Re: [css3-background] border-radius color transitions using gradients recommended but undefined from Zack Weinberg on 2010-01-29 (www-style@w3.org from January 2010)
Animated Borders In Pure CSS - animated-border.css | CSS Script
45 CSS Border Animations
CSS3 Border Radius Transitions
CSS border animations
Border Animation Pure CSS & HTML - Gradient Border Color - YouTube
CSS Draw Rounded Border Animation - Codeconvey
How to use CSS ::before and ::after to create custom animations and transitions - LogRocket Blog
Button Border and Text Color Fill On Hover – CodeMyUI