/* ============================================
   原网站内容样式覆盖
   保留原 class 名,只换皮肤(深色品牌主题)
   ⚠️ 此文件不改动任何 HTML 结构,仅样式重绘
   ============================================ */

/* ── 原 catalog-container / chapter-container 适配 ── */
.catalog-container,
.chapter-container {
    max-width: 880px;
    margin: 0 auto;
    padding: var(--space-xl) var(--space-lg) var(--space-2xl);
    color: var(--color-text);
}

/* ── 原 catalog-hero 重设计(深色品牌渐变) ── */
.catalog-hero {
    text-align: center;
    padding: var(--space-2xl) var(--space-xl) var(--space-xl);
    background: var(--gradient-hero);
    border-radius: var(--radius-xl);
    margin-bottom: var(--space-lg);
    position: relative;
    overflow: hidden;
    border: 1px solid var(--color-border);
}
.catalog-hero::before {
    content: '';
    position: absolute;
    top: -50%; right: -15%;
    width: 280px; height: 280px;
    background: radial-gradient(circle, rgba(6, 182, 212, 0.2) 0%, transparent 70%);
    border-radius: 50%;
}
.catalog-hero::after {
    content: '';
    position: absolute;
    bottom: -40%; left: -8%;
    width: 200px; height: 200px;
    background: radial-gradient(circle, rgba(30, 58, 138, 0.3) 0%, transparent 70%);
    border-radius: 50%;
}
.catalog-hero h1 {
    font-size: 28px;
    font-weight: 700;
    color: #fff;
    letter-spacing: 1px;
    margin-bottom: var(--space-sm);
    position: relative;
    z-index: 1;
}
.catalog-hero .subtitle {
    color: rgba(255, 255, 255, 0.85);
    font-size: 16px;
    font-weight: 500;
    letter-spacing: 2px;
    position: relative;
    z-index: 1;
}

/* ── 原 stats-bar ── */
.stats-bar {
    display: flex;
    justify-content: center;
    gap: var(--space-lg);
    flex-wrap: wrap;
    padding: var(--space-md) var(--space-lg);
    background: var(--color-bg-elevated);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    margin-bottom: var(--space-md);
}
.stats-item { text-align: center; }
.stats-number {
    font-size: 22px;
    font-weight: 700;
    color: var(--color-accent);
    line-height: 1.2;
}
.stats-label {
    font-size: 12px;
    color: var(--color-text-muted);
    letter-spacing: 0.5px;
}

/* ── 原 course-info ── */
.course-info {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 0;
    background: var(--color-bg-elevated);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    overflow: hidden;
    margin-bottom: var(--space-md);
}
.course-info-item {
    padding: var(--space-md);
    text-align: center;
    border-right: 1px solid var(--color-border);
}
.course-info-item:last-child { border-right: none; }
.course-info-icon { font-size: 22px; margin-bottom: var(--space-xs); }
.course-info-label {
    font-size: 12px;
    font-weight: 700;
    color: var(--color-accent);
    letter-spacing: 1.5px;
    margin-bottom: var(--space-xs);
}
.course-info-value {
    font-size: 13px;
    color: var(--color-text-secondary);
    line-height: 1.4;
}

/* ── 原 catalog-grid / catalog-card 重设计 ── */
.catalog-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--space-md);
}
.catalog-card-link {
    text-decoration: none;
    color: inherit;
    display: block;
}
.catalog-card-link:visited { color: inherit; }
.catalog-card {
    background: var(--color-bg-elevated);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--space-md);
    transition: all var(--transition-base);
    display: flex;
    flex-direction: column;
    height: 100%;
}
.catalog-card:hover {
    border-color: var(--color-accent);
    transform: translateY(-3px);
    box-shadow: var(--shadow-lg), 0 0 0 1px rgba(6, 182, 212, 0.2);
}
.card-number {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 30px;
    height: 30px;
    border-radius: var(--radius-sm);
    background: rgba(6, 182, 212, 0.15);
    color: var(--color-accent);
    font-size: 12px;
    font-weight: 700;
    margin-bottom: var(--space-sm);
    border: 1px solid rgba(6, 182, 212, 0.3);
}
.card-title {
    font-size: 14px;
    font-weight: 700;
    color: var(--color-text);
    margin-bottom: var(--space-sm);
    line-height: 1.4;
    min-height: 40px;
}
.card-points {
    list-style: none;
    padding: 0;
    margin: 0 0 var(--space-sm) 0;
    flex-grow: 1;
}
.card-points li {
    font-size: 12px;
    color: var(--color-text-secondary);
    line-height: 1.5;
    padding: 2px 0 2px 14px;
    position: relative;
}
.card-points li::before {
    content: '▸';
    position: absolute;
    left: 0;
    color: var(--color-accent);
    font-size: 12px;
    font-weight: 700;
}
.card-action {
    display: inline-block;
    font-size: 12px;
    font-weight: 600;
    color: #fff;
    background: var(--gradient-brand);
    padding: 6px 16px;
    border-radius: var(--radius-sm);
    margin-top: var(--space-sm);
    text-align: center;
    transition: all var(--transition-fast);
}
.catalog-card:hover .card-action {
    box-shadow: var(--shadow-glow);
}

/* ── 已完成章节标记 ── */
.catalog-card.card-completed {
    border-color: rgba(5, 150, 105, 0.45);
    background: rgba(5, 150, 105, 0.06);
}
.catalog-card.card-completed .card-number {
    color: #059669;
}
.card-action.card-action-done {
    background: rgba(5, 150, 105, 0.12);
    border-color: rgba(5, 150, 105, 0.45);
    color: #059669;
}
.card-action.card-action-done:hover {
    background: rgba(5, 150, 105, 0.2);
    box-shadow: none;
}

/* ── 课程目录:9 大章节分组(可展开/收起) ── */
/* 00.html 把 50 张平铺卡片重排为 9 个 <details> 章节容器,
   展开后显示该章小节卡片,层级关系:课程 → 9章 → 小节 → 开始学习 */
.catalog-chapters {
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
}
.catalog-chapter {
    background: var(--color-bg-elevated);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    overflow: hidden;
    transition: border-color var(--transition-base);
}
.catalog-chapter[open] {
    border-color: rgba(6, 182, 212, 0.5);
    box-shadow: 0 0 0 1px rgba(6, 182, 212, 0.15);
}
.catalog-chapter-header {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    padding: var(--space-md) var(--space-lg);
    cursor: pointer;
    list-style: none;
    user-select: none;
}
.catalog-chapter-header::-webkit-details-marker { display: none; }
.catalog-chapter-header::marker { content: ''; }
.catalog-chapter-num {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-width: 64px;
    padding: 5px 12px;
    background: rgba(6, 182, 212, 0.15);
    color: var(--color-accent);
    border: 1px solid rgba(6, 182, 212, 0.3);
    border-radius: var(--radius-sm);
    font-size: 13px;
    font-weight: 700;
    flex-shrink: 0;
}
.catalog-chapter-title {
    flex: 1;
    font-weight: 700;
    color: var(--color-text);
    font-size: 16px;
}
.catalog-chapter-count {
    color: var(--color-text-muted);
    font-size: 13px;
    flex-shrink: 0;
}
.catalog-chapter-toggle {
    color: var(--color-accent);
    font-size: 13px;
    font-weight: 600;
    flex-shrink: 0;
}
.catalog-chapter[open] > .catalog-chapter-header .catalog-chapter-toggle::before { content: '收起 ▲'; }
.catalog-chapter:not([open]) > .catalog-chapter-header .catalog-chapter-toggle::before { content: '展开 ▼'; }
.catalog-sections {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--space-md);
    padding: 0 var(--space-md) var(--space-md) var(--space-md);
    border-top: 1px solid var(--color-border-light);
    margin-top: -1px;
}
/* 目录卡片要点：≥2 条正常展示；仅 1 条(模块占位型,如 embedded-linux)隐藏避免与章节名重复 */
.catalog-sections .card-points:has(li:only-child) { display: none; }
.catalog-sections .card-title { min-height: 36px; }

/* ── 原 chapter-header ── */
.chapter-header {
    background: var(--gradient-hero);
    border-radius: var(--radius-lg);
    padding: var(--space-xl) var(--space-xl);
    margin-bottom: var(--space-xl);
    position: relative;
    overflow: hidden;
    border: 1px solid var(--color-border);
}
.chapter-header::before {
    content: '';
    position: absolute;
    top: -60%; right: -15%;
    width: 240px; height: 240px;
    background: radial-gradient(circle, rgba(6, 182, 212, 0.2) 0%, transparent 70%);
    border-radius: 50%;
}
.chapter-header h2 {
    color: #fff;
    font-size: 22px;
    font-weight: 700;
    letter-spacing: 0.5px;
    position: relative;
    z-index: 1;
}

/* ── 原 chapter-guide / guide-meta ── */
.chapter-guide {
    background: var(--color-bg-elevated);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    overflow: hidden;
    margin-bottom: var(--space-xl);
}
.guide-meta {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    background: var(--color-bg-surface);
    border-bottom: 1px solid var(--color-border);
    padding: 0;
}
.guide-meta-item {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: var(--space-md) var(--space-lg);
    font-size: 13px;
    color: var(--color-text-secondary);
    border-right: 1px solid var(--color-border);
    white-space: nowrap;
    line-height: 1;
}
.guide-meta-item:last-child { border-right: none; }

