Prototype is a starterkit Drupal theme leveraging Single Directory Components. The goal of Prototype is to provide a solid foundation for Drupal theme development by establishing a pattern of well organized components alongside a front-end build pipeline that utilizes SCSS, PostCSS, Webpack for JS bundling, Babel and Browsersync.
Post CSS and Babel respect .browserlistrc configuration, post processing CSS and JS as needed based on the browser versions defined.