header.txt

#+begin_export html
<div class="header">
<link rel="stylesheet" href="hamb.css">
<link rel="stylesheet" href="tufte.css">
<img src="./images/heading6.png"  style="padding: 0px 0px 22px 0px" alt="3-d graph" class="center">

<p>

<nav role="navigation">
  <div id="menuToggle">
    <!--
    A fake / hidden checkbox is used as click reciever,
    so you can use the :checked selector on it.
    -->
    <input type="checkbox" />
    
    <!--
    Some spans to act as a hamburger.
    
    They are acting like a real hamburger,
    not that McDonalds stuff.
    -->
    <span></span>
    <span></span>
    <span></span>
    
    <!--
    Too bad the menu has to be inside of the button
    but hey, it's pure CSS magic.
    -->
    <ul id="menu">
      <a href="index.html" target="_blank"><li>Home</li></a>
      <a href="preface.html" target="_blank"><li>Preface</li></a>
      <a href="preliminaries.html" target="_blank"><li>Rabbit Holes</li></a>
      <a href="numbers.html" target="_blank"><li>Numbers</li></a>
    </ul>
  </div>
</nav>
</div>
</p>
#+end_export