A squircle is a rounded square with no straight edges; the shape is a continuous curve.
Squircley is a simple tool for creating SVG "squircles."
From the author's (George Francis) dev.to article Soften up your designs with a Squircle!:
A Squircle, unlike an element with border-radius set, has no straight edges at all. The shape is a continuous curve! Apple love this trick and use it in both physical and digital design.
I love how squircles look! 🤩 Though funnily my brother doesn't like them, apparently because at some point they have been popular in Android as well so he has already received an overdose of them. 🤔