Rectangles with rounded corners are mathematically wrong. Once you know why, you can’t unsee it. Squircles, made iconic by Apple, are finally supported in browsers by the new CSS corner-shape: squircle property. I will show you how to approximate one squircle corner with just three pixel-perfect Bézier curves, so you can use squircles everywhere: canvas, SVG, clip-path, and even game engines. Your eyes deserve curves that actually make sense.
Lost me when it started talking about discontinuity of curvature as if that’s something that’s important. It’s important when building a railway, but not when drawing something squarish. I’m gonna complain that squircles aren’t third-differentiable.
I agree. C2 continuity does matter for aesthetics sometimes, but not for a button.