/* ========================================
   Python学习平台 - 全局样式
   ======================================== */

/* 基础重置 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* 极简配色 - Apple/Notion 风格 */
    --bg-primary: #ffffff;
    --bg-secondary: #f9fafb;
    --text-primary: #111827;
    --text-secondary: #6b7280;
    --hover-bg: #f3f4f6;

    /* 语言品牌色 */
    --python-color: #3776ab;
    --python-yellow: #ffd43b;
    --c-color: #00599c;

    /* 交互色 */
    --accent-color: #2563eb;
    --primary-color: #2563eb;
    --primary-gradient: linear-gradient(135deg, #2563eb 0%, #3b82f6 100%);

    /* 功能色 */
    --success-color: #10b981;
    --success-gradient: linear-gradient(135deg, #10b981 0%, #34d399 100%);
    --warning-color: #f59e0b;
    --warning-gradient: linear-gradient(135deg, #f59e0b 0%, #fbbf24 100%);
    --danger-color: #ef4444;
    --danger-gradient: linear-gradient(135deg, #ef4444 0%, #f87171 100%);
    --info-color: #6366f1;
    --info-gradient: linear-gradient(135deg, #6366f1 0%, #818cf8 100%);

    /* 兼容旧变量 */
    --dark-color: #111827;
    --text-color: #374151;
    --text-light: #6b7280;
    --text-muted: #9ca3af;
    --border-color: #e5e7eb;
    --bg-color: #ffffff;
    --card-bg: #ffffff;

    /* 代码相关 */
    --code-bg: #1f2937;
    --code-text: #f3f4f6;

    /* 阴影 - 极简风格 */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.04);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 20px -3px rgba(0, 0, 0, 0.08);
    --shadow-xl: 0 20px 40px -5px rgba(0, 0, 0, 0.1);
    --shadow-card-hover: 0 12px 24px rgba(0, 0, 0, 0.08);

    /* 圆角 */
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    --radius-xl: 24px;

    /* 动画 */
    --transition-fast: 0.15s ease;
    --transition-base: 0.2s ease;
    --transition-slow: 0.3s ease;

    /* 毛玻璃效果 */
    --glass-bg: rgba(255, 255, 255, 0.72);
    --glass-border: rgba(255, 255, 255, 0.5);
    --glass-shadow: 0 8px 32px rgba(31, 38, 135, 0.08);

    /* 发光效果 */
    --glow-primary: 0 0 20px rgba(37, 99, 235, 0.15);
    --glow-accent: 0 0 30px rgba(37, 99, 235, 0.2);
    --glow-success: 0 0 20px rgba(16, 185, 129, 0.15);

    /* 增强阴影 */
    --shadow-colored: 0 20px 40px -8px rgba(37, 99, 235, 0.12);
    --shadow-glow: 0 0 40px rgba(37, 99, 235, 0.08);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background:
        radial-gradient(ellipse at 20% 0%, rgba(37, 99, 235, 0.06) 0%, transparent 50%),
        radial-gradient(ellipse at 80% 0%, rgba(14, 165, 233, 0.05) 0%, transparent 50%),
        radial-gradient(ellipse at 50% 100%, rgba(99, 102, 241, 0.04) 0%, transparent 50%),
        linear-gradient(180deg, #f8fbff 0%, #ffffff 40%, #f6f9fd 100%);
    background-attachment: fixed;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* ========================================
   导航栏 - 极简风格
   ======================================== */
.navbar {
    background: rgba(255, 255, 255, 0.78);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid rgba(148, 163, 184, 0.15);
    padding: 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 4px 30px rgba(0, 0, 0, 0.03);
    transition: background 0.3s ease, box-shadow 0.3s ease;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 60px;
}

.nav-logo {
    color: var(--text-primary);
    font-size: 1.25rem;
    font-weight: 700;
    text-decoration: none;
    letter-spacing: -0.02em;
    transition: all 0.3s ease;
}

.nav-logo:hover {
    background: linear-gradient(135deg, #2563eb, #06b6d4);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.nav-logo::before {
    display: none;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 8px;
}

