/* ===== 基础样式 ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-color: #667eea;
    --secondary-color: #764ba2;
    --accent-color: #f59e0b;
    --bg-color: #ffffff;
    --bg-secondary: #f9fafb;
    --text-primary: #111827;
    --text-secondary: #6b7280;
    --border-color: #e5e7eb;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --transition: all 0.3s ease;
}

.dark-mode {
    --bg-color: #111827;
    --bg-secondary: #1f2937;
    --text-primary: #f9fafb;
    --text-secondary: #9ca3af;
    --border-color: #374151;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
}

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

/* ===== 导航栏 ===== */
.navbar {
    background-color: var(--bg-color);
    border-bottom: 1px solid var(--border-color);
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    transition: var(--transition);
}

.navbar.scrolled {
    box-shadow: var(--shadow);
}

.navbar .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

.nav-logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
    text-decoration: none;
}

.logo-icon {
    width: 32px;
    height: 32px;
    color: var(--primary-color);
}

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

.nav-link {
    color: var(--text-primary);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
    position: relative;
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    transition: var(--transition);
}

.nav-link:hover::after {
    width: 100%;
}

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

.theme-toggle {
    background: none;
    border: 1px solid var(--border-color);
    border-radius: 50%;
    width: 40px;
    height: 40px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.theme-toggle:hover {
    background-color: var(--bg-secondary);
}

.sun-icon, .moon-icon {
    width: 20px;
    height: 20px;
}

.dark-mode .sun-icon {
    display: none;
}

.moon-icon {
    display: none;
}

.dark-mode .moon-icon {
    display: block;
}

.mobile-menu-btn {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 5px;
}

.mobile-menu-btn span {
    width: 25px;
    height: 2px;
    background-color: var(--text-primary);
    transition: var(--transition);
}

/* ===== 首屏横幅 ===== */
.hero {
    padding: 150px 0 100px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: url('data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100"><circle cx="50" cy="50" r="40" fill="rgba(255,255,255,0.05)"/></svg>');
    background-size: 50px 50px;
}

.hero .container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
    align-items: center;
    position: relative;
    z-index: 1;
}

.hero-content {
    animation: fadeInUp 1s ease;
}

.hero-title {
    font-size: 4rem;
    font-weight: 800;
    margin-bottom: 20px;
    text-shadow: 2px 2px 10px rgba(0, 0, 0, 0.2);
}

.hero-subtitle {
    font-size: 1.8rem;
    font-weight: 600;
    margin-bottom: 20px;
    opacity: 0.95;
}

.hero-description {
    font-size: 1.1rem;
    margin-bottom: 30px;
    opacity: 0.9;
    line-height: 1.8;
}

.hero-plane {
    width: 100%;
    height: auto;
    max-width: 500px;
    margin: 0 auto;
    animation: float 3s ease-in-out infinite;
}

@keyframes float {
    0%, 100% { transform: translateY(0px); }
    50% { transform: translateY(-20px); }
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ===== 按钮样式 ===== */
.btn {
    display: inline-block;
    padding: 14px 32px;
    border-radius: 50px;
    font-weight: 600;
    text-decoration: none;
    cursor: pointer;
    transition: var(--transition);
    border: none;
    font-size: 1rem;
}

.btn-primary {
    background: white;
    color: var(--primary-color);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
}

.btn-secondary {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
}

.btn-secondary:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 30px rgba(102, 126, 234, 0.4);
}

.btn-large {
    padding: 18px 42px;
    font-size: 1.1rem;
}

/* ===== 特性区域 ===== */
.features {
    padding: 100px 0;
    background-color: var(--bg-secondary);
}

.section-title {
    font-size: 2.5rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: 15px;
    color: var(--text-primary);
}

.section-subtitle {
    font-size: 1.2rem;
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: 60px;
}

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

.feature-card {
    background-color: var(--bg-color);
    padding: 40px 30px;
    border-radius: 20px;
    box-shadow: var(--shadow);
    transition: var(--transition);
    text-align: center;
}

.feature-card:hover {
    transform: translateY(-10px);
    box-shadow: var(--shadow-lg);
}

.feature-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto 25px;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    border-radius: 20px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.feature-icon svg {
    width: 40px;
    height: 40px;
    color: white;
}

.feature-card h3 {
    font-size: 1.4rem;
    margin-bottom: 15px;
    color: var(--text-primary);
}

.feature-card p {
    color: var(--text-secondary);
    line-height: 1.8;
}

/* ===== 下载区域 ===== */
.download {
    padding: 100px 0;
    background-color: var(--bg-color);
}

