#ref {
    margin: 5px auto;
    display: inline-block;
    background: url("https://innovacube.com/assets/img/logo-white.svg") no-repeat;
    height: 18px;
    overflow: hidden;
    text-indent: 9999px;
    width: 105px;
    transition: .2s opacity
}

    #ref:hover {
        opacity: .8
    }