/* ===================================
   Excel Learn - 2026 现代 CSS 样式
   Excel 主题配色，现代化设计
   =================================== */

/* ===================================
   CSS 层叠层（Cascade Layers）
   =================================== */
@layer reset, base, layout, components, utilities;

/* ===================================
   CSS 变量（Excel 主题）
   =================================== */
:root {
  /* Excel 主题色 */
  --excel-green: #107c41;
  --excel-green-light: #21a366;
  --excel-green-dark: #0b5a32;
  --excel-bg: #f3f2f1;
  --excel-surface: #ffffff;
  --excel-border: #e1dfdd;
  --excel-header: #f8f9fa;
  --excel-cell-hover: #e6f2ea;
  --excel-selection: #cce8d6;

  /* 主色调 - Excel 绿 */
  --primary-color: #107c41;
  --primary-light: #21a366;
  --primary-dark: #0b5a32;
  --secondary-color: #2b88d8;
  --accent-color: #d83b01;
  --accent-light: #ea4300;

  /* AI 主题色 */
  --ai-gradient-start: #667eea;
  --ai-gradient-end: #764ba2;

  /* 文本颜色 */
  --text-primary: #24292e;
  --text-secondary: #586069;
  --text-tertiary: #6a737d;
  --text-inverse: #ffffff;

  /* 背景颜色 */
  --bg-primary: #ffffff;
  --bg-secondary: #f3f2f1;
  --bg-alt: #e6f2ea;
  --bg-elevated: #ffffff;
  --bg-code: #1d1f23;

  /* 边框颜色 */
  --border-color: #e1dfdd;
  --border-color-dark: #c8c6c4;

  /* 阴影 */
  --shadow-xs: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-sm: 0 2px 4px 0 rgba(16, 124, 65, 0.1);
  --shadow-md: 0 4px 8px 0 rgba(16, 124, 65, 0.12);
  --shadow-lg: 0 8px 16px 0 rgba(16, 124, 65, 0.15);
  --shadow-xl: 0 12px 24px 0 rgba(16, 124, 65, 0.2);

  /* 圆角 */
  --radius-sm: 4px;
  --radius-md: 6px;
  --radius-lg: 8px;
  --radius-xl: 12px;
  --radius-2xl: 16px;
  --radius-full: 9999px;

  /* 过渡 */
  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-base: 300ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 500ms cubic-bezier(0.4, 0, 0.2, 1);

  /* 字体 */
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'Noto Sans SC', sans-serif;
  --font-mono: 'Consolas', 'Monaco', 'Courier New', monospace;

  /* 容器最大宽度 */
  --container-max: 1400px;

  /* 安全区域 */
  --safe-area-top: env(safe-area-inset-top, 0px);
  --safe-area-bottom: env(safe-area-inset-bottom, 0px);
  --safe-area-left: env(safe-area-inset-left, 0px);
  --safe-area-right: env(safe-area-inset-right, 0px);
}

/* ===================================
   Reset 层
   =================================== */
@layer reset {
  *, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
  }

  html {
    -webkit-text-size-adjust: 100%;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    scroll-behavior: smooth;
    scroll-padding-top: calc(80px + var(--safe-area-top));
  }

  body {
    min-height: 100vh;
    min-height: 100dvh;
    font-family: var(--font-sans);
    font-size: 16px;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-primary);
    overflow-x: hidden;
  }

  img, picture, video, canvas, svg {
    display: block;
    max-width: 100%;
  }

  input, button, textarea, select {
    font: inherit;
  }

  button {
    cursor: pointer;
    border: none;
    background: none;
  }

  ul, ol {
    list-style: none;
  }

  a {
    color: var(--primary-color);
    text-decoration: none;
    transition: color var(--transition-fast);

    &:hover {
      color: var(--primary-dark);
      text-decoration: underline;
    }
  }

  pre, code {
    font-family: var(--font-mono);
  }

  ::selection {
    background-color: var(--excel-selection);
    color: var(--text-primary);
  }

