Brad Ellis on the very special corners of the iPhone X:
Here’s where the nerd part comes 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.
Now let’s talk about the notch itself. 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.
I love this type of design details. Almost three months later, sometimes I still stop and stare at the screen on my iPhone X to realize what a marvelous feat of industrial design and engineering it is.