This lesson has introduced you to some of the most powerful concepts Sass has to offer!
Mixins are a powerful tool that allow you to keep your code DRY. Their ability to take in arguments, assign default values to those arguments, and accept said arguments in whatever format is most readable and convenient for you makes the mixin Sass's most popular directive.
& selector* is a Sass construct that allows for expressive flexibility by referencing the parent selector when working with CSS psuedo elements and classes.
String interpolation is the glue that allows you to insert a string in the middle of another when it is in a variable format. Its applications vary, but the ability to interpolate is especially useful for passing in file names.
Let's keep up the awesome job in the next lesson, where we will learn about functions, arithmetic, and color operations in Sass!