/* ==========================================
   电子课本样式 — 数学必修一（高一）
   等宽字体 · 国内 CDN · 仿纸质书排版
   ========================================== */

/* 从国内 CDN 加载等宽字体（霞鹜文楷等宽） */
@import url('https://unpkg.zhimg.com/lxgw-wenkai-webfont@1.7.0/style.css');

/* ---------- 重置与基础 ---------- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  /* 配色方案 — 暖色调纸质书风格 */
  --bg-page: #f8f6f0;
  --bg-sidebar: #2c3e50;
  --bg-sidebar-hover: #34495e;
  --bg-active: #3498db;
  --bg-card: #ffffff;
  --text-primary: #2c3e50;
  --text-secondary: #5a6a7a;
  --text-sidebar: #ecf0f1;
  --text-sidebar-dim: #95a5a6;
  --text-sidebar-active: #ffffff;
  --border-light: #e8e4dc;
  --accent: #2980b9;
  --accent-light: #ebf5fb;
  --shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 4px 20px rgba(0, 0, 0, 0.12);
  --radius: 6px;

  /* 字体 — 等宽 */
  --font-body: 'LXGW WenKai Mono', 'JetBrains Mono', 'Source Han Mono SC', 'Noto Sans Mono CJK SC', 'Consolas', 'Courier New', monospace;
  --font-heading: 'LXGW WenKai Mono', 'JetBrains Mono', 'Source Han Mono SC', 'Noto Sans Mono CJK SC', 'Consolas', 'Courier New', monospace;
  --font-ui: 'LXGW WenKai Mono', 'JetBrains Mono', 'Source Han Mono SC', 'Noto Sans Mono CJK SC', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  --font-mono: 'Consolas', 'Courier New', monospace;

  /* 尺寸 */
  --sidebar-width: 280px;
  --content-max-width: 780px;
  --header-height: 0px;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-ui);
  background: var(--bg-page);
  color: var(--text-primary);
  line-height: 1.8;
  min-height: 100vh;
}

/* ---------- 布局 ---------- */
.layout {
  display: flex;
  min-height: 100vh;
}

/* ---------- 侧边栏 ---------- */
.sidebar-nav {
  width: var(--sidebar-width);
  min-width: var(--sidebar-width);
  background: var(--bg-sidebar);
  color: var(--text-sidebar);
  overflow-y: auto;
  position: fixed;
  top: 0;
  left: 0;
  bottom: 0;
  z-index: 100;
  scrollbar-width: thin;
  scrollbar-color: rgba(255,255,255,0.2) transparent;
}

.sidebar-nav::-webkit-scrollbar {
  width: 5px;
}
.sidebar-nav::-webkit-scrollbar-thumb {
  background: rgba(255,255,255,0.2);
  border-radius: 3px;
}

.sidebar-header {
  padding: 24px 20px 16px;
  border-bottom: 1px solid rgba(255,255,255,0.1);
}

.sidebar-header h2 {
  font-family: var(--font-heading);
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-sidebar);
  margin: 0;
}

.sidebar-subtitle {
  font-size: 0.8rem;
  color: var(--text-sidebar-dim);
  margin-top: 4px;
}

.chapter-list {
  list-style: none;
  padding: 12px 0;
}

.chapter-item {
  margin-bottom: 4px;
}

.chapter-label {
  font-family: var(--font-ui);
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--text-sidebar-dim);
  padding: 12px 20px 2px;
  font-weight: 600;
}

.chapter-title {
  font-family: var(--font-heading);
  font-size: 0.85rem;
  color: var(--text-sidebar);
  padding: 0 20px 6px;
  font-weight: 600;
}

.section-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.section-list li {
  position: relative;
}

.section-list a {
  display: block;
  padding: 5px 20px 5px 32px;
  font-size: 0.82rem;
  color: var(--text-sidebar);
  text-decoration: none;
  transition: all 0.2s ease;
  border-left: 3px solid transparent;
}

.section-list a:hover {
  background: var(--bg-sidebar-hover);
  color: var(--text-sidebar-active);
  border-left-color: var(--bg-active);
}

.section-list li.active a {
  background: var(--bg-active);
  color: var(--text-sidebar-active);
  border-left-color: #fff;
  font-weight: 600;
}

/* ---------- 主内容区 ---------- */
.main-content {
  flex: 1;
  margin-left: var(--sidebar-width);
  padding: 0;
  min-height: 100vh;
}

.content-body {
  max-width: var(--content-max-width);
  margin: 0 auto;
  padding: 40px 48px 60px;
  font-family: var(--font-body);
  font-size: 1rem;
  line-height: 2.1;
  color: var(--text-primary);
}

/* ---------- 页眉导航 ---------- */
.page-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  padding: 14px 48px;
  background: var(--bg-card);
  border-bottom: 1px solid var(--border-light);
  font-family: var(--font-ui);
  font-size: 0.85rem;
  position: sticky;
  top: 0;
  z-index: 50;
  box-shadow: 0 1px 3px rgba(0,0,0,0.04);
}

