/* ========== 导航栏下拉菜单 ========== */
.dropdown {
    position: relative;
}

.dropdown-menu {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    background: var(--white);
    box-shadow: var(--shadow-lg);
    border-radius: 8px;
    padding: 10px 0;
    min-width: 200px;
    z-index: 1001;
}

.dropdown:hover .dropdown-menu,
.dropdown.active .dropdown-menu {
    display: block;
}

.dropdown-menu li {
    list-style: none;
}

.dropdown-menu a {
    display: block;
    padding: 8px 20px;
    color: var(--dark);
    text-decoration: none;
    font-size: 0.9rem;
    transition: all 0.3s;
    white-space: nowrap;
}

.dropdown-menu a:hover {
    background: var(--light);
    color: var(--primary);
}

.dropdown-menu a.active {
    color: var(--primary);
    font-weight: 600;
    background: #fff8f0;
}

.dropdown-arrow {
    display: inline-block;
    margin-left: 4px;
    font-size: 0.7rem;
    transition: transform 0.3s;
}

.dropdown:hover .dropdown-arrow {
    transform: rotate(180deg);
}

/* ========== 知识点页面导航 ========== */
.lesson-nav {
    background: var(--white);
    border-bottom: 1px solid var(--light-gray);
    padding: 15px 0;
    position: sticky;
    top: 70px;
    z-index: 999;
}

.lesson-nav .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 10px;
}

.lesson-nav a {
    color: var(--gray);
    text-decoration: none;
    font-size: 0.9rem;
    transition: color 0.3s;
}

.lesson-nav a:hover {
    color: var(--primary);
}

.lesson-nav .prev-next {
    display: flex;
    gap: 20px;
    align-items: center;
}

.lesson-nav .prev-next a {
    display: flex;
    align-items: center;
    gap: 5px;
    padding: 6px 14px;
    border-radius: 6px;
    border: 1px solid var(--light-gray);
    transition: all 0.3s;
}

.lesson-nav .prev-next a:hover {
    border-color: var(--primary);
    background: #fff8f0;
}

.lesson-nav .prev-next .disabled {
    opacity: 0.4;
    pointer-events: none;
}

.lesson-nav .current-topic {
    font-weight: 600;
    color: var(--primary);
    font-size: 0.95rem;
}

/* ========== 练习题嵌入样式 ========== */
.lesson-quiz {
    background: linear-gradient(135deg, #fff8f0 0%, #ffffff 100%);
    border: 2px solid var(--primary);
    border-radius: 12px;
    padding: 30px;
    margin-top: 40px;
}

.lesson-quiz h2 {
    color: var(--primary);
    font-size: 1.5rem;
    margin-bottom: 20px;
    display: flex;
    align-items: center;
    gap: 10px;
    border: none;
    padding: 0;
}

.lesson-quiz h2::before {
    content: '📝';
}

.lesson-quiz .quiz-card {
    box-shadow: none;
    padding: 0;
    margin: 0;
    background: transparent;
}

.lesson-quiz .quiz-option {
    background: var(--white);
}

/* ========== 知识点卡片网格 ========== */
.topic-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 20px;
    margin-top: 30px;
}

.topic-card {
    background: var(--white);
    border-radius: 12px;
    padding: 25px;
    box-shadow: var(--shadow);
    transition: all 0.3s;
    text-decoration: none;
    color: var(--dark);
    border-left: 4px solid var(--primary);
}

.topic-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
    border-left-color: var(--accent);
}

.topic-card h3 {
    font-size: 1.1rem;
    margin-bottom: 10px;
    color: var(--dark);
}

.topic-card p {
    font-size: 0.9rem;
    color: var(--gray);
    margin: 0;
}

.topic-card .topic-number {
    display: inline-block;
    background: var(--light);
    color: var(--primary);
    font-weight: 700;
    padding: 2px 10px;
    border-radius: 20px;
    font-size: 0.85rem;
    margin-bottom: 12px;
}

/* ========== 基础样式重置 ========== */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary: #E76F00;
    --primary-dark: #D65A00;
    --secondary: #5382A1;
    --accent: #F89820;
    --dark: #1a1a2e;
    --darker: #16213e;
    --light: #f8f9fa;
    --gray: #6c757d;
    --light-gray: #e9ecef;
    --white: #ffffff;
    --code-bg: #282c34;
    --code-keyword: #c678dd;
    --code-string: #98c379;
    --code-number: #d19a66;
    --code-class: #e5c07b;
    --code-method: #61afef;
    --code-comment: #5c6370;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    line-height: 1.6;
    color: var(--dark);
    background: var(--light);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* ========== 导航栏 ========== */
.navbar {
    background: var(--white);
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 1000;
}

