title: Why is the background of the whole page colored when html height is 0?
body: <p>I understand the width &amp; height of the visual viewport, as defined by this <a href="https://www.quirksmode.org/mobile/viewports.html" rel="nofollow noreferrer">article</a>, at least on a desktop, is the dimensions of the visible rectangle a user can see when they scroll to the top left of the page.</p>
  <p>Why is the background red for, what looks like, the visual viewport when the <code>html</code>'s height is <code>0</code>?</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>html {
      background-color: red;
  }
  
  body {
      line-height: 20px;
      margin: 0px;
  } </code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;html&gt;
  &lt;body&gt;
  
  &lt;/body&gt;
  &lt;/html&gt;</code></pre>
  </div>
  </div>
  </p>