/* ── 正文段落/标题(原内容) ── */
.chapter-container h2,
.chapter-container h3,
.chapter-container h4 {
    color: var(--color-text);
    margin-top: var(--space-xl);
    margin-bottom: var(--space-md);
}
.chapter-container h3 {
    font-size: 20px;
    font-weight: 700;
    border-left: 4px solid var(--color-accent);
    padding-left: var(--space-md);
}
.chapter-container h4 {
    font-size: 16px;
    font-weight: 600;
    color: var(--color-accent);
}
.chapter-container p {
    color: var(--color-text-secondary);
    margin-bottom: var(--space-md);
    line-height: 1.9;
}
.chapter-container ul,
.chapter-container ol {
    color: var(--color-text-secondary);
    margin-bottom: var(--space-md);
}
.chapter-container strong,
.chapter-container b {
    color: var(--color-text);
    font-weight: 600;
}

/* ── 原代码块 ── */
.chapter-container pre,
.catalog-container pre {
    background: var(--color-code-bg);
    border: 1px solid var(--color-code-border);
    border-radius: var(--radius-md);
    padding: var(--space-md) var(--space-lg);
    overflow-x: auto;
    margin: var(--space-md) 0;
    font-family: var(--font-mono);
    font-size: 13px;
    line-height: 1.6;
    color: var(--color-code-text);
}
.chapter-container code,
.catalog-container code {
    font-family: var(--font-mono);
    background: var(--color-bg-surface);
    color: var(--color-accent-light);
    padding: 2px 6px;
    border-radius: var(--radius-sm);
    font-size: 13px;
}
.chapter-container pre code {
    background: transparent;
    color: var(--color-code-text);
    padding: 0;
}

/* ── 原表格 ── */
.chapter-container table {
    width: 100%;
    border-collapse: collapse;
    margin: var(--space-md) 0;
    background: var(--color-bg-elevated);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    overflow: hidden;
}
.chapter-container th {
    background: var(--color-bg-surface);
    color: var(--color-text);
    padding: var(--space-md);
    text-align: left;
    font-weight: 600;
    border-bottom: 1px solid var(--color-border);
}
.chapter-container td {
    padding: var(--space-md);
    color: var(--color-text-secondary);
    border-bottom: 1px solid var(--color-border-light);
}
.chapter-container tr:last-child td { border-bottom: none; }

/* ── 宽表横向滚动(仅对显式标记 .table-scroll 的表格生效,避免全站副作用) ── */
.chapter-container table.table-scroll {
    display: block;
    width: 100%;
    max-width: 100%;
    overflow-x: auto;
    overflow-y: hidden;
    -webkit-overflow-scrolling: touch;
}
.chapter-container table.table-scroll thead,
.chapter-container table.table-scroll tbody { width: max-content; }
.chapter-container table.table-scroll th,
.chapter-container table.table-scroll td { white-space: nowrap; }

/* ── 原 practice-box ── */
.practice-box {
    background: linear-gradient(135deg, rgba(6, 182, 212, 0.08) 0%, rgba(30, 58, 138, 0.08) 100%);
    border: 1px solid rgba(6, 182, 212, 0.25);
    border-left: 4px solid var(--color-accent);
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    padding: var(--space-lg) var(--space-xl);
    margin: var(--space-lg) 0;
}
.practice-box::before {
    content: '\1F527  动手试一试';
    display: block;
    font-weight: 700;
    color: var(--color-accent);
    font-size: 15px;
    margin-bottom: var(--space-sm);
    padding-bottom: var(--space-sm);
    border-bottom: 1px dashed rgba(6, 182, 212, 0.25);
}
.practice-box h4 { display: none; }
/* 思考题变体：覆盖固定标题「动手试一试」，改为「停下来想一想」 */
.practice-box.think-box::before {
    content: '\1F4AD  停下来想一想';
    color: #9b59b6;
    border-bottom: 1px dashed rgba(155, 89, 182, 0.35);
}
.practice-box ol,
.practice-box.think-box ol,
.practice-box.think-box ul {
    margin: var(--space-sm) 0 0 0;
    padding-left: 20px;
    color: var(--color-text-secondary);
}
.practice-box li {
    color: var(--color-text-secondary);
    margin-bottom: var(--space-sm);
    line-height: 1.7;
}
.practice-box p { color: var(--color-text-secondary); margin-bottom: var(--space-sm); }
.practice-box code {
    background: rgba(6, 182, 212, 0.15);
    color: var(--color-accent-light);
}

/* ── 原 self-check ── */
.self-check {
    background: rgba(245, 158, 11, 0.08);
    border: 1px solid rgba(245, 158, 11, 0.2);
    border-left: 4px solid var(--color-warning);
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    padding: var(--space-lg) var(--space-xl);
    margin: var(--space-lg) 0;
}
.self-check::before {
    content: '\2753  检验你的理解';
    display: block;
    font-weight: 700;
    color: var(--color-warning);
    font-size: 15px;
    margin-bottom: var(--space-sm);
    padding-bottom: var(--space-sm);
    border-bottom: 1px dashed rgba(245, 158, 11, 0.3);
}
.self-check h4 { display: none; }
.self-check ol {
    margin: var(--space-sm) 0 0 0;
    padding-left: 20px;
    counter-reset: check-counter;
    list-style: none;
}
.self-check ol li {
    counter-increment: check-counter;
    position: relative;
    padding-left: var(--space-sm);
    color: var(--color-text-secondary);
    margin-bottom: var(--space-sm);
    line-height: 1.7;
}
.self-check ol li::before {
    content: 'Q' counter(check-counter);
    position: absolute;
    left: -24px;
    color: var(--color-warning);
    font-weight: 700;
    font-size: 13px;
}
.self-check p { color: var(--color-text-secondary); margin-bottom: var(--space-sm); }
/* ── 自测题答案折叠（v1.6.3 原生 details/summary 交互） ── */
.self-check .check-answer,
.practice-box .check-answer {
    margin-top: var(--space-xs);
    padding-top: var(--space-xs);
    border-top: 1px dashed rgba(245, 158, 11, 0.2);
    color: var(--color-text-muted);
    font-size: 13px;
    font-style: italic;
}
.self-check .check-answer summary,
.practice-box .check-answer summary {
    cursor: pointer;
    color: var(--color-warning);
    font-size: 13px;
    font-style: italic;
    user-select: none;
    list-style: none;
    outline: none;
}
.self-check .check-answer summary::-webkit-details-marker,
.practice-box .check-answer summary::-webkit-details-marker { display: none; }
.self-check .check-answer summary::before,
.practice-box .check-answer summary::before { content: '\25B6 '; font-size: 10px; }
.self-check .check-answer[open] summary::before,
.practice-box .check-answer[open] summary::before { content: '\25BC '; }
.self-check .check-answer__body,
.practice-box .check-answer__body {
    margin-top: var(--space-xs);
    padding: var(--space-xs) var(--space-sm);
    background: rgba(245, 158, 11, 0.05);
    border-radius: var(--radius-sm);
    color: var(--color-text-muted);
    font-size: 13px;
    font-style: normal;
    line-height: 1.7;
}

/* ── 原 editor-note ── */
.editor-note {
    background: rgba(59, 130, 246, 0.08);
    border: 1px solid rgba(59, 130, 246, 0.2);
    border-left: 3px solid var(--color-info);
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
    padding: var(--space-md) var(--space-lg);
    margin: var(--space-md) 0;
    font-size: 14px;
    color: #93c5fd;
    line-height: 1.7;
}
.editor-note::before {
    content: '\1f4d6  编者提示';
    display: inline-block;
    font-weight: 700;
    font-size: 11px;
    letter-spacing: 1.5px;
    margin-right: var(--space-sm);
    padding: 2px var(--space-sm);
    background: rgba(59, 130, 246, 0.15);
    border-radius: var(--radius-sm);
    color: var(--color-info);
}

/* ── 原 difficulty-tag ── */
.difficulty-tag {
    display: inline-block;
    padding: 2px 10px;
    border-radius: var(--radius-full);
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 0.5px;
}
.diff-beginner {
    background: rgba(16, 185, 129, 0.15);
    color: var(--color-success);
    border: 1px solid rgba(16, 185, 129, 0.3);
}
.diff-intermediate {
    background: rgba(245, 158, 11, 0.15);
    color: var(--color-warning);
    border: 1px solid rgba(245, 158, 11, 0.3);
}
.diff-advanced {
    background: rgba(239, 68, 68, 0.15);
    color: var(--color-danger);
    border: 1px solid rgba(239, 68, 68, 0.3);
}

/* ── 规9 重点章节三处标记 ── */
.diff-key {
    background: rgba(6, 182, 212, 0.15);
    color: var(--color-accent);
    border: 1px solid rgba(6, 182, 212, 0.35);
}
.catalog-card.key-chapter {
    border-left: 3px solid var(--color-accent);
    position: relative;
}
.catalog-card.key-chapter::after {
    content: '重点';
    position: absolute;
    top: 8px; right: 8px;
    font-size: 11px; font-weight: 600;
    color: #fff;
    background: var(--color-accent);
    padding: 1px 6px;
    border-radius: var(--radius-full);
    letter-spacing: 0.5px;
    line-height: 1.4;
}
.key-chapter-tag {
    display: inline-block;
    padding: 2px 8px;
    margin-left: 8px;
    font-size: 12px; font-weight: 600;
    color: #fff;
    background: var(--color-accent);
    border-radius: var(--radius-full);
    letter-spacing: 0.5px;
    vertical-align: middle;
}

