header{
    background: url('https://static.igem.wiki/teams/4223/wiki/b/5.jpg') no-repeat;
    background-size: cover;
    height: 100vh;
    width: 100%;
    box-shadow: 0px 50px 40px #00bbfb63;
    position: relative;
    overflow: hidden;
}

.headback{
    height: 100vh;
    width: 100%;
    position: relative;
    background-color: rgba(255,255,255,0.2);
}

.header-title{
    position:absolute;
    display: inline-block;
    font-size: 15em;
    font-family: 'w5';
    top: 50%;
    left: 50%;
    text-align: center;
    transform: translate(-50%, -50%);
    color: #460484;
    text-shadow: 12px -3px 4px #d3ffff, 9px -3px 25px blue, 0 0 5px #cfffff;;
}

.header-back{
    height: 100%;
    width: 100%;
    background-color: rgba(255,255,255,0.4);
}


.video-background {
    position: absolute;
    left: 50%;
    top: 50%;
    /*保证视频内容始终居中*/
    transform: translate(-50%, -50%);
    width:75%;
    height: 90vh;
    object-fit:cover;
    min-height: 800px;
    border-radius: 52%;
}