CSS animation basics and Sass mixins

This was based on something a person was asking about on a facebook group. They were asking if there was a library that would make background animations. I saw their example and said "That looks like the bottom of 3 moving circles. I bet I can make that with just CSS". Here is the result of what I came up with. I ended up reviewing about SCSS mixins to reduce the amount of code. Below you'll find my codepen as well as a video where I walk through my process.

https://www.youtube.com/watch?v=plTkDxJh3zs

https://codepen.io/bushbass/pen/NeLmoL