/* ============================================
   Python 教程网站 - 现代重构样式
   ============================================ */

/* CSS 变量定义 - 统一主题管理 */
:root {
    /* 主色调 - 紫色渐变 */
    --primary-color: #667eea;
    --primary-dark: #764ba2;
    --primary-light: #8b9cf5;

    /* 辅助色 */
    --accent-green: #10b981;
    --accent-orange: #f59e0b;
    --accent-red: #ef4444;
    --accent-cyan: #06b6d4;

    /* 文字颜色 */
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --text-muted: #9ca3af;

    /* 背景色 */
    --bg-primary: #ffffff;
    --bg-secondary: #f9fafb;
    --bg-tertiary: #f3f4f6;
    --bg-code: #0d1117;

    /* 边框颜色 */
    --border-color: #e5e7eb;
    --border-light: #f3f4f6;

    /* 阴影 */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);

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

    /* 过渡 */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-slow: 350ms ease;

    /* 字体 */
    --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'Segoe UI', sans-serif;
    --font-mono: 'Fira Code', 'JetBrains Mono', 'Consolas', 'Monaco', monospace;

    /* 导航宽度 */
    --nav-width: 280px;
}

/* 暗色主题 */
[data-theme="dark"] {
    --text-primary: #f9fafb;
    --text-secondary: #d1d5db;
    --text-muted: #9ca3af;

    --bg-primary: #111827;
    --bg-secondary: #1f2937;
    --bg-tertiary: #374151;
    --bg-code: #0d1117;

    --border-color: #374151;
    --border-light: #4b5563;

    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.4);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.4);
}

/* 重置样式 */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

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

body {
    font-family: var(--font-sans);
    line-height: 1.7;
    color: var(--text-primary);
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    min-height: 100vh;
    transition: background var(--transition-base);
}

/* ============================================
   Header 样式
   ============================================ */
header {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    color: white;
    text-align: center;
    padding: 60px 20px;
    box-shadow: var(--shadow-lg);
    position: relative;
    overflow: hidden;
}

header::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: url("data:image/svg+xml,%3Csvg width='60' height='60' viewBox='0 0 60 60' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='none' fill-rule='evenodd'%3E%3Cg fill='%23ffffff' fill-opacity='0.05'%3E%3Cpath d='M36 34v-4h-2v4h-4v2h4v4h2v-4h4v-2h-4zm0-30V0h-2v4h-4v2h4v4h2V6h4V4h-4zM6 34v-4H4v4H0v2h4v4h2v-4h4v-2H6zM6 4V0H4v4H0v2h4v4h2V6h4V4H6z'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E");
    opacity: 0.5;
}

header h1 {
    font-size: 2.75rem;
    font-weight: 700;
    margin-bottom: 12px;
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.15);
    position: relative;
}

header p {
    font-size: 1.15rem;
    opacity: 0.92;
    position: relative;
}

/* ============================================
   导航栏样式
   ============================================ */
nav {
    background: rgba(255, 255, 255, 0.97);
    backdrop-filter: blur(12px);
    padding: 20px 0;
    position: fixed;
    left: 0;
    top: 0;
    width: var(--nav-width);
    height: 100vh;
    z-index: 1000;
    box-shadow: var(--shadow-lg);
    overflow-y: auto;
    overflow-x: hidden;
    transition: transform var(--transition-base), background var(--transition-base);
}

[data-theme="dark"] nav {
    background: rgba(17, 24, 39, 0.97);
}

nav::-webkit-scrollbar {
    width: 6px;
}

nav::-webkit-scrollbar-track {
    background: transparent;
}

nav::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: var(--radius-full);
}

nav::-webkit-scrollbar-thumb:hover {
    background: var(--text-muted);
}

/* 导航头部 */
.nav-header {
    padding: 0 16px 16px;
    border-bottom: 1px solid var(--border-color);
    margin-bottom: 12px;
}

.nav-header .logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--primary-color);
}

.nav-header .logo-icon {
    width: 36px;
    height: 36px;
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 1.2rem;
}

