* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: var(--bg, #f8f9fa);
    color: #333;
    line-height: 1.6;
    transition: background 0.3s, color 0.3s;
}

[data-theme="dark"] body {
    background: #1a1a2e;
    color: #e0e0e0;
}

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

/* 导航栏 */
.navbar {
    background: rgba(255,255,255,0.95);
    backdrop-filter: blur(10px);
    box-shadow: 0 2px 20px rgba(0,0,0,0.1);
    position: sticky;
    top: 0;
    z-index: 1000;
    padding: 15px 0;
}

[data-theme="dark"] .navbar {
    background: rgba(26,26,46,0.95);
}

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

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary, #007bff);
    text-decoration: none;
}

.logo i {
    margin-right: 8px;
}

.nav-links {
    display: flex;
    gap: 25px;
}

.nav-links a {
    text-decoration: none;
    color: #555;
    font-weight: 500;
    transition: color 0.3s;
    position: relative;
}

.nav-links a:hover, .nav-links a.active {
    color: var(--primary, #007bff);
}

[data-theme="dark"] .nav-links a {
    color: #ccc;
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: 10px;
}

.nav-actions button {
    background: none;
    border: none;
    font-size: 1.2rem;
    cursor: pointer;
    padding: 8px;
    border-radius: 50%;
    transition: background 0.3s;
    color: #555;
}

.nav-actions button:hover {
    background: rgba(0,0,0,0.1);
}

[data-theme="dark"] .nav-actions button {
    color: #ccc;
}

.btn-login {
    padding: 8px 20px;
    background: var(--primary, #007bff);
    color: #fff;
    border-radius: 25px;
    text-decoration: none;
    font-weight: 500;
    transition: transform 0.3s, box-shadow 0.3s;
}

.btn-login:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(0,123,255,0.3);
}

.hamburger {
    display: none;
    font-size: 1.5rem;
}

/* 英雄区 */
.hero {
    background: linear-gradient(135deg, var(--primary, #007bff) 0%, #6c63ff 100%);
    color: #fff;
    padding: 80px 0;
    text-align: center;
}

.hero-content h1 {
    font-size: 2.5rem;
    margin-bottom: 20px;
    font-weight: 800;
}

.hero-content p {
    font-size: 1.1rem;
    max-width: 700px;
    margin: 0 auto 30px;
    opacity: 0.9;
}

.search-box {
    display: flex;
    max-width: 500px;
    margin: 0 auto;
    background: #fff;
    border-radius: 50px;
    overflow: hidden;
    box-shadow: 0 5px 20px rgba(0,0,0,0.2);
}

.search-box input {
    flex: 1;
    padding: 15px 20px;
    border: none;
    outline: none;
    font-size: 1rem;
}

.search-box button {
    padding: 15px 30px;
    background: var(--primary, #007bff);
    color: #fff;
    border: none;
    cursor: pointer;
    font-size: 1rem;
    transition: background 0.3s;
}

.search-box button:hover {
    background: #0056b3;
}

.hero-stats {
    display: flex;
    justify-content: center;
    gap: 30px;
    margin-top: 30px;
    font-size: 0.95rem;
}

.hero-stats i {
    margin-right: 8px;
}

/* 分类筛选 */
.filters {
    padding: 40px 0;
}

.filters h2 {
    text-align: center;
    margin-bottom: 20px;
    font-size: 1.8rem;
}

.filter-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    justify-content: center;
    margin-bottom: 20px;
}

.filter-btn {
    padding: 10px 25px;
    border: 2px solid #ddd;
    background: #fff;
    border-radius: 30px;
    cursor: pointer;
    font-size: 0.95rem;
    transition: all 0.3s;
}

.filter-btn:hover, .filter-btn.active {
    background: var(--primary, #007bff);
    color: #fff;
    border-color: var(--primary, #007bff);
}

[data-theme="dark"] .filter-btn {
    background: #2a2a4a;
    border-color: #444;
    color: #ccc;
}

.filter-extra {
    display: flex;
    justify-content: center;
    gap: 15px;
}

.filter-extra select {
    padding: 8px 15px;
    border: 1px solid #ddd;
    border-radius: 8px;
    background: #fff;
}

[data-theme="dark"] .filter-extra select {
    background: #2a2a4a;
    color: #ccc;
    border-color: #444;
}

/* 课程网格 */
.courses-grid {
    padding: 40px 0;
}

.courses-grid h2 {
    text-align: center;
    margin-bottom: 30px;
    font-size: 1.8rem;
}

.grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 25px;
}

.course-card {
    background: #fff;
    border-radius: 15px;
    box-shadow: 0 5px 20px rgba(0,0,0,0.08);
    overflow: hidden;
    transition: transform 0.3s, box-shadow 0.3s;
}