.nav-menu {
    list-style: none;
    display: flex;
    gap: 4px;
}

.nav-link {
    color: var(--text-secondary);
    text-decoration: none;
    padding: 8px 16px;
    border-radius: var(--radius-sm);
    transition: all var(--transition-base);
    font-size: 14px;
    font-weight: 500;
}

.nav-link:hover {
    color: var(--text-primary);
    background: var(--hover-bg);
}

.nav-link.active {
    color: var(--text-primary);
    background: var(--hover-bg);
}

/* 语言切换器 */
.lang-switcher {
    display: flex;
    background: var(--hover-bg);
    border-radius: 8px;
    padding: 4px;
}

.lang-btn {
    padding: 6px 14px;
    border-radius: 6px;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    font-size: 13px;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-base);
    text-decoration: none;
}

.lang-btn:hover {
    color: var(--text-primary);
}

.lang-btn.active {
    background: #ffffff;
    color: var(--text-primary);
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
}

/* ========================================
   主内容区
   ======================================== */
.main-content {
    flex: 1;
    padding: 30px 0;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

/* ========================================
   首页样式
   ======================================== */
.hero {
    text-align: center;
    padding: 80px 40px;
    background: var(--primary-gradient);
    color: white;
    border-radius: var(--radius-xl);
    margin-bottom: 50px;
    position: relative;
    overflow: hidden;
}

.hero::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;
}

.hero > * {
    position: relative;
    z-index: 1;
}

.hero h1 {
    font-size: 3rem;
    margin-bottom: 16px;
    font-weight: 700;
}

.hero-subtitle {
    font-size: 1.3rem;
    opacity: 0.95;
    margin-bottom: 30px;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.hero-actions {
    display: flex;
    gap: 16px;
    justify-content: center;
    flex-wrap: wrap;
}

/* 特性卡片 */
.features {
    margin-bottom: 50px;
}

.features h2 {
    text-align: center;
    margin-bottom: 40px;
    color: var(--dark-color);
    font-size: 2rem;
}

.feature-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 24px;
}

.feature-card {
    background: var(--card-bg);
    padding: 32px;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    transition: all 0.3s;
    border: 1px solid var(--border-color);
}

.feature-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-xl);
    border-color: var(--primary-color);
}

.feature-icon {
    width: 60px;
    height: 60px;
    background: var(--primary-gradient);
    color: white;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.8rem;
    margin-bottom: 20px;
}

.feature-card h3 {
    color: var(--dark-color);
    margin-bottom: 12px;
    font-size: 1.25rem;
}

.feature-card p {
    color: var(--text-light);
    font-size: 0.95rem;
    line-height: 1.7;
}

/* 快速入口 */
.quick-actions {
    text-align: center;
    padding: 50px 0;
}

.quick-actions h2 {
    margin-bottom: 30px;
    color: var(--dark-color);
    font-size: 1.8rem;
}

.action-buttons {
    display: flex;
    gap: 20px;
    justify-content: center;
    flex-wrap: wrap;
}

/* ========================================
   按钮样式
   ======================================== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 28px;
    border: none;
    border-radius: var(--radius-md);
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    text-decoration: none;
    transition: all 0.3s;
    white-space: nowrap;
}

.btn-primary {
    background: var(--primary-gradient);
    color: white;
    box-shadow: 0 4px 14px rgba(102, 126, 234, 0.4);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(102, 126, 234, 0.5);
}

.btn-secondary {
    background: var(--success-gradient);
    color: white;
    box-shadow: 0 4px 14px rgba(0, 184, 148, 0.4);
}

.btn-secondary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(0, 184, 148, 0.5);
}

.btn-outline {
    background: transparent;
    border: 2px solid var(--primary-color);
    color: var(--primary-color);
}

.btn-outline:hover {
    background: var(--primary-color);
    color: white;
}

.btn-white {
    background: white;
    color: var(--primary-color);
    box-shadow: var(--shadow-md);
}

.btn-white:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-large {
    padding: 16px 36px;
    font-size: 1.1rem;
}

.btn-small {
    padding: 8px 16px;
    font-size: 0.875rem;
}

/* ========================================
   页面标题
   ======================================== */
.page-header {
    text-align: center;
    margin-bottom: 40px;
}

