I was absolutely floored by this tiny design touch on Making Software, a new book being written by Dan Hollick. The content is already interesting and warrants a full read, but, look!

It colors the line blue and highlights it with a squiggly blue underline. Just delightful! It felt like I was underlining it with a blue pen myself. The website was built in Next.JS and I really wanted to understand how it was recreated. So I asked Claude Code to look at the site and see how it was done using the Playwright MCP. After a few minutes, it recreated it in a demo file.

Here is the Codepen to try it yourself:

See the Pen Blue Highlight Wavy Effect by Ashraf Ali (@nerveband) on CodePen.

The font on the diagrams are set in Departure Mono, a free, open source font with a type specimen that has playful feel.