<!DOCTYPE html>
<!--
 | Opacity should compound on itself when it is nested within blocks that also
 | have opacity set on them.  The text of the inner-most div will share its
 | low opacity.
 |   https://www.w3.org/TR/css3-color/#transparency
 -->
<html>
<head>
  <style>
    #root {
      width: 400px;
      height: 400px;
      background-color: rgb(255, 0, 0);
      opacity: 1;
      font-size: 16px;
      font-weight: bold;
    }

    div {
      font-size: 2em;
      width: 2.5em;
      height: 2.5em;
      background-color: rgb(0, 0, 255);
      opacity: 0.5;
    }
  </style>
</head>
<body>
  <div id="root">
    <div>
      <div>
        <div>
          Hello?
        </div>
      </div>
    </div>
  </div>
</body>
</html>