:root {
    /* 主色调 - 橙色系 */
    --primary-color: #F47F38;
    --primary-light: #FF994D;
    --primary-dark: #E69800;
    
    /* 辅助色 - 红色系 */
    --accent-red: #C6393F;
    --accent-red-dark: #9D1419;
    
    /* 成功色 - 绿色系 */
    --success-color: #4CAF50;
    --success-dark: #1A5E20;
    
    /* 信息色 - 蓝色系 */
    --info-color: #26547C;
    --info-light: #007991;
    
    /* 特殊色 - 紫色系 */
    --special-color: #4A3758;
    --special-light: #8A7B98;
    
    /* 中性色 */
    --light-bg: #F8F9FA;
    --border-color: #E9ECEF;
    --text-primary: #2C3E50;
    --text-secondary: #6C757D;
    --text-muted: #95A5A6;
    
    /* 功能色 */
    --warning-color: #FFC107;
    --danger-color: #C6393F;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--light-bg);
    color: var(--text-primary);
    line-height: 1.6;
}

.sidebar {
    background-color: white;
    border-right: 1px solid var(--border-color);
    height: 100vh;
    position: sticky;
    top: 0;
    overflow-y: hidden; /* 改为hidden，防止双滚动条 */
    box-shadow: 2px 0 10px rgba(44, 62, 80, 0.1);
}

.sidebar-container {
    display: flex;
    flex-direction: column;
    height: 100%;
   /* overflow-y: visible;  只在容器上有滚动条 */
}

.sidebar-content {
    flex: 1 1 auto;
    overflow-y: auto; /* 移除内部滚动 */
    /* padding-bottom: 4.5rem; */
    -webkit-overflow-scrolling: touch;
}

.course-header {
    background: linear-gradient(135deg, 
        rgba(244, 127, 56, 0.08),
        rgba(255, 153, 77, 0.05)
    );
    color: var(--text-primary);
    padding: 1.2rem;
    border-radius: 0 0 12px 12px;
    box-shadow: 0 1px 3px rgba(44, 62, 80, 0.03);
    border-bottom: 1px solid rgba(244, 127, 56, 0.1);
}

.lesson-nav-item {
    padding: 12px 15px;
    border-bottom: 1px solid var(--border-color);
    cursor: pointer;
    transition: all 0.3s;
    border-radius: 8px;
    margin: 5px 0;
    background-color: white;
}

.lesson-nav-item:hover {
    background-color: rgba(244, 127, 56, 0.05);
    transform: translateX(5px);
    box-shadow: 0 4px 8px rgba(244, 127, 56, 0.1);
}

.lesson-nav-link {
    color: var(--text-primary);
    transition: all 0.3s;
    display: block;
}

.lesson-nav-link:hover {
    color: var(--primary-color);
    text-decoration: none;
}

.lesson-nav-item i {
    color: var(--primary-color);
    transition: all 0.3s;
}

.lesson-nav-item:hover i {
    color: var(--primary-light);
    transform: scale(1.1);
}

.lesson-title {
    font-weight: 500;
    transition: all 0.3s;
}

.lesson-nav-item:hover .lesson-title {
    font-weight: 600;
}

.lesson-meta {
    color: var(--text-secondary);
    opacity: 0.7;
    font-size: 0.8rem;
    transition: all 0.3s;
}

.lesson-nav-item:hover .lesson-meta {
    opacity: 0.9;
    color: var(--primary-color);
}

.lesson-nav-item.active {
    background: linear-gradient(to right, var(--primary-color), var(--primary-light));
    color: white;
    box-shadow: 0 4px 12px rgba(244, 127, 56, 0.3);
}

.lesson-nav-item.active .lesson-nav-link {
    color: white;
}

.lesson-nav-item.active i {
    color: white;
}

.lesson-nav-item.active .lesson-meta {
    color: rgba(255, 255, 255, 0.9);
    opacity: 0.9;
}

/* 移除课程列表的独立滚动条 */
#lesson-list-list {
    overflow-y: auto;
    padding-right: 8px;
}

/* 侧边栏容器滚动条样式 */
.sidebar-container::-webkit-scrollbar {
    width: 6px;
}

.sidebar-container::-webkit-scrollbar-track {
    background: var(--light-bg);
    border-radius: 3px;
}

.sidebar-container::-webkit-scrollbar-thumb {
    background: var(--primary-color);
    border-radius: 3px;
}

.sidebar-container::-webkit-scrollbar-thumb:hover {
    background: var(--primary-light);
}

