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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: #333;
    background: #f8f9fa;
}

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

/* 导航栏 */
.navbar {
    background: #2c3e50;
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

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

.logo {
    color: #fff;
    font-size: 1.5rem;
    font-weight: bold;
    text-decoration: none;
}

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

.nav-links a {
    color: #ecf0f1;
    text-decoration: none;
    padding: 0.5rem 1rem;
    border-radius: 4px;
    transition: all 0.3s ease;
}

.nav-links a:hover,
.nav-links a.active {
    background: #3498db;
    color: #fff;
}

/* 按钮样式 */
.btn {
    display: inline-block;
    padding: 0.8rem 2rem;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-size: 1rem;
    text-decoration: none;
    transition: all 0.3s ease;
}

.btn-primary {
    background: #3498db;
    color: #fff;
}

.btn-primary:hover {
    background: #2980b9;
    transform: translateY(-2px);
}

.btn-secondary {
    background: #2ecc71;
    color: #fff;
}

.btn-secondary:hover {
    background: #27ae60;
}

/* 英雄区域 */
.hero {
    background: linear-gradient(135deg, #3498db, #2c3e50);
    color: #fff;
    padding: 6rem 0;
    text-align: center;
}

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

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

.hero-stats {
    display: flex;
    justify-content: center;
    gap: 3rem;
    margin-bottom: 2rem;
}

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

.stat-number {
    display: block;
    font-size: 2rem;
    font-weight: bold;
}

.stat-label {
    font-size: 0.9rem;
    opacity: 0.9;
}

/* 通用章节样式 */
.section-padding {
    padding: 4rem 0;
}

.section-title {
    text-align: center;
    font-size: 2rem;
    margin-bottom: 3rem;
    color: #2c3e50;
}

.bg-light {
    background: #ecf0f1;
}

/* 特色卡片网格 */
.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.feature-card {
    background: #fff;
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 12px rgba(0,0,0,0.15);
}

.feature-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.feature-card h3 {
    margin-bottom: 0.5rem;
    color: #2c3e50;
}

/* 进度看板 */
.progress-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1.5rem;
}

.progress-item {
    background: #fff;
    padding: 1.5rem;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

.progress-item h4 {
    margin-bottom: 0.5rem;
    color: #2c3e50;
}

.progress-bar {
    width: 100%;
    height: 12px;
    background: #e0e0e0;
    border-radius: 6px;
    overflow: hidden;
    margin: 0.5rem 0;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, #3498db, #2ecc71);
    border-radius: 6px;
    transition: width 0.5s ease;
}

/* AI练习区域 */
.ai-card {
    background: #fff;
    padding: 2rem;
    border-radius: 8px;
    text-align: center;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}

.practice-result {
    margin-top: 1rem;
    padding: 1rem;
    background: #f0f0f0;
    border-radius: 4px;
    min-height: 50px;
}

/* 关于页面 */
.about-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    align-items: center;
}

.about-text h2 {
    color: #2c3e50;
    margin-top: 1.5rem;
    margin-bottom: 0.5rem;
}

.placeholder-img {
    width: 100%;
    height: 300px;
    background: #ecf0f1;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 5rem;
    border-radius: 8px;
}

/* 服务页面 */
.service-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.service-card {
    background: #fff;
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}

.service-card h3 {
    margin-bottom: 1rem;
    color: #2c3e50;
}

.service-card ul {
    list-style: none;
    padding: 1rem 0;
}

.service-card ul li {
    padding: 0.3rem 0;
    border-bottom: 1px solid #ecf0f1;
}

.service-card ul li:last-child {
    border-bottom: none;
}

/* 联系我们 */
.contact-wrapper {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
}

.contact-info h2 {
    color: #2c3e50;
    margin-bottom: 1rem;
}

.contact-info p {
    margin-bottom: 0.5rem;
}

.form-group {
    margin-bottom: 1rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.3rem;
    color: #555;
}

.form-group input,
.form-group textarea {
    width: 100%;
    padding: 0.5rem;
    border: 1px solid #ccc;
    border-radius: 4px;
    font-size: 1rem;
}

.form-message {
    margin-top: 1rem;
    padding: 0.5rem;
    border-radius: 4px;
}

/* 后台管理 */
.admin-tabs {
    display: flex;
    gap: 1rem;
    margin-bottom: 2rem;
}

.tab-btn {
    padding: 0.5rem 1.5rem;
    border: none;
    background: #ecf0f1;
    cursor: pointer;
    border-radius: 4px;
    transition: all 0.3s ease;
}

.tab-btn.active {
    background: #3498db;
    color: #fff;
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
}

/* 页脚 */
.footer {
    background: #2c3e50;
    color: #fff;
    text-align: center;
    padding: 1.5rem 0;
    margin-top: auto;
}

/* 响应式 */
@media (max-width: 768px) {
    .nav-links {
        gap: 0.5rem;
    }
    
    .hero h1 {
        font-size: 2rem;
    }
    
    .hero-stats {
        flex-direction: column;
        gap: 1rem;
    }
    
    .about-content,
    .contact-wrapper {
        grid-template-columns: 1fr;
    }
    
    .admin-tabs {
        flex-wrap: wrap;
    }
}