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.

And:

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.