/* 全局样式 */
:root {
    --primary-color: #4a90e2;
    --secondary-color: #2c3e50;
    --text-color: #333;
    --light-gray: #f5f5f5;
    --white: #ffffff;
}

* {
    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: var(--text-color);
}

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

/* 导航栏 */
header {
    background-color: var(--white);
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 1000;
}

nav {
    padding: 1rem 0;
}

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

.logo {
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--primary-color);
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 2rem;
}

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

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

/* 主要内容 */
main {
    margin-top: 70px;
}

/* 英雄区域 */
.hero {
    background: linear-gradient(135deg, var(--primary-color), #2980b9);
    color: var(--white);
    padding: 6rem 0;
    text-align: center;
}

.hero h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.hero p {
    font-size: 1.2rem;
    margin-bottom: 2rem;
}

.cta-button {
    display: inline-block;
    padding: 1rem 2rem;
    background-color: var(--white);
    color: var(--primary-color);
    text-decoration: none;
    border-radius: 5px;
    font-weight: bold;
    transition: transform 0.3s ease;
}

.cta-button:hover {
    transform: translateY(-2px);
}

/* 英雄区域统计数据 */
.hero-stats {
    display: flex;
    justify-content: center;
    gap: 2rem;
    margin: 2rem 0;
    flex-wrap: wrap;
}

.stat-item {
    background: rgba(255, 255, 255, 0.2);
    padding: 0.5rem 1rem;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 500;
}

/* 特色功能 */
.features {
    padding: 5rem 0;
    background-color: var(--light-gray);
}

.features h2 {
    text-align: center;
    margin-bottom: 3rem;
}

.feature-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
}

.feature-card {
    background: var(--white);
    padding: 2rem;
    border-radius: 10px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    text-align: center;
}

.feature-card h3 {
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.feature-card.highlight {
    border: 2px solid var(--primary-color);
    transform: scale(1.02);
}

/* AI讲书人区域 */
.ai-teachers {
    padding: 5rem 0;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: var(--white);
}

.ai-teachers h2 {
    text-align: center;
    margin-bottom: 1rem;
    color: var(--white);
}

.section-desc {
    text-align: center;
    margin-bottom: 3rem;
    font-size: 1.1rem;
    opacity: 0.9;
}

.teacher-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.teacher-card {
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
    padding: 2rem;
    border-radius: 15px;
    text-align: center;
    border: 1px solid rgba(255, 255, 255, 0.2);
    transition: transform 0.3s ease;
}

.teacher-card:hover {
    transform: translateY(-5px);
}

.teacher-avatar {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.teacher-card h3 {
    color: var(--white);
    margin-bottom: 1rem;
    font-size: 1.3rem;
}

.teacher-card p {
    margin-bottom: 1.5rem;
    opacity: 0.9;
    line-height: 1.5;
}

.chat-count {
    display: inline-block;
    background: rgba(255, 255, 255, 0.2);
    padding: 0.5rem 1rem;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 500;
}

/* 下载区域 */
.download {
    padding: 5rem 0;
    text-align: center;
}

.download h2 {
    margin-bottom: 1rem;
}

.download p {
    margin-bottom: 2rem;
}

.download-buttons {
    display: flex;
    justify-content: center;
    gap: 1rem;
}

.download-button {
    display: inline-block;
    padding: 1rem 2rem;
    background-color: var(--primary-color);
    color: var(--white);
    text-decoration: none;
    border-radius: 5px;
    font-weight: bold;
    transition: background-color 0.3s ease;
}

.download-button:hover {
    background-color: #357abd;
}

/* 联系我们 */
.contact {
    padding: 5rem 0;
    background-color: var(--light-gray);
    text-align: center;
}

.contact h2 {
    margin-bottom: 1rem;
}

.contact p {
    margin-bottom: 2rem;
}

.contact-info {
    max-width: 600px;
    margin: 0 auto;
}

/* 页脚 */
footer {
    background-color: var(--secondary-color);
    color: var(--white);
    padding: 2rem 0;
    text-align: center;
}

.icp-info {
    margin-top: 1rem;
    font-size: 0.9rem;
}

.icp-info a {
    color: var(--white);
    text-decoration: none;
    margin: 0 0.5rem;
    opacity: 0.8;
    transition: opacity 0.3s ease;
}

.icp-info a:hover {
    opacity: 1;
}

/* 响应式设计 */
@media (max-width: 768px) {
    .nav-links {
        display: none;
    }
    
    .hero h1 {
        font-size: 2rem;
    }
    
    .feature-grid {
        grid-template-columns: 1fr;
    }
    
    .download-buttons {
        flex-direction: column;
    }
    
    .hero-stats {
        gap: 1rem;
    }
    
    .stat-item {
        font-size: 0.8rem;
        padding: 0.4rem 0.8rem;
    }
    
    .teacher-grid {
        grid-template-columns: 1fr;
    }
    
    .teacher-avatar {
        font-size: 2.5rem;
    }
}