.download-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
    margin-top: 50px;
}

.download-card {
    background-color: var(--bg-secondary);
    padding: 40px 30px;
    border-radius: 20px;
    text-align: center;
    transition: var(--transition);
    border: 2px solid transparent;
}

.download-card:hover {
    border-color: var(--primary-color);
    transform: scale(1.02);
}

.download-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto 25px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.download-icon svg {
    width: 60px;
    height: 60px;
    color: var(--text-primary);
}

.download-card h3 {
    font-size: 1.5rem;
    margin-bottom: 10px;
    color: var(--text-primary);
}

.download-card p {
    color: var(--text-secondary);
    margin-bottom: 25px;
}

/* ===== 常见问题 ===== */
.faq {
    padding: 100px 0;
    background-color: var(--bg-secondary);
}

.faq-list {
    max-width: 800px;
    margin: 0 auto;
}

.faq-item {
    background-color: var(--bg-color);
    border-radius: 15px;
    margin-bottom: 15px;
    overflow: hidden;
    box-shadow: var(--shadow);
    transition: var(--transition);
}

.faq-item:hover {
    box-shadow: var(--shadow-lg);
}

.faq-question {
    padding: 25px 30px;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-weight: 600;
    color: var(--text-primary);
}

.faq-icon {
    width: 20px;
    height: 20px;
    transition: var(--transition);
}

.faq-item.active .faq-icon {
    transform: rotate(180deg);
}

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease;
    padding: 0 30px;
}

.faq-item.active .faq-answer {
    max-height: 500px;
    padding: 0 30px 25px;
}

.faq-answer p {
    color: var(--text-secondary);
    line-height: 1.8;
    padding-top: 10px;
    border-top: 1px solid var(--border-color);
}

/* ===== 底部行动号召 ===== */
.cta {
    padding: 100px 0;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    text-align: center;
    color: white;
}

.cta h2 {
    font-size: 2.5rem;
    margin-bottom: 20px;
}

.cta p {
    font-size: 1.2rem;
    margin-bottom: 30px;
    opacity: 0.95;
}

.cta .btn-primary {
    background: white;
    color: var(--primary-color);
}

/* ===== 页脚 ===== */
.footer {
    background-color: var(--bg-color);
    border-top: 1px solid var(--border-color);
    padding: 60px 0 30px;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 40px;
    margin-bottom: 40px;
}

.footer-section h4 {
    font-size: 1.1rem;
    margin-bottom: 20px;
    color: var(--text-primary);
}

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

.footer-section ul li {
    margin-bottom: 12px;
}

.footer-section ul li a {
    color: var(--text-secondary);
    text-decoration: none;
    transition: var(--transition);
}

.footer-section ul li a:hover {
    color: var(--primary-color);
}

.social-links {
    display: flex;
    gap: 15px;
}

.social-links a {
    width: 40px;
    height: 40px;
    background-color: var(--bg-secondary);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.social-links a:hover {
    background-color: var(--primary-color);
    color: white;
}

.social-links a svg {
    width: 20px;
    height: 20px;
}

.footer-bottom {
    text-align: center;
    padding-top: 30px;
    border-top: 1px solid var(--border-color);
    color: var(--text-secondary);
}

/* ===== 响应式设计 ===== */
@media (max-width: 968px) {
    .hero .container {
        grid-template-columns: 1fr;
        text-align: center;
        gap: 40px;
    }
    
    .hero-title {
        font-size: 3rem;
    }
    
    .hero-plane {
        max-width: 300px;
    }
    
    .nav-menu {
        position: fixed;
        top: 70px;
        left: 0;
        right: 0;
        background-color: var(--bg-color);
        flex-direction: column;
        padding: 20px;
        gap: 15px;
        box-shadow: var(--shadow-lg);
        transform: translateY(-150%);
        transition: var(--transition);
    }
    
    .nav-menu.active {
        transform: translateY(0);
    }
    
    .mobile-menu-btn {
        display: flex;
    }
    
    .section-title {
        font-size: 2rem;
    }
    
    .features-grid,
    .download-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 640px) {
    .hero-title {
        font-size: 2.2rem;
    }
    
    .hero-subtitle {
        font-size: 1.4rem;
    }
    
    .hero {
        padding: 120px 0 80px;
    }
    
    .section-title {
        font-size: 1.8rem;
    }
    
    .footer-content {
        grid-template-columns: 1fr 1fr;
    }
}