/* ── 原 question-section ── */
.question-section {
    background: var(--color-bg-elevated);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    padding: var(--space-lg);
    margin: var(--space-md) 0;
}
.question-section h4 {
    color: var(--color-accent);
    font-size: 13px;
    margin-bottom: var(--space-sm);
}
.question-section p {
    color: var(--color-text-secondary);
    line-height: 1.7;
}
.question-section.quick-answer h4 { color: var(--color-success); }
.question-section.quick-answer h4::before { content: '\26A1 '; }
.question-section.quick-answer p {
    color: #6ee7b7;
    font-weight: 500;
    font-size: 15px;
    line-height: 1.7;
}

/* ── 原 chapter-nav 章节导航(三列网格:返回目录严格水平居中) ── */
/* 无论上一章/下一章按钮是否存在或宽度不同,中间「返回目录」始终处于几何中心,
   与下方「完成本节学习」按钮共用同一条页面中心轴。 */
.chapter-nav {
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    align-items: center;
    gap: var(--space-md);
    margin-top: var(--space-2xl);
    padding: 0 var(--space-lg);
}
/* 旧版占位符在 grid 布局下不再需要,统一隐藏 */
.chapter-nav .nav-placeholder { display: none; }
.chapter-nav a {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: var(--space-md) var(--space-xl);
    border-radius: var(--radius-md);
    font-size: 14px;
    font-weight: 600;
    text-decoration: none;
    transition: all var(--transition-fast);
    cursor: pointer;
}
.chapter-nav .nav-prev,
.chapter-nav .nav-next {
    background: var(--color-bg-elevated);
    color: var(--color-accent);
    border: 1px solid var(--color-border);
}
.chapter-nav .nav-prev { grid-column: 1; justify-self: start; }
.chapter-nav .nav-next { grid-column: 3; justify-self: end; }
.chapter-nav .nav-prev:hover,
.chapter-nav .nav-next:hover {
    background: var(--color-bg-surface);
    border-color: var(--color-accent);
    box-shadow: var(--shadow-glow);
}
/* 「返回目录」按钮:01-10.html 用 .nav-catalog,11-50.html 用 .nav-home,统一样式与居中 */
.chapter-nav .nav-catalog,
.chapter-nav .nav-home {
    grid-column: 2;
    justify-self: center;
    background: var(--gradient-brand);
    color: #fff;
    border: none;
}
.chapter-nav .nav-catalog:hover,
.chapter-nav .nav-home:hover {
    opacity: 0.9;
    box-shadow: var(--shadow-brand);
    color: #fff;
}

/* ── 原 page-footer ── */
.page-footer {
    text-align: center;
    padding: var(--space-xl) 0 var(--space-md) 0;
    color: var(--color-text-muted);
    font-size: 12px;
    letter-spacing: 1px;
    border-top: 1px solid var(--color-border);
    margin-top: var(--space-xl);
}

/* ============================================
   原网站更多 class: guide-body / chapter-content /
   key-point / concept-block / tip-box / 代码高亮 /
   表格 / 小结 / 流程图 / 时间线 / 对比区 / 架构图 /
   面试题卡片 / 评分标准 / 多场景卡片
   ============================================ */

.guide-meta-item .meta-icon { font-size: 14px; flex-shrink: 0; }
.guide-body { padding: var(--space-md) var(--space-lg); }
.guide-learn { margin-bottom: var(--space-md); }
.guide-learn-label {
    font-size: 13px; font-weight: 700; color: var(--color-accent);
    letter-spacing: 1.5px; margin-bottom: 8px; display: block;
}
.guide-learn-label::before {
    content: ''; display: inline-block; width: 7px; height: 7px;
    border-radius: 50%; background: var(--color-accent); margin-right: 8px; vertical-align: middle;
}
.guide-learn ul { list-style: decimal inside; padding: 0; margin: 0; }
.guide-learn li { font-size: 14px; color: var(--color-text-secondary); line-height: 1.7; padding-left: 6px; position: relative; margin-bottom: 8px; }
.guide-learn li:last-child { margin-bottom: 0; }
.guide-concepts { display: flex; align-items: center; flex-wrap: wrap; gap: 8px; }
.guide-concepts-label {
    font-size: 13px; font-weight: 700; color: var(--color-accent);
    letter-spacing: 1.5px; margin-right: 4px;
}
.guide-concepts-label::before {
    content: ''; display: inline-block; width: 7px; height: 7px;
    border-radius: 50%; background: var(--color-accent); margin-right: 8px; vertical-align: middle;
}
.guide-concept-tag {
    display: inline-block; background: rgba(6, 182, 212, 0.1);
    border: 1px solid rgba(6, 182, 212, 0.25);
    color: var(--color-accent-light); padding: 3px 12px; border-radius: 14px;
    font-size: 13px; font-weight: 500;
}

.chapter-content { padding: 0; }
.chapter-content h3 {
    color: var(--color-text); font-size: 18px; font-weight: 700;
    margin: 32px 0 14px 0; padding: 10px 16px;
    background: rgba(6, 182, 212, 0.08); border-left: 3px solid var(--color-accent);
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
}
.chapter-content h4 {
    color: var(--color-text); font-size: 15px; font-weight: 600;
    margin: 22px 0 10px 0; padding-bottom: 6px; border-bottom: 1px solid var(--color-border);
}
.chapter-content p { line-height: 1.85; text-align: justify; }
.chapter-content li { margin-bottom: 6px; padding-left: 4px; }
.chapter-content li::marker { color: var(--color-accent); font-weight: 600; }

/* ── 核心概念 / 重点知识 ── */
.concept-block {
    background: rgba(30, 58, 138, 0.15); border: 1px solid rgba(30, 58, 138, 0.3);
    border-radius: var(--radius-md); padding: 18px 22px; margin: 18px 0;
}
.concept-block h4 { color: var(--color-accent-light); border-bottom: none; margin-top: 0; padding-bottom: 4px; }
.key-point {
    background: rgba(6, 182, 212, 0.1); border: 1px solid rgba(6, 182, 212, 0.25);
    border-radius: var(--radius-md); padding: 18px 22px; margin: 18px 0;
}
.key-point h4 { color: var(--color-accent); border-bottom: none; margin-top: 0; }

/* ── 提示框 ── */
.tip-box {
    background: var(--color-bg-surface); border: 1px solid var(--color-border);
    border-left: 3px solid var(--color-primary-light);
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
    padding: 14px 18px; margin: 18px 0;
}
.tip-box::before {
    content: 'TIP'; display: inline-block; font-weight: 700; color: var(--color-primary-light);
    font-size: 11px; letter-spacing: 2px; margin-bottom: 5px;
    padding: 1px 7px; background: rgba(30, 58, 138, 0.2); border-radius: 3px;
}
.tip-box.warning { border-left-color: var(--color-warning); background: rgba(245, 158, 11, 0.08); }
.tip-box.warning::before { content: 'CAUTION'; color: var(--color-warning); background: rgba(245, 158, 11, 0.15); }
.tip-box.important { border-left-color: var(--color-danger); background: rgba(239, 68, 68, 0.08); }
.tip-box.important::before { content: 'IMPORTANT'; color: var(--color-danger); background: rgba(239, 68, 68, 0.15); }

/* ── 代码块语法高亮 ── */
pre code .kw { color: #c792ea; }
pre code .str { color: #c3e88d; }
pre code .cmt { color: #546e7a; font-style: italic; }
pre code .num { color: #f78c6c; }
pre code .func { color: #82aaff; }
pre .code-header {
    background: var(--color-bg-surface); padding: 7px 14px; font-size: 12px;
    color: var(--color-text-muted); font-family: var(--font-mono);
    border-bottom: 1px solid var(--color-border);
}

/* ── 表格增强 ── */
.chapter-container table thead th,
.catalog-container table thead th {
    background: var(--color-bg-surface); color: var(--color-text); font-weight: 600;
    padding: 11px 16px; text-align: left; font-size: 13px;
}
.chapter-container table tbody tr:nth-child(odd),
.catalog-container table tbody tr:nth-child(odd) { background: var(--color-bg-elevated); }
.chapter-container table tbody tr:nth-child(even),
.catalog-container table tbody tr:nth-child(even) { background: var(--color-bg-surface); }
.chapter-container table tbody tr:hover,
.catalog-container table tbody tr:hover { background: rgba(6, 182, 212, 0.08); }

/* ── 小结框 ── */
.summary-box {
    background: var(--color-bg-elevated); border: 1px solid var(--color-border);
    border-radius: var(--radius-lg); padding: 22px 26px; margin-top: 36px;
    position: relative; box-shadow: var(--shadow-sm);
}
.summary-box::before {
    content: ''; position: absolute; top: 0; left: 0; right: 0; height: 3px;
    background: var(--gradient-brand); border-radius: var(--radius-lg) var(--radius-lg) 0 0;
}
.summary-box h3 { color: var(--color-accent) !important; border-left: none !important; background: none !important; padding: 0 !important; margin: 0 0 12px 0 !important; font-size: 15px !important; }
.summary-box ul { list-style: none; padding-left: 0; margin-left: 0; }
.summary-box li { padding-left: 20px; position: relative; color: var(--color-text-secondary); margin-bottom: 6px; }
.summary-box li::before { content: '→'; position: absolute; left: 0; color: var(--color-accent); font-weight: 600; }