.page-header h1 {
    color: var(--dark-color);
    font-size: 2.2rem;
    margin-bottom: 12px;
}

.page-header p {
    color: var(--text-light);
    font-size: 1.1rem;
}

/* ========================================
   课程列表
   ======================================== */
.lessons-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
    gap: 24px;
}

.lesson-card {
    display: flex;
    flex-direction: column;
    background: rgba(255, 255, 255, 0.8);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border-radius: var(--radius-lg);
    text-decoration: none;
    box-shadow: var(--shadow-md);
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    overflow: hidden;
    border: 1px solid rgba(148, 163, 184, 0.15);
}

.lesson-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-colored);
    border-color: rgba(37, 99, 235, 0.2);
}

.lesson-card-header {
    background: var(--primary-gradient);
    padding: 24px;
    color: white;
}

.lesson-chapter {
    font-size: 0.9rem;
    opacity: 0.9;
    margin-bottom: 8px;
    font-weight: 500;
}

.lesson-title {
    font-size: 1.3rem;
    font-weight: 600;
    margin: 0;
}

.lesson-card-body {
    padding: 20px 24px;
    flex: 1;
}

.lesson-desc {
    color: var(--text-light);
    font-size: 0.95rem;
    line-height: 1.6;
    margin-bottom: 16px;
}

.lesson-meta {
    display: flex;
    gap: 16px;
    color: var(--text-muted);
    font-size: 0.85rem;
}

.lesson-meta span {
    display: flex;
    align-items: center;
    gap: 4px;
}

.lesson-card-footer {
    padding: 16px 24px;
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.start-btn {
    color: var(--primary-color);
    font-weight: 500;
    font-size: 0.95rem;
    display: flex;
    align-items: center;
    gap: 6px;
}

/* ========================================
   练习题列表
   ======================================== */
.exercises-filter {
    margin-bottom: 30px;
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
}

.filter-btn {
    padding: 10px 20px;
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 50px;
    color: var(--text-color);
    font-size: 0.9rem;
    cursor: pointer;
    transition: all 0.3s;
}

.filter-btn:hover, .filter-btn.active {
    background: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
}

.exercises-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 20px;
}

.exercise-card {
    display: block;
    background: rgba(255, 255, 255, 0.8);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    padding: 24px;
    border-radius: var(--radius-lg);
    text-decoration: none;
    box-shadow: var(--shadow-md);
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    border: 1px solid rgba(148, 163, 184, 0.15);
}

.exercise-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-colored);
    border-color: rgba(37, 99, 235, 0.2);
}

.exercise-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 12px;
}

.exercise-title {
    color: var(--dark-color);
    font-size: 1.15rem;
    font-weight: 600;
}

.difficulty-badge {
    padding: 4px 12px;
    border-radius: 50px;
    font-size: 0.75rem;
    font-weight: 600;
}

.difficulty-1 {
    background: #d1fae5;
    color: #065f46;
}

.difficulty-2 {
    background: #fef3c7;
    color: #92400e;
}

.difficulty-3 {
    background: #fee2e2;
    color: #991b1b;
}

.exercise-desc {
    color: var(--text-light);
    font-size: 0.9rem;
    line-height: 1.6;
    margin-bottom: 16px;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.exercise-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: 16px;
    border-top: 1px solid var(--border-color);
}

.exercise-chapter {
    font-size: 0.85rem;
    color: var(--text-muted);
}

.exercise-arrow {
    color: var(--primary-color);
    font-size: 1.2rem;
}

/* ========================================
   代码编辑器（Playground）
   ======================================== */
.playground-container {
    max-width: 100%;
}

.editor-layout {
    display: grid;
    grid-template-columns: 1fr 420px;
    gap: 24px;
    min-height: calc(100vh - 200px);
}

.editor-section,
.io-section {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 16px 20px;
    background: var(--dark-color);
    color: white;
}

.section-header h3 {
    font-size: 1rem;
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: 8px;
}

.CodeMirror {
    height: 100% !important;
    font-size: 14px;
    font-family: 'JetBrains Mono', 'Fira Code', Consolas, monospace;
    flex: 1;
}

