/* ===== CSS Variables ===== */
:root {
    /* Colors - 颜色方案 */
    --primary: #1E3A8A;        /* 深蓝 - 信任、专业 */
    --primary-dark: #1e40af;
    --primary-light: #3b82f6;
    --secondary: #F59E0B;      /* 金色 - 金融、价值 */
    --accent: #10B981;         /* 青绿 - 创新、成长 */
    --dark: #0f172a;
    --dark-lighter: #1e293b;
    --gray: #64748b;
    --gray-light: #cbd5e1;
    --white: #ffffff;
    --background: #f8fafc;

    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 2rem;
    --spacing-lg: 4rem;
    --spacing-xl: 6rem;

    /* Typography */
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 1.875rem;
    --font-size-4xl: 2.25rem;
    --font-size-5xl: 3rem;
    --font-size-6xl: 3.75rem;

    /* Transitions */
    --transition: all 0.3s ease;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--dark);
    background-color: var(--background);
    overflow-x: hidden;
}

.container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

/* ===== Navigation ===== */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    z-index: 1000;
    padding: var(--spacing-sm) 0;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
}

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

.logo-container {
    display: flex;
    align-items: center;
}

.logo-placeholder {
    font-size: var(--font-size-2xl);
    font-weight: 900;
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

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

.nav-links a:not(.btn-primary):hover {
    color: var(--primary);
}

.nav-links a:not(.btn-primary)::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--secondary);
    transition: width 0.3s ease;
}

.nav-links a:not(.btn-primary):hover::after {
    width: 100%;
}

/* Language Toggle Button */
.lang-toggle {
    background: var(--primary);
    color: var(--white);
    border: none;
    padding: 0.5rem 1rem;
    border-radius: 50px;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    font-size: 0.9rem;
}

.lang-toggle:hover {
    background: var(--primary-light);
    transform: translateY(-2px);
}

/* Language switching logic - simplified */
/* Default: show English, hide Chinese */
.lang-zh {
    display: none;
}

.lang-en {
    display: block;
}

/* When Chinese is selected */
body[data-lang="zh"] .lang-zh {
    display: block;
}

body[data-lang="zh"] .lang-en {
    display: none;
}

/* When English is selected (explicit) */
body[data-lang="en"] .lang-en {
    display: block;
}

body[data-lang="en"] .lang-zh {
    display: none;
}

.mobile-menu-btn {
    display: none;
    flex-direction: column;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
}

.mobile-menu-btn span {
    width: 24px;
    height: 2px;
    background: var(--dark);
    transition: var(--transition);
}

.mobile-menu {
    display: none;
    position: fixed;
    top: 73px;
    left: 0;
    right: 0;
    background: white;
    padding: var(--spacing-md);
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
    z-index: 999;
}

.mobile-menu.active {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.mobile-menu a {
    text-decoration: none;
    color: var(--dark);
    font-weight: 500;
    padding: var(--spacing-sm);
    border-radius: 8px;
    transition: var(--transition);
}

.mobile-menu a:hover {
    background: var(--background);
    color: var(--primary);
}

/* ===== Buttons ===== */
.btn-primary {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
    color: var(--white);
    padding: 0.75rem 1.5rem;
    border-radius: 50px;
    text-decoration: none;
    font-weight: 600;
    transition: var(--transition);
    display: inline-block;
    border: none;
    cursor: pointer;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 30px rgba(30, 58, 138, 0.3);
}

.btn-secondary {
    background: transparent;
    color: var(--primary);
    padding: 0.75rem 1.5rem;
    border-radius: 50px;
    text-decoration: none;
    font-weight: 600;
    transition: var(--transition);
    display: inline-block;
    border: 2px solid var(--primary);
}

.btn-secondary:hover {
    background: var(--primary);
    color: var(--white);
    transform: translateY(-2px);
    box-shadow: 0 10px 30px rgba(30, 58, 138, 0.2);
}

.btn-large {
    padding: 1rem 2rem;
    font-size: var(--font-size-lg);
}

/* ===== Hero Section ===== */
.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
    padding-top: 73px;
}

.hero-background {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(135deg, #0f172a 0%, #1e3a8a 50%, #1e40af 100%);
    opacity: 0.95;
    z-index: -1;
}

