postcss-plugins VS Sass

the author of the most popular PostCSS plugin himself recommended the postcss-preset-env over his own creation which is cssnex, and

The example in A) won't work as the plugin can't convert the functions with variables in it. https://github.com/csstools/postcss-plugins/tree/main/plugin...

You can use this today if you're using PostCSS in your build process (which is the case if you use autoprefixer)! https://preset-env.cssdb.org/

Switching from a ready-made tool like Sass or a recommendation package like cssnext (deprecated since 2019) or PostCSS Preset Env (archived in 2022), to the modular PostCSS Preset Env plugin set we can choose a helpful and convenient set of future CSS features beyond the current stable client CSS.

To implement :has support, the css-has-pseudo polyfill can be used. This polyfill includes both a PostCSS plugin and a JS function to be used in the HTML page.

Yes, it's behind a flag and only in future versions, but it is a huge step forward. Those versions will soon be available, and we can try it locally (unfortunately, not on production without a polyfill or a plugin).

w/ postcss-preset-env(v7.8.3): convert modern CSS into something most browsers can understand, determining the polyfills you need based on your targeted browsers or runtime environments. It takes the support data that comes from MDN and Can I Use and determine from a browserlist whether those transformations are needed. It also packs Autoprefixer within and shares the list with it, so prefixes are only applied when you're going to need them given your browser support list.

There's a @ custom-media proposal (and PostCSS plugin) that can make it a lot easier to use media queries across components. Define your MQs in your global CSS, use everywhere. If you're worried about repeating MQs in your CSS from a bloat perspective, there are PostCSS plugins for that as well.

The term you are looking for is "nesting". CSS currently does not support it. But there is a draft being worked on. No browser currently supports it, though. Most CSS Pre- or Postprocessors like Sass, Less, Stylus, PostCSS support nesting.

SASS(.scss) [ https://sass-lang.com ]

Traditionally CSS lacked features such as variables, nesting, mixins, and functions. This was frustrating for Developers as it often led to CSS quickly becoming complex and cumbersome. In an attempt to make code easier and less repetitive CSS pre-processors were born. You would write CSS in the format the pre-processor understood and, at build time, you'd have some nice CSS. The most common pre-processors these days are Sass, Less, and Stylus. Any examples I give going forward will be about Sass as that's what I'm most familiar with.

CSS stands for Cascading Style Sheets, and is a scripting language used to style web pages. SCSS stands for Syntactically Awesome Style Sheet, and is a superset of CSS. You can think of SCSS as the more advanced version of CSS, which comes with several features that CSS does not support, such as the SCSS nested syntax, as shown below.

Scss

In the past, you’d need to rely on pre-processors such as SaSS or Less, but not anymore… Native CSS nesting has landed on all major modern browsers.

Sass is also a css preprocessor. Op is likely confused

sass -> An improvement over CSS. It provides nice features for managing CSS. good for mid-sized or even larger projects.

Sass (Syntactically Awesome Style Sheets) - A CSS preprocessor that simplifies and enhances your CSS workflow. Website: https://sass-lang.com/

Personally, my preference is Sass: I find that the mixins, partials, and operators are hugely useful when it comes to creating re-usable snippets of code for a design system. And, since it’s “just” a pre-processor and not a framework, it’s not opinionated in a design sense and there’s no default values (colors, spacing values, etc.) that will need to be overwritten.

Preprocessors: SSGs leverage preprocessors to streamline the development process. Preprocessors like SASS for CSS or Babel for JavaScript offer additional features and simplify code development.