.input-section {
    border-bottom: 1px solid var(--border-color);
}

.input-section textarea,
#stdin-input {
    width: 100%;
    height: 100px;
    padding: 16px;
    border: none;
    font-family: 'JetBrains Mono', Consolas, monospace;
    font-size: 14px;
    resize: vertical;
    outline: none;
    background: #f8fafc;
}

.output-section {
    flex: 1;
    display: flex;
    flex-direction: column;
}

.output-area {
    flex: 1;
    padding: 16px;
    margin: 0;
    min-height: 200px;
    overflow: auto;
    font-family: 'JetBrains Mono', Consolas, monospace;
    font-size: 14px;
    background: var(--code-bg);
    color: var(--code-text);
    white-space: pre-wrap;
    word-wrap: break-word;
}

.output-area.error {
    color: #f85149;
}

/* ========================================
   练习题详情
   ======================================== */
.exercise-detail-container {
    max-width: 100%;
}

.exercise-info {
    background: var(--card-bg);
    padding: 28px;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    margin-bottom: 24px;
}

.exercise-info h1 {
    color: var(--dark-color);
    margin-bottom: 16px;
    font-size: 1.5rem;
}

.exercise-info .markdown-content {
    color: var(--text-color);
    line-height: 1.8;
}

.exercise-editor {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    margin-bottom: 24px;
    overflow: hidden;
}

.editor-actions {
    display: flex;
    gap: 10px;
}

.result-section,
.hint-section,
.solution-section {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    margin-bottom: 24px;
    overflow: hidden;
}

.result-content {
    padding: 0;
}

/* 代码运行结果 */
.code-output-section {
    margin-bottom: 16px;
    border-radius: var(--radius-md);
    overflow: hidden;
    background: var(--code-bg);
}

.code-output-header {
    padding: 12px 16px;
    background: linear-gradient(135deg, #3b82f6 0%, #8b5cf6 100%);
    color: white;
    font-weight: 600;
    font-size: 0.95rem;
}

.code-output-content {
    padding: 16px;
    margin: 0;
    color: #a5f3fc;
    font-family: 'JetBrains Mono', Consolas, monospace;
    font-size: 14px;
    line-height: 1.6;
    white-space: pre-wrap;
    word-break: break-word;
    min-height: 40px;
    max-height: 200px;
    overflow-y: auto;
}

.code-output-content .code-error {
    color: #f87171;
    display: block;
    margin-top: 8px;
    padding-top: 8px;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

.code-output-content .code-empty {
    color: #64748b;
    font-style: italic;
}

/* 测试用例标题 */
.test-results-header {
    padding: 12px 16px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    font-weight: 600;
    font-size: 0.95rem;
}

.test-result {
    padding: 16px 20px;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    gap: 16px;
}

.test-result:last-child {
    border-bottom: none;
}

.test-result.passed {
    background: #ecfdf5;
}

.test-result.failed {
    background: #fef2f2;
}

.test-icon {
    font-size: 1.4rem;
}

.test-info {
    flex: 1;
}

.test-description {
    font-weight: 600;
    color: var(--dark-color);
    margin-bottom: 4px;
}

.test-detail {
    font-size: 0.85rem;
    color: var(--text-light);
    font-family: 'JetBrains Mono', monospace;
}

.result-summary {
    padding: 16px 20px;
    text-align: center;
    font-weight: 600;
    font-size: 1rem;
}

.result-summary.success {
    background: var(--success-color);
    color: white;
}

.result-summary.partial {
    background: var(--warning-color);
    color: white;
}

#hint-content {
    padding: 20px;
    color: var(--text-color);
    line-height: 1.7;
}

#solution-content {
    background: var(--code-bg);
    color: var(--code-text);
    padding: 20px;
    margin: 0;
    font-family: 'JetBrains Mono', monospace;
    font-size: 14px;
    white-space: pre-wrap;
}

.exercise-nav {
    display: flex;
    gap: 16px;
    justify-content: center;
}

/* ========================================
   Markdown内容样式
   ======================================== */
.markdown-content h1,
.markdown-content h2,
.markdown-content h3 {
    color: var(--dark-color);
    margin: 1.5rem 0 1rem;
}

