Josh W. Comeau on Twitter: "🌠 PSA: if you nest elements with rounded edges, you need to tweak the radius! Otherwise you get chunky corners. ✨ The formula I use: outerRadius =
css - Background with radius-top inside - Stack Overflow
CSS border-top-right-radius Property - Lena Design
Re: [CSS3, Backgrounds and Borders Module] some questions about border- radius from fantasai on 2009-08-24 (www-style@w3.org from August 2009)