.hero-background::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background:
        radial-gradient(circle at 20% 50%, rgba(245, 158, 11, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 80% 80%, rgba(16, 185, 129, 0.1) 0%, transparent 50%);
}

.hero-content {
    text-align: center;
    z-index: 1;
    padding: var(--spacing-xl) var(--spacing-md);
}

.hero-title {
    font-size: var(--font-size-6xl);
    font-weight: 900;
    color: var(--white);
    margin-bottom: var(--spacing-md);
    line-height: 1.2;
}

.hero-title .highlight {
    background: linear-gradient(135deg, var(--secondary) 0%, var(--accent) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-title .lang-en,
.hero-title .lang-zh {
    display: block;
}

.hero-subtitle {
    font-size: var(--font-size-xl);
    color: var(--gray-light);
    margin-bottom: var(--spacing-lg);
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
}

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

.scroll-indicator {
    position: absolute;
    bottom: 40px;
    left: 50%;
    transform: translateX(-50%);
}

.mouse {
    width: 26px;
    height: 40px;
    border: 2px solid var(--gray-light);
    border-radius: 13px;
    display: flex;
    justify-content: center;
    padding-top: 8px;
}

.wheel {
    width: 4px;
    height: 8px;
    background: var(--gray-light);
    border-radius: 2px;
    animation: scroll 1.5s infinite;
}

@keyframes scroll {
    0% { opacity: 1; transform: translateY(0); }
    100% { opacity: 0; transform: translateY(12px); }
}

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

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

.section-title {
    font-size: var(--font-size-5xl);
    font-weight: 900;
    text-align: center;
    margin-bottom: var(--spacing-lg);
}

.section-dark .section-title {
    color: var(--white);
}

.section-intro {
    text-align: center;
    font-size: var(--font-size-xl);
    color: var(--gray);
    max-width: 800px;
    margin: 0 auto var(--spacing-lg);
}

.section-dark .section-intro {
    color: var(--gray-light);
}

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

.card {
    background: var(--white);
    padding: var(--spacing-lg);
    border-radius: 16px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
    transition: var(--transition);
}

.card:hover {
    transform: translateY(-8px);
    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.12);
}

.card-icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-sm);
}

.card h3 {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
    color: var(--primary);
}

.card p {
    color: var(--gray);
    line-height: 1.8;
}

/* ===== Value Grid ===== */
.value-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-md);
}

.value-card {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
    padding: var(--spacing-lg);
    border-radius: 16px;
    color: var(--white);
    position: relative;
    overflow: hidden;
    transition: var(--transition);
}

.value-card::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle, rgba(255, 255, 255, 0.1) 0%, transparent 70%);
    transition: var(--transition);
}

.value-card:hover::before {
    top: -60%;
    right: -60%;
}

.value-card:hover {
    transform: translateY(-8px);
    box-shadow: 0 12px 40px rgba(30, 58, 138, 0.3);
}

.value-number {
    font-size: var(--font-size-4xl);
    font-weight: 900;
    opacity: 0.3;
    margin-bottom: var(--spacing-sm);
}

.value-card h3 {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
    position: relative;
}

.value-card p {
    opacity: 0.9;
    line-height: 1.8;
    position: relative;
}

/* ===== Architecture Grid ===== */
.architecture-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-md);
}

.arch-card {
    background: var(--dark-lighter);
    padding: var(--spacing-lg);
    border-radius: 16px;
    border: 1px solid rgba(245, 158, 11, 0.2);
    transition: var(--transition);
}

.arch-card:hover {
    border-color: var(--secondary);
    transform: translateY(-8px);
    box-shadow: 0 12px 40px rgba(245, 158, 11, 0.2);
}

.arch-icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-sm);
}

.arch-card h3 {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
    color: var(--secondary);
}

.arch-card p {
    color: var(--gray-light);
    line-height: 1.8;
}

/* ===== Features List ===== */
.features-list {
    max-width: 900px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.feature-item {
    display: flex;
    gap: var(--spacing-md);
    padding: var(--spacing-lg);
    background: var(--white);
    border-radius: 16px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
    transition: var(--transition);
}

.feature-item:hover {
    transform: translateX(8px);
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.12);
}

.feature-icon {
    font-size: 3rem;
    flex-shrink: 0;
}

.feature-content h3 {
    font-size: var(--font-size-xl);
    font-weight: 700;
    margin-bottom: var(--spacing-xs);
    color: var(--primary);
}

