Edit in JSFiddle

<div class="page">
  <div class="background">

    <iframe allowtransparence="true" width="640" height="360" frameborder="0" src="https://www.shadertoy.com/embed/XlSBzd?gui=false&t=10&paused=false&muted=false" frameborder="0" style="overflow:hidden;height:100%;width:100%" height="100%" width="100%"></iframe>
  </div>
  <content>
    <h1>HTML Ipsum Presents</h1>

    <p><strong>Pellentesque habitant morbi tristique</strong> senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. Donec eu libero sit amet quam egestas semper. <em>Aenean ultricies mi vitae est.</em>      Mauris placerat eleifend leo. Quisque sit amet est et sapien ullamcorper pharetra. Vestibulum erat wisi, condimentum sed, <code>commodo vitae</code>, ornare sit amet, wisi. Aenean fermentum, elit eget tincidunt condimentum, eros ipsum rutrum orci,
      sagittis tempus lacus enim ac dui. <a href="#">Donec non enim</a> in turpis pulvinar facilisis. Ut felis.</p>

    <h2>Header Level 2</h2>

    <ol>
      <li>Lorem ipsum dolor sit amet, consectetuer adipiscing elit.</li>
      <li>Aliquam tincidunt mauris eu risus.</li>
    </ol>

    <blockquote>
      <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vivamus magna. Cras in mi at felis aliquet congue. Ut a est eget ligula molestie gravida. Curabitur massa. Donec eleifend, libero at sagittis mollis, tellus est malesuada tellus, at luctus
        turpis elit sit amet quam. Vivamus pretium ornare est.</p>
    </blockquote>

    <h3>Header Level 3</h3>

    <ul>
      <li>Lorem ipsum dolor sit amet, consectetuer adipiscing elit.</li>
      <li>Aliquam tincidunt mauris eu risus.</li>
    </ul>

    <pre><code>
#header h1 a {
  display: block;
  width: 300px;
  height: 80px;
}
</code></pre>

  </content>
</div>

* {
  color: #fff;
  text-shadow: 1px 1px 2px #000;
}

.background {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: -1;
  pointer-events: none;
}

iframe {
  position: relative;
  width: 100%;
}

content {}