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

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary);
    text-decoration: none;
}

.logo-icon {
    font-size: 1.8rem;
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 30px;
}

.nav-links a {
    text-decoration: none;
    color: var(--dark);
    font-weight: 500;
    transition: color 0.3s;
    position: relative;
}

.nav-links a:hover,
.nav-links a.active {
    color: var(--primary);
}

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--primary);
    transition: width 0.3s;
}

.nav-links a:hover::after,
.nav-links a.active::after {
    width: 100%;
}

.hamburger {
    display: none;
    flex-direction: column;
    cursor: pointer;
    gap: 5px;
}

.hamburger span {
    width: 25px;
    height: 3px;
    background: var(--dark);
    border-radius: 3px;
    transition: all 0.3s;
}

/* ========== 英雄区域 ========== */
.hero {
    background: linear-gradient(135deg, var(--dark) 0%, var(--darker) 100%);
    color: var(--white);
    padding: 100px 0;
    overflow: hidden;
}

.hero .container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
    align-items: center;
}

.hero h1 {
    font-size: 3rem;
    line-height: 1.2;
    margin-bottom: 20px;
}

.hero p {
    font-size: 1.2rem;
    color: var(--light-gray);
    margin-bottom: 30px;
}

.btn {
    display: inline-block;
    padding: 12px 30px;
    border-radius: 8px;
    text-decoration: none;
    font-weight: 600;
    transition: all 0.3s;
    cursor: pointer;
    border: none;
    font-size: 1rem;
}

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

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

.btn-secondary {
    background: transparent;
    color: var(--white);
    border: 2px solid var(--white);
    margin-left: 15px;
}

.btn-secondary:hover {
    background: var(--white);
    color: var(--dark);
}

/* 代码窗口 */
.hero-code {
    display: flex;
    justify-content: center;
}

.code-window {
    background: var(--code-bg);
    border-radius: 12px;
    overflow: hidden;
    width: 100%;
    max-width: 500px;
    box-shadow: 0 20px 40px rgba(0,0,0,0.3);
}

.code-header {
    background: #21252b;
    padding: 12px 15px;
    display: flex;
    align-items: center;
    gap: 8px;
}

.dot {
    width: 12px;
    height: 12px;
    border-radius: 50%;
}

.dot.red { background: #ff5f56; }
.dot.yellow { background: #ffbd2e; }
.dot.green { background: #27c93f; }

.code-header .title {
    margin-left: 10px;
    color: #abb2bf;
    font-size: 0.85rem;
}

.code-window pre {
    padding: 20px;
    overflow-x: auto;
}

.code-window code {
    font-family: 'Fira Code', 'Consolas', 'Monaco', monospace;
    font-size: 0.95rem;
    line-height: 1.6;
    color: #abb2bf;
}

/* 代码高亮 */
.keyword { color: #c678dd; }
.class { color: #e5c07b; }
.method { color: #61afef; }
.string { color: #98c379; }
.number { color: #d19a66; }
.comment { color: #5c6370; font-style: italic; }

/* ========== 特性区域 ========== */
.features {
    padding: 80px 0;
    background: var(--white);
}

.features h2,
.course-path h2,
.code-demo h2 {
    text-align: center;
    font-size: 2.2rem;
    margin-bottom: 50px;
    color: var(--dark);
}

.feature-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 30px;
}

.feature-card {
    text-align: center;
    padding: 30px;
    border-radius: 12px;
    background: var(--light);
    transition: transform 0.3s, box-shadow 0.3s;
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.feature-card .icon {
    font-size: 3rem;
    margin-bottom: 15px;
}

.feature-card h3 {
    font-size: 1.2rem;
    margin-bottom: 10px;
    color: var(--dark);
}

.feature-card p {
    color: var(--gray);
    font-size: 0.95rem;
}

/* ========== 学习路线 ========== */
.course-path {
    padding: 80px 0;
    background: var(--light);
}

.path-timeline {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 30px;
}

.path-item {
    display: flex;
    gap: 20px;
    background: var(--white);
    padding: 30px;
    border-radius: 12px;
    box-shadow: var(--shadow);
    transition: transform 0.3s;
}

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

.path-number {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--primary);
    opacity: 0.3;
    line-height: 1;
}