/* 主题切换按钮 */
.theme-toggle {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 10px 16px;
    margin: 8px 16px;
    background: var(--bg-tertiary);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: background var(--transition-fast);
}

.theme-toggle:hover {
    background: var(--border-color);
}

.theme-toggle span {
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.theme-toggle .toggle-icon {
    font-size: 1.1rem;
}

/* 导航分类 */
.nav-category {
    margin-bottom: 8px;
}

.nav-category > h3 {
    display: flex;
    align-items: center;
    padding: 10px 16px;
    color: var(--primary-dark);
    font-size: 0.9rem;
    font-weight: 600;
    border-left: 3px solid transparent;
    cursor: pointer;
    transition: all var(--transition-fast);
    user-select: none;
}

.nav-category > h3:hover {
    background: rgba(102, 126, 234, 0.08);
    border-left-color: var(--primary-color);
    color: var(--primary-color);
}

.nav-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 22px;
    height: 22px;
    margin-right: 10px;
    background: rgba(102, 126, 234, 0.1);
    border-radius: var(--radius-sm);
    font-size: 14px;
    font-weight: 700;
    color: var(--primary-color);
    transition: all var(--transition-fast);
}

.nav-category > h3:hover .nav-toggle {
    background: var(--primary-color);
    color: white;
    transform: rotate(90deg);
}

.nav-category.expanded > h3 .nav-toggle {
    transform: rotate(45deg);
    background: var(--primary-dark);
    color: white;
}

.nav-items {
    max-height: 0;
    overflow: hidden;
    transition: max-height var(--transition-base);
}

.nav-category.expanded > .nav-items {
    max-height: 500px;
}

.nav-items ul {
    list-style: none;
    padding: 4px 8px 12px 28px;
}

.nav-items li {
    margin: 2px 0;
}

.nav-items li a {
    display: block;
    padding: 6px 12px;
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.85rem;
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

.nav-items li a:hover {
    background: var(--primary-color);
    color: white;
    transform: translateX(4px);
}

.nav-items li a.active {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    color: white;
    font-weight: 500;
}

/* ============================================
   主内容区域
   ============================================ */
main {
    max-width: 100%;
    margin: 0 auto;
    padding: 0 20px 20px calc(var(--nav-width) + 20px);
    min-height: calc(100vh - 200px);
}

.content-section {
    background: var(--bg-primary);
    border-radius: var(--radius-xl);
    padding: 32px 40px;
    margin: 20px auto;
    box-shadow: var(--shadow-lg);
    transition: transform var(--transition-base), box-shadow var(--transition-base), background var(--transition-base);
}

.content-section:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-xl);
}

.content-section h2 {
    color: var(--primary-color);
    font-size: 1.75rem;
    font-weight: 700;
    margin-bottom: 16px;
    padding-bottom: 12px;
    border-bottom: 2px solid var(--border-color);
    position: relative;
}

.content-section h2::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 60px;
    height: 2px;
    background: linear-gradient(90deg, var(--primary-color), var(--primary-dark));
}

.content-section h3 {
    color: var(--primary-dark);
    font-size: 1.25rem;
    font-weight: 600;
    margin: 24px 0 12px 0;
}

.content-section h4 {
    color: var(--text-primary);
    font-size: 1.05rem;
    font-weight: 600;
    margin: 16px 0 8px 0;
}

.content-section p {
    margin-bottom: 14px;
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.content-section ul,
.content-section ol {
    margin-left: 20px;
    margin-bottom: 14px;
}

.content-section li {
    margin-bottom: 6px;
    color: var(--text-secondary);
    font-size: 0.95rem;
}

/* ============================================
   代码块样式 - 现代化设计
   ============================================ */
pre {
    background: var(--bg-code);
    color: #e6edf3;
    padding: 0;
    border-radius: var(--radius-lg);
    overflow: hidden;
    margin: 16px 0;
    box-shadow: var(--shadow-lg), 0 0 0 1px rgba(255, 255, 255, 0.05);
    position: relative;
    font-family: var(--font-mono);
    font-size: 0.9rem;
    line-height: 1.6;
}

