      <a class="is-active" href="elements.html">
                  Elements
                </a>
              </li>
              <li>
                <a href="form.html">
                  Form
                </a>
              </li>
            </ul>
          </nav>
          <br/>
          <button id="themeBtn" class="button" onclick="switchTheme();"></button>
        </div>
        <div class="column">
          <h1 class="title">Elements</h1>
          <h3 class="subtitle">Box</h3>
          <div c