/* ========================================
   Bu Geng Technology - Main Stylesheet
   Flat Design System
   ======================================== */

/* CSS Variables */
:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --primary-light: #3b82f6;
    --secondary: #0f172a;
    --accent: #06b6d4;
    --accent-light: #22d3ee;
    --success: #10b981;
    --warning: #f59e0b;
    --error: #ef4444;
    
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --bg-dark: #0f172a;
    --bg-dark-secondary: #1e293b;
    
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-tertiary: #94a3b8;
    --text-light: #ffffff;
    
    --border-color: #e2e8f0;
    --border-light: #f1f5f9;
    
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1);
    
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-xl: 16px;
    --radius-full: 9999px;
    
    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
    --transition-slow: 350ms ease;
    
    --font-sans: 'Inter', 'Noto Sans SC', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
}

/* Reset & Base */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

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

body {
    font-family: var(--font-sans);
    font-size: 1rem;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-primary);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

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

img {
    max-width: 100%;
    height: auto;
    display: block;
}

ul, ol {
    list-style: none;
}

button {
    font-family: inherit;
    cursor: pointer;
    border: none;
    background: none;
}

/* Container */
.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    line-height: 1.3;
    color: var(--text-primary);
}

h1 { font-size: 3rem; }
h2 { font-size: 2.25rem; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }
h5 { font-size: 1.125rem; }
h6 { font-size: 1rem; }

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 24px;
    font-size: 0.9375rem;
    font-weight: 500;
    border-radius: var(--radius-md);
    transition: all var(--transition-normal);
    cursor: pointer;
    border: none;
}

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

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

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

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

.btn-large {
    padding: 16px 32px;
    font-size: 1rem;
}

/* Navigation */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background-color: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-light);
    transition: all var(--transition-normal);
}

.nav-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    max-width: 1200px;
    margin: 0 auto;
    padding: 16px 24px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
}

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

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

.nav-links a {
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--text-secondary);
    position: relative;
    padding: 8px 0;
}

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--primary);
    transition: width var(--transition-normal);
}

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

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

.nav-actions {
    display: flex;
    align-items: center;
    gap: 16px;
}

.lang-switch {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 8px 16px;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    background-color: var(--bg-secondary);
    border-radius: var(--radius-full);
    transition: all var(--transition-fast);
}

.lang-switch:hover {
    background-color: var(--bg-tertiary);
    color: var(--primary);
}

.mobile-menu-btn {
    display: none;
    flex-direction: column;
    gap: 5px;
    padding: 8px;
}

.mobile-menu-btn span {
    display: block;
    width: 24px;
    height: 2px;
    background-color: var(--text-primary);
    transition: all var(--transition-fast);
}

/* Hero Section */
.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    padding: 120px 24px 80px;
    overflow: hidden;
}

.hero-bg {
    position: absolute;
    inset: 0;
    z-index: -1;
    background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-primary) 100%);
}

.hero-shape {
    position: absolute;
    border-radius: 50%;
    opacity: 0.5;
}

.shape-1 {
    width: 600px;
    height: 600px;
    background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
    top: -200px;
    right: -200px;
    opacity: 0.1;
}

.shape-2 {
    width: 400px;
    height: 400px;
    background: linear-gradient(135deg, var(--accent) 0%, var(--success) 100%);
    bottom: -100px;
    left: -100px;
    opacity: 0.1;
}

.shape-3 {
    width: 200px;
    height: 200px;
    background: var(--primary);
    top: 50%;
    left: 50%;
    opacity: 0.05;
}

.hero-content {
    max-width: 700px;
    z-index: 1;
}

.hero h1 {
    font-size: 3.5rem;
    font-weight: 700;
    line-height: 1.1;
    margin-bottom: 24px;
    background: linear-gradient(135deg, var(--text-primary) 0%, var(--primary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: 40px;
    line-height: 1.7;
}

.hero-buttons {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
}

.hero-visual {
    position: absolute;
    right: 10%;
    top: 50%;
    transform: translateY(-50%);
    z-index: 0;
}

.tech-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 20px;
    transform: rotate(15deg);
}

.grid-item {
    width: 120px;
    height: 120px;
    background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
    border-radius: var(--radius-lg);
    opacity: 0.1;
}

.grid-item:nth-child(2) {
    transform: translateY(30px);
}

.grid-item:nth-child(3) {
    transform: translateY(-30px);
}

/* Section Styles */
section {
    padding: 100px 0;
}

.section-header {
    text-align: center;
    margin-bottom: 60px;
}

.section-tag {
    display: inline-block;
    padding: 8px 16px;
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--primary);
    background-color: rgba(37, 99, 235, 0.1);
    border-radius: var(--radius-full);
    margin-bottom: 16px;
}

.section-header h2 {
    font-size: 2.5rem;
    margin-bottom: 16px;
}

.section-header p {
    font-size: 1.125rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
}

/* Features Section */
.features {
    background-color: var(--bg-primary);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 30px;
}

.feature-card {
    padding: 32px;
    background-color: var(--bg-secondary);
    border-radius: var(--radius-lg);
    transition: all var(--transition-normal);
}

.feature-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-xl);
    background-color: var(--bg-primary);
}

.feature-icon {
    width: 56px;
    height: 56px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
    border-radius: var(--radius-md);
    margin-bottom: 20px;
}

