:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --secondary-color: #f1f5f9;
    --text-main: #1e293b;
    --text-muted: #64748b;
    --bg-main: #ffffff;
    --bg-dark: #0f172a;
    --border-color: #e2e8f0;
    --transition: all 0.3s ease;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 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);
}

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

body {
    font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';
    color: var(--text-main);
    background-color: var(--bg-main);
    line-height: 1.6;
    overflow-x: hidden;
}

/* Language Switcher Logic */
body.lang-en .zh {
    display: none !important;
}

body.lang-zh .en {
    display: none !important;
}

a {
    text-decoration: none;
    color: var(--primary-color);
    transition: var(--transition);
}

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

ul {
    list-style: none;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

/* Header & Nav */
header {
    background-color: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 1000;
}

nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 80px;
}

.logo {
    font-size: 24px;
    font-weight: 700;
    color: var(--primary-color);
    display: flex;
    align-items: center;
    gap: 12px;
}

.nav-links {
    display: flex;
    gap: 32px;
    align-items: center;
}

.nav-links a {
    color: var(--text-main);
    font-weight: 500;
    font-size: 16px;
}

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

.lang-switch {
    background-color: var(--secondary-color);
    border: none;
    padding: 8px 16px;
    border-radius: 20px;
    cursor: pointer;
    font-weight: 600;
    color: var(--text-main);
    transition: var(--transition);
}

.lang-switch:hover {
    background-color: #e2e8f0;
}

/* Hero Section */
.hero {
    padding: 160px 0 100px;
    background: linear-gradient(135deg, #f8fafc 0%, #e0e7ff 100%);
    text-align: center;
}

.hero h1 {
    font-size: 48px;
    font-weight: 800;
    line-height: 1.2;
    margin-bottom: 24px;
    color: var(--bg-dark);
}

.hero p {
    font-size: 20px;
    color: var(--text-muted);
    max-width: 800px;
    margin: 0 auto 40px;
}

.btn {
    display: inline-block;
    padding: 14px 32px;
    background-color: var(--primary-color);
    color: white !important;
    font-weight: 600;
    border-radius: 8px;
    font-size: 18px;
    border: none;
    cursor: pointer;
    box-shadow: var(--shadow-md);
}

.btn:hover {
    background-color: var(--primary-hover);
    box-shadow: var(--shadow-lg);
    transform: translateY(-2px);
}

.btn-secondary {
    background-color: white;
    color: var(--primary-color) !important;
    border: 1px solid var(--primary-color);
}

.btn-secondary:hover {
    background-color: var(--secondary-color);
}

/* Sections */
.section {
    padding: 100px 0;
}

.section-title {
    text-align: center;
    font-size: 36px;
    font-weight: 700;
    margin-bottom: 16px;
}

.section-subtitle {
    text-align: center;
    color: var(--text-muted);
    font-size: 18px;
    margin-bottom: 60px;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

/* Services / Features Grid */
.grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 32px;
}

.card {
    background: white;
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 40px 32px;
    transition: var(--transition);
}

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

.card-icon {
    width: 64px;
    height: 64px;
    background-color: var(--secondary-color);
    border-radius: 16px;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 24px;
    color: var(--primary-color);
}

.card-icon svg {
    width: 32px;
    height: 32px;
}

.card h3 {
    font-size: 24px;
    margin-bottom: 16px;
}

.card p {
    color: var(--text-muted);
}

/* Contact Info */
.contact-section {
    background-color: var(--bg-dark);
    color: white;
    padding: 80px 0;
}

.contact-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
}

.contact-info h2 {
    font-size: 32px;
    margin-bottom: 24px;
}

.contact-item {
    display: flex;
    align-items: flex-start;
    gap: 16px;
    margin-bottom: 24px;
}

.contact-item svg {
    width: 24px;
    height: 24px;
    color: var(--primary-color);
    flex-shrink: 0;
}

/* Footer */
footer {
    background-color: #020617;
    color: #94a3b8;
    padding: 60px 0 24px;
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: 40px;
    margin-bottom: 40px;
}

.footer-brand h3 {
    color: white;
    font-size: 24px;
    margin-bottom: 16px;
}

.footer-links h4 {
    color: white;
    font-size: 18px;
    margin-bottom: 20px;
}

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

.footer-links a {
    color: #94a3b8;
}

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

.footer-bottom {
    border-top: 1px solid #1e293b;
    padding-top: 24px;
    text-align: center;
    font-size: 14px;
}

/* Document Pages (Privacy, Terms) */
.doc-page {
    padding: 160px 0 100px;
}

.doc-content {
    max-width: 800px;
    margin: 0 auto;
    background: white;
    padding: 60px;
    border-radius: 12px;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-color);
}

.doc-content h1 {
    font-size: 40px;
    margin-bottom: 16px;
    color: var(--bg-dark);
}

.doc-content .last-updated {
    color: var(--text-muted);
    margin-bottom: 40px;
    font-size: 14px;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 24px;
}

.doc-content h2 {
    font-size: 24px;
    margin: 40px 0 16px;
    color: var(--bg-dark);
}

.doc-content h3 {
    font-size: 20px;
    margin: 24px 0 12px;
}

.doc-content p {
    margin-bottom: 16px;
    color: var(--text-main);
}

.doc-content ul {
    list-style: disc;
    margin-left: 24px;
    margin-bottom: 24px;
}

.doc-content li {
    margin-bottom: 8px;
}

/* Responsive */
@media (max-width: 768px) {
    .nav-links {
        display: none;
    }
    
    .hero h1 {
        font-size: 36px;
    }
    
    .contact-grid, .footer-grid {
        grid-template-columns: 1fr;
    }
    
    .doc-content {
        padding: 32px 24px;
    }
}