Any files that require compilation (e.g., via a build process) will go in the /Source directory. This commonly includes pre-processed CSS (e.g., Sass or Less) and pre-compiled JavaScript (e.g., TypeScript or ECMAScript 6.0 files).
Note: Files that are usable in a development build "as is" but go through additional processing for a production build (e.g., minification, obscufication) can be placed directly in the
/Builds/Developmentdirectory.