  :focus-visible {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
  }
}

/* ===================================
   Base 层
   =================================== */
@layer base {
  h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.2;
    color: var(--text-primary);
  }

  h1 { font-size: clamp(2rem, 5vw, 3.5rem); }
  h2 { font-size: clamp(1.5rem, 4vw, 2.5rem); }
  h3 { font-size: clamp(1.25rem, 3vw, 1.75rem); }
  h4 { font-size: clamp(1.1rem, 2.5vw, 1.25rem); }

  p {
    margin-bottom: 1rem;
    color: var(--text-secondary);
  }

  strong {
    font-weight: 600;
    color: var(--text-primary);
  }

  code {
    background-color: var(--bg-secondary);
    padding: 0.2rem 0.4rem;
    border-radius: var(--radius-sm);
    font-size: 0.85em;
    color: var(--text-primary);
    border: 1px solid var(--border-color);
  }

  pre {
    background-color: #f8f9fa;
    padding: 1rem;
    border-radius: var(--radius-md);
    overflow-x: auto;
    color: var(--text-primary);
    border: 1px solid var(--border-color);
  }

  pre code {
    background: none;
    padding: 0;
    color: inherit;
    border: none;
  }

  table {
    width: 100%;
    border-collapse: collapse;
    margin: 1rem 0;
  }

  th, td {
    padding: 0.75rem 1rem;
    text-align: left;
    border: 1px solid var(--border-color);
  }

  th {
    background-color: var(--excel-header);
    font-weight: 600;
    color: var(--text-primary);
  }

  td {
    color: var(--text-secondary);
  }

  tr:nth-child(even) {
    background-color: var(--bg-secondary);
  }

  tr:hover {
    background-color: var(--excel-cell-hover);
  }
}

/* ===================================
   Layout 层
   =================================== */
@layer layout {
  .container {
    width: 100%;
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 1.5rem;

    container-type: inline-size;
    container-name: main-container;
  }

  .section {
    padding: clamp(3rem, 8vw, 6rem) 0;
  }

  .section-alt {
    background-color: var(--bg-secondary);
  }

  .section-title {
    text-align: center;
    font-size: clamp(1.75rem, 4vw, 2.5rem);
    margin-bottom: 1rem;
    color: var(--text-primary);
    position: relative;
  }

  .section-title::after {
    content: '';
    display: block;
    width: 60px;
    height: 4px;
    background: var(--primary-color);
    margin: 1rem auto 0;
    border-radius: var(--radius-full);
  }

  .section-description {
    text-align: center;
    font-size: clamp(1rem, 2vw, 1.25rem);
    color: var(--text-secondary);
    max-width: 800px;
    margin: 0 auto 3rem;
  }
}

/* ===================================
   Components 层
   =================================== */
@layer components {
  /* ========== 导航栏 ========== */
  .navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background-color: rgba(255, 255, 255, 0.98);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    box-shadow: 0 2px 8px rgba(16, 124, 65, 0.1);
    z-index: 1000;
    transition: all var(--transition-base);
    border-bottom: 2px solid var(--excel-green);
  }

  .navbar .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 1.5rem;
    height: 70px;
  }

  .nav-brand {
    font-size: 1.5rem;
    font-weight: 800;
    display: flex;
    align-items: center;
    gap: 0.5rem;
  }

  .logo {
    color: var(--text-primary);
  }

  .highlight {
    color: var(--excel-green);
  }

  .nav-menu {
    display: flex;
    gap: 2rem;
  }

  .nav-menu a {
    font-weight: 500;
    color: var(--text-secondary);
    transition: color var(--transition-fast);
    position: relative;

    &:hover {
      color: var(--excel-green);
    }

    &::after {
      content: '';
      position: absolute;
      bottom: -5px;
      left: 0;
      width: 0;
      height: 2px;
      background: var(--excel-green);
      transition: width var(--transition-base);
    }