.content-area {
    padding: 2rem;
    background-color: white;
    border-radius: 15px;
    box-shadow: 0 5px 15px rgba(44, 62, 80, 0.08);
    margin-bottom: 2rem;
    border: 1px solid var(--border-color);
}

.section-title {
    color: var(--text-primary);
    border-bottom: 3px solid var(--primary-color);
    padding-bottom: 0.5rem;
    margin-bottom: 1.5rem;
    display: inline-block;
}

.material-item {
    padding: 12px 15px;
    background-color: rgba(244, 127, 56, 0.05);
    border-radius: 8px;
    margin-bottom: 10px;
    display: flex;
    align-items: center;
    transition: all 0.3s;
    border-left: 4px solid var(--primary-color);
}

.material-item:hover {
    background-color: rgba(244, 127, 56, 0.1);
    transform: translateY(-3px);
}

.material-item i {
    margin-right: 10px;
    color: var(--primary-color);
}

.knowledge-point {
    display: inline-block;
    background: rgba(76, 175, 80, 0.1);
    color: var(--success-dark);
    padding: 8px 15px;
    border-radius: 20px;
    margin: 5px;
    font-size: 0.9rem;
    box-shadow: 0 2px 5px rgba(26, 94, 32, 0.1);
    border: 1px solid rgba(76, 175, 80, 0.3);
}

.sub-lesson {
    background: var(--light-bg);
    border-radius: 8px;
    padding: 15px;
    margin: 10px 0;
    border-left: 4px solid var(--info-color);
}

.sub-lesson-title {
    font-weight: bold;
    color: var(--info-color);
    margin-bottom: 8px;
}

.feature-card {
    border-left: 4px solid var(--primary-color);
    transition: transform 0.3s;
    border-radius: 10px;
    overflow: hidden;
    background: linear-gradient(to bottom right, white, var(--light-bg));
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 20px rgba(44, 62, 80, 0.1);
}

.stats-card {
    text-align: center;
    padding: 1.5rem;
    border-radius: 15px;
    box-shadow: 0 5px 15px rgba(44, 62, 80, 0.08);
    transition: transform 0.3s;
    background: linear-gradient(to bottom right, white, rgba(244, 127, 56, 0.05));
    border: 1px solid var(--border-color);
}

.stats-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 20px rgba(44, 62, 80, 0.15);
}

.stats-card h3 {
    color: var(--primary-color);
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
}

.objective-item {
    padding: 12px 15px;
    margin-bottom: 10px;
    border-radius: 8px;
    background: rgba(244, 127, 56, 0.05);
    border-left: 4px solid var(--primary-light);
    display: flex;
    align-items: center;
}

.objective-item i {
    color: var(--primary-color);
    margin-right: 10px;
}

.card {
    border-radius: 10px;
    border: 1px solid var(--border-color);
    overflow: hidden;
    transition: all 0.3s;
}

.card:hover {
    box-shadow: 0 8px 20px rgba(44, 62, 80, 0.1);
}

.btn-warm {
    background: linear-gradient(to right, var(--primary-color), var(--primary-light));
    color: white;
    border: none;
    border-radius: 25px;
    padding: 8px 20px;
    transition: all 0.3s;
}

.btn-warm:hover {
    background: linear-gradient(to right, var(--primary-light), var(--primary-color));
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(244, 127, 56, 0.3);
}

.warm-bg {
    background-color: rgba(244, 127, 56, 0.05);
}

.warm-accent {
    color: var(--primary-color);
}

.certificate-badge {
    background: linear-gradient(135deg, var(--warning-color), var(--primary-dark));
    color: white;
    padding: 10px 20px;
    border-radius: 25px;
    font-weight: bold;
    display: inline-block;
    margin: 10px 0;
}

.course-hero-banner {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--info-color) 100%);
    border: none;
    box-shadow: 0 8px 25px rgba(38, 84, 124, 0.2);
}

.bg-gradient-primary {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-light));
}

.course-hero-banner h1,
.course-hero-banner p {
    color: white;
    text-shadow: 0 1px 3px rgba(38, 84, 124, 0.5);
}

.course-hero-banner .badge {
    background-color: rgba(255, 255, 255, 0.9);
    color: var(--info-color);
    font-weight: 600;
    box-shadow: 0 2px 8px rgba(38, 84, 124, 0.2);
}

/* 合并的用户状态区域 */
.user-status-area {
    flex-shrink: 0;
    background-color: rgba(248, 249, 250, 0.9);
    border-top: 1px solid var(--border-color);
    margin-top: auto;
    padding: 0.75rem !important;
    position: sticky; 
    bottom: 0;
    z-index: 5; 
}

