Ugh. Before the advent of CSS3 and canvas, I would have rated myself an 8 out of 10 in terms of "frontend knowledge/skills" compared to other frontend developers I'd met. I was never the cream of the crop (as a backend "expert"), but I could take a photoshop and replicate it, and knew most of the browser compatibility issues and how to work around them.

With all the CSS transforms, animations, canvas, 3d libraries, etc., I'm now utterly lost. I've gone from being an intermediate frontend guy to a 6/10 on the core necessities (all that earlier knowledge is still the foundation), but like a 1/10 or 2/10 with all the new stuff. I could probably get to 4/10 if I put in the effort, but I have a very strong gut feeling that I simply do not have the... faculties... required to be an intermediate frontend guy in 2015.

All that to say... codepens like these I've seen blow me away. I don't even bother trying to dig into the CSS. It's just beyond me. ;)