    &:hover::after {
      width: 100%;
    }
  }

  .mobile-menu-btn {
    display: none;
    flex-direction: column;
    gap: 5px;
    padding: 5px;

    span {
      width: 25px;
      height: 3px;
      background-color: var(--text-primary);
      border-radius: var(--radius-full);
      transition: all var(--transition-fast);
    }
  }

  /* ========== Hero 区域 ========== */
  .hero {
    padding: calc(120px + var(--safe-area-top)) 0 4rem;
    background: linear-gradient(135deg, #f3f2f1 0%, #e6f2ea 100%);
    border-bottom: 1px solid var(--border-color);
    color: var(--text-primary);
    text-align: center;
    position: relative;
    overflow: hidden;
  }

  .hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: 
      linear-gradient(135deg, rgba(16, 124, 65, 0.05) 0%, transparent 50%),
      repeating-linear-gradient(
        0deg,
        transparent,
        transparent 40px,
        rgba(16, 124, 65, 0.03) 40px,
        rgba(16, 124, 65, 0.03) 41px
      );
    pointer-events: none;
  }

  .hero-title {
    font-size: clamp(2.5rem, 8vw, 4.5rem);
    font-weight: 800;
    margin-bottom: 0.5rem;
    animation: fadeInUp 0.8s ease-out;
    color: var(--excel-green-dark);
    position: relative;
  }

  .hero-subtitle {
    font-size: clamp(1.25rem, 3vw, 1.75rem);
    margin-bottom: 0.75rem;
    animation: fadeInUp 0.8s ease-out 0.2s both;
    color: var(--text-secondary);
  }

  .hero-description {
    font-size: clamp(1rem, 2vw, 1.25rem);
    margin-bottom: 2rem;
    animation: fadeInUp 0.8s ease-out 0.4s both;
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
    color: var(--text-secondary);
  }

  .hero-buttons {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
    animation: fadeInUp 0.8s ease-out 0.6s both;
  }

  .hero-stats {
    display: flex;
    gap: 3rem;
    justify-content: center;
    margin-top: 4rem;
    animation: fadeInUp 0.8s ease-out 0.8s both;
    flex-wrap: wrap;
  }

  .stat-item {
    text-align: center;
  }

  .stat-number {
    display: block;
    font-size: 2.5rem;
    font-weight: 800;
    color: var(--excel-green);
  }

  .stat-label {
    display: block;
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-top: 0.25rem;
  }

  /* ========== 按钮 ========== */
  .btn {
    padding: 0.875rem 2rem;
    border-radius: var(--radius-md);
    font-weight: 600;
    font-size: 1.05rem;
    transition: all var(--transition-base);
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    border: 2px solid transparent;

    &:hover {
      transform: translateY(-2px);
      box-shadow: var(--shadow-md);
      text-decoration: none;
    }

    &:active {
      transform: translateY(0);
    }
  }

  .btn-primary {
    background: linear-gradient(135deg, var(--excel-green) 0%, var(--excel-green-light) 100%);
    color: white;

    &:hover {
      background: linear-gradient(135deg, var(--excel-green-dark) 0%, var(--excel-green) 100%);
      box-shadow: 0 6px 20px rgba(16, 124, 65, 0.3);
    }
  }

  .btn-secondary {
    background-color: transparent;
    color: var(--excel-green);
    border: 2px solid var(--excel-green);

    &:hover {
      background-color: var(--excel-green);
      color: white;
    }
  }

  /* ========== Excel 卡片 ========== */
  .excel-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
    margin: 2rem 0;
  }

  .excel-card {
    background: var(--excel-surface);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    transition: all var(--transition-base);
    position: relative;
    overflow: hidden;
    opacity: 0;
    transform: translateY(20px);