/* 代码块头部 */
.code-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 10px 16px;
    background: rgba(255, 255, 255, 0.05);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.code-header .code-lang {
    font-size: 0.75rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    font-weight: 500;
}

.code-header .copy-btn {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 6px 12px;
    background: rgba(255, 255, 255, 0.1);
    border: none;
    border-radius: var(--radius-sm);
    color: var(--text-muted);
    font-size: 0.8rem;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.code-header .copy-btn:hover {
    background: var(--primary-color);
    color: white;
}

.code-header .copy-btn.copied {
    background: var(--accent-green);
    color: white;
}

pre code {
    display: block;
    padding: 16px;
    overflow-x: auto;
    color: #e6edf3;
}

/* Prism.js 语法高亮主题 - 现代化暗色 */
code[class*="language-"],
pre[class*="language-"] {
    color: #e6edf3;
    background: none;
    font-family: var(--font-mono);
    font-size: 0.9rem;
    text-align: left;
    white-space: pre;
    word-spacing: normal;
    word-break: normal;
    word-wrap: normal;
    line-height: 1.6;
    tab-size: 4;
    hyphens: none;
}

pre[class*="language-"] code {
    padding: 0;
}

.token.comment,
.token.prolog,
.token.doctype,
.token.cdata {
    color: #8b949e;
    font-style: italic;
}

.token.punctuation {
    color: #c9d1d9;
}

.token.namespace {
    opacity: 0.7;
}

.token.property,
.token.tag,
.token.boolean,
.token.number,
.token.constant,
.token.symbol,
.token.deleted {
    color: #79c0ff;
}

.token.selector,
.token.attr-name,
.token.string,
.token.char,
.token.builtin,
.token.inserted {
    color: #a5d6ff;
}

.token.operator,
.token.entity,
.token.url,
.language-css .token.string,
.style .token.string {
    color: #d2a8ff;
}

.token.atrule,
.token.attr-value,
.token.keyword {
    color: #ff7b72;
}

.token.function,
.token.class-name {
    color: #d2a8ff;
}

.token.regex,
.token.important,
.token.variable {
    color: #ffa657;
}

/* ============================================
   特殊框样式
   ============================================ */
.feature-box {
    background: linear-gradient(135deg, rgba(102, 126, 234, 0.08) 0%, rgba(118, 75, 162, 0.08) 100%);
    border-left: 4px solid var(--primary-color);
    padding: 16px 20px;
    margin: 16px 0;
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    transition: all var(--transition-base);
}

.feature-box:hover {
    background: linear-gradient(135deg, rgba(102, 126, 234, 0.12) 0%, rgba(118, 75, 162, 0.12) 100%);
}

.feature-box h3 {
    color: var(--primary-color);
    margin-top: 0;
    margin-bottom: 10px;
    font-size: 1.05rem;
}

.feature-box ul {
    list-style: none;
    margin-left: 0;
}

.feature-box li {
    padding: 4px 0;
    font-size: 0.9rem;
    color: var(--text-secondary);
    position: relative;
    padding-left: 20px;
}

.feature-box li::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--accent-green);
    font-weight: 600;
}

.tip-box {
    background: #fef3c7;
    border-left: 4px solid var(--accent-orange);
    padding: 16px 20px;
    margin: 16px 0;
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    font-size: 0.9rem;
    transition: all var(--transition-base);
}

[data-theme="dark"] .tip-box {
    background: rgba(245, 158, 11, 0.15);
}

.tip-box strong {
    color: #92400e;
}

[data-theme="dark"] .tip-box strong {
    color: var(--accent-orange);
}

/* 警告框 */
.warning-box {
    background: #fee2e2;
    border-left: 4px solid var(--accent-red);
    padding: 16px 20px;
    margin: 16px 0;
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
}

