In the workshop demo, defer let a script written in the head safely use document.body. The seed-library page also links script.js in the head, but the starter tag has no defer, and the script has no initialization. The waiting badge should become Seed library ready once HTML parsing finishes.
For comparison, a museum guide could use this different page-ready attribute:
<script src="script.js" defer></script>
document.body.dataset.guide = "open";
The museum CSS could watch [data-guide="open"]. Here the existing CSS watches [data-ready="yes"] instead. Add the defer attribute in index.html, then set document.body.dataset.ready to "yes" in script.js. Try Run to see the badge, and Submit to check both the loading setup and the resulting DOM state.
script.js tag in the document head a defer attribute so it waits until the HTML has been parsed.document.body.dataset.ready to "yes" in script.js to reveal the seed-library ready badge.