/* ── 流程图 ── */
.flowchart {
    display: flex; align-items: center; justify-content: center; flex-wrap: wrap; gap: 14px 0;
    margin: 20px 0; padding: 24px 20px; background: var(--color-bg-elevated);
    border-radius: var(--radius-md); border: 1px solid var(--color-border);
}
.flow-step {
    background: rgba(6, 182, 212, 0.1); border: 1px solid rgba(6, 182, 212, 0.25);
    border-radius: var(--radius-sm); padding: 8px 16px; color: var(--color-accent-light);
    font-size: 13px; font-weight: 500; text-align: center; white-space: nowrap;
}
.flow-arrow { color: var(--color-accent); font-size: 18px; margin: 0 5px; flex-shrink: 0; }
/* 流程图换行占位：占满一行强制折行（行间距由 .flowchart 的 row-gap 统一提供） */
.flowchart > .flow-brk { flex-basis: 100%; height: 0; margin: 0; }

/* ── 时间线 ── */
.timeline { position: relative; padding: 10px 0 10px 34px; margin: 20px 0; }
.timeline::before {
    content: ''; position: absolute; left: 9px; top: 0; bottom: 0; width: 2px;
    background: var(--gradient-brand); border-radius: 1px;
}
.timeline-item {
    position: relative; margin-bottom: 14px; padding: 12px 16px;
    background: var(--color-bg-elevated); border-radius: var(--radius-sm); border: 1px solid var(--color-border);
}
.timeline-item::before {
    content: ''; position: absolute; left: -29px; top: 16px; width: 10px; height: 10px;
    border-radius: 50%; background: var(--color-accent); border: 2px solid var(--color-bg); z-index: 1;
}
.timeline-item .step-title { color: var(--color-accent-light); font-weight: 600; margin-bottom: 3px; font-size: 14px; }
.timeline-item p { font-size: 13px; color: var(--color-text-muted); margin-bottom: 0; }

/* ── 对比区块 ── */
.compare-block { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin: 20px 0; }
.compare-item { background: var(--color-bg-elevated); border: 1px solid var(--color-border); border-radius: var(--radius-md); padding: 16px 18px; }
.compare-item.pros { border-top: 3px solid var(--color-accent); }
.compare-item.cons { border-top: 3px solid var(--color-warning); }
.compare-item h4 { margin-top: 0; padding-bottom: 5px; border-bottom: none; font-size: 14px; }

/* ── 架构图 ── */
.arch-diagram {
    display: flex; flex-direction: column; align-items: center; gap: 4px;
    padding: 20px; background: var(--color-bg-elevated);
    border: 1px solid var(--color-border); border-radius: var(--radius-md); margin: 20px 0;
}
.arch-row { display: flex; align-items: center; justify-content: center; gap: 8px; flex-wrap: wrap; }
.arch-node {
    padding: 8px 18px; border-radius: var(--radius-sm);
    font-size: 13px; font-weight: 600; text-align: center; min-width: 90px; line-height: 1.4;
    /* 默认边框:保证裸 .arch-node(无 primary/secondary/accent)也有边框,
       避免出现"前面节点有框、后面节点突然变裸文字"的语义不统一 */
    border: 2px solid var(--color-border); background: var(--color-bg-elevated); color: var(--color-text);
}
.arch-node.primary { background: rgba(6, 182, 212, 0.1); border: 2px solid var(--color-accent); color: var(--color-accent-light); }
.arch-node.secondary { background: rgba(245, 158, 11, 0.1); border: 2px solid var(--color-warning); color: #fbbf24; }
.arch-node.accent { background: rgba(59, 130, 246, 0.1); border: 2px solid var(--color-info); color: #93c5fd; }
.arch-connector { color: var(--color-text-muted); font-size: 20px; font-weight: 700; flex-shrink: 0; }
/* 箭头旁标签文字：小字号（模板把标签包进 .arch-conn-label，箭头符号保持 20px 大字）。
   文字与符号同字号会撑爆 flex 行导致换行错位、箭头指不到目标节点 */
.arch-conn-label { font-size: 12px; font-weight: 500; line-height: 1.3; vertical-align: middle; }
.flow-arrow .arch-conn-label { color: var(--color-text-muted); }

/* ── 流程图 v2:箭头与节点严格对齐(embedded-linux 图示整改) ──
   旧 .flowchart 用 flex-row + flex-wrap,↓ 箭头被横向排列导致指向空白。
   新增 .flow-v / .flow-h 用明确方向,保证每个箭头起终点都与节点中心对齐。
   仅 embedded-linux 课程 HTML 引用,不影响其他课程。 */

/* 纵向单链路:节点垂直堆叠,↓ 位于所有节点共享的中心轴 → 箭头必指下一节点中心 */
.flow-v {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 6px;
    margin: 20px 0;
    padding: 24px 20px;
    background: var(--color-bg-elevated);
    border-radius: var(--radius-md);
    border: 1px solid var(--color-border);
}
.flow-v .flow-step { max-width: 92%; }
/* 纵向连接器（旧标记回退：裸文本"↓ 标签"无法分列，只能箭头居中、标签排下方）。
   新标记（箭头包 .arch-conn-glyph）见下方三列 grid 规则：箭头钉中线、标签在右侧。 */
.flow-v .flow-arrow {
    margin: 0; line-height: 1.2;
    display: flex; flex-direction: column; align-items: center; gap: 2px;
}
/* 独占行连接器（新标记）：三列 grid【等宽左列 | auto符号列 | 等宽右列】，
   左右两列永远等宽 → 箭头符号天然钉在整行中线上，与标签宽度完全无关；
   标签占右列、排符号右侧，过长自动折行（2~3 行），满足"文字在箭头旁边"的要求。 */
.flow-v .flow-arrow:has(> .arch-conn-glyph),
.arch-row .arch-connector:only-child:has(> .arch-conn-glyph),
.flow-grid .grid-col .flow-arrow:has(> .arch-conn-glyph) {
    margin: 0;
    width: 100%;
    box-sizing: border-box;
    display: grid;
    grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr);
    align-items: center;
    column-gap: 10px;
    line-height: 1.3;
    white-space: normal;
}
.flow-v .flow-arrow:has(> .arch-conn-glyph) > .arch-conn-glyph,
.arch-row .arch-connector:only-child:has(> .arch-conn-glyph) > .arch-conn-glyph,
.flow-grid .grid-col .flow-arrow:has(> .arch-conn-glyph) > .arch-conn-glyph {
    grid-column: 2;
    justify-self: center;
    white-space: nowrap;
}
.flow-v .flow-arrow:has(> .arch-conn-glyph) > .arch-conn-label,
.arch-row .arch-connector:only-child:has(> .arch-conn-glyph) > .arch-conn-label,
.flow-grid .grid-col .flow-arrow:has(> .arch-conn-glyph) > .arch-conn-label {
    grid-column: 3;
    justify-self: start;
    text-align: left;
    white-space: normal;
}
/* arch-node 也能在 .flow-v 里用(保留 primary/secondary/accent 语义) */
.flow-v .arch-node { max-width: 92%; }

/* 横向流水线:节点水平排列,→ 位于节点中心线,禁止换行(溢出横向滚动) */
.flow-h {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
    flex-wrap: nowrap;
    overflow-x: auto;
    margin: 20px 0;
    padding: 24px 20px;
    background: var(--color-bg-elevated);
    border-radius: var(--radius-md);
    border: 1px solid var(--color-border);
}
.flow-h .flow-arrow { margin: 0 2px; flex-shrink: 0; }

/* ── 流程图 v3 补充(edge-ai 多形式图示) ──
   1) flow-v/flow-h 内嵌 arch-diagram 时去掉内层框,只保留一层外框,避免"盒中盒"
   2) 多行架构图(arch-row 直接作为 arch-diagram 子级)的行距与连接器换行规则 */
.arch-diagram > .flow-v,
.arch-diagram > .flow-h {
    margin: 0;
    padding: 6px 0;
    background: transparent;
    border: none;
    width: 100%;
}
.arch-diagram > .arch-row { margin: 2px 0; }
.arch-diagram .arch-connector { white-space: nowrap; line-height: 1.3; }
/* 层间独占连接器行（旧标记回退：整行只有一个裸文本箭头）：箭头居中、标签排下方。
   新标记走上面的三列 grid（箭头钉中线、标签排右侧）；
   只作用于独占行；节点之间的行内连接器仍是行内布局（且行内连接器按规则5不带标签）。 */
.arch-row .arch-connector:only-child {
    display: inline-flex; flex-direction: column; align-items: center; gap: 2px;
}
.arch-row .arch-connector:only-child .arch-conn-label,
.flow-v .flow-arrow .arch-conn-label { white-space: normal; }
/* 图内注解行：箭头/节点之间的一行弱化说明（如汇聚箭头下方的对齐说明），区别于图底 .arch-caption */
.arch-note {
    width: 100%; box-sizing: border-box;
    text-align: center; font-size: 12px; color: var(--color-text-muted);
    line-height: 1.4; padding: 1px 12px 3px;
}
.arch-diagram.arch-flow .arch-row { gap: 10px; }
.arch-diagram .arch-node { white-space: normal; }