[data-theme="dark"] .warning-box {
    background: rgba(239, 68, 68, 0.15);
}

.warning-box strong {
    color: #b91c1c;
}

[data-theme="dark"] .warning-box strong {
    color: var(--accent-red);
}

/* 成功框 */
.success-box {
    background: #d1fae5;
    border-left: 4px solid var(--accent-green);
    padding: 16px 20px;
    margin: 16px 0;
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
}

[data-theme="dark"] .success-box {
    background: rgba(16, 185, 129, 0.15);
}

.success-box strong {
    color: #065f46;
}

[data-theme="dark"] .success-box strong {
    color: var(--accent-green);
}

/* ============================================
   链接样式
   ============================================ */
a {
    color: var(--primary-color);
    text-decoration: none;
    transition: all var(--transition-fast);
    border-bottom: 1px solid transparent;
}

a:hover {
    color: var(--primary-dark);
    border-bottom-color: var(--primary-dark);
}

/* ============================================
   资源卡片网格
   ============================================ */
.resource-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 24px;
    margin: 30px 0;
}

.resource-card {
    background: linear-gradient(135deg, rgba(102, 126, 234, 0.06) 0%, rgba(118, 75, 162, 0.06) 100%);
    padding: 28px;
    border-radius: var(--radius-xl);
    text-align: center;
    transition: all var(--transition-base);
    border: 2px solid transparent;
    position: relative;
    overflow: hidden;
}

.resource-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, var(--primary-color), var(--primary-dark));
    transform: scaleX(0);
    transition: transform var(--transition-base);
}

.resource-card:hover {
    transform: translateY(-8px);
    border-color: var(--primary-color);
    box-shadow: 0 20px 40px rgba(102, 126, 234, 0.2);
}

.resource-card:hover::before {
    transform: scaleX(1);
}

.resource-card h3 {
    font-size: 1.25rem;
    margin-bottom: 12px;
    color: var(--primary-color);
    font-weight: 600;
}

.resource-card p {
    margin-bottom: 18px;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.resource-card a {
    display: inline-block;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    color: white;
    padding: 12px 28px;
    border-radius: var(--radius-full);
    text-decoration: none;
    font-weight: 600;
    font-size: 0.9rem;
    transition: all var(--transition-base);
    border: none;
    border-bottom: none;
}

.resource-card a:hover {
    transform: scale(1.05);
    box-shadow: 0 8px 20px rgba(102, 126, 234, 0.4);
    color: white;
    border-bottom: none;
}

/* ============================================
   表格样式
   ============================================ */
.info-table {
    width: 100%;
    border-collapse: separate;
    border-spacing: 0;
    margin: 20px 0;
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-md);
}

.info-table th {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    color: white;
    padding: 14px 18px;
    text-align: left;
    font-weight: 600;
    font-size: 0.9rem;
    white-space: nowrap;
}

.info-table td {
    padding: 12px 18px;
    border-bottom: 1px solid var(--border-color);
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.info-table tr:last-child td {
    border-bottom: none;
}

.info-table tr:hover td {
    background: var(--bg-secondary);
}

.comparison-table {
    width: 100%;
    border-collapse: separate;
    border-spacing: 0;
    margin: 20px 0;
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-md);
}

.comparison-table th {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    color: white;
    padding: 14px 18px;
    text-align: left;
    font-weight: 600;
}

.comparison-table td {
    padding: 12px 18px;
    border-bottom: 1px solid var(--border-color);
}

.comparison-table tr:hover td {
    background: var(--bg-secondary);
}

.comparison-table tr:last-child td {
    border-bottom: none;
}

.comparison-table .check {
    color: var(--accent-green);
    font-weight: 700;
}

.comparison-table .cross {
    color: var(--accent-red);
    font-weight: 700;
}

/* ============================================
   步骤卡片
   ============================================ */
.step-card {
    background: var(--bg-primary);
    border-left: 4px solid var(--primary-color);
    border-radius: var(--radius-md);
    padding: 20px 24px;
    margin: 16px 0;
    box-shadow: var(--shadow-md);
    transition: all var(--transition-base);
}

