.nav .a:before {
    display: block;
    position: absolute;
    bottom: 0;
    right: 0px;
    height: 4px;
    width: 0px;
    z-index: 0;
    content: '';
    background: #8f000b;
    transition: all 0.4s cubic-bezier(0.42, 0, 0.58, 1);}