id="spec_core">Core Symbols</h4>
      <div class="indent">
        <p>The core <a href="#allowed_chars">symbols</a> of an alphabet can either 
        be defined on their own or two per line with a '~' between them to show 
        them as complements.</p>
        <p>For example you can define the symbol 'A' and the symbol 'T' to be
        complements of each other as follows:</p>
        <div class="example">
          A ~ T
        </div>
        <p>However if 'A' and 'T' do not have complements then yo