.path-content h3 {
    font-size: 1.3rem;
    margin-bottom: 8px;
    color: var(--dark);
}

.path-content p {
    color: var(--gray);
    margin-bottom: 12px;
    font-size: 0.95rem;
}

.path-link {
    color: var(--primary);
    text-decoration: none;
    font-weight: 600;
    transition: color 0.3s;
}

.path-link:hover {
    color: var(--primary-dark);
}

.path-link.soon {
    color: var(--gray);
    cursor: default;
}

/* ========== 代码演示 ========== */
.code-demo {
    padding: 80px 0;
    background: var(--white);
}

.demo-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 25px;
}

.demo-card {
    background: var(--code-bg);
    border-radius: 12px;
    overflow: hidden;
    box-shadow: var(--shadow);
}

.demo-card h3 {
    background: #21252b;
    color: #abb2bf;
    padding: 15px 20px;
    font-size: 1rem;
    font-weight: 600;
}

.demo-card pre {
    padding: 20px;
    overflow-x: auto;
}

.demo-card code {
    font-family: 'Fira Code', 'Consolas', 'Monaco', monospace;
    font-size: 0.9rem;
    line-height: 1.6;
    color: #abb2bf;
}

/* ========== 页脚 ========== */
.footer {
    background: var(--dark);
    color: var(--white);
    padding: 60px 0 20px;
}

.footer-content {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: 40px;
    margin-bottom: 40px;
}

.footer-section h4 {
    font-size: 1.1rem;
    margin-bottom: 20px;
    color: var(--accent);
}

.footer-section p {
    color: var(--light-gray);
    opacity: 0.8;
}

.footer-section ul {
    list-style: none;
}

.footer-section ul li {
    margin-bottom: 10px;
}

.footer-section ul a {
    color: var(--light-gray);
    text-decoration: none;
    opacity: 0.8;
    transition: opacity 0.3s;
}

.footer-section ul a:hover {
    opacity: 1;
    color: var(--accent);
}

.footer-bottom {
    border-top: 1px solid rgba(255,255,255,0.1);
    padding-top: 20px;
    text-align: center;
    color: var(--light-gray);
    opacity: 0.6;
    font-size: 0.9rem;
}

/* ========== 页面通用内容样式 ========== */
.page-header {
    background: linear-gradient(135deg, var(--dark) 0%, var(--darker) 100%);
    color: var(--white);
    padding: 80px 0 60px;
    text-align: center;
}

.page-header h1 {
    font-size: 2.5rem;
    margin-bottom: 15px;
}

.page-header p {
    font-size: 1.1rem;
    color: var(--light-gray);
    opacity: 0.9;
}

.content-section {
    padding: 60px 0;
}

.content-section:nth-child(even) {
    background: var(--light);
}

.content-section h2 {
    font-size: 1.8rem;
    margin-bottom: 25px;
    color: var(--dark);
    padding-bottom: 10px;
    border-bottom: 3px solid var(--primary);
    display: inline-block;
}

.content-section h3 {
    font-size: 1.3rem;
    margin: 30px 0 15px;
    color: var(--secondary);
}

.content-section p {
    margin-bottom: 15px;
    line-height: 1.8;
    color: #444;
}

.content-section ul,
.content-section ol {
    margin-left: 25px;
    margin-bottom: 20px;
}

.content-section li {
    margin-bottom: 10px;
    line-height: 1.7;
}

.code-block {
    background: var(--code-bg);
    border-radius: 10px;
    overflow: hidden;
    margin: 25px 0;
    box-shadow: var(--shadow);
}

.code-block .code-header {
    background: #21252b;
    padding: 10px 15px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.code-block .code-title {
    color: #abb2bf;
    font-size: 0.85rem;
}

.code-block .copy-btn {
    background: transparent;
    border: 1px solid #5c6370;
    color: #abb2bf;
    padding: 4px 12px;
    border-radius: 4px;
    cursor: pointer;
    font-size: 0.8rem;
    transition: all 0.3s;
}

.code-block .copy-btn:hover {
    border-color: var(--accent);
    color: var(--accent);
}

.code-block pre {
    padding: 20px;
    overflow-x: auto;
}

.code-block code {
    font-family: 'Fira Code', 'Consolas', 'Monaco', monospace;
    font-size: 0.95rem;
    line-height: 1.7;
    color: #abb2bf;
}

.tip-box {
    background: #fff3cd;
    border-left: 4px solid var(--accent);
    padding: 20px;
    border-radius: 0 8px 8px 0;
    margin: 25px 0;
}

