Sass is the greatest, and libsass (via node-sass) is the fastest! Put your Sass here.
If you're using the Icon Font task, a generated folder containing _icons.sass will be automatically created. Be sure to @import generated/icons in app.sass.
I've provided a web font mixin in base/mixins.sass for use with any fonts you may include.
Normalize.css is also installed and @import'd by default, mostly as an example of how to include css from node_modules.
gulpfile.js/tasks/css
Your Sass gets run through Autoprefixer, so don't prefix! The examples use the indented .sass syntax, but use whichever you prefer. In the production task, output is minfified with cssnano.
You may also provide additional node-sass options to the sass property in css task config in config.json. By default, i've enabled indentedSyntax and added the path to normalize.css via the includePaths option. See #190 for details.