.loading {
    position: fixed;
    z-index: 99999;
    top: 0px;
    left: 0px;
    width: 100%;
    height: 100%;
    background-color: #FFF;
    opacity: 0.6;
}
    .loading > button {
        position: absolute;
        top: 40%;
        left: 50%;
        transform: translateX(-50%);
        -webkit-transform: translateX(-50%);
    }