.course-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 30px rgba(0,0,0,0.15);
}

[data-theme="dark"] .course-card {
    background: #2a2a4a;
}

.card-img {
    height: 120px;
    background: linear-gradient(135deg, var(--primary, #007bff), #6c63ff);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 3rem;
    color: #fff;
}

.card-body {
    padding: 20px;
}

.card-body h3 {
    margin-bottom: 10px;
    font-size: 1.2rem;
}

.card-body p {
    color: #666;
    margin-bottom: 15px;
    font-size: 0.9rem;
}

[data-theme="dark"] .card-body p {
    color: #aaa;
}

.card-meta {
    display: flex;
    justify-content: space-between;
    margin-bottom: 10px;
}

.rating {
    color: #f39c12;
    font-weight: 600;
}

.price {
    font-weight: 700;
    color: var(--primary, #007bff);
}

.card-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 5px;
    margin-bottom: 15px;
}

.tag {
    padding: 3px 10px;
    background: #f0f0f0;
    border-radius: 15px;
    font-size: 0.8rem;
    color: #555;
}

[data-theme="dark"] .tag {
    background: #3a3a5a;
    color: #ccc;
}

.btn-enroll {
    width: 100%;
    padding: 10px;
    background: var(--primary, #007bff);
    color: #fff;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 1rem;
    transition: background 0.3s;
}

.btn-enroll:hover {
    background: #0056b3;
}

/* 统计热力图 */
.stats-heatmap {
    padding: 40px 0;
    background: #f0f0f5;
}

[data-theme="dark"] .stats-heatmap {
    background: #1a1a2e;
}

.stats-heatmap h2 {
    text-align: center;
    margin-bottom: 20px;
}

.stats-row {
    display: flex;
    justify-content: center;
    gap: 30px;
    margin-bottom: 20px;
    flex-wrap: wrap;
}

.stat-item {
    background: #fff;
    padding: 15px 25px;
    border-radius: 10px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
    font-weight: 500;
}

[data-theme="dark"] .stat-item {
    background: #2a2a4a;
}

.heatmap {
    display: flex;
    gap: 5px;
    justify-content: center;
    align-items: flex-end;
    height: 120px;
    padding: 10px;
    background: #fff;
    border-radius: 10px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}

[data-theme="dark"] .heatmap {
    background: #2a2a4a;
}

.heat-cell {
    width: 40px;
    background: linear-gradient(to top, #3498db, #e74c3c);
    border-radius: 5px 5px 0 0;
    transition: height 0.3s;
    opacity: 0.8;
}

.heat-cell:hover {
    opacity: 1;
}

/* 页脚 */
.footer {
    background: #2c3e50;
    color: #fff;
    padding: 40px 0;
    text-align: center;
}

[data-theme="dark"] .footer {
    background: #0d0d1a;
}

.footer-links {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 20px;
    margin-bottom: 20px;
}

.footer-links a {
    color: #ccc;
    text-decoration: none;
    transition: color 0.3s;
}

.footer-links a:hover {
    color: #fff;
}

.social-share {
    margin-bottom: 20px;
}

.social-share a {
    color: #ccc;
    font-size: 1.5rem;
    margin: 0 10px;
    transition: color 0.3s, transform 0.3s;
    display: inline-block;
}

.social-share a:hover {
    color: var(--primary, #007bff);
    transform: translateY(-3px);
}

.footer p {
    font-size: 0.9rem;
    opacity: 0.8;
}

/* 管理后台样式 */
.admin-login-body, .admin-body {
    background: #f0f2f5;
}

[data-theme="dark"] .admin-login-body, [data-theme="dark"] .admin-body {
    background: #1a1a2e;
}

.login-container {
    max-width: 400px;
    margin: 100px auto;
    background: #fff;
    padding: 40px;
    border-radius: 20px;
    box-shadow: 0 10px 40px rgba(0,0,0,0.1);
}

[data-theme="dark"] .login-container {
    background: #2a2a4a;
}

.login-container h2 {
    text-align: center;
    margin-bottom: 30px;
}

.login-container input {
    width: 100%;
    padding: 12px;
    margin-bottom: 15px;
    border: 1px solid #ddd;
    border-radius: 8px;
}

[data-theme="dark"] .login-container input {
    background: #3a3a5a;
    border-color: #444;
    color: #fff;
}

.login-container button {
    width: 100%;
    padding: 12px;
    background: var(--primary, #007bff);
    color: #fff;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 1rem;
}

.back-link {
    text-align: center;
    margin-top: 15px;
}

.back-link a {
    color: var(--primary, #007bff);
    text-decoration: none;
}

.admin-container {
    max-width: 1300px;
    margin: 0 auto;
    padding: 20px;
}