.markdown-content h2 {
    font-size: 1.4rem;
    padding-bottom: 10px;
    border-bottom: 2px solid var(--primary-color);
}

.markdown-content h3 {
    font-size: 1.2rem;
}

.markdown-content p {
    margin-bottom: 16px;
}

.markdown-content pre {
    background: var(--code-bg);
    padding: 20px;
    border-radius: var(--radius-md);
    overflow-x: auto;
    margin: 20px 0;
}

.markdown-content code {
    font-family: 'JetBrains Mono', 'Fira Code', Consolas, monospace;
    font-size: 0.9rem;
}

.markdown-content p code,
.markdown-content li code {
    background: #f1f5f9;
    padding: 2px 8px;
    border-radius: 4px;
    color: #e11d48;
}

.markdown-content ul,
.markdown-content ol {
    margin: 16px 0;
    padding-left: 24px;
}

.markdown-content li {
    margin-bottom: 8px;
}

.markdown-content blockquote {
    border-left: 4px solid var(--primary-color);
    padding: 16px 20px;
    margin: 20px 0;
    background: #f0f9ff;
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    color: #0c4a6e;
}

.markdown-content table {
    width: 100%;
    border-collapse: collapse;
    margin: 20px 0;
    border-radius: var(--radius-md);
    overflow: hidden;
}

.markdown-content th,
.markdown-content td {
    border: 1px solid var(--border-color);
    padding: 12px 16px;
    text-align: left;
}

.markdown-content th {
    background: var(--primary-gradient);
    color: white;
    font-weight: 500;
}

.markdown-content tr:nth-child(even) {
    background: #f8fafc;
}

/* ========================================
   加载状态和消息
   ======================================== */
.loading {
    text-align: center;
    padding: 60px 20px;
    color: var(--text-light);
}

.loading-spinner {
    width: 40px;
    height: 40px;
    border: 3px solid var(--border-color);
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto 20px;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

.empty-message,
.error-message {
    text-align: center;
    padding: 60px 20px;
    color: var(--text-light);
}

.error-message {
    color: var(--danger-color);
}

/* ========================================
   页脚 - 极简风格
   ======================================== */
.footer {
    background: rgba(255, 255, 255, 0.78);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-top: 1px solid rgba(148, 163, 184, 0.15);
    color: var(--text-secondary);
    padding: 32px 0;
    text-align: center;
    font-size: 14px;
    margin-top: auto;
    position: relative;
}

.footer::before {
    content: '';
    position: absolute;
    top: 0;
    left: 20%;
    right: 20%;
    height: 1px;
    background: linear-gradient(90deg, transparent, rgba(37, 99, 235, 0.3), transparent);
}

.footer-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

.footer a {
    color: rgba(255, 255, 255, 0.9);
    text-decoration: none;
}

.footer a:hover {
    color: white;
}

/* ========================================
   响应式设计
   ======================================== */
@media (max-width: 1024px) {
    .editor-layout {
        grid-template-columns: 1fr;
    }

    .io-section {
        min-height: 400px;
    }
}

@media (max-width: 768px) {
    .nav-container {
        padding: 8px 16px;
        height: auto;
        min-height: 60px;
        flex-wrap: wrap;
        align-items: center;
        gap: 8px 12px;
    }

    .nav-links {
        width: 100%;
        order: 3;
        overflow-x: auto;
        gap: 6px;
        padding-bottom: 2px;
        scrollbar-width: none;
    }

    .nav-links::-webkit-scrollbar {
        display: none;
    }

    .nav-link {
        flex: 0 0 auto;
        padding: 8px 12px;
        font-size: 14px;
        white-space: nowrap;
    }

    .lang-switcher {
        order: 4;
        width: 100%;
        overflow-x: auto;
        padding: 4px;
        scrollbar-width: none;
    }

    .lang-switcher::-webkit-scrollbar {
        display: none;
    }

    .hero {
        padding: 50px 24px;
    }

    .hero h1 {
        font-size: 2rem;
    }

    .hero-subtitle {
        font-size: 1rem;
    }

    .container {
        padding: 0 16px;
    }

    .main-content {
        padding: 20px 0;
    }

    .lessons-container,
    .exercises-container {
        grid-template-columns: 1fr;
    }

