.main-box{width:800px;height:600px;margin:10px auto;border:1px solid #c1c1c1}.student{background-color:#f4f5f8;min-height:100vh;padding-top:3%}.student .max-width{max-width:80%;margin:0 auto}.student .student-box{width:100%;display:-webkit-box;display:-ms-flexbox;display:flex;height:80vh}.student .student-box .video-div{-webkit-box-flex:1;-ms-flex:1;flex:1;height:80vh;background-color:#000;position:relative}.student .student-box .video-div video{height:100%;width:100%}.student .student-box .on{width:206px}