.feature-icon svg {
    width: 28px;
    height: 28px;
    color: white;
}

.feature-card h3 {
    font-size: 1.125rem;
    margin-bottom: 12px;
}

.feature-card p {
    font-size: 0.9375rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* Stats Section */
.stats {
    background: linear-gradient(135deg, var(--bg-dark) 0%, var(--bg-dark-secondary) 100%);
    padding: 80px 0;
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 40px;
    text-align: center;
}

.stat-item {
    padding: 20px;
}

.stat-number {
    display: block;
    font-size: 3rem;
    font-weight: 700;
    color: var(--text-light);
    margin-bottom: 8px;
    background: linear-gradient(135deg, var(--text-light) 0%, var(--accent) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.stat-label {
    font-size: 1rem;
    color: var(--text-tertiary);
}

/* Services Preview */
.services-preview {
    background-color: var(--bg-secondary);
}

.services-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 30px;
}

.service-card {
    padding: 40px;
    background-color: var(--bg-primary);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
    transition: all var(--transition-normal);
    position: relative;
    overflow: hidden;
}

.service-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 4px;
    background: linear-gradient(90deg, var(--primary) 0%, var(--accent) 100%);
    transform: scaleX(0);
    transform-origin: left;
    transition: transform var(--transition-normal);
}

.service-card:hover::before {
    transform: scaleX(1);
}

.service-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-xl);
    border-color: transparent;
}

.service-number {
    font-size: 3rem;
    font-weight: 700;
    color: var(--bg-tertiary);
    margin-bottom: 20px;
}

.service-card h3 {
    font-size: 1.25rem;
    margin-bottom: 16px;
}

.service-card p {
    font-size: 0.9375rem;
    color: var(--text-secondary);
    margin-bottom: 24px;
    line-height: 1.7;
}

.service-link {
    font-size: 0.9375rem;
    font-weight: 600;
    color: var(--primary);
    transition: all var(--transition-fast);
}

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

/* CTA Section */
.cta {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    padding: 100px 0;
}

.cta-content {
    text-align: center;
    max-width: 700px;
    margin: 0 auto;
}

.cta h2 {
    font-size: 2.5rem;
    color: var(--text-light);
    margin-bottom: 20px;
}

.cta p {
    font-size: 1.125rem;
    color: rgba(255, 255, 255, 0.8);
    margin-bottom: 40px;
}

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

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

/* Footer */
.footer {
    background-color: var(--bg-dark);
    padding: 80px 0 40px;
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1.5fr;
    gap: 60px;
    margin-bottom: 60px;
}

.footer-brand .logo {
    margin-bottom: 20px;
}

.footer-brand .logo-text {
    color: var(--text-light);
}

.footer-brand p {
    font-size: 0.9375rem;
    color: var(--text-tertiary);
    line-height: 1.7;
}

.footer-address {
    margin-top: 12px;
}

.footer-links h4,
.footer-contact h4 {
    font-size: 1rem;
    color: var(--text-light);
    margin-bottom: 24px;
}

.footer-links ul {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.footer-links a {
    font-size: 0.9375rem;
    color: var(--text-tertiary);
    transition: color var(--transition-fast);
}

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

.footer-contact p {
    margin-bottom: 12px;
}

.footer-contact a {
    font-size: 0.9375rem;
    color: var(--text-tertiary);
}

.footer-contact a:hover {
    color: var(--primary-light);
}

.footer-bottom {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: 40px;
    border-top: 1px solid var(--bg-dark-secondary);
}

.footer-bottom p {
    font-size: 0.875rem;
    color: var(--text-tertiary);
}

.footer-legal {
    display: flex;
    gap: 24px;
}

.footer-legal a {
    font-size: 0.875rem;
    color: var(--text-tertiary);
}

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

/* Mobile Menu */
.mobile-menu {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: var(--bg-primary);
    z-index: 999;
    padding: 100px 24px 40px;
    transform: translateX(100%);
    transition: transform var(--transition-normal);
}

.mobile-menu.active {
    transform: translateX(0);
}

.mobile-menu ul {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.mobile-menu a {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-primary);
}

/* Responsive Design */
@media (max-width: 1024px) {
    .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .services-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .footer-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 40px;
    }
    
    .hero-visual {
        display: none;
    }
}

@media (max-width: 768px) {
    h1 { font-size: 2.25rem; }
    h2 { font-size: 1.75rem; }
    
    .nav-links {
        display: none;
    }
    
    .mobile-menu-btn {
        display: flex;
    }
    
    .hero {
        padding: 100px 24px 60px;
        min-height: auto;
    }
    
    .hero h1 {
        font-size: 2.5rem;
    }
    
    .hero-subtitle {
        font-size: 1.125rem;
    }
    
    section {
        padding: 60px 0;
    }
    
    .section-header h2 {
        font-size: 2rem;
    }
    
    .features-grid,
    .services-grid {
        grid-template-columns: 1fr;
    }
    
    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 20px;
    }
    
    .stat-number {
        font-size: 2.25rem;
    }
    
    .footer-grid {
        grid-template-columns: 1fr;
        gap: 40px;
    }
    
    .footer-bottom {
        flex-direction: column;
        gap: 20px;
        text-align: center;
    }
    
    .cta h2 {
        font-size: 2rem;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 16px;
    }
    
    .hero-buttons {
        flex-direction: column;
    }
    
    .btn {
        width: 100%;
    }
}