    .page-header h1 {
        font-size: 1.8rem;
    }

    .btn-large {
        padding: 14px 28px;
        font-size: 1rem;
    }

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

    .footer {
        padding: 24px 0;
    }
}

/* ========================================
   动画关键帧
   ======================================== */
@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeInDown {
    from {
        opacity: 0;
        transform: translateY(-30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes slideInLeft {
    from {
        opacity: 0;
        transform: translateX(-30px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

@keyframes slideInRight {
    from {
        opacity: 0;
        transform: translateX(30px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

@keyframes scaleIn {
    from {
        opacity: 0;
        transform: scale(0.9);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

@keyframes pulse {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.05); }
}

@keyframes shimmer {
    0% { background-position: -200% 0; }
    100% { background-position: 200% 0; }
}

@keyframes float {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-10px); }
}

@keyframes glow {
    0%, 100% { box-shadow: 0 0 5px rgba(14, 165, 233, 0.3); }
    50% { box-shadow: 0 0 20px rgba(14, 165, 233, 0.6); }
}

/* ========================================
   入场动画类
   ======================================== */
.animate-fadeIn { animation: fadeIn 0.6s ease forwards; }
.animate-fadeInUp { animation: fadeInUp 0.6s ease forwards; }
.animate-fadeInDown { animation: fadeInDown 0.6s ease forwards; }
.animate-slideInLeft { animation: slideInLeft 0.6s ease forwards; }
.animate-slideInRight { animation: slideInRight 0.6s ease forwards; }
.animate-scaleIn { animation: scaleIn 0.4s ease forwards; }

.delay-1 { animation-delay: 0.1s; }
.delay-2 { animation-delay: 0.2s; }
.delay-3 { animation-delay: 0.3s; }
.delay-4 { animation-delay: 0.4s; }
.delay-5 { animation-delay: 0.5s; }

/* ========================================
   增强卡片效果
   ======================================== */
.lesson-card,
.exercise-card,
.feature-card {
    position: relative;
    overflow: hidden;
}

/* 卡片光泽效果 */
.lesson-card::before,
.exercise-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(
        90deg,
        transparent,
        rgba(255, 255, 255, 0.2),
        transparent
    );
    transition: left 0.6s ease;
    z-index: 1;
    pointer-events: none;
}

.lesson-card:hover::before,
.exercise-card:hover::before {
    left: 100%;
}

/* 特性卡片悬停效果增强 */
.feature-card {
    transform: translateY(0);
    transition: all var(--transition-base);
}

.feature-card:hover {
    transform: translateY(-12px);
    box-shadow: var(--shadow-card-hover);
}

.feature-card:hover .feature-icon {
    animation: pulse 0.6s ease;
}

/* ========================================
   按钮涟漪效果
   ======================================== */
.btn {
    position: relative;
    overflow: hidden;
    transition: all var(--transition-base);
}

.btn::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 0;
    height: 0;
    background: rgba(255, 255, 255, 0.3);
    border-radius: 50%;
    transform: translate(-50%, -50%);
    transition: width 0.6s ease, height 0.6s ease;
}

.btn:active::after {
    width: 300px;
    height: 300px;
}

/* 按钮悬停发光效果 */
.btn-primary:hover {
    box-shadow: 0 8px 25px rgba(102, 126, 234, 0.5);
}

.btn-secondary:hover {
    box-shadow: 0 8px 25px rgba(0, 184, 148, 0.5);
}

/* ========================================
   导航栏增强
   ======================================== */
.nav-link {
    position: relative;
    transition: all var(--transition-base);
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 50%;
    width: 0;
    height: 2px;
    background: var(--primary-light);
    transition: all var(--transition-base);
    transform: translateX(-50%);
    border-radius: 2px;
}

.nav-link:hover::after {
    width: 70%;
}

.nav-link.active::after {
    width: 80%;
    background: white;
}

/* ========================================
   Hero区域增强动画
   ======================================== */
.hero {
    animation: fadeIn 0.8s ease;
}

