.loading {
    position: fixed;
    z-index: 9999;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: #444;
    opacity: 0.5;
    display: none;
}

    .loading .mask {
        position: absolute;
        width: 100%;
        height: 100%;
        background-color: #444;
        opacity: 0.5;
    }