/* 顺序多行架构图:每行内部 → 不换行,行间用居中 ↓ 衔接,保证行间流程不悬空 */
.arch-flow .arch-row { flex-wrap: nowrap; justify-content: center; }
.arch-flow .arch-link {
    display: flex; align-items: center; justify-content: center;
    width: 100%; padding: 2px 0;
}
.arch-flow .arch-link .arch-connector { font-size: 22px; }

/* 移动端:横向流程降级为纵向,避免窄屏箭头错位与节点中心偏移 */
@media (max-width: 768px) {
    .flow-h { flex-direction: column; overflow-x: visible; }
    /* 窄屏降级为纵向后，独占整行的箭头同样三列 grid：符号钉中线、标签在右侧折行 */
    .flow-h .flow-arrow:has(> .arch-conn-glyph) {
        margin: 0; width: 100%; box-sizing: border-box;
        display: grid;
        grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr);
        align-items: center; column-gap: 10px; line-height: 1.3;
    }
    .flow-h .flow-arrow:has(> .arch-conn-glyph) > .arch-conn-glyph { grid-column: 2; justify-self: center; white-space: nowrap; }
    .flow-h .flow-arrow:has(> .arch-conn-glyph) > .arch-conn-label { grid-column: 3; justify-self: start; text-align: left; white-space: normal; }
    /* 旧标记回退 */
    .flow-h .flow-arrow:not(:has(> .arch-conn-glyph)) { margin: 0; display: inline-flex; flex-direction: column; align-items: center; gap: 2px; }
    /* 多行架构图窄屏也纵向堆叠,行内节点允许换行 */
    .arch-flow .arch-row { flex-wrap: wrap; }
    /* 上下对应网格窄屏降级为单列纵向,保证箭头仍对齐节点中心 */
    .flow-grid { grid-template-columns: 1fr !important; }
}

/* ── 流程图 v3:统一排版规范(embedded-linux 图示整改第二轮) ──
   解决问题:节点无框、上下两行不对齐、孤儿说明文字散落、横向纵向无意义混用。
   规则:【节点】=带边框盒子;【动作/关系】=箭头旁说明文字;【图示整体说明】=caption。
   优先级:逻辑方向 > 箭头连接 > 不重叠 > 中心对齐 > 间距统一 > 装饰。 */

/* 上下对应关系网格:列坐标稳定,上节点↓下说明严格同列对齐
   适用:阶段→推荐方案、平台→技术选型、产品阶段→工具选择 */
.flow-grid {
    display: grid;
    grid-template-columns: repeat(var(--flow-cols, 4), 1fr);
    gap: 10px 14px;
    margin: 20px 0;
    padding: 24px 20px;
    background: var(--color-bg-elevated);
    border-radius: var(--radius-md);
    border: 1px solid var(--color-border);
}
.flow-grid .grid-col {
    display: flex; flex-direction: column; align-items: center; gap: 6px;
}
.flow-grid .grid-col .flow-arrow:not(:has(> .arch-conn-glyph)) {
    margin: 0; line-height: 1.2;
    display: flex; flex-direction: column; align-items: center; gap: 2px;
}
.flow-grid .grid-col .arch-node { width: 100%; box-sizing: border-box; }
.flow-grid .grid-col { min-width: 0; overflow: hidden; }
.flow-grid .grid-col pre,
.flow-grid .grid-col .arch-code {
    width: 100%;
    max-width: 100%;
    box-sizing: border-box;
    overflow-x: auto;
    white-space: pre;
    margin: 0;
}

/* 图示说明文字(非节点、非箭头):整段居中小字,不再以孤立的 arch-row 形式散落
   适用:"USB 摄像头备选输入""phandle 让设备之间能互相打电话"这类整体注解 */
.arch-caption {
    text-align: center; font-size: 13px; color: var(--color-text-muted);
    font-style: italic; margin: 6px 0 2px; line-height: 1.5;
}

/* ── 多场景卡片 ── */
.scenario-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin: 20px 0; }
.scenario-card { padding: 16px 18px; border-radius: var(--radius-md); border-left: 4px solid; }
.scenario-card h4 { margin-top: 0; font-size: 14px; padding-bottom: 4px; border-bottom: none; }
.scenario-card ul { margin: 6px 0 0 0; padding-left: 16px; }
.scenario-card li { font-size: 13px; color: var(--color-text-secondary); margin-bottom: 4px; line-height: 1.5; }
.scenario-card.blue { border-color: var(--color-info); background: rgba(59, 130, 246, 0.08); }
.scenario-card.blue h4 { color: #93c5fd; }
.scenario-card.green { border-color: var(--color-accent); background: rgba(6, 182, 212, 0.08); }
.scenario-card.green h4 { color: var(--color-accent-light); }
.scenario-card.purple { border-color: #8b5cf6; background: rgba(139, 92, 246, 0.08); }
.scenario-card.purple h4 { color: #c4b5fd; }
.scenario-card.orange { border-color: var(--color-warning); background: rgba(245, 158, 11, 0.08); }
.scenario-card.orange h4 { color: #fbbf24; }

/* ── 面试题卡片 ── */
.question-card {
    background: var(--color-bg-elevated); border: 1px solid var(--color-border);
    border-radius: var(--radius-lg); margin-bottom: 24px; overflow: hidden;
    transition: box-shadow 0.2s;
}
.question-card:hover { box-shadow: var(--shadow-lg); }
.question-header {
    background: var(--gradient-hero); padding: 14px 22px;
    font-size: 15px; font-weight: 600; color: #fff;
}
.question-section { padding: 14px 22px; border-bottom: 1px solid var(--color-border-light); }
.question-section:last-child { border-bottom: none; }
.question-section h4 {
    color: var(--color-accent); font-size: 12px; font-weight: 700;
    margin-bottom: 6px; margin-top: 0; padding-bottom: 0; border-bottom: none;
    text-transform: uppercase; letter-spacing: 2px;
}
.question-section p { margin-bottom: 6px; font-size: 14px; }
.question-section.answer-section { background: var(--color-bg-surface); }
.question-section.followup-section { background: rgba(6, 182, 212, 0.06); }
.keyword-tags { display: flex; flex-wrap: wrap; gap: 6px; }
.keyword-tags .tag {
    background: rgba(6, 182, 212, 0.1); border: 1px solid rgba(6, 182, 212, 0.25);
    color: var(--color-accent-light); padding: 3px 12px; border-radius: 20px;
    font-size: 12px; font-weight: 500;
}

/* ── 面试评分标准 ── */
.scoring-rubric {
    border: 1px solid var(--color-border); border-radius: var(--radius-md);
    overflow: hidden; margin: 12px 22px 14px 22px;
}
.score-level {
    display: flex; align-items: flex-start; gap: 12px;
    padding: 10px 18px; border-bottom: 1px solid var(--color-border); font-size: 13px;
}
.score-level:last-child { border-bottom: none; }
.score-level p { margin: 0; color: var(--color-text-secondary); line-height: 1.5; }
.score-badge {
    display: inline-block; padding: 2px 10px; border-radius: 10px;
    font-size: 12px; font-weight: 700; white-space: nowrap; flex-shrink: 0;
}
.score-excellent { background: rgba(16, 185, 129, 0.06); }
.score-excellent .score-badge { background: rgba(16, 185, 129, 0.15); color: var(--color-success); }
.score-pass { background: rgba(245, 158, 11, 0.06); }
.score-pass .score-badge { background: rgba(245, 158, 11, 0.15); color: var(--color-warning); }
.score-fail { background: rgba(239, 68, 68, 0.06); }
.score-fail .score-badge { background: rgba(239, 68, 68, 0.15); color: var(--color-danger); }

/* ── 响应式(补充) ── */
@media (max-width: 768px) {
    .catalog-grid { grid-template-columns: repeat(2, 1fr); }
    .course-info { grid-template-columns: repeat(2, 1fr); }
    .course-info-item:nth-child(2) { border-right: none; }
    .course-info-item:nth-child(1),
    .course-info-item:nth-child(2) { border-bottom: 1px solid var(--color-border); }
    .chapter-container { padding: var(--space-lg) var(--space-md); }
    .chapter-header { padding: var(--space-lg); }
    .chapter-header h2 { font-size: 18px; }
    .chapter-nav a { padding: var(--space-sm) var(--space-md); font-size: 13px; }
    /* 移动端:上一章/返回目录/下一章 上下排列,返回目录仍处于页面中心 */
    .chapter-nav {
        grid-template-columns: 1fr;
        justify-items: center;
        gap: var(--space-sm);
    }
    .chapter-nav .nav-prev,
    .chapter-nav .nav-next { grid-column: 1; justify-self: center; }
    .catalog-sections { grid-template-columns: repeat(2, 1fr); }
    .catalog-chapter-header { flex-wrap: wrap; }
    .catalog-chapter-title { font-size: 14px; }
    .compare-block, .scenario-grid { grid-template-columns: 1fr; }
    .arch-diagram { padding: var(--space-md); }
}
@media (max-width: 480px) {
    /* 超小屏(390/430px):章节内小节卡片单列,避免横向溢出 */
    .catalog-sections { grid-template-columns: 1fr; }
    .stats-bar { flex-wrap: wrap; }
}

