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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f8f9fa;
}

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

/* 按钮样式 */
.btn {
    display: inline-block;
    padding: 10px 20px;
    border: none;
    border-radius: 6px;
    text-decoration: none;
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s ease;
    text-align: center;
}

.btn-primary {
    background-color: #007bff;
    color: white;
}

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

.btn-outline {
    background-color: transparent;
    color: #007bff;
    border: 1px solid #007bff;
}

.btn-outline:hover {
    background-color: #007bff;
    color: white;
}

.btn-large {
    padding: 15px 30px;
    font-size: 16px;
}

.btn-success {
    background-color: #28a745;
    color: white;
}

.btn-success:hover {
    background-color: #218838;
}

.btn-danger {
    background-color: #dc3545;
    color: white;
}

.btn-danger:hover {
    background-color: #c82333;
}

/* 头部样式 */
.header {
    background-color: white;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    position: sticky;
    top: 0;
    z-index: 1000;
}

.header-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 15px 0;
}

.logo a {
    font-size: 24px;
    font-weight: bold;
    color: #007bff;
    text-decoration: none;
}

.nav {
    display: flex;
    gap: 30px;
}

.nav-link {
    color: #333;
    text-decoration: none;
    font-weight: 500;
    transition: color 0.3s ease;
}

.nav-link:hover,
.nav-link.active {
    color: #007bff;
}

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

.user-menu {
    display: flex;
    align-items: center;
    gap: 15px;
}

/* 主要内容 */
.main {
    min-height: calc(100vh - 200px);
}

/* 英雄区域 */
.hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 80px 0;
    text-align: center;
}

.hero-content h1 {
    font-size: 48px;
    margin-bottom: 20px;
    font-weight: 700;
}

.hero-content p {
    font-size: 20px;
    margin-bottom: 30px;
    opacity: 0.9;
}

/* 搜索区域 */
.search-section {
    padding: 40px 0;
    background-color: white;
}

.search-form {
    max-width: 800px;
    margin: 0 auto;
}

.search-input-group {
    display: flex;
    gap: 15px;
    align-items: center;
}

.search-input {
    flex: 1;
    padding: 12px 16px;
    border: 1px solid #ddd;
    border-radius: 6px;
    font-size: 16px;
}

.search-select {
    padding: 12px 16px;
    border: 1px solid #ddd;
    border-radius: 6px;
    font-size: 16px;
    min-width: 150px;
}

/* 课程网格 */
.courses-section,
.featured-courses {
    padding: 60px 0;
}

.section-title {
    font-size: 32px;
    margin-bottom: 40px;
    text-align: center;
    color: #333;
}

.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 40px;
}

.section-meta {
    color: #666;
    font-size: 14px;
}

.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 30px;
}

.course-card {
    background: white;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.course-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 25px rgba(0,0,0,0.15);
}

.course-image {
    position: relative;
    height: 200px;
    overflow: hidden;
}

.course-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.course-image-placeholder {
    width: 100%;
    height: 100%;
    background-color: #f8f9fa;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #666;
}

.course-badge {
    position: absolute;
    top: 10px;
    right: 10px;
    background-color: #ff6b6b;
    color: white;
    padding: 4px 8px;
    border-radius: 4px;
    font-size: 12px;
    font-weight: 500;
}

.course-content {
    padding: 20px;
}

.course-category {
    color: #007bff;
    font-size: 12px;
    font-weight: 500;
    text-transform: uppercase;
    margin-bottom: 8px;
}

.course-title {
    margin-bottom: 12px;
}

.course-title a {
    color: #333;
    text-decoration: none;
    font-size: 18px;
    font-weight: 600;
    line-height: 1.4;
}

.course-title a:hover {
    color: #007bff;
}

.course-description {
    color: #666;
    font-size: 14px;
    line-height: 1.5;
    margin-bottom: 15px;
}

.course-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.course-price {
    font-size: 18px;
    font-weight: 700;
    color: #e74c3c;
}

