Chapter 3. Using Variables and Mixins
In this chapter, you will learn about the following:
- Deriving a set of variables from a single base variable
 - Value escaping with the 
~"value"syntax - Using variable interpolation
 - Redeclaring variables based on lazy loading
 - Using mixins to set properties
 - Declaring a class and mixin at once
 - Using selectors inside mixins
 - Using parametric mixins