This is a good example of a reasonable style guide for CSS development. Study it, learn from it.
If you’re working with WordPress (or if you intend to work with WordPress), this will be an incredibly useful resource for you.
Find out what modular scale is and why you should use it to keep consistent vertical rhythm down the page.
Today’s browsers will always download all stylesheets that are referenced with media queries. This means that there is no performance upside in having media queries in separate files.
CSS was designed to be forgiving of errors. How forgiving exactly CSS is, find out in this article.
It’s mind-blowing what you can create with pure CSS. However, this certainly doesn’t mean that you should create something like this with pure CSS.
Until next week