Look out! There’s an app barreling toward your skull, and it’s going as fast as a car.
Among the most powerful things about the first iPhone was how it made old software metaphors — pressing buttons, scrolling through pages — much more literal. Scrolling was now linked, one-to-one, to the tip of your finger. You didn't click a button on a mouse to command a software cursor to press a button for you, you just tapped it with your thumb. This was a profound change and one that was hard to advertise or talk about. But it was something that users were able to grasp almost immediately.
Movement in iOS, and in Android, is generally directly connected to one of two actions: a tapping or swiping, or hitting a button or dragging (or pushing!) something around. The weirdest these direct actions really get is pinch-to-zoom, which is somehow intuitive but doesn't really have a real-world equivalent. These are all vital in making iOS feel like iOS.
Also vital: the animations, which, in iOS 7, are centered around zooming. Or, more accurately, flying. Tapping an icon sends it flying at your face, at which point it begins to transform into an app. Closing it pulls it back away from you; it's as if the app is falling into the screen. Our minds take every other movement metaphor in iOS literally, but this one is weird. It feels three-dimensional in a way that others don't.
The sensation of depth is exaggerated in iOS 7, and profound enough that it led some users to complain of a sort of seasickness (which Apple both acknowledged and provided a fix for, in an update).
Just how deep is the interface? BuzzFeed data team member Jake Levy ran the numbers:
I used the small-angle approximation since the size of the object (in this case the app) is significantly smaller than the distance from which you are observing it. This allowed us to assume that the apparent size of the object is inversely proportional to the distance from which you are observing it.
Here's what he came up with:
