/* ========================================
   Beijing Digital Square - Main Styles
   Corporate Website for European & American Markets
   ======================================== */

/* CSS Variables */
:root {
    /* Primary Colors - Audi-inspired */
    --primary-color: #1a1a1a;
    --secondary-color: #2c2c2c;
    --accent-color: #e63946;
    --accent-hover: #c1121f;
    --text-primary: #ffffff;
    --text-secondary: #b0b0b0;
    --text-dark: #1a1a1a;
    --background-dark: #0a0a0a;
    --background-light: #f5f5f5;
    --border-color: #333333;
    --gradient-start: #1a1a1a;
    --gradient-end: #2c2c2c;
    --shadow-light: rgba(255, 255, 255, 0.1);
    --shadow-dark: rgba(0, 0, 0, 0.3);
    
    /* Typography */
    --font-primary: 'Montserrat', 'Arial', sans-serif;
    --font-secondary: 'Roboto', 'Arial', sans-serif;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 2rem;
    --spacing-lg: 4rem;
    --spacing-xl: 8rem;
    
    /* Transitions */
    --transition-fast: 0.3s ease;
    --transition-medium: 0.5s ease;
    --transition-slow: 0.8s ease;
    
    /* Z-index layers */
    --z-dropdown: 1000;
    --z-sticky: 1020;
    --z-fixed: 1030;
    --z-modal-backdrop: 1040;
    --z-modal: 1050;
    --z-popover: 1060;
    --z-tooltip: 1070;
}

/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: var(--font-secondary);
    background-color: var(--background-dark);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-primary);
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: var(--spacing-sm);
}

h1 {
    font-size: 4rem;
    letter-spacing: -0.02em;
}

h2 {
    font-size: 3rem;
    letter-spacing: -0.01em;
}

h3 {
    font-size: 2rem;
}

h4 {
    font-size: 1.5rem;
}

p {
    margin-bottom: var(--spacing-sm);
    font-size: 1.1rem;
    color: var(--text-secondary);
}

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

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

/* Container */
.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

/* Navigation */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: var(--z-fixed);
    background: rgba(10, 10, 10, 0.95);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border-color);
    transition: var(--transition-medium);
}

.navbar.scrolled {
    background: rgba(10, 10, 10, 0.98);
    box-shadow: 0 4px 30px rgba(0, 0, 0, 0.5);
}

.nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-sm) var(--spacing-md);
    max-width: 1400px;
    margin: 0 auto;
}

.nav-logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-family: var(--font-primary);
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
}

.nav-logo svg {
    width: 50px;
    height: 50px;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: var(--spacing-lg);
}

.nav-link {
    font-family: var(--font-primary);
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
    padding: var(--spacing-xs) 0;
    position: relative;
    transition: var(--transition-fast);
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--accent-color);
    transition: var(--transition-fast);
}

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

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    cursor: pointer;
    padding: 10px;
}

.nav-toggle span {
    width: 30px;
    height: 3px;
    background: var(--text-primary);
    transition: var(--transition-fast);
}

/* Hero Section */
.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
    background: linear-gradient(135deg, var(--gradient-start) 0%, var(--gradient-end) 100%);
}

.hero-bg {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-size: cover;
    background-position: center;
    opacity: 0.3;
}

.hero-overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(180deg, rgba(10,10,10,0.7) 0%, rgba(10,10,10,0.9) 100%);
}

.hero-content {
    position: relative;
    z-index: 2;
    text-align: center;
    max-width: 1200px;
    padding: var(--spacing-xl) var(--spacing-md);
}

.hero h1 {
    font-size: 5rem;
    margin-bottom: var(--spacing-md);
    background: linear-gradient(135deg, var(--text-primary) 0%, var(--text-secondary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.5rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
}

.hero-buttons {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    flex-wrap: wrap;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: 1rem 2.5rem;
    font-family: var(--font-primary);
    font-size: 1rem;
    font-weight: 600;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    transition: var(--transition-fast);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

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

.btn-primary:hover {
    background: var(--accent-hover);
    transform: translateY(-2px);
    box-shadow: 0 10px 30px rgba(230, 57, 70, 0.3);
}

.btn-secondary {
    background: transparent;
    color: var(--text-primary);
    border: 2px solid var(--text-primary);
}

.btn-secondary:hover {
    background: var(--text-primary);
    color: var(--text-dark);
    transform: translateY(-2px);
}

/* Sections */
.section {
    padding: var(--spacing-xl) 0;
    position: relative;
}

.section-dark {
    background: var(--background-dark);
}

.section-light {
    background: var(--background-light);
    color: var(--text-dark);
}

.section-header {
    text-align: center;
    margin-bottom: var(--spacing-lg);
}

.section-header h2 {
    position: relative;
    display: inline-block;
    margin-bottom: var(--spacing-sm);
}

.section-header h2::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 50%;
    transform: translateX(-50%);
    width: 80px;
    height: 4px;
    background: var(--accent-color);
}

.section-header p {
    max-width: 800px;
    margin: var(--spacing-md) auto 0;
    color: var(--text-secondary);
}

/* Service Cards */
.services-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-md);
    margin-top: var(--spacing-lg);
}

.service-card {
    background: var(--secondary-color);
    border-radius: 8px;
    padding: var(--spacing-md);
    transition: var(--transition-medium);
    position: relative;
    overflow: hidden;
    border: 1px solid var(--border-color);
}

.service-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, var(--accent-color) 0%, transparent 100%);
    opacity: 0;
    transition: var(--transition-medium);
}

.service-card:hover {
    transform: translateY(-10px);
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.5);
}

.service-card:hover::before {
    opacity: 0.1;
}

.service-icon {
    width: 80px;
    height: 80px;
    margin-bottom: var(--spacing-md);
    position: relative;
    z-index: 1;
}

.service-icon svg {
    width: 100%;
    height: 100%;
    fill: var(--accent-color);
}

.service-card h3 {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-sm);
    position: relative;
    z-index: 1;
}

.service-card p {
    color: var(--text-secondary);
    position: relative;
    z-index: 1;
}

/* App Showcase */
.app-showcase {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-lg);
    align-items: center;
    margin: var(--spacing-lg) 0;
}

.app-content h3 {
    font-size: 2.5rem;
    margin-bottom: var(--spacing-md);
}

.app-features {
    list-style: none;
    margin-top: var(--spacing-md);
}

.app-features li {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-sm);
    font-size: 1.1rem;
}

.app-features li svg {
    width: 24px;
    height: 24px;
    fill: var(--accent-color);
}

.app-image {
    position: relative;
    display: flex;
    justify-content: center;
    align-items: center;
}

.app-mockup {
    width: 100%;
    max-width: 400px;
    height: auto;
    filter: drop-shadow(0 30px 60px rgba(0, 0, 0, 0.5));
}

/* Statistics */
.stats-section {
    background: linear-gradient(135deg, var(--accent-color) 0%, var(--accent-hover) 100%);
    padding: var(--spacing-xl) 0;
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-md);
    text-align: center;
}

.stat-item {
    padding: var(--spacing-md);
}

.stat-number {
    font-family: var(--font-primary);
    font-size: 4rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: var(--spacing-xs);
}

.stat-label {
    font-size: 1.2rem;
    color: rgba(255, 255, 255, 0.9);
    text-transform: uppercase;
    letter-spacing: 0.1em;
}

/* About Section */
.about-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-lg);
    align-items: center;
}

.about-content h2 {
    margin-bottom: var(--spacing-md);
}

.about-list {
    list-style: none;
    margin-top: var(--spacing-md);
}

.about-list li {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-sm);
    padding: var(--spacing-sm);
    background: var(--secondary-color);
    border-radius: 4px;
    transition: var(--transition-fast);
}

.about-list li:hover {
    background: var(--accent-color);
    transform: translateX(10px);
}

.about-list svg {
    width: 30px;
    height: 30px;
    fill: var(--accent-color);
}

.about-list li:hover svg {
    fill: var(--text-primary);
}

/* News Grid */
.news-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: var(--spacing-md);
}

.news-card {
    background: var(--secondary-color);
    border-radius: 8px;
    overflow: hidden;
    transition: var(--transition-medium);
    border: 1px solid var(--border-color);
}

.news-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 15px 40px rgba(0, 0, 0, 0.3);
}

.news-image {
    width: 100%;
    height: 200px;
    background-size: cover;
    background-position: center;
    position: relative;
}

.news-date {
    position: absolute;
    top: var(--spacing-sm);
    left: var(--spacing-sm);
    background: var(--accent-color);
    color: var(--text-primary);
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: 4px;
    font-size: 0.9rem;
    font-weight: 600;
}

.news-content {
    padding: var(--spacing-md);
}

.news-category {
    display: inline-block;
    background: var(--accent-color);
    color: var(--text-primary);
    padding: 4px 12px;
    border-radius: 4px;
    font-size: 0.85rem;
    margin-bottom: var(--spacing-xs);
}

.news-content h3 {
    font-size: 1.3rem;
    margin: var(--spacing-sm) 0;
    transition: var(--transition-fast);
}

.news-card:hover .news-content h3 {
    color: var(--accent-color);
}

/* Contact Section */
.contact-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-lg);
}

.contact-info {
    padding: var(--spacing-lg);
    background: var(--secondary-color);
    border-radius: 8px;
    border: 1px solid var(--border-color);
}

.contact-item {
    display: flex;
    align-items: flex-start;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-md);
    padding: var(--spacing-sm);
    transition: var(--transition-fast);
}

.contact-item:hover {
    background: rgba(230, 57, 70, 0.1);
    border-radius: 4px;
}

.contact-item svg {
    width: 40px;
    height: 40px;
    fill: var(--accent-color);
    flex-shrink: 0;
}

.contact-item h4 {
    font-size: 1.2rem;
    margin-bottom: var(--spacing-xs);
}

.contact-form {
    background: var(--secondary-color);
    padding: var(--spacing-lg);
    border-radius: 8px;
    border: 1px solid var(--border-color);
}

.form-group {
    margin-bottom: var(--spacing-md);
}

.form-group label {
    display: block;
    margin-bottom: var(--spacing-xs);
    font-weight: 600;
    font-size: 1rem;
}

.form-group input,
.form-group textarea,
.form-group select {
    width: 100%;
    padding: 1rem;
    background: var(--background-dark);
    border: 2px solid var(--border-color);
    border-radius: 4px;
    color: var(--text-primary);
    font-family: var(--font-secondary);
    font-size: 1rem;
    transition: var(--transition-fast);
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 20px rgba(230, 57, 70, 0.2);
}

.form-group textarea {
    min-height: 150px;
    resize: vertical;
}

/* Footer */
.footer {
    background: var(--background-dark);
    border-top: 1px solid var(--border-color);
    padding: var(--spacing-xl) 0 var(--spacing-md);
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr;
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
}

.footer-section h3 {
    font-size: 1.3rem;
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
}

.footer-section p {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
}

.footer-links {
    list-style: none;
}

.footer-links li {
    margin-bottom: var(--spacing-xs);
}

.footer-links a {
    color: var(--text-secondary);
    transition: var(--transition-fast);
}

.footer-links a:hover {
    color: var(--accent-color);
    padding-left: 5px;
}

.footer-bottom {
    padding-top: var(--spacing-md);
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: var(--spacing-md);
}

.footer-legal {
    display: flex;
    gap: var(--spacing-md);
}

.footer-legal a {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.footer-legal a:hover {
    color: var(--accent-color);
}

/* Legal Pages */
.legal-page {
    padding: 120px 0 var(--spacing-xl);
}

.legal-content {
    max-width: 900px;
    margin: 0 auto;
    background: var(--secondary-color);
    padding: var(--spacing-lg);
    border-radius: 8px;
    border: 1px solid var(--border-color);
}