.tip-box.info {
    background: #d1ecf1;
    border-left-color: var(--secondary);
}

.tip-box.success {
    background: #d4edda;
    border-left-color: #28a745;
}

.tip-box strong {
    display: block;
    margin-bottom: 8px;
    color: var(--dark);
}

.tip-box p {
    margin: 0;
    color: #555;
}

/* ========== 练习题样式 ========== */
.quiz-container {
    max-width: 800px;
    margin: 0 auto;
}

.quiz-card {
    background: var(--white);
    border-radius: 12px;
    padding: 30px;
    margin-bottom: 30px;
    box-shadow: var(--shadow);
}

.quiz-card h3 {
    font-size: 1.2rem;
    margin-bottom: 20px;
    color: var(--dark);
}

.quiz-options {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.quiz-option {
    padding: 15px 20px;
    border: 2px solid var(--light-gray);
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s;
    display: flex;
    align-items: center;
    gap: 10px;
}

.quiz-option:hover {
    border-color: var(--primary);
    background: #fff8f0;
}

.quiz-option.selected {
    border-color: var(--primary);
    background: #fff8f0;
}

.quiz-option.correct {
    border-color: #28a745;
    background: #f0fff4;
}

.quiz-option.wrong {
    border-color: #dc3545;
    background: #fff5f5;
}

.quiz-option input {
    display: none;
}

.option-label {
    font-weight: 600;
    color: var(--primary);
    min-width: 25px;
}

.quiz-result {
    margin-top: 20px;
    padding: 15px;
    border-radius: 8px;
    display: none;
}

.quiz-result.show {
    display: block;
}

.quiz-result.correct-msg {
    background: #d4edda;
    color: #155724;
}

.quiz-result.wrong-msg {
    background: #f8d7da;
    color: #721c24;
}

/* ========== 响应式设计 ========== */
@media (max-width: 992px) {
    .hero .container {
        grid-template-columns: 1fr;
        text-align: center;
    }

    .hero h1 {
        font-size: 2.2rem;
    }

    .hero-code {
        display: none;
    }

    .feature-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .path-timeline {
        grid-template-columns: 1fr;
    }

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

    .footer-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
}

@media (max-width: 768px) {
    .nav-links {
        display: none;
        position: absolute;
        top: 70px;
        left: 0;
        right: 0;
        background: var(--white);
        flex-direction: column;
        padding: 10px 20px;
        box-shadow: var(--shadow);
        gap: 0;
    }

    .nav-links.active {
        display: flex;
    }

    .nav-links > li {
        border-bottom: 1px solid var(--light-gray);
    }

    .nav-links > li:last-child {
        border-bottom: none;
    }

    .dropdown-menu {
        display: none;
        position: static;
        box-shadow: none;
        padding: 0 0 0 15px;
        border-radius: 0;
    }

    .dropdown.active .dropdown-menu {
        display: block;
    }

    .dropdown-arrow {
        float: right;
    }

    .dropdown:hover .dropdown-menu {
        display: none;
    }

    .dropdown.active .dropdown-menu {
        display: block;
        position: static;
        box-shadow: none;
        padding: 0 0 0 20px;
        background: var(--white);
    }

    .dropdown-menu a {
        padding: 8px 15px;
    }
}
        padding: 60px 0;
    }

    .hero h1 {
        font-size: 1.8rem;
    }

    .btn-secondary {
        margin-left: 0;
        margin-top: 10px;
    }

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

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

    .lesson-nav .prev-next {
        width: 100%;
        justify-content: space-between;
    }

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

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

.feature-card,
.path-item,
.demo-card,
.quiz-card {
    animation: fadeInUp 0.6s ease-out;
}

/* 表格样式 */
.data-table {
    width: 100%;
    border-collapse: collapse;
    margin: 25px 0;
    background: var(--white);
    box-shadow: var(--shadow);
    border-radius: 8px;
    overflow: hidden;
}

.data-table th,
.data-table td {
    padding: 15px;
    text-align: left;
    border-bottom: 1px solid var(--light-gray);
}

.data-table th {
    background: var(--dark);
    color: var(--white);
    font-weight: 600;
}

.data-table tr:hover {
    background: var(--light);
}

/* 两栏布局 */
.two-column {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 40px;
    align-items: start;
}

@media (max-width: 768px) {
    .two-column {
        grid-template-columns: 1fr;
    }
}