*
{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: #000;
}
ul {
    position: relative;
    display: flex;
}
ul li {
    position: relative;
    list-style: none;
    margin: 0 20px;
    cursor: pointer;
}
ul li a {
    text-decoration: none;
}
ul li a .fa {
    font-size: 6em;
    color:#222;
}
ul li::before {
    font-family:fontAwesome;
    position: absolute;
    top: 0;
    left: 0;
    font-size: 6em;
    height: 0;
    overflow: hidden;
    transition: 0.5s ease-in-out;
}
ul li:nth-child(1)::before {
    content: '\f16a';
    color: #f50c0c ;
    border-bottom:4px solid #f50c0c;
}
ul li:hover::before {
    height:100%;
}