css/css-scoping/host-descendant-001.html

<!doctype html>
<link rel="author" title="Emilio Cobos Álvarez" href="mailto:emilio@crisal.io">
<link rel="help" href="https://drafts.csswg.org/css-scoping/#host-selector">
<link rel="match" href="reference/green-box.html">
<p>Test passes if you see a single 100px by 100px green box below.</p>
<div id="host"><div></div></div>
<script>
  let root = host.attachShadow({ mode: "open" });
  root.innerHTML = `
    <style>
      :host ::slotted(div) { width: 100px; height: 100px; background: green; }
      * :host ::slotted(div) { background: red; }
    </style>
    <slot></slot>
  `;
</script>