This article will explain the principle of vector rotation in a two-dimensional space.
This article explains CSS through a series of gifs.
This article gives a thorough explanation of CSS-in-JS, including where it is today and where it is going in the future.
Part 2 of this 2-part article discusses many CSS features that can be used now or soon.
Part 1 of this 2-part article discusses many CSS features that can be used now or soon.