Sass Fundamentals - Define and Implement Mixins

This topic is for the [Define and Implement Mixins] exercise in the [Sass Fundamentals] trail. Post any questions, corrections, or pointers you have to share with other Upcase subscribers.
[Define and Implement Mixins]: https://exercises.upcase.com/exercises/define-and-implement-mixins
[Sass Fundamentals]: Sass Fundamentals | Online Tutorial by thoughtbot