    &.visible {
      opacity: 1;
      transform: translateY(0);
    }

    &::before {
      content: '';
      position: absolute;
      top: 0;
      left: 0;
      right: 0;
      height: 4px;
      background: linear-gradient(90deg, var(--excel-green) 0%, var(--excel-green-light) 100%);
      transform: scaleX(0);
      transition: transform var(--transition-base);
    }

    &:hover {
      box-shadow: var(--shadow-lg);
      transform: translateY(-4px);
      border-color: var(--excel-green);
    }

    &:hover::before {
      transform: scaleX(1);
    }

    h3 {
      color: var(--excel-green);
      margin-bottom: 0.75rem;
      display: flex;
      align-items: center;
      gap: 0.5rem;
    }
  }

  /* ========== 函数卡片 ========== */
  .function-card {
    border-left: 4px solid var(--excel-green);
    border-top: none;

    &::before {
      height: 0;
    }

    &:hover::before {
      transform: scaleX(0);
    }
  }

  .function-syntax {
    background: #f8f9fa;
    padding: 1rem;
    border-radius: var(--radius-sm);
    font-family: var(--font-mono);
    font-size: 0.85rem;
    margin: 1rem 0;
    border: 1px solid var(--border-color);
    overflow-x: auto;

    code {
      color: var(--excel-green-dark);
      white-space: pre-wrap;
      word-break: break-all;
    }
  }

  /* ========== 版本标签 ========== */
  .version-badge {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-full);
    font-size: 0.75rem;
    font-weight: 600;
    margin-left: 0.5rem;
    vertical-align: middle;
  }

  .version-new {
    background: linear-gradient(135deg, #d4edda 0%, #c3e6cb 100%);
    color: #155724;
  }

  .version-2026 {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
  }

  /* ========== 信息框 ========== */
  .info-box {
    background-color: var(--bg-secondary);
    border-left: 4px solid var(--primary-color);
    padding: 1.5rem;
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    margin: 2rem 0;
    border: 1px solid var(--border-color);

    h3 {
      font-size: 1.25rem;
      margin-bottom: 1rem;
      color: var(--text-primary);
    }

    h4 {
      font-size: 1rem;
      margin: 1.5rem 0 0.75rem;
      color: var(--text-primary);
    }

    p {
      color: var(--text-secondary);
    }
  }

  .feature-list {
    list-style: none;
    padding: 0;

    li {
      padding: 0.5rem 0 0.5rem 2rem;
      position: relative;
      color: var(--text-secondary);

      &::before {
        content: '✓';
        position: absolute;
        left: 0;
        color: var(--excel-green);
        font-weight: 700;
        font-size: 1.1rem;
      }
    }
  }

  /* ========== Mermaid 图表包装器 ========== */
  .mermaid-wrapper {
    background-color: var(--bg-elevated);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    margin: 2rem 0;
    box-shadow: var(--shadow-sm);
    overflow-x: auto;
    border: 1px solid var(--border-color);

    .mermaid {
      display: flex;
      justify-content: center;

      svg {
        max-width: 100%;
        height: auto;
      }
    }
  }

  .diagram-title {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--text-primary);
    text-align: center;
  }

  /* ========== 代码块 ========== */
  .code-block {
    background-color: #f8f9fa;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    margin: 2rem 0;
    overflow: hidden;

    h3, h4 {
      padding: 0.75rem 1.25rem;
      background: linear-gradient(135deg, #e9ecef 0%, #f8f9fa 100%);
      border-bottom: 1px solid var(--border-color);
      font-size: 0.95rem;
      font-weight: 600;
      color: var(--text-primary);
      display: flex;
      justify-content: space-between;
      align-items: center;
      flex-wrap: wrap;
      gap: 0.5rem;
    }

    pre {
      margin: 0;
      padding: 1.25rem;
      overflow-x: auto;
      background-color: #2d3748;
      max-height: 500px;
      transition: max-height 0.3s ease, padding 0.3s ease;

