This week at Apple's Worldwide Developers Conference, the company will release the tenth major version of iOS. Which, thanks to humanity's slavish devotion to base-10, means it’s high time for a retrospective, a hard look back at the most seminal features. At least, that was the plan.

Some days back, I made a Google Doc: The N Ways iOS Changed User Interfaces Forever. (Listicles, we have them!) I shared it with some folks around the office. We added to it, and we took things away. We tracked down versions of every iPhone ever made, turned them on, squinted at their tiny, pixelated screens, and laughed at their lack of push notifications. Things got nostalgic.

And then we realized: Yes, iOS, like the hardware on which it runs, has changed a lot. But far more interesting is what hasn't changed. The most impressive thing about iOS is how much Apple got right on its very first try.

Our lives are so interwoven with the influence of iOS that explaining it is a little like trying to explain the mystical powers of your car's steering wheel.

In 2007, smartphones had reached a breaking point. They could do so many things—email, calendars, phone calls, text messages, net surfin'—but the old ways of doing them weren't cutting it. The BlackBerry scroll wheel and trackball worked beautifully for scrolling through emails and BBMs, but left-left-left-down-downing your way to on-screen buttons felt like the past. A stylus helped, kind of, but even if you managed not to lose it you still had to figure out where to put it when you wanted to use the keypad. Smartphones' abilities had quietly begun to outstrip their interfaces.

The last keyboarded phone I ever owned was a gray Motorola Q9. It had email, Solitaire, and a D-pad just below the screen. I bought it on eBay (2007!). A few weeks later, my friend bought an iPhone. It didn't have 3G or GPS like my Q, couldn't send picture messages like my Q, couldn't even shoot a video like my Q. In every way we'd ever measured phones, the iPhone was inferior. But the first time I swiped my finger to unlock its screen, it was clear the iPhone was the future.

Wait wait wait! Don’t go. This is not a love letter to the touchscreen. Sure, it's tempting, today, to say it was the touchscreen that revolutionized smartphones—just as it was tempting in 2007 to say it was what made the iPhone different. Here’s Mark Rolston, a very smart designer, describing the iPhone to USA Today shortly after it launched: “Touch introduces all sorts of compromises,” he said, “but you can directly interact with the screen.” That's all true! But it doesn't tell the whole story.

The real magic of the iPhone was that you didn't actually interact with the screen at all. You interacted with a world on the other side—and you believed that you were interacting with something real.

Lots of smartphones had touchscreens. The iPhone had physics.

Apple imagined the iPhone's operating system (first called OS X, then iPhone OS, then finally iOS—but we'll just call it iOS) as a set of real objects, each with weight and size and a place in a world. What's more—and this is crucial—iOS had low latency and laws of motion. It really sold the illusion that collections of illuminated pixels were objects that you could directly manipulate.

That illusion was the death knell for devices like the BlackBerry Curve 8300 (the raddest non-iPhone phone of 2007), for which a task like zooming-in on a map was so complicated, my editor made me delete my description of the process. The first iOS, by comparison, had pinch-to-zoom. Need a bigger map? Just put your fingers on the map and spread them apart. The "map" (there was no map) got "bigger" (the picture changed). That paradigm still sets the iPhone apart. For years after the iPhone came out, swiping or scrolling on anything else was an awkward, stutter-y mess. Lots of smartphones had touchscreens. The iPhone had physics.

It is true that this illusion had its dangers. Apple would, on occasion, wrongthink that green felt was an appropriate background for an app like Game Center, or that the Notepad app really needed to look like it was wrapped in the exact same ugly leather that Scott Forstall had in his car. But mostly, it made the iPhone dynamic and usable—a UX/UI leap no less significant than the jump from text-based, command-line computing to the graphical user interface.

With that leap, iOS initiated a revolution in design—of graphics and interfaces, sure, but also experiences. The gesture-driven touchscreen changed work, entertainment, transportation, socializing, everything. Our lives are so interwoven with its influence that explaining it is a little like trying to explain the mystical powers of your car's steering wheel.

You could argue that Apple has not innovated much since, or that it stole a lot of ideas from competitors. But it comes down to this: Smartphones changed forever that day in January 2007, when Steve Jobs introduced us to the first iPhone. Not because the device itself was so incredible; Apple understood reinventing the phone was about more than hardware. It was about the way people understood what was inside. The way they saw it, interacted with it, and felt it under their fingertips.

Nearly ten years later, our devices are again beginning to test the limits of our interfaces. Once again, our phones can do so much more than our screens and fingers know how to handle. Apple's working out what comes next. It's working to make your iPhone feel more like a single device than a gallery of disparate applications, and working to make Siri into the digital assistant everyone wants it to be. It's trying to find ways to make things faster, simpler, and more powerful. It's working out how to make software as understandable as iOS for a television, or a watch, or a light bulb. These are problems no one has solved. It's like we're back in 2007, waiting for Steve Jobs to swipe and unlock an iPhone so he can show the world how they'll use their next computer. Except this time, multitouch won't cut it. From where we stand today, the future looks less like pinch and zoom, and more like say and do.