.foooter a {
    color: #fff;
    font-size: 3rem;
    cursor: pointer;
    position: relative;
}

.foooter a::after {
    content: '';
    position: absolute;
    height: 2px;
    left: 0;
    bottom: 0;
    width: 0;
    background: #558ffb79;
    transition: width .2s;
}

.foooter a:hover::after {
    width: 100%;
}