/* 全局样式 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-color: #4a90e2;
    --secondary-color: #f39c12;
    --success-color: #27ae60;
    --danger-color: #e74c3c;
    --light-bg: #f8f9fa;
    --dark-text: #2c3e50;
    --light-text: #7f8c8d;
    --border-color: #e0e0e0;
    --shadow: 0 2px 10px rgba(0,0,0,0.1);
    --shadow-hover: 0 5px 20px rgba(0,0,0,0.15);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Microsoft YaHei", sans-serif;
    line-height: 1.6;
    color: var(--dark-text);
    background-color: var(--light-bg);
}

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

/* 头部样式 */
.header {
    background: linear-gradient(135deg, var(--primary-color), #6a5acd);
    color: white;
    padding: 40px 0;
    text-align: center;
    box-shadow: var(--shadow);
}

.logo {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 15px;
    margin-bottom: 10px;
}

.logo i {
    font-size: 2.5em;
}

.logo h1 {
    font-size: 2.5em;
    font-weight: 700;
}

.tagline {
    font-size: 1.1em;
    opacity: 0.9;
    margin-top: 5px;
}

/* 搜索区域 */
.search-section {
    padding: 30px 0;
    background: white;
    box-shadow: 0 2px 5px rgba(0,0,0,0.05);
}

.search-box {
    display: flex;
    align-items: center;
    background: var(--light-bg);
    border: 2px solid var(--border-color);
    border-radius: 50px;
    padding: 12px 25px;
    transition: all 0.3s;
    max-width: 600px;
    margin: 0 auto;
}

.search-box:focus-within {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(74, 144, 226, 0.1);
}

.search-box i {
    color: var(--light-text);
    font-size: 1.2em;
    margin-right: 15px;
}

.search-box input {
    flex: 1;
    border: none;
    background: transparent;
    font-size: 1em;
    outline: none;
    color: var(--dark-text);
}

/* 筛选区域 */
.filter-section {
    padding: 30px 0;
    background: white;
    margin-top: 2px;
}

.filter-group {
    margin-bottom: 20px;
}

.filter-group:last-child {
    margin-bottom: 0;
}

.filter-group label {
    display: block;
    font-weight: 600;
    margin-bottom: 10px;
    color: var(--dark-text);
    font-size: 0.95em;
}

.filter-group label i {
    color: var(--primary-color);
    margin-right: 8px;
}

.filter-options {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.filter-btn {
    padding: 8px 20px;
    border: 2px solid var(--border-color);
    background: white;
    border-radius: 25px;
    cursor: pointer;
    font-size: 0.9em;
    transition: all 0.3s;
    color: var(--dark-text);
    font-weight: 500;
}

.filter-btn:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
    transform: translateY(-2px);
}

.filter-btn.active {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
    box-shadow: 0 3px 10px rgba(74, 144, 226, 0.3);
}

/* 统计区域 */
.stats-section {
    padding: 40px 0;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    margin-top: 2px;
}

.stats {
    display: flex;
    justify-content: space-around;
    flex-wrap: wrap;
    gap: 30px;
}

.stat-item {
    text-align: center;
    color: white;
}

.stat-item i {
    font-size: 2.5em;
    margin-bottom: 10px;
    opacity: 0.9;
}

.stat-item span {
    display: block;
    font-size: 2.5em;
    font-weight: 700;
    margin-bottom: 5px;
}

.stat-item p {
    font-size: 1em;
    opacity: 0.9;
}

/* 资源列表 */
.resources-section {
    padding: 50px 0;
}

.section-header {
    text-align: center;
    margin-bottom: 40px;
}

.section-header h2 {
    font-size: 2em;
    color: var(--dark-text);
    margin-bottom: 10px;
}

.section-header h2 i {
    color: var(--primary-color);
    margin-right: 10px;
}

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

.resources-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: 25px;
}

/* 资源卡片 */
.resource-card {
    background: white;
    border-radius: 15px;
    padding: 25px;
    box-shadow: var(--shadow);
    transition: all 0.3s;
    border: 2px solid transparent;
}

.resource-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-hover);
    border-color: var(--primary-color);
}

.card-header {
    display: flex;
    align-items: center;
    gap: 15px;
    margin-bottom: 15px;
}