      &.collapsed {
        max-height: 0;
        padding: 0;
        overflow: hidden;
      }

      code {
        color: #e2e8f0;
        background: none;
        padding: 0;
        font-size: 0.85rem;
        line-height: 1.6;
      }
    }

    .collapse-btn {
      padding: 4px 8px;
      font-size: 12px;
      cursor: pointer;
      border: 1px solid var(--border-color);
      border-radius: var(--radius-sm);
      background: #e9ecef;
      color: var(--text-secondary);
      transition: all var(--transition-fast);

      &:hover {
        background: var(--bg-alt);
        border-color: var(--primary-color);
      }
    }

    .copy-btn {
      background: rgba(255, 255, 255, 0.2) !important;
      border: 1px solid rgba(255, 255, 255, 0.3) !important;
      color: #e2e8f0 !important;
    }
  }

  /* ========== 表格 ========== */
  .table-wrapper {
    margin: 2rem 0;
    overflow-x: auto;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-color);
  }

  .table-title {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--text-primary);
    padding: 1rem 1.25rem;
    background: linear-gradient(135deg, #f8f9fa 0%, #e9ecef 100%);
    border-bottom: 1px solid var(--border-color);
  }

  .comparison-table,
  .detail-table {
    width: 100%;
    border-collapse: collapse;
    background-color: var(--bg-elevated);

    th {
      background: linear-gradient(135deg, var(--excel-header) 0%, #f1f1f1 100%);
      padding: 1rem 1.5rem;
      font-weight: 600;
      border-bottom: 2px solid var(--border-color);
      color: var(--text-primary);
      white-space: nowrap;
    }

    td {
      padding: 1rem 1.5rem;
      border: 1px solid var(--border-color);
      color: var(--text-secondary);
    }

    tr {
      transition: background-color var(--transition-fast);

      &:hover {
        background-color: var(--excel-cell-hover);
      }
    }

    code {
      background: var(--excel-selection);
      color: var(--excel-green-dark);
      padding: 0.2rem 0.5rem;
      border: 1px solid var(--excel-border);
    }
  }

  /* ========== 内容网格 ========== */
  .content-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
    margin: 2rem 0;
  }

  .card {
    background-color: var(--bg-elevated);
    border-radius: var(--radius-md);
    padding: 1.5rem;
    box-shadow: var(--shadow-sm);
    transition: all var(--transition-base);
    opacity: 0;
    transform: translateY(20px);
    border: 1px solid var(--border-color);

    &.visible {
      opacity: 1;
      transform: translateY(0);
    }

    &:hover {
      box-shadow: var(--shadow-md);
      border-color: var(--excel-green);
    }

    h3 {
      font-size: 1.15rem;
      font-weight: 600;
      margin-bottom: 0.75rem;
      color: var(--text-primary);
    }
  }

  /* ========== 公式高亮 ========== */
  .formula-highlight {
    background: linear-gradient(135deg, var(--excel-selection) 0%, var(--bg-secondary) 100%);
    border: 2px solid var(--excel-green);
    border-radius: var(--radius-md);
    padding: 1rem;
    font-family: var(--font-mono);
    font-size: 0.95rem;
    margin: 1rem 0;
    overflow-x: auto;
  }

  /* ========== 单元格引用样式 ========== */
  .cell-ref {
    display: inline-block;
    background: var(--excel-selection);
    padding: 0.2rem 0.5rem;
    border-radius: var(--radius-sm);
    font-family: var(--font-mono);
    font-weight: 600;
    color: var(--excel-green-dark);
    border: 1px solid var(--excel-border);
  }