.page-nav a {
  color: var(--accent);
  text-decoration: none;
  transition: color 0.2s;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.page-nav a:hover {
  color: #1a5276;
  text-decoration: underline;
}

.nav-home {
  font-weight: 600;
  flex-shrink: 0;
}

.nav-prev, .nav-next {
  max-width: 40%;
}

.disabled {
  color: var(--text-sidebar-dim) !important;
  font-style: italic;
  cursor: default;
}

/* ---------- 内容排版 ---------- */
.content-body h1,
.content-body h2,
.content-body h3,
.content-body h4 {
  font-family: var(--font-heading);
  font-weight: 700;
  color: #1a1a2e;
  line-height: 1.4;
  margin-top: 1.8em;
  margin-bottom: 0.6em;
}

.content-body h1 {
  font-size: 1.8rem;
  border-bottom: 2px solid var(--accent);
  padding-bottom: 0.3em;
  margin-top: 0.5em;
}

.content-body h2 {
  font-size: 1.4rem;
  color: var(--accent);
}

.content-body h3 {
  font-size: 1.15rem;
  color: #34495e;
}

.content-body h4 {
  font-size: 1.05rem;
  color: #5a6a7a;
}

/* 段落 */
.content-body p {
  margin: 0.8em 0;
  text-align: justify;
  text-indent: 2em;
}

/* 强调文本 */
.content-body strong {
  color: #1a1a2e;
  font-weight: 700;
}

/* 列表 */
.content-body ul, .content-body ol {
  margin: 0.6em 0 0.6em 2em;
  padding: 0;
}

.content-body li {
  margin: 0.3em 0;
}

/* ---------- KaTeX 公式 ---------- */
.content-body .katex {
  font-size: 1.05em;
  line-height: 1.4;
}

.content-body .katex-display {
  margin: 1.2em 0;
  padding: 0.6em 0;
  overflow-x: auto;
  overflow-y: hidden;
  text-align: center;
  background: rgba(255, 255, 255, 0.6);
  border-radius: 4px;
}

.content-body .katex-error {
  color: #e74c3c;
  background: #fdf0ef;
  padding: 2px 6px;
  border-radius: 3px;
  font-family: var(--font-mono);
  font-size: 0.85rem;
}

/* ---------- 图片 ---------- */
.content-body img {
  display: block;
  max-width: 100%;
  height: auto;
  margin: 1.2em auto;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  transition: box-shadow 0.3s ease;
}

.content-body img:hover {
  box-shadow: var(--shadow-lg);
}

/* 图片旁的说明文字（如果有的话） */
.content-body img + em {
  display: block;
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-top: -0.5em;
  margin-bottom: 1em;
}

/* ---------- 代码 ---------- */
.content-body code {
  font-family: var(--font-mono);
  font-size: 0.88em;
  background: #f0eee8;
  padding: 1px 5px;
  border-radius: 3px;
  color: #c0392b;
}

.content-body pre {
  background: #2c3e50;
  color: #ecf0f1;
  padding: 1em 1.2em;
  border-radius: var(--radius);
  overflow-x: auto;
  font-size: 0.85rem;
  line-height: 1.6;
  margin: 1em 0;
}

.content-body pre code {
  background: none;
  color: inherit;
  padding: 0;
  font-size: inherit;
}

/* ---------- 引用 ---------- */
.content-body blockquote {
  margin: 1em 0;
  padding: 0.5em 1em;
  border-left: 4px solid var(--accent);
  background: var(--accent-light);
  border-radius: 0 var(--radius) var(--radius) 0;
  color: #2c3e50;
}

.content-body blockquote p {
  text-indent: 0;
  margin: 0.3em 0;
}

/* ---------- 分割线 ---------- */
.content-body hr {
  border: none;
  border-top: 1px solid var(--border-light);
  margin: 2em 0;
}

/* ---------- 表格 ---------- */
.content-body table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.2em 0;
  font-size: 0.92rem;
}

.content-body th,
.content-body td {
  padding: 8px 12px;
  border: 1px solid var(--border-light);
  text-align: center;
}

.content-body th {
  background: #f0eee8;
  font-weight: 700;
  color: #2c3e50;
}

.content-body tr:nth-child(even) {
  background: #faf8f4;
}

/* ==========================================
   目录页面
   ========================================== */
.toc-page .content-body {
  max-width: 860px;
}

.toc-page h1 {
  font-family: var(--font-heading);
  font-size: 2.2rem;
  text-align: center;
  border-bottom: none;
  margin-top: 0.5em;
  margin-bottom: 0.2em;
  color: #1a1a2e;
}

.toc-intro {
  text-align: center;
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-bottom: 0.5em;
}

