Quite impressive to be honest. I always enjoy seeing how creative and powerful CSS can be.

Though, I feel like there is some level of understanding of HTML/CSS that I will never be able to grasp -- like this demonstration. This person is out here making frosted windows, and I can't even center a div.

When I was working out how web dev works, I learned the hard way that adding a div is often a good idea, and when you see most modern websites they are a huge pile of divs. If you want a centered div, add another div that is just the full size of the space to center inside, then centering within that div is relatively easy.

The same sort of goes with many visual tricks, although this one is very clean, which makes it all the more impressive.