JSFiddle - React, Tailwind, and code Playground

by SchmalzyB

HTML

<ul class="nav">
  <li class="active"> <a href="/">Home</a></li>
  <li> <a href="/about/">About</a></li>
  <li> <a href="/archive/">Archive</a></li>
  <li> <a href="/contact/">Contact</a></li>
</ul>

CSS

.nav {
    list-style: none;
    margin: 1rem 0 0;
    padding: 0;
}
@media (min-width: 20rem) {
    .nav {
        margin: 0;
        padding: 1.75rem 0;
    }
}
.nav > li {
    position: relative;
    display: inline-block;
}
.nav > li + li {
    margin-left: 0.5rem;
}
.nav > li > a {
    color: #16a085;
    font-weight: 300;
    text-rendering: optimizeLegibility;
}
.nav > li > a:hover {
    text-decoration: none;
}
@media (min-width: 20rem) {
    .nav > li.active:after {
        content:"";
        position: absolute;
        width: 0px;
        top: 100%;
        height: 0px;
        border-top: 8px solid #16a085;
        border-right: 8px solid transparent;
        border-bottom: 8px solid transparent;
        border-left: 8px solid transparent;
        left: 50%;
        margin-left: -8px;
    }
}