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.

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 ...