I appreciate you noticed the cleanness. It was a challenge to get it down to 2 divs and 2 classes. I’m disappointed that `background-attachment: fixed` isn’t supported on mobile after all these years. If it were, the full effect could easily be applied to any element with a single CSS class.

If I were to make serious use of this on a site, I’d probably opt for the non-JavaScript one class version anyways and optimize for simplicity.

For what it's worth, I have a site that I wrote in HTTP/CSS where I make use of blur in the top bar, and I will be switching over to this effect soon using your blog post as a guide. Thank you.