in a single circle.

The larger screen also allows for showing two different home screens at once when it’s unfolded, or even two different apps. For an app like Email, full-screen mode shows both the inbox and messages at the same time. The iPhone Duo is also the first iPhone to support the Apple Pencil.

Despite the changes, Apple said it designed the new system to feel natural and familiar. The UI for the phone might be on a different axis, but it’s meant to be intuitive for longtime iPhone users.