.legal-content h1 {
    font-size: 3rem;
    margin-bottom: var(--spacing-md);
    text-align: center;
}

.legal-content h2 {
    font-size: 2rem;
    margin-top: var(--spacing-lg);
    margin-bottom: var(--spacing-md);
    color: var(--accent-color);
}

.legal-content h3 {
    font-size: 1.5rem;
    margin-top: var(--spacing-md);
    margin-bottom: var(--spacing-sm);
}

.legal-content p {
    margin-bottom: var(--spacing-sm);
    line-height: 1.8;
}

.legal-content ul {
    margin-left: var(--spacing-md);
    margin-bottom: var(--spacing-md);
}

.legal-content li {
    margin-bottom: var(--spacing-xs);
    color: var(--text-secondary);
}

/* Ad Network Section Styling */
.ad-network-item {
    background: var(--background-dark);
    padding: var(--spacing-md);
    border-radius: 4px;
    margin-bottom: var(--spacing-md);
    border-left: 4px solid var(--accent-color);
}

.ad-network-item h4 {
    color: var(--accent-color);
    margin-bottom: var(--spacing-xs);
}

/* Responsive Design */
@media (max-width: 1024px) {
    .nav-menu {
        gap: var(--spacing-md);
    }
    
    .hero h1 {
        font-size: 3.5rem;
    }
    
    .about-grid,
    .contact-grid,
    .app-showcase {
        grid-template-columns: 1fr;
    }
    
    .footer-grid {
        grid-template-columns: 1fr 1fr;
    }
}

@media (max-width: 768px) {
    .nav-toggle {
        display: flex;
    }
    
    .nav-menu {
        position: fixed;
        top: 70px;
        left: 0;
        right: 0;
        background: rgba(10, 10, 10, 0.98);
        flex-direction: column;
        padding: var(--spacing-md);
        gap: var(--spacing-md);
        transform: translateX(-100%);
        transition: var(--transition-medium);
        border-bottom: 1px solid var(--border-color);
    }
    
    .nav-menu.active {
        transform: translateX(0);
    }
    
    .hero h1 {
        font-size: 2.5rem;
    }
    
    .hero-subtitle {
        font-size: 1.2rem;
    }
    
    h2 {
        font-size: 2rem;
    }
    
    .services-grid,
    .news-grid {
        grid-template-columns: 1fr;
    }
    
    .stats-grid {
        grid-template-columns: 1fr 1fr;
    }
    
    .footer-grid {
        grid-template-columns: 1fr;
    }
    
    .footer-bottom {
        flex-direction: column;
        text-align: center;
    }
}

@media (max-width: 480px) {
    .hero-buttons {
        flex-direction: column;
    }
    
    .btn {
        width: 100%;
        justify-content: center;
    }
    
    .stat-number {
        font-size: 3rem;
    }
    
    .legal-content {
        padding: var(--spacing-md);
    }
    
    .legal-content h1 {
        font-size: 2rem;
    }
    
    .legal-content h2 {
        font-size: 1.5rem;
    }
}

/* Utility Classes */
.text-center {
    text-align: center;
}

.text-accent {
    color: var(--accent-color);
}

.mb-0 {
    margin-bottom: 0;
}

.mt-lg {
    margin-top: var(--spacing-lg);
}

.hidden {
    display: none !important;
}

.visible {
    display: block !important;
}

/* Performance optimizations */
.gpu-accelerated {
    transform: translateZ(0);
    -webkit-transform: translateZ(0);
    will-change: transform;
}

/* Focus states for accessibility */
a:focus,
button:focus,
input:focus,
textarea:focus,
select:focus {
    outline: 2px solid var(--accent-color);
    outline-offset: 2px;
}

/* Print styles */
@media print {
    .navbar,
    .hero-buttons,
    .contact-form,
    .footer {
        display: none !important;
    }
    
    body {
        background: white;
        color: black;
    }
    
    .legal-content {
        border: none;
        box-shadow: none;
    }
}