.hero h1 {
    animation: fadeInDown 0.8s ease;
}

.hero-subtitle {
    animation: fadeInUp 0.8s ease 0.2s both;
}

.hero-actions {
    animation: fadeInUp 0.8s ease 0.4s both;
}

/* Hero背景动态效果 */
.hero::after {
    content: "";
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle, rgba(255,255,255,0.1) 0%, transparent 60%);
    animation: float 6s ease-in-out infinite;
    pointer-events: none;
}

/* ========================================
   页面标题增强
   ======================================== */
.page-header {
    animation: fadeInUp 0.6s ease;
}

.page-header h1 {
    position: relative;
    display: inline-block;
}

.page-header h1::after {
    content: '';
    position: absolute;
    bottom: -8px;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 4px;
    background: var(--primary-gradient);
    border-radius: 2px;
}

/* ========================================
   代码块增强
   ======================================== */
.markdown-content pre {
    position: relative;
    border: 1px solid rgba(255, 255, 255, 0.1);
    box-shadow: inset 0 0 20px rgba(0, 0, 0, 0.2);
}

.markdown-content pre::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: var(--primary-gradient);
    border-radius: var(--radius-md) var(--radius-md) 0 0;
}

/* 行内代码增强 */
.markdown-content p code,
.markdown-content li code {
    background: linear-gradient(135deg, #fef2f2 0%, #fff1f2 100%);
    border: 1px solid #fecaca;
    font-weight: 500;
}

/* ========================================
   练习题难度标签增强
   ======================================== */
.difficulty-1 {
    background: linear-gradient(135deg, #d1fae5 0%, #a7f3d0 100%);
    color: #065f46;
    font-weight: 600;
    border: 1px solid #6ee7b7;
}

.difficulty-2 {
    background: linear-gradient(135deg, #fef3c7 0%, #fde68a 100%);
    color: #92400e;
    font-weight: 600;
    border: 1px solid #fcd34d;
}

.difficulty-3 {
    background: linear-gradient(135deg, #fee2e2 0%, #fecaca 100%);
    color: #991b1b;
    font-weight: 600;
    border: 1px solid #f87171;
}

/* ========================================
   测试结果增强
   ======================================== */
.test-result.passed {
    background: linear-gradient(135deg, #ecfdf5 0%, #d1fae5 100%);
    border-left: 4px solid var(--success-color);
}

.test-result.failed {
    background: linear-gradient(135deg, #fef2f2 0%, #fee2e2 100%);
    border-left: 4px solid var(--danger-color);
}

.result-summary.success {
    background: var(--success-gradient);
    animation: pulse 0.5s ease;
}

/* ========================================
   输出区域增强
   ======================================== */
.output-area {
    position: relative;
    border: 1px solid rgba(255, 255, 255, 0.05);
}

.output-area::before {
    content: '输出';
    position: absolute;
    top: 8px;
    right: 12px;
    font-size: 0.7rem;
    color: rgba(255, 255, 255, 0.3);
    text-transform: uppercase;
    letter-spacing: 1px;
}

/* ========================================
   滚动条美化
   ======================================== */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

::-webkit-scrollbar-track {
    background: var(--bg-color);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb {
    background: linear-gradient(180deg, var(--primary-color), var(--primary-dark));
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--primary-dark);
}

/* ========================================
   选中文本样式
   ======================================== */
::selection {
    background: rgba(102, 126, 234, 0.3);
    color: var(--dark-color);
}

/* ========================================
   加载状态增强
   ======================================== */
.loading-spinner {
    background: linear-gradient(135deg, transparent 0%, transparent 40%, var(--primary-color) 40%, var(--primary-color) 60%, transparent 60%);
    background-size: 100% 100%;
}

/* ========================================
   表格增强
   ======================================== */
.markdown-content tr {
    transition: background var(--transition-fast);
}

.markdown-content tr:hover {
    background: rgba(102, 126, 234, 0.05) !important;
}

/* ========================================
   引用块增强
   ======================================== */
.markdown-content blockquote {
    position: relative;
    background: linear-gradient(135deg, #f0f9ff 0%, #e0f2fe 100%);
    border-left: 4px solid var(--primary-color);
}

.markdown-content blockquote::before {
    content: '\201C';
    position: absolute;
    top: -10px;
    left: 10px;
    font-size: 3rem;
    color: rgba(102, 126, 234, 0.2);
    font-family: Georgia, serif;
}

