You'd hope there would be at least an example that doesn't require JavaScript if this is a CSS thing. It could have made a good <noscript> block to remind you to enable to see the editor.
It just seems a very strange way of going about demoing a CSS library.
It's there, but you can't see it because the rule requires JavaScript to view the rule.
In this specific case, one should be able to view the default demo without JS because it's a CSS library/demo and not a JS one. You can (and should) progressively enhance it with JS.