.admin-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
    flex-wrap: wrap;
}

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

.admin-actions {
    display: flex;
    gap: 15px;
    align-items: center;
}

.btn-logout, .btn-back {
    padding: 8px 20px;
    border-radius: 8px;
    text-decoration: none;
    color: #fff;
    font-weight: 500;
}

.btn-logout {
    background: #e74c3c;
}

.btn-back {
    background: var(--primary, #007bff);
}

.alert {
    padding: 15px;
    border-radius: 8px;
    margin-bottom: 20px;
}

.alert.success {
    background: #d4edda;
    color: #155724;
    border: 1px solid #c3e6cb;
}

.admin-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(400px, 1fr));
    gap: 20px;
}

.admin-card {
    background: #fff;
    padding: 25px;
    border-radius: 15px;
    box-shadow: 0 2px 15px rgba(0,0,0,0.05);
}

[data-theme="dark"] .admin-card {
    background: #2a2a4a;
}

.admin-card.full-width {
    grid-column: 1 / -1;
}

.admin-card h2 {
    font-size: 1.3rem;
    margin-bottom: 20px;
    border-bottom: 2px solid var(--primary, #007bff);
    padding-bottom: 10px;
}

.form-group {
    margin-bottom: 15px;
}

.form-group label {
    display: block;
    margin-bottom: 5px;
    font-weight: 500;
}

.form-group input, .form-group textarea, .form-group select {
    width: 100%;
    padding: 10px;
    border: 1px solid #ddd;
    border-radius: 8px;
}

[data-theme="dark"] .form-group input, [data-theme="dark"] .form-group textarea, [data-theme="dark"] .form-group select {
    background: #3a3a5a;
    border-color: #444;
    color: #fff;
}

.btn-primary {
    padding: 10px 25px;
    background: var(--primary, #007bff);
    color: #fff;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 1rem;
    transition: background 0.3s;
}

.btn-primary:hover {
    background: #0056b3;
}

.btn-danger {
    padding: 5px 15px;
    background: #e74c3c;
    color: #fff;
    border-radius: 5px;
    text-decoration: none;
    font-size: 0.9rem;
}

.table-wrapper {
    overflow-x: auto;
}

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

table th, table td {
    padding: 12px;
    text-align: left;
    border-bottom: 1px solid #eee;
}

[data-theme="dark"] table th, [data-theme="dark"] table td {
    border-color: #444;
}

table th {
    background: #f8f9fa;
    font-weight: 600;
}

[data-theme="dark"] table th {
    background: #3a3a5a;
}

.ai-result {
    margin-top: 15px;
    padding: 15px;
    background: #f8f9fa;
    border-radius: 8px;
}

[data-theme="dark"] .ai-result {
    background: #3a3a5a;
}

/* 内页通用样式 */
.page-hero {
    background: linear-gradient(135deg, var(--primary, #007bff), #6c63ff);
    color: #fff;
    padding: 60px 0;
    text-align: center;
}

.page-hero h1 {
    font-size: 2.2rem;
    margin-bottom: 15px;
}

.page-content {
    padding: 40px 0;
}

.page-content h2 {
    margin-top: 30px;
    margin-bottom: 15px;
}

.page-content p {
    margin-bottom: 15px;
    line-height: 1.8;
}

.faq-item {
    margin-bottom: 20px;
    padding: 20px;
    background: #fff;
    border-radius: 10px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}

[data-theme="dark"] .faq-item {
    background: #2a2a4a;
}

.faq-item h3 {
    margin-bottom: 10px;
    color: var(--primary, #007bff);
}

.blog-card {
    background: #fff;
    border-radius: 15px;
    padding: 20px;
    margin-bottom: 20px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}

[data-theme="dark"] .blog-card {
    background: #2a2a4a;
}

.blog-card h3 {
    margin-bottom: 10px;
}

.blog-card .date {
    color: #888;
    font-size: 0.9rem;
}

/* 响应式 */
@media (max-width: 768px) {
    .nav-links {
        display: none;
        position: absolute;
        top: 70px;
        left: 0;
        right: 0;
        background: #fff;
        flex-direction: column;
        padding: 20px;
        box-shadow: 0 5px 20px rgba(0,0,0,0.1);
    }

    [data-theme="dark"] .nav-links {
        background: #1a1a2e;
    }

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

    .hamburger {
        display: block;
    }

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

    .hero-stats {
        flex-direction: column;
        gap: 10px;
    }

    .filter-extra {
        flex-direction: column;
        align-items: center;
    }

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

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

    .stats-row {
        flex-direction: column;
        align-items: center;
    }

    .heatmap {
        height: 80px;
    }

    .heat-cell {
        width: 25px;
    }
}