.videos {
    display: none;
    position: fixed;
    top: 50%;
    left: 50%;
    width: 802px;
    transform: translate(-50%,-50%);
    z-index: 100;
}

.mask {
    display: none;
    width: 100%;
    height: 100%;
    position: fixed;
    z-index: 99;
    background: rgba(0, 0, 0, .75);
    left: 0;
    top: 0;
}