Fela VS PostCSS

[Fela](https://fela.js.org/) and [Griffel](https://github.com/microsoft/griffel) are also not bad choice.

Speaking of libraries and implementation. I implemented themes for white label (and not only) on UI via styles as a function of state on UI. I used https://fela.js.org/ for this. So basically, when a React app initializes, a part of the state is initialized (via identity of a user, like email they log in or meta info, or additional API call, or via URL) with a value telling if it's a partner X vs partner Y vs your own brand. Then the styles that have colours, backgrounds, borders, box-shadows, fonts are applied by fela. So I created a bunch of styled components like buttons, toggles, styled divs, etc and each of them has access to that piece of state holding the UI theme, and depending on that theme, it will apply CSS classes in the runtime. You can use the same mechanism to implement multiple themes for your own brand (not just light/dark modes). The only thing you need to manually code is a JSON spec for themes like:

the plugins in the official PostCSS website were old like IE6 or the marquee tag, and

Hello internet. I just published a new blog post on how to implement dark mode with SvelteKit, optionally with PostCSS and TailwindCSS:

There are many frontend tools available for this purpose. For example, PostCSS is a popular CSS processor that can combine and minimize your code. With the right plugin, it can even fix your code for compatibility issues, making sure your CSS styles work for all browsers.

I use PostCSS to extend CSS’s features and to add a few things that make writing styles a little more convenient, but it could easily be swapped for another preprocessor like Sass or vanilla CSS. It’s up to you. You can view my PostCSS config here.

Code transpilation isn't specific to JavaScript, You can also add a level of transformation to your CSS source using tools like post-css. Most languages with a fairly mature ecosystem will probably have some tools to help with code transformation.

In large projects, it is still a good idea to use PostCSS, which will translate new CSS features to something that browsers understand today.

LiveCodes provides many of the commonly used developer tools. These include Monaco editor (that powers VS Code), Prettier, Emmet, Vim/Emacs modes, Babel, TypeScript, SCSS, Less, PostCSS, Jest and Testing Library, among others. All these tools run seamlessly in the browser without any installations or configurations. It feels like a very light-weight version of your own local development environment including the keyboard shortcuts, IntelliSense and code navigation features.

Usually, one of the first things I do on creating a new web app is to throw a UI library in to help style components. There are several UI libraries that can be used by Svelte, but in this case I went with daisyUI because it's a fairly popular UI library which includes tailwind. To install daisyUI, you first need to install tailwind. There's a few different ways to do this (such as this guide), but the easiest way I've found is the following command, which also adds PostCSS and AutoPrefixer:

Vanilla CSS has taken a similar path with ambitious working drafts, better browser support, and PostCSS to fill the gap for user agents lagging behind. So why is Sass/SCSS still so popular? Maybe we go so used to it that we might have forgotten what problems it was meant to solve in the first place.