.feature-content p {
    color: var(--gray);
    line-height: 1.8;
}

/* ===== Standards Grid ===== */
.standards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-md);
}

.standard-card {
    background: var(--dark-lighter);
    padding: var(--spacing-lg);
    border-radius: 16px;
    text-align: center;
    border: 2px solid transparent;
    transition: var(--transition);
}

.standard-card:hover {
    border-color: var(--accent);
    transform: translateY(-8px);
}

.standard-badge {
    display: inline-block;
    background: linear-gradient(135deg, var(--secondary) 0%, var(--accent) 100%);
    color: var(--dark);
    padding: 0.5rem 1.5rem;
    border-radius: 50px;
    font-weight: 700;
    font-size: var(--font-size-sm);
    margin-bottom: var(--spacing-md);
}

.standard-card h3 {
    font-size: var(--font-size-3xl);
    font-weight: 900;
    margin-bottom: var(--spacing-xs);
    color: var(--white);
}

.standard-card p {
    color: var(--gray-light);
}

/* ===== CTA Section ===== */
.cta-section {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
    color: var(--white);
    text-align: center;
}

.cta-content h2 {
    font-size: var(--font-size-5xl);
    font-weight: 900;
    margin-bottom: var(--spacing-md);
}

.cta-content p {
    font-size: var(--font-size-xl);
    margin-bottom: var(--spacing-lg);
    opacity: 0.9;
}

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

.cta-section .btn-secondary {
    border-color: var(--white);
    color: var(--white);
}

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

.cta-section .btn-primary {
    background: var(--secondary);
}

.cta-section .btn-primary:hover {
    box-shadow: 0 10px 30px rgba(245, 158, 11, 0.4);
}

/* ===== Footer ===== */
.footer {
    background: var(--dark);
    color: var(--white);
    padding: var(--spacing-xl) 0 var(--spacing-md);
}

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

.footer-section h4 {
    font-size: var(--font-size-lg);
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
    color: var(--secondary);
}

.footer-section a {
    display: block;
    color: var(--gray-light);
    text-decoration: none;
    margin-bottom: var(--spacing-xs);
    transition: var(--transition);
}

.footer-section a:hover {
    color: var(--accent);
    transform: translateX(4px);
}

.footer-logo {
    font-size: var(--font-size-2xl);
    font-weight: 900;
    background: linear-gradient(135deg, var(--secondary) 0%, var(--accent) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-xs);
}

.footer-tagline {
    color: var(--gray-light);
    margin-bottom: var(--spacing-xs);
}

.footer-company {
    color: var(--gray);
    font-size: 0.9rem;
    margin-bottom: var(--spacing-sm);
}

.footer-social {
    display: flex;
    gap: var(--spacing-sm);
    align-items: flex-start;
}

.social-link {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    background: var(--dark-lighter);
    border-radius: 50%;
    color: var(--gray-light);
    transition: var(--transition);
}

.social-link:hover {
    background: var(--secondary);
    color: var(--dark);
    transform: translateY(-4px);
}

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

.footer-bottom {
    border-top: 1px solid var(--dark-lighter);
    padding-top: var(--spacing-md);
    text-align: center;
    color: var(--gray);
}

/* ===== Responsive Design ===== */
@media (max-width: 768px) {
    :root {
        --font-size-6xl: 2rem;
        --font-size-5xl: 1.75rem;
        --font-size-4xl: 1.5rem;
        --spacing-xl: 3rem;
    }

    .nav-links {
        display: none;
    }

    .mobile-menu-btn {
        display: flex;
    }

    .hero-title {
        font-size: var(--font-size-4xl);
    }

    .hero-subtitle {
        font-size: var(--font-size-base);
    }

    .hero-actions {
        flex-direction: column;
    }

    .cards-grid,
    .value-grid,
    .architecture-grid,
    .standards-grid {
        grid-template-columns: 1fr;
    }

    .feature-item {
        flex-direction: column;
        text-align: center;
    }

    .cta-actions {
        flex-direction: column;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 var(--spacing-sm);
    }

    .hero-title {
        font-size: var(--font-size-3xl);
    }

    .section-title {
        font-size: var(--font-size-3xl);
    }
}

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

.fade-in-up {
    animation: fadeInUp 0.6s ease-out;
}