/* ── 章节页 chapter-header 内的序号小方框 pill（v1.4，与目录 card-number 同色板）── */
.chapter-num-pill {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 34px;
    height: 34px;
    border-radius: var(--radius-sm);
    background: rgba(6, 182, 212, 0.20);
    border: 1px solid rgba(6, 182, 212, 0.35);
    color: var(--color-accent);
    font-size: 13px;
    font-weight: 700;
    letter-spacing: 0.5px;
    line-height: 1;
    margin-right: 12px;
    vertical-align: middle;
    font-variant-numeric: tabular-nums;
    flex-shrink: 0;
}
@media (max-width: 640px) {
    .chapter-num-pill {
        width: 28px;
        height: 28px;
        font-size: 11px;
        margin-right: 8px;
    }
}

/* ── 课程学习页三栏布局(目录 | 正文 | 笔记) ── */
/* 由 router.js 自动注入,无需 HTML 改动 */
.course-learn-layout {
    display: flex;
    gap: 16px;
    width: 100%;
    max-width: 100vw;
    margin: 0;
    padding: 0;
    align-items: flex-start;
    box-sizing: border-box;
}
.course-sidebar {
    width: 260px;
    flex-shrink: 0;
    position: sticky;
    top: var(--nav-height);
    height: calc(100vh - var(--nav-height));
    /* 三段式:header 固定 + nav 独立滚动;不再整体 overflow */
    display: flex;
    flex-direction: column;
    min-height: 0;
    background: var(--color-bg-surface);
    border: 1px solid var(--color-border);
    border-radius: 0;
    padding: 0;
    font-size: 13px;
    box-sizing: border-box;
    transition: margin-left 0.25s ease, transform 0.25s ease;
}
/* 折叠状态:目录滑出视口,toggle 固定在左上角 */
body.sidebar-collapsed .course-sidebar {
    margin-left: -260px;
}
/* 折叠按钮(独立 fixed,始终可点,在 nav 下方) */
.sidebar-toggle {
    position: fixed;
    left: 260px;
    top: var(--nav-height, 60px);
    width: auto;
    min-width: 32px;
    height: 32px;
    background: var(--color-bg-elevated);
    border: 1px solid var(--color-border);
    color: var(--color-text-muted);
    font-size: 13px;
    cursor: pointer;
    z-index: 1001;
    padding: 0 8px;
    transition: left 0.25s ease, background 0.15s, color 0.15s;
}
.sidebar-toggle:hover { color: var(--color-accent); background: rgba(6, 182, 212, 0.1); }
.sidebar-toggle .icon-expand { display: none; margin-left: 4px; }
.sidebar-toggle .icon-collapse { display: inline; }
body.sidebar-collapsed .sidebar-toggle {
    left: 0;
}
body.sidebar-collapsed .sidebar-toggle .icon-collapse { display: none; }
body.sidebar-collapsed .sidebar-toggle .icon-expand { display: inline; }
.course-sidebar .sidebar-header {
    padding: 10px 16px;
    border-bottom: 1px solid var(--color-border);
    flex-shrink: 0;            /* 顶部标题区固定,不随列表滚动 */
}
.course-sidebar .sidebar-header a {
    color: var(--color-accent); font-weight: 600; font-size: 14px; text-decoration: none;
}
.course-sidebar .sidebar-header a:hover { text-decoration: underline; }
/* 章节列表:真正独立滚动的区域 */
.course-sidebar .sidebar-nav {
    flex: 1;
    min-height: 0;            /* 关键:允许 flex 子项收缩,内部滚动 */
    overflow-y: auto;
}
.course-sidebar .sidebar-nav ul { list-style: none; padding: 0; margin: 0; }
/* 侧边栏当前章节标题(embedded-linux 动态目录:只显示当前章的小节) */
.course-sidebar .sidebar-chapter-name {
    padding: 12px 16px 8px 16px;
    color: var(--color-text);
    font-size: 13px;
    font-weight: 700;
    line-height: 1.4;
    border-bottom: 1px solid var(--color-border-light);
    margin: 0 0 4px 0;
}
.course-sidebar .sidebar-section { margin-bottom: 2px; }
.course-sidebar .sidebar-section-title {
    padding: 9px 16px 5px 16px;
    color: var(--color-text-muted);
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 0.5px;
    display: flex;
    align-items: center;
    gap: 6px;
}
.course-sidebar .sidebar-section-link a {
    display: flex;
    align-items: center;
    gap: 6px;
    color: var(--color-text-muted);
    text-decoration: none;
    padding: 9px 16px;
}
.course-sidebar .sidebar-section-link a:hover { background: rgba(6, 182, 212, 0.06); color: var(--color-text); }
.course-sidebar .sidebar-section-link.active > a {
    background: rgba(6, 182, 212, 0.1);
    color: var(--color-accent);
    font-weight: 600;
    border-left: 3px solid var(--color-accent);
    padding-left: 13px;
}
.course-sidebar .sidebar-section-num {
    display: inline-block;
    min-width: 22px;
    padding: 1px 5px;
    background: rgba(6, 182, 212, 0.12);
    color: var(--color-accent);
    border-radius: 4px;
    font-size: 11px;
    text-align: center;
}
.course-sidebar .sidebar-section-list { list-style: none; padding: 0; margin: 0 0 4px 0; }
.course-sidebar .sidebar-section-item a {
    display: block;
    padding: 6px 16px 6px 32px;
    color: var(--color-text-secondary);
    text-decoration: none;
    font-size: 12.5px;
    line-height: 1.5;
    border-left: 2px solid transparent;
    transition: background 0.15s, border-color 0.15s, color 0.15s;
}
.course-sidebar .sidebar-section-item a:hover { background: rgba(6, 182, 212, 0.06); color: var(--color-text); }
.course-sidebar .sidebar-section-item.active > a {
    background: rgba(6, 182, 212, 0.1);
    border-left-color: var(--color-accent);
    color: var(--color-accent);
    font-weight: 600;
}
/* 侧边栏重点章标记:数据源为 00 目录卡片 key-chapter class,router.js 渲染 */
.course-sidebar .sidebar-key-tag {
    display: inline-block;
    padding: 0 6px;
    margin-left: 6px;
    font-size: 10px;
    font-weight: 600;
    line-height: 16px;
    vertical-align: middle;
    white-space: nowrap;
    color: #fff;
    background: var(--color-accent);
    border-radius: var(--radius-full);
    letter-spacing: 0.5px;
}
/* 侧边栏模块分组:全课程目录树,每个模块可独立展开/收拢 */
.course-sidebar .sidebar-module { margin: 2px 0 4px 0; }
.course-sidebar .sidebar-module-header {
    display: flex;
    align-items: center;
    gap: 6px;
    width: 100%;
    padding: 8px 12px 8px 14px;
    background: transparent;
    border: none;
    border-left: 2px solid transparent;
    color: var(--color-text);
    font-family: inherit;
    font-size: 12.5px;
    font-weight: 700;
    line-height: 1.4;
    text-align: left;
    cursor: pointer;
    transition: background 0.15s, color 0.15s;
}
.course-sidebar .sidebar-module-header:hover { background: rgba(6, 182, 212, 0.06); color: var(--color-accent); }
.course-sidebar .sidebar-module.current > .sidebar-module-header {
    border-left-color: var(--color-accent);
    color: var(--color-accent);
    background: rgba(6, 182, 212, 0.08);
}
.course-sidebar .sidebar-module-arrow {
    flex-shrink: 0;
    display: inline-block;
    font-size: 10px;
    color: var(--color-text-muted);
    transition: transform 0.15s ease;
}
.course-sidebar .sidebar-module.open > .sidebar-module-header .sidebar-module-arrow { transform: rotate(90deg); }
.course-sidebar .sidebar-module-num { flex-shrink: 0; font-size: 11px; font-weight: 600; color: var(--color-text-muted); }
.course-sidebar .sidebar-module.current .sidebar-module-num { color: var(--color-accent); }
.course-sidebar .sidebar-module-title { flex: 1; min-width: 0; }
.course-sidebar .sidebar-module .sidebar-section-list { margin: 0 0 2px 0; }
.course-learn-layout .chapter-container {
    flex: 1;
    min-width: 0;
    min-height: 0;            /* 关键:允许 flex 子项收缩,内部滚动 */
    max-width: 900px;
    padding: var(--space-lg);
    padding-top: var(--space-lg);
    margin: 0 auto;
    /* 中间正文独立滚动:高度 = nav 下方可视区,顶部粘在 nav 下方 */
    position: sticky;
    top: var(--nav-height);
    height: calc(100vh - var(--nav-height));
    overflow-y: auto;
    box-sizing: border-box;
}

/* ── "完成本节学习"按钮 ── */
.chapter-complete-btn {
    display: block;
    margin: var(--space-lg) auto 0;
    padding: 10px 32px;
    background: transparent;
    color: var(--color-accent);
    border: 1px solid var(--color-accent);
    border-radius: var(--radius-md);
    font-size: 14px;
    cursor: pointer;
    transition: all 0.2s;
}
.chapter-complete-btn:hover:not(:disabled) {
    background: rgba(6, 182, 212, 0.1);
    box-shadow: 0 0 12px rgba(6, 182, 212, 0.3);
}
.chapter-complete-btn:disabled { cursor: default; }
.chapter-complete-btn.completed {
    color: var(--color-success, #10b981);
    border-color: var(--color-success, #10b981);
    background: rgba(16, 185, 129, 0.1);
}