.original-price {
    font-size: 14px;
    color: #999;
    text-decoration: line-through;
    margin-left: 8px;
    font-weight: normal;
}

.course-stats {
    display: flex;
    gap: 15px;
    font-size: 12px;
    color: #666;
}

.course-views,
.course-purchases {
    display: flex;
    align-items: center;
}

/* 分页样式 */
.pagination {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 10px;
    margin-top: 40px;
}

.page-link {
    padding: 8px 12px;
    border: 1px solid #ddd;
    border-radius: 4px;
    color: #007bff;
    text-decoration: none;
    transition: all 0.3s ease;
}

.page-link:hover,
.page-link.active {
    background-color: #007bff;
    color: white;
    border-color: #007bff;
}

/* 空状态 */
.empty-state {
    text-align: center;
    padding: 60px 0;
    color: #666;
}

/* 页脚样式 */
.footer {
    background-color: #2c3e50;
    color: white;
    padding: 40px 0 20px;
    margin-top: 60px;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 40px;
    margin-bottom: 30px;
}

.footer-section h4 {
    margin-bottom: 15px;
    font-size: 18px;
}

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

.footer-section ul li {
    margin-bottom: 8px;
}

.footer-section a {
    color: #bdc3c7;
    text-decoration: none;
    transition: color 0.3s ease;
}

.footer-section a:hover {
    color: white;
}

.footer-bottom {
    border-top: 1px solid #34495e;
    padding-top: 20px;
    text-align: center;
    color: #bdc3c7;
}

/* 表单样式 */
.form-group {
    margin-bottom: 20px;
}

.form-label {
    display: block;
    margin-bottom: 5px;
    font-weight: 500;
    color: #333;
}

.form-control {
    width: 100%;
    padding: 12px 16px;
    border: 1px solid #ddd;
    border-radius: 6px;
    font-size: 16px;
    transition: border-color 0.3s ease;
}

.form-control:focus {
    outline: none;
    border-color: #007bff;
    box-shadow: 0 0 0 3px rgba(0,123,255,0.1);
}

.form-text {
    font-size: 12px;
    color: #666;
    margin-top: 5px;
}

/* 警告框 */
.alert {
    padding: 12px 16px;
    border-radius: 6px;
    margin-bottom: 20px;
}

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

.alert-error {
    background-color: #f8d7da;
    color: #721c24;
    border: 1px solid #f5c6cb;
}

.alert-info {
    background-color: #d1ecf1;
    color: #0c5460;
    border: 1px solid #bee5eb;
}

/* 响应式设计 */
@media (max-width: 768px) {
    .container {
        padding: 0 15px;
    }
    
    .header-content {
        flex-direction: column;
        gap: 20px;
    }
    
    .nav {
        gap: 20px;
    }
    
    .hero-content h1 {
        font-size: 32px;
    }
    
    .hero-content p {
        font-size: 16px;
    }
    
    .search-input-group {
        flex-direction: column;
    }
    
    .courses-grid {
        grid-template-columns: 1fr;
        gap: 20px;
    }
    
    .section-header {
        flex-direction: column;
        align-items: flex-start;
        gap: 10px;
    }
    
    .footer-content {
        grid-template-columns: 1fr;
        gap: 30px;
    }
}

/* 加载动画 */
.loading {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 3px solid #f3f3f3;
    border-top: 3px solid #007bff;
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* 工具类 */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.mt-10 { margin-top: 10px; }
.mt-20 { margin-top: 20px; }
.mt-30 { margin-top: 30px; }

.mb-10 { margin-bottom: 10px; }
.mb-20 { margin-bottom: 20px; }
.mb-30 { margin-bottom: 30px; }

.d-none { display: none; }
.d-block { display: block; }
.d-flex { display: flex; }

.justify-center { justify-content: center; }
.justify-between { justify-content: space-between; }
.align-center { align-items: center; }