I created cssnext in 2014 - a PostCSS plugin pack that let developers write tomorrow's CSS syntax today (variables, custom properties, nesting, color functions…) and transpile it for every browser. Think "Babel for CSS." It grew to millions of weekly downloads and now lives on as postcss-preset-env, still maintained today.

I built a plugin architecture orchestrating dozens of CSS transformations, a configuration system targeting specific browsers, and a release process maintaining backward compatibility across hundreds of versions.

Hardest parts: API design at scale (every default affects thousands of projects), interpreting W3C specs written for browser implementers, and handing the project off to a worthy successor.

Building for an ecosystem teaches discipline client work rarely does - when other developers depend on your defaults and semver, you think carefully about every decision. I bring that rigor to every client project I architect.