    <input id="mark-required-input" required placeholder="A required label">
                  <label for="mark-required-input">My required label</label>
                </div>
              </div>
            </form>
            <hr>
            <h2 id="checkbox_radio">Checkbox and Radio</h2>
            <p>Do you know somebody who uses JS to build nice <code>checkbox</code>es and <code>radio</code>s? <br>
              You don't need any extra markup or class, just use them!
            </p>
            <