.user-status-area .btn {
    padding: 0.25rem 0.5rem;
    font-size: 0.75rem;
}

.user-status-area .user-avatar img,
.user-status-area .user-avatar i {
    width: 32px !important;
    height: 32px !important;
}

.user-status-area .user-info .fw-bold {
    font-size: 0.9rem;
}

.requirements-content, .grading-criteria-content, .feedback-content {
    line-height: 1.6;
}

.requirements-content ul, .grading-criteria-content ul, .feedback-content ul {
    padding-left: 1.5rem;
}

.requirements-content li, .grading-criteria-content li, .feedback-content li {
    margin-bottom: 0.5rem;
}

.submission-history-item {
    border-left: 4px solid var(--info-color);
    padding-left: 15px;
    margin-bottom: 20px;
}

.submission-history-item.latest {
    border-left-color: var(--success-color);
    background-color: rgba(76, 175, 80, 0.05);
}

.submission-history-item.old {
    border-left-color: var(--text-muted);
    background-color: var(--light-bg);
}

.submission-content {
    max-height: 200px;
    overflow-y: auto;
    border: 1px solid var(--border-color);
    border-radius: 4px;
    padding: 10px;
    background-color: var(--light-bg);
}

.attachment-badge {
    cursor: pointer;
}

.section-container {
    background: #fff;
    border-radius: 12px;
    padding: 2rem;
    box-shadow: 0 2px 10px rgba(0,0,0,0.08);
    margin-bottom: 2.5rem;
    position: relative;
}

/* 为课程材料和阅读材料容器添加额外间距 */
.section-container.mb-5 {
    margin-bottom: 3rem !important;
}

/* 确保最后一个容器不会有过大的底部间距 */
.content-area > .section-container:last-child {
    margin-bottom: 1.5rem;
}

.material-card, .reading-card {
    transition: all 0.3s ease;
    border-radius: 12px;
    overflow: hidden;
}

.material-card:hover, .reading-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 25px rgba(0,0,0,0.15) !important;
}

.material-card .card-body, .reading-card .card-body {
    padding: 1.5rem;
}

.material-card .card-footer, .reading-card .card-footer {
    padding: 1rem 1.5rem;
    background: var(--light-bg);
}

.material-icon, .reading-icon {
    flex-shrink: 0;
}

.material-meta, .reading-meta {
    margin-top: 0.25rem;
}

.file-size {
    color: var(--text-muted);
    font-size: 0.8rem;
}

.duration-info {
    background: rgba(0, 121, 145, 0.1);
    padding: 0.5rem;
    border-radius: 6px;
    border-left: 3px solid var(--info-light);
}

.url-preview {
    background: rgba(76, 175, 80, 0.1);
    padding: 0.5rem;
    border-radius: 6px;
    border-left: 3px solid var(--success-color);
}

.empty-state {
    background: var(--light-bg);
    border-radius: 12px;
    border: 2px dashed var(--border-color);
}

.btn-group .btn {
    border-radius: 6px;
}

/* 徽章颜色调整 */
.badge.bg-primary { background-color: var(--primary-color) !important; }
.badge.bg-success { background-color: var(--success-color) !important; }
.badge.bg-info { background-color: var(--info-color) !important; }
.badge.bg-warning { background-color: var(--warning-color) !important; color: var(--text-primary); }
.badge.bg-danger { background-color: var(--danger-color) !important; }
.badge.bg-secondary { background-color: var(--text-secondary) !important; }

/* 按钮颜色调整 */
.btn-primary { background-color: var(--primary-color); border-color: var(--primary-color); }
.btn-primary:hover { background-color: var(--primary-light); border-color: var(--primary-light); }
.btn-success { background-color: var(--success-color); border-color: var(--success-color); }
.btn-info { background-color: var(--info-color); border-color: var(--info-color); }
.btn-warning { background-color: var(--warning-color); border-color: var(--warning-color); color: var(--text-primary); }
.btn-danger { background-color: var(--danger-color); border-color: var(--danger-color); }

/* 响应式调整 */
@media (max-width: 768px) {
    .sidebar {
        height: auto;
        position: static;
        overflow-y: visible;
    }
    
    .sidebar-container {
        height: auto;
        overflow-y: visible;
    }
    
    .section-container {
        padding: 1.5rem;
        margin: 0 -1rem;
        border-radius: 0;
    }
    
    .material-card .card-body, .reading-card .card-body {
        padding: 1rem;
    }
    
    .content-area {
        padding: 1rem;
    }
    
    .user-status-area .d-flex.gap-1 {
        flex-direction: column;
    }
    
    .user-status-area .btn {
        margin-bottom: 0.25rem;
    }
}