.main-content {
    max-width: 100% !important;
    padding: 0 !important;
    gap: 0 !important;
}

.main-content {
    display: flex;
    flex-direction: row;
    
    position: fixed;
    top: 5rem;
    left: 0;
    right: 0;
    bottom: 0;
}

.gutter {
    background-color: #eee;
    background-repeat: no-repeat;
    background-position: 50%;
}

.gutter.gutter-horizontal {
    cursor: col-resize;
}



.col2 {
    background-color: #fff;
    padding: .5rem 1.25rem 1.25rem 1.25rem;
    font-size: .9375rem;
    display: flex;
    flex-direction: column;
    overflow-y: auto;
}

.col2 h1 {
    font-size: 1.2rem;
    margin-bottom: 1rem;
}

.col2 h1 a {
    color: #0a8be1;
}
.col2 h1 a:hover {
    color: #0a8be1;
}

.col2 .course-info {
    
    padding:.5rem .5rem 1.5rem .5rem;
    color: #333;
    display: flex;
    flex-direction: column;
    gap: 1rem;
    border-bottom:1px solid #eee;
}

.col2 .course-info h2 {
    font-size: 1.2rem;
    font-weight: bold;

    display: flex;
    flex-direction: column;
}

.col2 .course-info h2 a {
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}


.col2 .catalog-label {
    padding:.5rem;
    color: #333;
    margin-top: 1rem;
    display: flex;
    flex-direction: row;
    align-items: baseline;
    gap: .5rem;

}


.col2 .catalog-label a {
    padding: 0;
    color: #0a8be1;
    font-size: .75rem;
}
.col2 .catalog-label a:hover {
    background-color: transparent;
}

.col2 ul {
    display: flex;
    flex-direction: column;
    gap: .15rem;
}

.col2 ul li {
    display: flex;
    flex-direction: column;
}
.col2 > ul > li > a {
    font-weight: bold;
}

.col2 ul li ul {
    padding-left: 2rem;
}

.col2 a {
    color: #333;
    padding: .45rem .75rem;
    border-radius: 5px;
}
.col2 a:hover {
    color: #000;
    background-color: #f5f5f5;
}

.col2 a.active {
    color: #000;
    background-color: #f0f0f0;
}

/** col3 **/
.col3 {
    display: flex;
    flex-direction: column;
    padding:2rem;
    background-color: #fff;
    overflow-y: auto;
}

.col3 .col3-wrapper {
    display: flex;
    flex-direction: column;
    width: 100%;
    max-width: 1100px;
    margin: 0 auto;
    gap: 1rem;
}





/* 美化滚动条样式 #col2 */
#col2::-webkit-scrollbar {
    width: 2px;
}

#col2::-webkit-scrollbar-track {
    background: #f5f5f5;
}

#col2::-webkit-scrollbar-thumb {
    background: #e0e0e0;
    border-radius: 2px;
}

#col2::-webkit-scrollbar-thumb:hover {
    background: #d0d0d0;
}