/* 主要内容区域样式 */
main {
    background-color: #d8e5fa;
    padding: 40px 16%;
}

.course-container {
    background-color: white;
    border-radius: 12px;
    box-shadow: 0 5px 20px rgba(0,0,0,0.1);
    overflow: hidden;
}


/* 课程头部信息 */
.course-header-section {
    background: white;
    padding: 40px;
    margin-bottom: 40px;
    box-shadow: 0 15px 35px rgba(26, 115, 232, 0.25);
    display: flex;
    align-items: center;
    color: white;
    position: relative;
    overflow: hidden;
}

.course-header-section::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle, rgba(255,255,255,0.1) 0%, transparent 70%);
}

.course-image {
    width: 300px;
    height: 160px;
    border-radius: 8px;
    overflow: hidden;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 50px;
}

.course-info {
    flex: 1;
    padding: 0 30px;
}

.course-title {
    font-size: 28px;
    color: black;
    margin-bottom: 15px;
}


.course-description {
    color: #555;
    line-height: 1.8;
    margin-bottom: 20px;
}

.course-actions {
    display: flex;
    gap: 15px;
}

.btn {
    padding: 10px 20px;
    border-radius: 6px;
    border: none;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s;
}

.btn-primary {
    background: #1a73e8;
    color: white;
}

.btn-primary:hover {
    background: #0d62d9;
    transform: translateY(-2px);
}

.btn-outline {
    background: transparent;
    border: 1px solid #1a73e8;
    color: #1a73e8;
}

.btn-outline:hover {
    background: #f0f7ff;
}

/* 课程独立内容区域 */
.course-container-section{
    background: white;
    box-shadow: 0 10px 35px rgba(0, 0, 0, 0.08);
    overflow: hidden;
}

/* 选项卡区域 - 修复部分 */
.course-tabs {
    padding: 0 30px;
}

.tab-header {
    display: flex;
    border-bottom: 1px solid #eee;
}

.tab-item {
    padding: 15px 25px;
    cursor: pointer;
    font-weight: 500;
    color: #666;
    transition: all 0.3s;
    position: relative;
}

.tab-item:hover {
    color: #1a73e8;
}

.tab-item.active {
    color: #1a73e8;
}

.tab-item.active::after {
    content: '';
    position: absolute;
    bottom: -1px;
    left: 0;
    width: 100%;
    height: 3px;
    background: #1a73e8;
    border-radius: 3px 3px 0 0;
}

.tab-content {
    padding: 30px 0;
    min-height: 400px;
}

.tab-pane {
    display: none;
}

.tab-pane.active {
    display: block;
    animation: fadeIn 0.5s;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

/* 详情页内容 */
.detail-section {
    margin-bottom: 30px;
}

.section-title {
    font-size: 20px;
    color: black;
}

.detail-content {
    color: #555;
    line-height: 1.8;
}

.detail-content p {
    margin-bottom: 15px;
}

.detail-image {
    width: 100%;
    max-width: 800px;
    height: 1000px;
    background: linear-gradient(135deg, #ff9a9e 0%, #fad0c4 100%);
    border-radius: 8px;
    margin-top: 20px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #333;
    font-weight: bold;
}

/* 目录页内容 */
.directory-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}

.sort-controls {
    display: flex;
    gap: 10px;
}

.sort-btn {
    padding: 8px 15px;
    background: #f1f1f1;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    transition: all 0.3s;
}

.sort-btn:hover {
    background: #e0e0e0;
}

.sort-btn.active {
    background: #1a73e8;
    color: white;
}

/* 修改部分：黑色小方框+视频文字 */
.video-tag {
    display: flex;
    align-items: center;
    gap: 10px;
    background: #f5f5f5;
    padding: 5px 12px;
    border-radius: 4px;
}


.video-text {
    font-size: 14px;
    color: #333;
    font-weight: 500;
}

.chapter-list {
    list-style: none;
}

.chapter-item {
    padding: 20px;
    border-radius: 8px;
    margin-bottom: 15px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: all 0.3s;
    cursor: pointer;
}

.chapter-item:hover {
    background: #f0f7ff;
    border-color: #1a73e8;
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(26, 115, 232, 0.1);
}

.chapter-info {
    display: flex;
    align-items: center;
    gap: 15px;
}

.chapter-number {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    background: #e8f0fe;
    color: #1a73e8;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    flex-shrink: 0;
}

.chapter-title {
    font-weight: 500;
    color: #333;
}

.chapter-duration {
    color: #666;
    font-size: 14px;
}

.learn-btn {
    padding: 8px 20px;
    background: #1a73e8;
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    opacity: 0;
    transition: all 0.3s;
}

.chapter-item:hover .learn-btn {
    opacity: 1;
}


/* 评价内容 */
.review-summary {
    display: flex;
    align-items: center;
    gap: 20px;
    margin-bottom: 30px;
    padding: 20px;
    background: #f9f9f9;
    border-radius: 8px;
}

.rating-value {
    font-size: 48px;
    font-weight: bold;
    color: #1a237e;
}

.rating-stars {
    color: #ffc107;
    font-size: 24px;
    letter-spacing: 2px;
}

.rating-count {
    color: #666;
}

.review-list {
    list-style: none;
}

.review-item {
    padding: 20px;
    border-bottom: 1px solid #eee;
}

.review-header {
    display: flex;
    justify-content: space-between;
    margin-bottom: 10px;
}

.reviewer {
    font-weight: 500;
}

.review-date {
    color: #888;
}

.review-content {
    color: #555;
    line-height: 1.7;
}

/* 响应式设计 */
@media (max-width: 900px) {
    .course-header {
        flex-direction: column;
    }

    .course-image {
        width: 100%;
        margin-bottom: 20px;
    }

    .course-info {
        padding: 0;
    }

    .footer-container {
        flex-direction: column;
    }
}

@media (max-width: 600px) {
    .nav-container {
        flex-wrap: wrap;
    }

    .nav-links {
        order: 3;
        width: 100%;
        margin-top: 15px;
        justify-content: center;
    }

    .course-meta {
        flex-wrap: wrap;
    }

    .course-actions {
        flex-direction: column;
    }

    .tab-header {
        flex-wrap: wrap;
    }
}