I was really really good at CSS circa 2010 and understood and could apply a very broad set of its features, but I stepped away from web front-end around 2013 or

I was really really good at CSS circa 2010 and understood and could apply a very broad set of its features, but I stepped away from web front-end around 2013 or 14 and when I look at a modern stylesheet I struggle to make any sense of it. And that's without SASS or whatever in the mix.