When the iPhone X launched, a lot of designers were put off about the screen shape. Those complaints have mostly died down, but I haven’t seen much design-nerd talk about cool corner treatment details
Once Apple knew they wanted to take advantage of new full-screen technology, that gave them the opportunity to alter screen shape because they would need to address the manufacturing process anyway. Presumably, the expense was mostly built in.
iPhone X rounded screen corners don’t use the classic rounding method where you move in a straight line and then arc using a single quadrant of a circle. Instead, the math is a bit more complicated. Commonly called a squircle, the slope starts sooner, but is more gentle.
Apple has been doing this to the corners of laptops and iMacs for years, but this type of rounding didn’t penetrate iOS until version 7. This shape has classically been difficult to achieve, because it wasn’t available in 2D design editors, though that’s starting to change.
The left and right sides have two rounded corners. Because of the curve falloff, one curve doesn’t complete before the next one starts — they blend seamlessly into each other.
As a result, no tangent line on this edge actually hits a perfect vertical.
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