Here’s a great tutorial from Eleventy guru Stephanie Eckles in which she explains how to create a page that displays multiple code demos, similar to SmolCSS.dev.
It’s interesting that Stephanie uses 11ty shortcodes over other 11ty templating options and that she sometimes declares a variable (via Nunjucks’s set) at the top of the page then intentionally reuses it unchanged in repeated shortcode instances… the example being times where you want to illustrate the same HTML code (variable) being styled differently in progressive demos.
I also like the Open in CodePen feature and section on scoped styling.