If you’re used to the vertical flip opening of phones like the Motorola Razr, or still fondly remember snapping your vintage not-so-smart cellphone open and shut, think different. The just-announced folding iPhone Duo opens horizontally, like a book, and its size and fold direction make it reminiscent of a paper passport. The much-anticipated phone was revealed Wednesday at Apple’s latest event.

While it wasn’t confirmed until this week, the folding phone was the worst-kept secret in tech, with hundreds of articles reporting that it was on the way. And it joins a crowded field of foldable phones, with key players including Samsung, Google and…

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