.step-card:hover {
    box-shadow: var(--shadow-lg);
    transform: translateX(4px);
}

.step-card .step-header {
    display: flex;
    align-items: center;
    margin-bottom: 12px;
}

.step-card .step-number {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    color: white;
    width: 32px;
    height: 32px;
    border-radius: 50%;
    font-weight: 700;
    font-size: 0.9rem;
    margin-right: 12px;
}

.step-card h4 {
    color: var(--primary-color);
    margin: 0;
    font-size: 1rem;
    font-weight: 600;
}

/* ============================================
   Mermaid 图表容器
   ============================================ */
.mermaid-container {
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    padding: 24px;
    margin: 24px 0;
    box-shadow: var(--shadow-md);
    overflow-x: auto;
}

.mermaid-container h4 {
    color: var(--primary-color);
    margin-bottom: 16px;
    font-size: 1rem;
    text-align: center;
    font-weight: 600;
}

.mermaid {
    display: flex;
    justify-content: center;
    min-width: 400px;
}

/* ============================================
   流程图样式
   ============================================ */
.flowchart {
    background: linear-gradient(135deg, rgba(102, 126, 234, 0.06) 0%, rgba(118, 75, 162, 0.06) 100%);
    border: 2px solid var(--primary-color);
    border-radius: var(--radius-lg);
    padding: 28px;
    margin: 24px 0;
    overflow-x: auto;
}

.flow-step {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-primary);
    border: 2px solid var(--primary-dark);
    border-radius: var(--radius-md);
    padding: 14px 24px;
    margin: 10px;
    min-width: 140px;
    font-weight: 600;
    font-size: 0.9rem;
    box-shadow: var(--shadow-md);
    transition: all var(--transition-base);
}

.flow-step:hover {
    transform: scale(1.05);
    box-shadow: var(--shadow-lg);
}

.flow-step.start {
    background: linear-gradient(135deg, #11998e, #38ef7d);
    color: white;
    border: none;
}

.flow-step.process {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    color: white;
    border: none;
}

.flow-step.decision {
    background: linear-gradient(135deg, #f093fb, #f5576c);
    color: white;
    border: none;
    border-radius: var(--radius-full);
}

.flow-step.end {
    background: linear-gradient(135deg, #eb3349, #f45c43);
    color: white;
    border: none;
    border-radius: var(--radius-full);
}

.flow-arrow {
    text-align: center;
    font-size: 1.4rem;
    color: var(--primary-color);
    margin: 8px 0;
}

.flow-row {
    text-align: center;
    margin: 10px 0;
}

/* ============================================
   知识点导航样式
   ============================================ */
.topic-nav {
    display: flex;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 12px;
    margin: 24px 0;
    padding: 16px;
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
}

.topic-nav a {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    color: var(--primary-color);
    text-decoration: none;
    padding: 10px 18px;
    border-radius: var(--radius-full);
    background: var(--bg-primary);
    font-weight: 500;
    font-size: 0.9rem;
    transition: all var(--transition-base);
    border: 1px solid var(--border-color);
    border-bottom: 1px solid var(--border-color);
}

.topic-nav a:hover {
    background: var(--primary-color);
    color: white;
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
    border-color: var(--primary-color);
    border-bottom: 1px solid var(--primary-color);
}

/* ============================================
   滚动条美化
   ============================================ */
::-webkit-scrollbar {
    width: 10px;
    height: 10px;
}

::-webkit-scrollbar-track {
    background: var(--bg-tertiary);
    border-radius: var(--radius-full);
}

::-webkit-scrollbar-thumb {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    border-radius: var(--radius-full);
}

::-webkit-scrollbar-thumb:hover {
    background: linear-gradient(135deg, var(--primary-dark), var(--primary-color));
}

/* ============================================
   移动端导航切换按钮
   ============================================ */
.nav-toggle-btn {
    display: none;
    position: fixed;
    top: 16px;
    left: 16px;
    z-index: 1001;
    width: 48px;
    height: 48px;
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    border: none;
    border-radius: var(--radius-lg);
    cursor: pointer;
    box-shadow: var(--shadow-lg);
    transition: all var(--transition-base);
}

