Font size calculator mixin
The following snippet of code takes a px value font size and converts it into rem, with a px fallback. This is a really cool idea that I saw in the OOCSS repo and have been using ever since. It’s a really great way to see how Sass can help you beyond just nesting blocks of CSS!
Rems are similar to ems in that they are a scalable CSS unit but they are much more predictable. They were introduced in CSS3 and they are relative to the root HTML element as opposed to the parent - so you wouldn’t have to worry about confusing em calculations anymore.