anchor.diff:      <div class="card">
         <div class="card-content">
           <div class="card-title">Word complexity</div>
  -        <div id="graph-word-complexity"></div>
  +        <p>
  +          Number of unique...
  +        </p>
  +        <%=
  +          pie_chart({
  +            'simple words'  => analysis.simple_words_count,
  +            'complex words' => analysis.complex_words_count
  +          })
  +        %>
         </div>
         <div class="card-action">
           <a class="activator blue-text text-darken-4">
  
positive.code:         </a>
        </div>
        <div class="card-reveal">
          explanation
        </div>
      </div>
    </div>
  
negative.code:     <div class="card">
        <div class="card-content">
          <div class="card-title">N-syllable words</div>
          <%= column_chart analysis.n_syllable_words.map { |k, v| [k, v] } %>
        </div>
      </div>
    </div>
  