////////遮罩////////
.mask {
    position: absolute;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,.4);
}

// 视频遮罩
.mask-video {
    background-image: url(data:image/png;base64,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);
    background-repeat: no-repeat;
    background-position: center center;
    background-size: 60px 60px;
    cursor: pointer;
}