/* ========================================
   导航补充
   ======================================== */
.nav-link-home {
    opacity: 0.75;
    font-size: 0.9em;
}

.nav-link-home:hover {
    opacity: 1;
}

/* ========================================
   滚动入场动画系统
   ======================================== */
.scroll-reveal {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.8s cubic-bezier(0.4, 0, 0.2, 1),
                transform 0.8s cubic-bezier(0.4, 0, 0.2, 1);
}

.scroll-reveal.revealed {
    opacity: 1;
    transform: translateY(0);
}

.scroll-reveal.reveal-left {
    transform: translateX(-30px);
}

.scroll-reveal.reveal-left.revealed {
    transform: translateX(0);
}

.scroll-reveal.reveal-right {
    transform: translateX(30px);
}

.scroll-reveal.reveal-right.revealed {
    transform: translateX(0);
}

.scroll-reveal.reveal-scale {
    transform: scale(0.95);
}

.scroll-reveal.reveal-scale.revealed {
    transform: scale(1);
}

.scroll-delay-1 { transition-delay: 0.1s; }
.scroll-delay-2 { transition-delay: 0.2s; }
.scroll-delay-3 { transition-delay: 0.3s; }
.scroll-delay-4 { transition-delay: 0.4s; }
.scroll-delay-5 { transition-delay: 0.5s; }

/* ========================================
   浮动装饰元素
   ======================================== */
@keyframes float-slow {
    0%, 100% { transform: translateY(0) rotate(0deg); }
    50% { transform: translateY(-20px) rotate(3deg); }
}

@keyframes float-medium {
    0%, 100% { transform: translateY(0) rotate(0deg); }
    50% { transform: translateY(-15px) rotate(-2deg); }
}

@keyframes gradient-shift {
    0%, 100% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
}

@keyframes border-glow {
    0%, 100% { border-color: rgba(37, 99, 235, 0.15); }
    50% { border-color: rgba(37, 99, 235, 0.35); }
}

/* 主内容背景装饰 */
.main-content {
    position: relative;
}

.main-content::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-image:
        linear-gradient(rgba(148, 163, 184, 0.06) 1px, transparent 1px),
        linear-gradient(90deg, rgba(148, 163, 184, 0.06) 1px, transparent 1px);
    background-size: 80px 80px;
    mask-image: linear-gradient(180deg, rgba(255, 255, 255, 0.6) 0%, rgba(255, 255, 255, 0) 60%);
    -webkit-mask-image: linear-gradient(180deg, rgba(255, 255, 255, 0.6) 0%, rgba(255, 255, 255, 0) 60%);
    pointer-events: none;
    z-index: -1;
}

/* ========================================
   卡片发光边框效果
   ======================================== */
.lesson-card::after,
.exercise-card::after {
    content: '';
    position: absolute;
    inset: 0;
    border-radius: inherit;
    padding: 1px;
    background: linear-gradient(135deg, rgba(37, 99, 235, 0), rgba(37, 99, 235, 0.15), rgba(99, 102, 241, 0.1), rgba(37, 99, 235, 0));
    -webkit-mask: linear-gradient(#fff 0 0) content-box, linear-gradient(#fff 0 0);
    -webkit-mask-composite: xor;
    mask-composite: exclude;
    opacity: 0;
    transition: opacity 0.4s ease;
    pointer-events: none;
    z-index: 2;
}

.lesson-card:hover::after,
.exercise-card:hover::after {
    opacity: 1;
}

/* ========================================
   增强按钮发光效果
   ======================================== */
.btn-primary:hover {
    box-shadow: 0 8px 25px rgba(37, 99, 235, 0.35), 0 0 40px rgba(37, 99, 235, 0.1);
}

.btn-secondary:hover {
    box-shadow: 0 8px 25px rgba(16, 185, 129, 0.35), 0 0 40px rgba(16, 185, 129, 0.1);
}

/* ========================================
   毛玻璃面板通用类
   ======================================== */
.glass-panel {
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid var(--glass-border);
    box-shadow: var(--glass-shadow);
    border-radius: var(--radius-lg);
}