css/mediaqueries/relative-units-003.html

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>CSS Test: Font-relative length units (ex) in width media queries</title>
  <link rel="author" title="Chris Rebert" href="http://chrisrebert.com">
  <link rel="help" href="https://www.w3.org/TR/css3-mediaqueries/#units">
  <link rel="help" href="https://www.w3.org/TR/mediaqueries-4/#units">
  <link rel="match" href="reference/ref-green-body.xht">
  <meta name="assert" content="Font-relative length units (such as 'ex') in media queries should be calculated based on the initial value of 'font-size', not based on author style declarations, such as: html { font-size: 200%; }">
  <style>
:root {
  font-size: 100000px;/* ~87ft */
}
body {
  background: red;
}
p {
  font-size: 24px;
}
  </style>
</head>
<body>
  <p>This should have a green background.</p>
  <script>
    document.body.offsetTop;
  </script>
  <style>
    @media (min-width: 1ex) {
      body {
        background: green;
      }
    }
  </style>
</body>
</html>