body{
    margin: 0;
}
.bg{
    width:100vw;
    height:100vh;
    filter: opacity(0.7);
    position: fixed;
    top:0;
    z-index: -1;
    background:url(/img/leaves.webp);
}
.clear{
    clear: both;
}
h1{
    text-align: center;
    font-size: 40px;
    color: #222;
    text-shadow:2px 2px 6px #8888;
    margin-bottom: 8px;
}
.main-box{
    width: 1200px;
    margin:0 auto;
    /* background-color: #ddd; */
    margin-bottom: 16px;
}
.main-box>.top{
    display: flex;
}
.box1>.left{
    display: block;
    float: left;
    width:460px;
    background-color: #eee;
    border-radius: 5px;
    box-shadow: 3px 2px 10px #aaa;
}
.box1>.right{
    float: right;
    width: 730px;
    height: 300px;
}
.box1>.right>div{
    width:233px;
    height: 145px;
    background-color: #aff;
    float: left;
    margin-bottom: 10px;
    margin-left: 10px;
    border-radius: 5px;
    box-shadow: 3px 2px 8px #8886;
    overflow: hidden;
    line-height: 145px;
    font-size: 24px;
    text-align: center;
    color: #222;
    text-shadow:2px 2px 5px #8886;
    cursor: pointer;
}
.window{
    width: 90vw;
    height: 90vh;
    background-color: #eeeeeeee;
    backdrop-filter: blur(10px);
    position: fixed;
    top:5vh;
    left: 5vw;
    border-radius: 10px;
}
/* 弹出窗口 */
.before_window{
    width: 100vw;
    height: 100vh;
    position: fixed;
    top:0;left: 0;
    background-color: #8888;
}
.window>.close_window{
    width: 50px;
    height: 50px;
    font-size: 50px;
    line-height: 50px;
    position: absolute;
    top: 0;
    right: 0;
    cursor: pointer;
}
.window>h3{
    width: 100%;
    position: absolute;
    top:38vh;
    font-size:28px;
    text-align: center;
    font-weight: 400;
}
.window>h4{
    width: 100%;
    position: absolute;
    top:0;
    font-size:28px;
    text-align: center;
    font-weight: 400;
    margin: 16px;
}
.window>iframe{
    width: calc(100% - 64px);
    height: calc(100% - 82px);
    position: fixed;
    left: 32px;
    bottom: 32px;
}
.a_video{
    width:380px;
    float:left;
    margin-right: 30px;
}
.a_video:nth-child(3n+1){
    margin-right: 0;
}
.a_video>.cover{
    display: block;
    width: 380px;
    height: 210px;
    background-color: #ddd;
    
    background-size: cover;
    background-position: 50% 50%;
    border-radius: 5px;
}
.a_video>h4{
    text-align: center;
    font-weight: 400;
    font-size: 20px;
    margin:12px 0;
}
.box3>a{
    display: block;
    width:400px;
    height:260px;
    font-size: 32px;
    font-style: italic;
    font-weight: 700;
    text-align: center;
    line-height: 260px;
    background-color: #eee;
    background-image: url(/img/flappybird.png);
    background-size: cover;
    background-position: 50% 50%;
    text-decoration: none;
    color: #fff;
    border-radius: 5px;
    text-shadow:2px 2px 8px #8886;
    box-shadow: 3px 2px 8px #8884;
}
.box4>p{
    font-size: 24px;
    line-height: 40px;
    margin: 8px 0;
    text-indent: 2em;
}