.nav-toggle-btn:hover {
    transform: scale(1.05);
    box-shadow: var(--shadow-xl);
}

.nav-toggle-btn span {
    display: block;
    width: 24px;
    height: 2px;
    background: white;
    margin: 6px auto;
    transition: all var(--transition-fast);
    border-radius: 2px;
}

.nav-toggle-btn.active span:nth-child(1) {
    transform: rotate(45deg) translate(5px, 6px);
}

.nav-toggle-btn.active span:nth-child(2) {
    opacity: 0;
}

.nav-toggle-btn.active span:nth-child(3) {
    transform: rotate(-45deg) translate(5px, -6px);
}

/* 遮罩层 */
.nav-overlay {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    z-index: 999;
    opacity: 0;
    transition: opacity var(--transition-base);
}

.nav-overlay.active {
    opacity: 1;
}

/* ============================================
   Footer 样式
   ============================================ */
footer {
    display: none;
}

/* ============================================
   响应式设计
   ============================================ */
@media (max-width: 1024px) {
    :root {
        --nav-width: 260px;
    }
}

@media (max-width: 768px) {
    :root {
        --nav-width: 280px;
    }

    /* 显示移动导航按钮 */
    .nav-toggle-btn {
        display: block;
    }

    /* 移动端导航 */
    nav {
        transform: translateX(-100%);
        width: var(--nav-width);
    }

    nav.open {
        transform: translateX(0);
    }

    .nav-overlay {
        display: block;
    }

    /* 调整主要内容区域 */
    main {
        padding: 80px 16px 20px;
    }

    /* 减小内容区内边距 */
    .content-section {
        padding: 24px 20px;
    }

    header h1 {
        font-size: 2rem;
    }

    header p {
        font-size: 1rem;
    }

    .content-section h2 {
        font-size: 1.5rem;
    }

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

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

    .feature-list {
        grid-template-columns: 1fr;
    }

    .topic-nav {
        flex-direction: column;
    }

    .topic-nav a {
        width: 100%;
        justify-content: center;
    }
}

@media (max-width: 480px) {
    header h1 {
        font-size: 1.75rem;
    }

    .content-section {
        padding: 20px 16px;
    }

    .content-section h2 {
        font-size: 1.35rem;
    }

    .resource-card {
        padding: 20px;
    }

    .info-table,
    .comparison-table {
        font-size: 0.85rem;
    }

    .info-table th,
    .info-table td,
    .comparison-table th,
    .comparison-table td {
        padding: 10px 12px;
    }
}

/* ============================================
   动画效果
   ============================================ */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

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

@keyframes pulse {
    0%, 100% {
        opacity: 1;
    }
    50% {
        opacity: 0.6;
    }
}

.content-section {
    animation: fadeIn 0.5s ease forwards;
}

.category-card {
    animation: fadeIn 0.5s ease forwards;
    animation-fill-mode: both;
}

.category-card:nth-child(1) { animation-delay: 0.1s; }
.category-card:nth-child(2) { animation-delay: 0.15s; }
.category-card:nth-child(3) { animation-delay: 0.2s; }
.category-card:nth-child(4) { animation-delay: 0.25s; }
.category-card:nth-child(5) { animation-delay: 0.3s; }
.category-card:nth-child(6) { animation-delay: 0.35s; }
.category-card:nth-child(7) { animation-delay: 0.4s; }
.category-card:nth-child(8) { animation-delay: 0.45s; }
.category-card:nth-child(9) { animation-delay: 0.5s; }
.category-card:nth-child(10) { animation-delay: 0.55s; }

/* ============================================
   打印样式
   ============================================ */
@media print {
    nav,
    .nav-toggle-btn,
    .nav-overlay {
        display: none !important;
    }

    main {
        padding: 0 !important;
    }

    .content-section {
        box-shadow: none !important;
        break-inside: avoid;
    }
}