/* ── 章节页"收藏课程"按钮 ── */
.chapter-fav-btn {
    position: absolute;
    top: var(--space-sm);
    right: var(--space-sm);
    padding: 6px 14px;
    background: transparent;
    color: var(--color-text-muted);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    font-size: 13px;
    cursor: pointer;
    transition: all 0.2s;
    z-index: 5;
}
.chapter-fav-btn:hover { color: var(--color-accent); border-color: var(--color-accent); }
.chapter-fav-btn.favorited {
    color: #f59e0b;
    border-color: #f59e0b;
    background: rgba(245, 158, 11, 0.12);
}

/* ── 首页课程卡片收藏按钮 ── */
.course-fav-btn {
    position: absolute;
    top: 10px;
    right: 10px;
    width: 32px;
    height: 32px;
    border-radius: 50%;
    background: rgba(0,0,0,0.55);
    color: var(--color-text-muted);
    border: 1px solid var(--color-border);
    font-size: 16px;
    cursor: pointer;
    z-index: 3;
    transition: all 0.2s;
    display: flex;
    align-items: center;
    justify-content: center;
}
.course-fav-btn:hover { color: #f59e0b; border-color: #f59e0b; }
.course-fav-btn.favorited { color: #f59e0b; border-color: #f59e0b; background: rgba(245,158,11,0.15); }

/* ── AI 助教面板 ── */
.ai-panel {
    width: 300px;
    flex: 0 0 300px;
    background: var(--color-bg-surface);
    border-left: 1px solid var(--color-border);
    display: flex;
    flex-direction: column;
    min-height: 0;            /* 关键:允许内部 flex 子项正确收缩 */
    position: sticky;
    top: var(--nav-height);   /* 顶部粘在 nav 下方,不再被 nav 遮挡 */
    height: calc(100vh - var(--nav-height)); /* 高度 = nav 下方可视区 */
    overflow: hidden;
    transition: margin-right 0.25s ease;
}
.ai-header {
    display: flex; justify-content: space-between; align-items: center;
    padding: 12px 16px;
    border-bottom: 1px solid var(--color-border);
    color: #a78bfa;
    font-weight: 600; font-size: 15px;
    flex-shrink: 0;            /* 顶部工具栏固定,不随消息滚动 */
}
.ai-clear {
    background: transparent; color: var(--color-text-muted);
    border: 1px solid var(--color-border); border-radius: var(--radius-sm);
    font-size: 12px; padding: 2px 8px; cursor: pointer;
}
.ai-clear:hover { color: var(--color-danger, #ef4444); border-color: var(--color-danger, #ef4444); }
.ai-meta {
    padding: 6px 16px; font-size: 12px; color: var(--color-text-muted);
    border-bottom: 1px solid var(--color-border);
    display:flex; flex-direction:column; gap:2px;
    flex-shrink: 0;            /* 固定区,不随消息滚动 */
}
.ai-meta strong { color: var(--color-text); font-weight: 600; }
.ai-quick-actions {
    display: grid; grid-template-columns: 1fr 1fr; gap: 6px;
    padding: 8px 12px; border-bottom: 1px solid var(--color-border);
    flex-shrink: 0;            /* 固定区,不随消息滚动 */
}
.ai-quick-btn {
    padding: 6px 8px; background: var(--color-bg-elevated);
    color: var(--color-text-secondary); border: 1px solid var(--color-border);
    border-radius: var(--radius-sm); font-size: 12px; cursor: pointer;
    transition: all 0.2s; text-align: left;
}
.ai-quick-btn:hover { color: #a78bfa; border-color: #a78bfa; background: rgba(167,139,252,0.08); }
.ai-messages {
    flex: 1;
    min-height: 0;            /* 关键:允许 flex 子项收缩,内部滚动 */
    overflow-y: auto;
    padding: 12px 16px;
    display: flex; flex-direction: column; gap: 10px;
}
.ai-msg { display: flex; flex-direction: column; gap: 4px; }
.ai-msg-role { font-size: 11px; color: var(--color-text-muted); font-weight: 600; }
.ai-msg-user .ai-msg-role { color: var(--color-accent); }
.ai-msg-ai .ai-msg-role { color: #a78bfa; }
.ai-msg-text {
    font-size: 13px; line-height: 1.6; color: var(--color-text);
    background: var(--color-bg-elevated); border-radius: 8px; padding: 8px 10px;
    white-space: pre-wrap; word-break: break-word;
}
.ai-msg-user .ai-msg-text { background: rgba(6,182,212,0.08); border-left: 2px solid var(--color-accent); }
.ai-msg-ai .ai-msg-text { background: rgba(167,139,252,0.08); border-left: 2px solid #a78bfa; }
.ai-thinking .ai-msg-text { color: var(--color-text-muted); font-style: italic; }
.ai-msg-source {
    display: flex; flex-wrap: wrap; gap: 6px 10px;
    margin-top: 6px; padding: 6px 10px;
    font-size: 11px; line-height: 1.4; color: var(--color-text-muted);
    background: rgba(167,139,252,0.04); border-radius: 6px;
    border-left: 2px dashed rgba(167,139,252,0.4);
}
.ai-msg-source .src-line {
    display: inline-flex; align-items: center; gap: 2px;
    white-space: nowrap;
}
.ai-msg-source .src-line-general { color: var(--color-text-muted); font-style: italic; }
.ai-input-area {
    display: flex; gap: 8px; padding: 12px 16px;
    border-top: 1px solid var(--color-border);
    flex-shrink: 0;            /* 底部输入区固定,发送按钮始终可见 */
}
.ai-input {
    flex: 1; resize: vertical; min-height: 40px; max-height: 120px;
    background: var(--color-bg-elevated); color: var(--color-text);
    border: 1px solid var(--color-border); border-radius: var(--radius-sm);
    padding: 8px 10px; font-size: 13px; font-family: inherit; line-height: 1.5;
}
.ai-input:focus { outline: none; border-color: #a78bfa; }
.ai-send {
    align-self: stretch; padding: 0 16px;
    background: #a78bfa; color: #fff; border: none;
    border-radius: var(--radius-sm); cursor: pointer; font-size: 13px; font-weight: 600;
    transition: background 0.2s;
}
.ai-send:hover:not(:disabled) { background: #8b5cf6; }
.ai-send:disabled { opacity: 0.6; cursor: default; }
/* ── 悬浮按钮统一变量(收拢态打开入口定位) ── */
:root {
    --floating-right: 20px;
    --note-toggle-top: 100px;
    --ai-toggle-top: 144px;
}
.ai-toggle {
    /* 收拢态打开入口:右侧中上区域;展开态隐藏(内部 × 负责关闭) */
    position: fixed;
    right: var(--floating-right, 20px);
    top: var(--ai-toggle-top, 260px);
    bottom: auto;
    z-index: 1001;
    width: 36px; height: 36px;
    background: var(--color-bg-surface);
    border: 1px solid var(--color-border);
    border-radius: 8px;
    color: #a78bfa; cursor: pointer;
    display: none;
    align-items: center; justify-content: center;
    transition: top 0.25s ease, background 0.15s, color 0.15s;
}
.ai-toggle:hover { color: #8b5cf6; border-color: #a78bfa; background: rgba(167,139,252,0.08); }
body.ai-collapsed .ai-panel { margin-right: -300px; }
body.ai-collapsed .ai-toggle {
    display: flex;
    right: var(--floating-right, 20px);
    top: var(--ai-toggle-top, 260px);
}
.ai-toggle .icon-expand { display: none; }
body.ai-collapsed .ai-toggle .icon-collapse { display: none; }
body.ai-collapsed .ai-toggle .icon-expand { display: inline; }
/* AI 内部关闭按钮(标题栏右上角,紧跟清空按钮) */
.ai-close {
    background: transparent; color: var(--color-text-muted);
    border: 1px solid var(--color-border); border-radius: var(--radius-sm);
    font-size: 16px; line-height: 1; padding: 2px 8px; cursor: pointer;
    transition: color 0.15s, border-color 0.15s;
}
.ai-close:hover { color: var(--color-danger, #ef4444); border-color: var(--color-danger, #ef4444); }
@media (max-width: 1200px) { .ai-panel { display: none; } .ai-toggle { display: none; } }

/* ── AI 助教 · 模式按钮 + 限额 + Markdown + 代码块复制 + 错误提示 ── */
.ai-header-right { display: flex; align-items: center; gap: 8px; }
.ai-quota {
    font-size: 11px; color: var(--color-text-muted);
    padding: 2px 8px; border: 1px solid var(--color-border);
    border-radius: 10px; background: var(--color-bg-elevated);
    white-space: nowrap;
}
.ai-quota.low { color: var(--color-warning, #f59e0b); border-color: var(--color-warning, #f59e0b); }
.ai-quota.empty { color: var(--color-danger, #ef4444); border-color: var(--color-danger, #ef4444); }