  /* ========== 示例表格 ========== */
  .sample-table {
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    overflow: hidden;
    margin: 1rem 0;
    background: white;

    table {
      width: 100%;
      border-collapse: collapse;
    }

    th {
      background: var(--excel-header);
      border: 1px solid var(--border-color);
      padding: 0.75rem;
      font-weight: 600;
    }

    td {
      border: 1px solid var(--border-color);
      padding: 0.75rem;
    }

    tr:hover {
      background: var(--excel-cell-hover);
    }
  }

  /* ========== Chart.js 图表容器 ========== */
  .chart-wrapper {
    background: var(--bg-elevated);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    margin: 2rem 0;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-color);
  }

  /* ========== 交互式流程图 ========== */
  .interactive-flowchart {
    background-color: var(--bg-elevated);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    margin: 2rem 0;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-color);
    overflow-x: auto;
  }

  .flowchart-steps {
    display: flex;
    align-items: stretch;
    gap: 0.5rem;
    min-width: max-content;
  }

  .flowchart-step {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
    padding: 1rem 1.25rem;
    background-color: var(--bg-secondary);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all var(--transition-base);
    min-width: 100px;
    border: 1px solid var(--border-color);

    &:hover, &.active {
      background: linear-gradient(135deg, var(--excel-green) 0%, var(--excel-green-light) 100%);
      transform: translateY(-2px);

      .step-number {
        background-color: white;
        color: var(--excel-green);
      }

      .step-content h4,
      .step-content p {
        color: white;
      }
    }
  }

  .step-number {
    width: 40px;
    height: 40px;
    border-radius: var(--radius-sm);
    background: linear-gradient(135deg, var(--excel-green) 0%, var(--excel-green-light) 100%);
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    flex-shrink: 0;
    transition: all var(--transition-base);
  }

  .step-content {
    text-align: center;

    h4 {
      font-size: 0.9rem;
      margin-bottom: 0.25rem;
      color: var(--text-primary);
      white-space: nowrap;
    }

    p {
      font-size: 0.75rem;
      color: var(--text-tertiary);
      margin: 0;
    }
  }

  .flowchart-detail {
    margin-top: 1rem;
    padding: 1rem;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);

    h4 {
      color: var(--excel-green);
      margin-bottom: 0.5rem;
    }

    p {
      color: var(--text-secondary);
      margin: 0;
    }
  }

  /* ========== AI 功能卡片 ========== */
  .ai-card {
    border-top: 4px solid var(--ai-gradient-start);
    background: linear-gradient(135deg, rgba(102, 126, 234, 0.05) 0%, rgba(118, 75, 162, 0.05) 100%);
  }
}

/* ===================================
   动画关键帧
   =================================== */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

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

@keyframes slideIn {
  from {
    transform: translateX(-20px);
    opacity: 0;
  }
  to {
    transform: translateX(0);
    opacity: 1;
  }
}

/* ===================================
   响应式设计
   =================================== */
@container main-container (max-width: 768px) {
  .nav-menu {
    display: none;
  }

  .mobile-menu-btn {
    display: flex;
  }

  .nav-menu.active {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: 70px;
    left: 0;
    right: 0;
    background: white;
    padding: 1rem;
    box-shadow: var(--shadow-lg);
    gap: 1rem;
  }

  .hero-stats {
    gap: 2rem;
  }

  .stat-number {
    font-size: 2rem;
  }

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

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

  .hero-buttons {
    flex-direction: column;
    align-items: center;
  }

  .btn {
    width: 100%;
    max-width: 280px;
    justify-content: center;
  }
}

/* ===================================
   打印样式
   =================================== */
@media print {
  .navbar,
  .hero-buttons,
  .theme-toggle,
  .mobile-menu-btn {
    display: none !important;
  }

  body {
    font-size: 12pt;
    line-height: 1.5;
  }

  .section {
    page-break-inside: avoid;
  }

  .code-block pre {
    max-height: none;
    page-break-inside: avoid;
  }

  .mermaid-wrapper {
    page-break-inside: avoid;
  }
}

/* ===================================
   减少动画（无障碍支持）
   =================================== */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }

  html {
    scroll-behavior: auto;
  }
}