.course-header {
    background: #fff;
    z-index: 2;
    box-shadow: 0 4px 8px 0 rgba(28, 31, 33, .1);
    height: 60px;
    width: 100%;
}

.course-header .nv-goback a {
    width: 70px;
    height: 60px;
    text-align: center;
    display: block;
}

.course-header .nv-goback a i {
    font-size: 24px;
    color: #9199a1;
    line-height: 60px;
    transition: .3s all linear;
}

.course-header .nv-menu {
    padding-right: 24px;
    position: relative;
    font-size: 16px;
    color: #1c1f21;
    font-weight: 700;
    line-height: 60px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    width: 80%;
}

.course-header .nv-follow i {
    font-size: 20px;
    color: #b2b8bd;
    margin-right: 4px;
    float: left;
    line-height: 60px;
    transition: .3s all linear;
}

.course-header .nv-follow span {
    font-size: 12px;
    color: #9199a1;
    float: left;
    line-height: 60px;
    transition: .3s all linear;
}

.course-main {}

.course-main .video-con {
    position: relative;
    background-color: #000;
    overflow: hidden;
}

.course-main .course-layout {
    display: flex;
    display: -webkit-flex;
    position: relative;
    zindex: 1;
}

.course-main .section-list {
    position: absolute;
    left: -400px;
    top: 0;
    bottom: 0;
    width: 400px;
    background: #26292c;
    box-shadow: 0 8px 16px 0 #1c1f21;
    z-index: 9999;
    transition: .3s all linear;
    opacity: 0;
    padding: 8px 0;
    box-sizing: border-box;
}

.course-main .section-list.active {
    left: 60px;
    opacity: 1;
}

.course-main .section-list ul {
    padding: 0 24px;
    margin-top: 30px;
}

.course-main .section-list li {
    margin: 8px 0;
    position: relative;
    padding-left: 30px;
}

.course-main .section-list li a {
    font-size: 14px;
    color: #fff;
    line-height: 30px;
}

.course-main .section-list li a.current {
    color: red;
}

.course-main .section-list li em {
    position: absolute;
    left: 8px;
    top: 6px;
    font-size: 16px;
    line-height: 18px;
}


.course-main .section-list .chapter-list {
    position: absolute;
    overflow: scroll;
    overflow-x: hidden;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

.course-main .course-sidebar-layout {
    background: #1c1f21;
    width: 60px;
    display: flex;
    display: -webkit-flex;
    align-items: center;
    z-index: 10000;
}

.course-main .course-sidebar-layout dl {
    flex: 1;
    width: 100%;
}

.course-main .course-sidebar-layout dd {
    display: flex;
    display: -webkit-flex;
    height: 72px;
    flex-direction: column;
    text-align: center;
    justify-content: center;
    cursor: pointer;
}

.course-main .course-sidebar-layout i {
    font-size: 24px;
    color: rgba(255, 255, 255, .6);
    line-height: 24px;
}

.course-main .course-sidebar-layout span {
    font-size: 12px;
    color: rgba(255, 255, 255, .4);
    line-height: 18px;
}

.course-main .course-center-layout {
    box-sizing: border-box;
    width: 100%;
    height: 701px;
    position: relative;
    flex: 1;
    background: #1c1f21;
    overflow:auto;
}

.fl {
    float: left;
    display: inline;
}

@media screen and (max-width: 991px) {

    .course-header .nv-goback a {
        width: 40px;
        height: 30px;
    }

    .course-main .video-con{
        background: none;
    }

    .course-main .course-layout {
        display: block;
    }

    .course-main .section-list .chapter-list {
        position: unset;
    }

    .course-header .nv-goback a i {
        font-size: 15px;
    }

    .course-main .course-sidebar-layout {
        display: none;
    }

    .course-main .section-list {
        opacity: 1;
        background: #f7f7f7;
        box-shadow: none;
        width: 100%;
        padding: 0;
        height: calc(75vh - 150px);
        position:unset;
    }

    .course-main .section-list li a {
        color: #333;
    }

    .course-header .nv-menu {
        font-size: 13px;
    }

    .course-header .nv-follow span {
        font-size: 11px
    }

    .course-main .course-center-layout {
        height: 25vh;
        overflow:auto;
    }

    .prism-player .prism-big-play-btn {
        width: 45px!important;
        height: 45px!important;
        bottom: 25px!important;
    }

    .prism-player .prism-big-play-btn .outter {
        width: 45px!important;
        height: 45px!important;
    }
}