Atlas is a starter theme for Drupal websites that is designed as a starting point for designers and frontend developers who have some knowledge of Drupal theming. It is meant to take care of some common theming tasks as well as remove Drupal's CSS and markup bloat.
The Sass files are structured according to SMACSS principles which means the rules are divided up in a modular way - one for views, one for blocks, etc. This makes things much more maintainable and if you don't like the way I've handled something, you can easily chuck the file and replace it with your own without touching the rest.
On the TODO list:
- Add Gulp tasks
- Remove some of the Prometheus related CSS
- Improve according to the feedback I get