.ai-mode-actions {
    display: grid; grid-template-columns: 1fr 1fr 1fr; gap: 4px;
    padding: 6px 12px; border-bottom: 1px solid var(--color-border);
    flex-shrink: 0;            /* 模式切换栏固定,不随消息滚动 */
}
.ai-mode-btn {
    padding: 6px 4px; background: var(--color-bg-elevated);
    color: var(--color-text-secondary); border: 1px solid var(--color-border);
    border-radius: var(--radius-sm); font-size: 12px; cursor: pointer;
    transition: all 0.15s; text-align: center;
}
.ai-mode-btn:hover { color: #a78bfa; border-color: #a78bfa; }
.ai-mode-btn.active {
    color: #fff; background: #a78bfa; border-color: #a78bfa;
    box-shadow: 0 1px 4px rgba(167,139,252,0.35);
}

/* AI 消息文本:覆盖 white-space,允许 Markdown 子元素分行 */
.ai-msg-ai .ai-msg-text.ai-md { white-space: normal; }
.ai-msg-text p { margin: 0 0 6px 0; }
.ai-msg-text p:last-child { margin-bottom: 0; }
.ai-msg-text .ai-md-h {
    margin: 8px 0 4px 0; font-weight: 700; line-height: 1.4;
    color: var(--color-text);
}
.ai-msg-text .ai-md-h1 { font-size: 15px; }
.ai-msg-text .ai-md-h2 { font-size: 14px; }
.ai-msg-text .ai-md-h3 { font-size: 13px; }
.ai-msg-text ul.ai-md-ul,
.ai-msg-text ol.ai-md-ol {
    margin: 4px 0 6px 18px; padding: 0;
}
.ai-msg-text ul.ai-md-ul { list-style: disc; }
.ai-msg-text ol.ai-md-ol { list-style: decimal; }
.ai-msg-text ul.ai-md-ul li,
.ai-msg-text ol.ai-md-ol li { margin: 2px 0; }
.ai-msg-text .ai-md-inline-code {
    font-family: var(--font-mono);
    background: rgba(167,139,252,0.12);
    color: #c4b5fd;
    padding: 1px 4px; border-radius: 3px; font-size: 12px;
}
.ai-msg-text a { color: var(--color-accent); text-decoration: underline; }

/* 代码块 + 复制按钮 */
.ai-md-code-block {
    margin: 6px 0; border: 1px solid var(--color-border);
    border-radius: 6px; overflow: hidden;
    background: var(--color-bg-elevated);
}
.ai-md-code-bar {
    display: flex; justify-content: space-between; align-items: center;
    padding: 4px 8px; font-size: 11px; color: var(--color-text-muted);
    background: rgba(167,139,252,0.06);
    border-bottom: 1px solid var(--color-border);
}
.ai-md-code-lang { font-family: var(--font-mono); }
.ai-md-copy {
    background: transparent; border: 1px solid var(--color-border);
    color: var(--color-text-muted); font-size: 11px;
    padding: 1px 8px; border-radius: 3px; cursor: pointer;
    transition: all 0.15s;
}
.ai-md-copy:hover { color: #a78bfa; border-color: #a78bfa; }
.ai-md-code-block pre {
    margin: 0; padding: 8px 10px; overflow-x: auto;
    background: var(--color-bg-elevated);
}
.ai-md-code-block code {
    font-family: var(--font-mono); font-size: 12px;
    color: var(--color-text); white-space: pre;
}

/* 加载动画(AI 正在思考) */
.ai-thinking .ai-msg-text {
    display: flex; align-items: center; gap: 6px;
    color: var(--color-text-muted); font-style: italic;
}
.ai-thinking-dot {
    width: 6px; height: 6px; border-radius: 50%;
    background: #a78bfa; display: inline-block;
    animation: ai-thinking-pulse 1.2s ease-in-out infinite;
}
@keyframes ai-thinking-pulse {
    0%, 100% { opacity: 0.3; transform: scale(0.8); }
    50% { opacity: 1; transform: scale(1.2); }
}

/* 错误提示 */
.ai-msg.ai-error .ai-msg-text.ai-error-text {
    background: rgba(239,68,68,0.08);
    border-left: 2px solid var(--color-danger, #ef4444);
    color: var(--color-danger, #ef4444);
}

/* "回答依据"细分颜色 */
.ai-msg-source .src-course { color: #60a5fa; }
.ai-msg-source .src-chapter { color: #34d399; }
.ai-msg-source .src-subchapter { color: #a78bfa; }
.ai-msg-source .src-blocks { color: var(--color-text-muted); }

/* ── 右侧笔记面板 ── */
.course-note-panel {
    width: 280px;
    flex-shrink: 0;
    position: sticky;
    top: var(--nav-height);   /* 顶部粘在 nav 下方,不再被 nav 遮挡 */
    height: calc(100vh - var(--nav-height)); /* 高度 = nav 下方可视区 */
    background: var(--color-bg-surface);
    border: 1px solid var(--color-border);
    border-radius: 0;
    display: flex;
    flex-direction: column;
    min-height: 0;            /* 关键:允许内部 flex 子项正确收缩 */
    box-sizing: border-box;
    transition: margin-right 0.25s ease;
}
body.note-collapsed .course-note-panel { margin-right: -280px; }
.note-toggle {
    /* 收拢态打开入口:右侧中上区域,在 AI 按钮上方(笔记 top:160, AI top:260,间距 100px>60px);展开态隐藏 */
    position: fixed;
    right: var(--floating-right, 20px);
    top: var(--note-toggle-top, 160px);
    bottom: auto;
    width: auto;
    min-width: 36px;
    height: 36px;
    background: var(--color-bg-elevated);
    border: 1px solid var(--color-border);
    border-radius: 8px;
    color: var(--color-text-muted);
    font-size: 14px;
    cursor: pointer;
    z-index: 1001;
    padding: 0 10px;
    display: none;
    align-items: center; justify-content: center;
    transition: top 0.25s ease, background 0.15s, color 0.15s;
}
.note-toggle:hover { color: var(--color-accent); background: rgba(6, 182, 212, 0.1); border-color: var(--color-accent); }
.note-toggle .icon-expand { display: none; margin-left: 4px; }
.note-toggle .icon-collapse { display: inline; }
body.note-collapsed .note-toggle {
    display: flex;
    right: var(--floating-right, 20px);
    top: var(--note-toggle-top, 160px);
}
body.note-collapsed .note-toggle .icon-collapse { display: none; }
body.note-collapsed .note-toggle .icon-expand { display: inline; }
.note-header {
    display: flex; justify-content: space-between; align-items: center;
    padding: 12px 16px 4px 16px;
    color: var(--color-accent);
    font-weight: 600;
    font-size: 14px;
    flex-shrink: 0;            /* 顶部标题栏固定,始终可见 */
}
.note-header-right { display: flex; gap: 8px; align-items: center; }
.note-clear {
    background: transparent; color: var(--color-text-muted);
    border: 1px solid var(--color-border); border-radius: var(--radius-sm);
    font-size: 12px; padding: 2px 8px; cursor: pointer;
    transition: color 0.15s, border-color 0.15s;
}
.note-clear:hover { color: var(--color-danger, #ef4444); border-color: var(--color-danger, #ef4444); }
.note-close {
    background: transparent; color: var(--color-text-muted);
    border: 1px solid var(--color-border); border-radius: var(--radius-sm);
    font-size: 16px; line-height: 1; padding: 2px 8px; cursor: pointer;
    transition: color 0.15s, border-color 0.15s;
}
.note-close:hover { color: var(--color-danger, #ef4444); border-color: var(--color-danger, #ef4444); }
.note-meta {
    padding: 0 16px 8px 16px;
    color: var(--color-text-muted);
    font-size: 11px;
    border-bottom: 1px solid var(--color-border);
    flex-shrink: 0;            /* 固定区,不随笔记内容滚动 */
}
.note-textarea {
    flex: 1;
    min-height: 0;            /* 关键:允许 flex 子项收缩,textarea 自身滚动 */
    width: 100%;
    border: none;
    background: transparent;
    color: var(--color-text);
    padding: 12px 16px;
    font-size: 13px;
    line-height: 1.6;
    font-family: var(--font-mono);
    resize: none;
    outline: none;
    box-sizing: border-box;
    /* textarea 自带 overflow,内容多时只在此区域滚动 */
    overflow-y: auto;
}
.note-textarea::placeholder { color: var(--color-text-muted); font-style: italic; }
.note-footer {
    padding: 8px 16px;
    border-top: 1px solid var(--color-border);
    background: var(--color-bg-elevated);
    flex-shrink: 0;            /* 底部状态栏固定,"已保存"始终可见 */
}
.note-status { font-size: 11px; color: var(--color-text-muted); }
.note-status.saving { color: var(--color-warning); }

/* ── 响应式 ── */
@media (max-width: 1100px) {
    .course-note-panel { display: none; }
    body.note-collapsed .course-note-panel { display: none; }
}
@media (max-width: 900px) {
    .course-sidebar {
        position: fixed;
        left: 0;
        top: var(--nav-height);  /* 移动端也对齐 nav 下方,顶部不被遮挡 */
        z-index: 100;
        height: calc(100vh - var(--nav-height));
    }
    body:not(.sidebar-collapsed) .course-sidebar {
        box-shadow: var(--shadow-lg);
    }
    .course-learn-layout .chapter-container {
        padding: var(--space-md);
    }
}

/* 跨课程跳转链接(如 pthread 章节 → C++ 并发篇) */
.cross-ref {
    color: var(--color-accent-dark);
    font-weight: 600;
    text-decoration: none;
    border-bottom: 1.5px dashed var(--color-accent);
}
.cross-ref:hover {
    color: var(--color-accent);
}