There's also this https://github.com/HackerThemes/theme-machine/blob/master/scss/_common-utils.scss https://github.com/HackerThemes/theme-machine/blob/master/s

There's also this https://github.com/HackerThemes/theme-machine/blob/master/scss/_common-utils.scss https://github.com/HackerThemes/theme-machine/blob/master/sc... which is imported in the file that you linked. That's all in terms of SCSS. Then the gulp task runs the SCSS build and the autoprefixer.