Sustainability is key in Sass, planning out the structure of your files and sticking to naming conventions for both variables, mixins, and selectors can reduce complexity.
Understanding CSS output is also essential to writing sustainable SCSS. In order to make the best choices about what functions and directives to use, it is important to first understand how this will translate in CSS.
Mixins should only be used if they take in an argument, otherwise, you should extend the selector's rules, whether it be a class, id, or placeholder.
In addition to the directives you have learned in this course, be sure to check out the many additional available Sass functions and directives.