                 <li class="nav-item">
                                <a href="#opacity" class="nav-link " data-smooth-scroll>Opacity</a>
                            </li>
                            <li class="nav-item">
                                <a href="#z-index" class="nav-link " data-smooth-scroll>Z-index</a>
                            </li>
                            <li class="nav-item">
                                <a href="#overflow" class="nav-link " data-smooth-scroll>Overflow</a>
   