.toc-intro,
.toc-stats {
  text-align: center !important;
  text-indent: 0 !important;
}

.toc-stats {
  text-align: center;
  color: var(--text-sidebar-dim);
  font-size: 0.85rem;
  margin-bottom: 2em;
}

.toc-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 24px;
  margin-top: 1.5em;
}

.toc-chapter {
  background: var(--bg-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  overflow: hidden;
  transition: box-shadow 0.3s ease;
}

.toc-chapter:hover {
  box-shadow: var(--shadow-lg);
}

.toc-chapter-header {
  background: var(--accent);
  color: white;
  padding: 16px 20px;
}

.toc-chapter-label {
  font-family: var(--font-ui);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  opacity: 0.85;
}

.toc-chapter-header h2 {
  font-family: var(--font-heading);
  font-size: 1.1rem;
  margin: 4px 0 0;
  color: white;
  border: none;
  padding: 0;
}

.toc-section-list {
  list-style: none;
  padding: 8px 0;
}

.toc-section-list li {
  border-bottom: 1px solid var(--border-light);
}

.toc-section-list li:last-child {
  border-bottom: none;
}

.toc-section-list a {
  display: block;
  padding: 8px 20px;
  color: var(--text-primary);
  text-decoration: none;
  font-size: 0.9rem;
  transition: all 0.2s ease;
}

.toc-section-list a:hover {
  background: var(--accent-light);
  color: var(--accent);
  padding-left: 28px;
}

/* ---------- 页脚 ---------- */
.page-footer {
  text-align: center;
  padding: 24px 48px;
  color: var(--text-sidebar-dim);
  font-size: 0.8rem;
  border-top: 1px solid var(--border-light);
  margin-top: 2em;
}

/* ==========================================
   侧边栏返回首页链接
   ========================================== */
.sidebar-home-link {
  display: inline-block;
  margin-top: 10px;
  font-family: var(--font-ui);
  font-size: 0.78rem;
  color: var(--text-sidebar-dim);
  text-decoration: none;
  transition: color 0.2s;
}

.sidebar-home-link:hover {
  color: var(--text-sidebar-active);
  text-decoration: underline;
}

/* ==========================================
   教材目录页 - 返回首页链接
   ========================================== */
.back-to-home {
  display: inline-block;
  margin-bottom: 1.5em;
  font-family: var(--font-ui);
  font-size: 0.9rem;
  color: var(--accent);
  text-decoration: none;
}

.back-to-home:hover {
  text-decoration: underline;
}

/* ==========================================
   教材聚合首页 - 卡片网格
   ========================================== */
.layout-home .main-content {
  margin-left: 0 !important;
}

.textbook-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 24px;
  margin-top: 1.5em;
}

.textbook-card {
  display: block;
  background: var(--bg-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  text-decoration: none;
  color: inherit;
  overflow: hidden;
  transition: all 0.3s ease;
  border-left: 4px solid var(--accent, #2980b9);
}

.textbook-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-3px);
}

.textbook-card-header {
  padding: 20px 20px 12px;
}

.textbook-icon {
  font-size: 2rem;
  display: block;
  margin-bottom: 8px;
}

.textbook-card-header h2 {
  font-family: var(--font-heading);
  font-size: 1.15rem;
  margin: 0;
  color: #1a1a2e;
}

.textbook-subtitle {
  font-size: 0.8rem;
  color: var(--text-secondary);
  margin-top: 4px;
}

.textbook-card-body {
  padding: 0 20px 16px;
}

.textbook-card-body p {
  font-size: 0.85rem;
  color: var(--text-secondary);
  line-height: 1.6;
  margin: 0;
}

.textbook-stats {
  margin-top: 8px !important;
  font-size: 0.78rem !important;
  color: var(--text-sidebar-dim) !important;
}

@media (max-width: 640px) {
  .textbook-grid {
    grid-template-columns: 1fr;
  }
}

/* ==========================================
   响应式：窄屏适配
   ========================================== */
@media (max-width: 900px) {
  :root {
    --sidebar-width: 240px;
  }

  .content-body {
    padding: 24px 28px 40px;
  }

  .page-nav {
    padding: 10px 20px;
    flex-wrap: wrap;
  }

  .nav-prev, .nav-next {
    max-width: 35%;
    font-size: 0.8rem;
  }
}

@media (max-width: 640px) {
  .layout {
    flex-direction: column;
  }

  .sidebar-nav {
    position: relative;
    width: 100%;
    min-width: 100%;
    height: auto;
    max-height: 35vh;
    border-right: none;
    border-bottom: 2px solid rgba(255,255,255,0.1);
  }

  .main-content {
    margin-left: 0;
  }

  .content-body {
    padding: 20px 16px 32px;
    font-size: 1rem;
  }

  .page-nav {
    padding: 10px 16px;
    flex-wrap: wrap;
  }

  .toc-grid {
    grid-template-columns: 1fr;
  }
}