.card-icon {
    width: 50px;
    height: 50px;
    background: linear-gradient(135deg, var(--primary-color), #6a5acd);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 1.5em;
}

.card-title {
    flex: 1;
}

.card-title h3 {
    font-size: 1.2em;
    color: var(--dark-text);
    margin-bottom: 5px;
}

.card-title .website-url {
    font-size: 0.85em;
    color: var(--light-text);
    word-break: break-all;
}

.card-description {
    color: var(--light-text);
    font-size: 0.95em;
    line-height: 1.6;
    margin-bottom: 15px;
}

.card-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 15px;
}

.tag {
    padding: 4px 12px;
    border-radius: 15px;
    font-size: 0.85em;
    font-weight: 500;
}

.tag-grade {
    background: #e3f2fd;
    color: #1976d2;
}

.tag-subject {
    background: #f3e5f5;
    color: #7b1fa2;
}

.tag-format {
    background: #e8f5e9;
    color: #388e3c;
}

.card-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: 15px;
    border-top: 1px solid var(--border-color);
}

.card-features {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
}

.feature {
    font-size: 0.85em;
    color: var(--light-text);
}

.feature i {
    color: var(--success-color);
    margin-right: 3px;
}

.visit-btn {
    padding: 8px 20px;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 20px;
    cursor: pointer;
    font-size: 0.9em;
    font-weight: 600;
    transition: all 0.3s;
    text-decoration: none;
    display: inline-block;
}

.visit-btn:hover {
    background: #357abd;
    transform: scale(1.05);
}

/* 使用说明 */
.guide-section {
    padding: 50px 0;
    background: white;
    margin-top: 2px;
}

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

.guide-section h2 i {
    color: var(--primary-color);
    margin-right: 10px;
}

.guide-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
}

.guide-card {
    text-align: center;
    padding: 30px 20px;
    border-radius: 15px;
    background: var(--light-bg);
    transition: all 0.3s;
}

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

.guide-icon {
    width: 60px;
    height: 60px;
    background: linear-gradient(135deg, var(--primary-color), #6a5acd);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5em;
    font-weight: 700;
    margin: 0 auto 20px;
}

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

.guide-card p {
    color: var(--light-text);
    font-size: 0.95em;
}

/* 页脚 */
.footer {
    background: var(--dark-text);
    color: white;
    text-align: center;
    padding: 30px 0;
}

.footer p {
    margin: 5px 0;
}

.footer-note {
    font-size: 0.9em;
    opacity: 0.7;
    margin-top: 10px;
}

/* 返回顶部按钮 */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    font-size: 1.2em;
    box-shadow: var(--shadow);
    transition: all 0.3s;
    opacity: 0;
    visibility: hidden;
    z-index: 1000;
}

.back-to-top.visible {
    opacity: 1;
    visibility: visible;
}

.back-to-top:hover {
    background: #357abd;
    transform: scale(1.1);
}

/* 无结果提示 */
.no-results {
    text-align: center;
    padding: 60px 20px;
    color: var(--light-text);
    grid-column: 1 / -1;
}

.no-results i {
    font-size: 4em;
    margin-bottom: 20px;
    opacity: 0.3;
}

.no-results h3 {
    font-size: 1.5em;
    margin-bottom: 10px;
}

.no-results p {
    font-size: 1em;
}

/* 响应式设计 */
@media (max-width: 768px) {
    .logo h1 {
        font-size: 1.8em;
    }
    
    .logo i {
        font-size: 1.8em;
    }
    
    .tagline {
        font-size: 0.95em;
    }
    
    .stats {
        flex-direction: column;
        gap: 20px;
    }
    
    .resources-grid {
        grid-template-columns: 1fr;
    }
    
    .filter-options {
        justify-content: flex-start;
    }
    
    .filter-btn {
        padding: 6px 15px;
        font-size: 0.85em;
    }
    
    .section-header h2 {
        font-size: 1.5em;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 15px;
    }
    
    .header {
        padding: 30px 0;
    }
    
    .logo h1 {
        font-size: 1.5em;
    }
    
    .card-header {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .card-footer {
        flex-direction: column;
        gap: 15px;
        align-items: flex-start;
    }
    
    .visit-btn {
        width: 100%;
        text-align: center;
    }
}

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

.resource-card {
    animation: fadeIn 0.5s ease-out;
}