If you find yourself working in CSS and missing the ability to use SASS variables, oh boy do I have a treat for you. You can use variables in CSS. They just look a little bit different than they do in SASS.

Set them up in a root block at the top of your stylesheet:

:root {
--brand-color: #2C9C20;
--secondary-color: #317BE1;
--fave-size: 50px;
}

And use them in a class with a var():

:root {
--brand-color: #2C9C20;
--secondary-color: #317BE1;
--fave-size: 50px;
}

.awesome-class {
background-color: var(--brand-color);
height: var(--fave-size);
}

They even work inside the CSS calc() function:

.awesome-class {
...
margin-bottom: calc(var(--height) * 2);
}

Hooray! This discovery really made my day.