Bourbon Fundamentals - Border Radius Mixin

This topic is for the [Border Radius Mixin] exercise in the [Bourbon Fundamentals] trail. Post any questions, corrections, or pointers you have to share with other Upcase subscribers.
[Border Radius Mixin]: https://exercises.upcase.com/exercises/border-radius-mixin
[Bourbon Fundamentals]: Bourbon Fundamentals | Online Tutorial by thoughtbot