https://twitter.com/sumusiriwardana/status/1438027601612656640?s=21

A List Apart: https://alistapart.com/blog/topic/css/

Frameworks

https://tailwindcss.com/

Guides and tools

https://css-tricks.com/snippets/css/a-guide-to-flexbox/

https://semicolon.dev/tutorial/css/complete-css-flex-tutorial

Animations

Button animations

3D transforms with Webflow

Examples

CSS Zen Garden: http://www.csszengarden.com/