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

:root {
    /* Colors */
    --primary: #0066cc;
    --primary-dark: #004499;
    --primary-light: #3388dd;
    --accent: #00a0e9;
    --accent-dark: #0077b6;
    --text: #1a1a2e;
    --text-light: #5a5a7a;
    --text-muted: #8888a0;
    --bg: #ffffff;
    --bg-light: #f4f6f9;
    --bg-dark: #0f0f1a;
    --surface: #ffffff;
    --surface-hover: #f0f2f5;
    --border: #e2e6ed;
    --shadow: rgba(0, 0, 0, 0.08);
    --shadow-lg: rgba(0, 0, 0, 0.15);
    --gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --sky-gradient: linear-gradient(135deg, #0066cc 0%, #00a0e9 50%, #00d4ff 100%);
    --dark-gradient: linear-gradient(135deg, #0f0f1a 0%, #1a1a3e 100%);

    /* Typography */
    --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-mono: 'SF Mono', 'Fira Code', 'Fira Mono', 'Roboto Mono', monospace;

    /* Spacing */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 3rem;
    --space-3xl: 5rem;

    /* Layout */
    --max-width: 1200px;
    --header-height: 64px;
    --radius: 12px;
    --radius-lg: 20px;

    /* Transitions */
    --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Dark Mode */
@media (prefers-color-scheme: dark) {
    :root {
        --text: #e8e8f0;
        --text-light: #b0b0cc;
        --text-muted: #8888a0;
        --bg: #0f0f1a;
        --bg-light: #1a1a2e;
        --surface: #1e1e32;
        --surface-hover: #2a2a42;
        --border: #2a2a42;
        --shadow: rgba(0, 0, 0, 0.3);
        --shadow-lg: rgba(0, 0, 0, 0.5);
    }

    .header {
        background: rgba(15, 15, 26, 0.92);
        border-bottom-color: var(--border);
    }
}

html {
    scroll-behavior: smooth;
    scroll-padding-top: var(--header-height);
}

body {
    font-family: var(--font-sans);
    line-height: 1.7;
    color: var(--text);
    background: var(--bg);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Skip Link */
.skip-link {
    position: absolute;
    top: -100%;
    left: var(--space-md);
    background: var(--primary);
    color: white;
    padding: var(--space-sm) var(--space-md);
    border-radius: 0 0 var(--radius) var(--radius);
    z-index: 10000;
    font-weight: 600;
    text-decoration: none;
    transition: top var(--transition);
}

.skip-link:focus {
    top: 0;
}

/* ===== Header ===== */
.header {
    position: fixed;
    top: 0;
    width: 100%;
    background: rgba(255, 255, 255, 0.92);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
    z-index: 1000;
    transition: box-shadow var(--transition);
}

@media (prefers-color-scheme: dark) {
    .header {
        background: rgba(15, 15, 26, 0.92);
        border-bottom-color: var(--border);
    }
}

.header.scrolled {
    box-shadow: 0 4px 30px var(--shadow);
}

.navbar {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 var(--space-xl);
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: var(--header-height);
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    font-weight: 700;
    font-size: 1.15rem;
    color: var(--text);
    text-decoration: none;
    transition: opacity var(--transition);
}

.logo:hover {
    opacity: 0.8;
}

.logo-icon {
    width: 36px;
    height: 36px;
}

.nav-links {
    display: flex;
    list-style: none;
    gap: var(--space-xl);
    align-items: center;
}

.nav-links a {
    text-decoration: none;
    color: var(--text-light);
    font-weight: 500;
    font-size: 0.95rem;
    transition: color var(--transition);
    position: relative;
}

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--primary);
    transition: width var(--transition);
}

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

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

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

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



.menu-toggle {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--space-sm);
    position: relative;
    width: 32px;
    height: 32px;
}

.menu-icon,
.menu-icon::before,
.menu-icon::after {
    display: block;
    width: 24px;
    height: 2px;
    background: var(--text);
    border-radius: 2px;
    transition: var(--transition);
}

.menu-icon {
    position: relative;
    margin: 0 auto;
}

.menu-icon::before,
.menu-icon::after {
    content: '';
    position: absolute;
    left: 0;
}

.menu-icon::before {
    top: -7px;
}

.menu-icon::after {
    top: 7px;
}

/* ===== Hero ===== */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--sky-gradient);
    color: white;
    text-align: center;
    padding: calc(var(--header-height) + var(--space-3xl)) var(--space-xl) var(--space-3xl);
    position: relative;
    overflow: hidden;
}

.hero-bg {
    position: absolute;
    inset: 0;
    overflow: hidden;
    pointer-events: none;
}

.cloud-particle {
    position: absolute;
    width: 200px;
    height: 200px;
    background: rgba(255, 255, 255, 0.05);
    border-radius: 50%;
    animation: float 20s infinite ease-in-out;
}

.cloud-particle:nth-child(1) {
    top: 10%;
    left: 10%;
    animation-delay: 0s;
    width: 300px;
    height: 300px;
}

.cloud-particle:nth-child(2) {
    top: 60%;
    right: 10%;
    animation-delay: -7s;
    width: 250px;
    height: 250px;
}

.cloud-particle:nth-child(3) {
    bottom: 10%;
    left: 40%;
    animation-delay: -14s;
    width: 180px;
    height: 180px;
}

@keyframes float {
    0%, 100% { transform: translate(0, 0) scale(1); opacity: 0.3; }
    25% { transform: translate(30px, -40px) scale(1.1); opacity: 0.5; }
    50% { transform: translate(-20px, 20px) scale(0.95); opacity: 0.2; }
    75% { transform: translate(40px, 30px) scale(1.05); opacity: 0.4; }
}

.hero-content {
    position: relative;
    z-index: 1;
    max-width: 800px;
}

.trust-bar {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-md);
    margin-bottom: var(--space-xl);
    flex-wrap: wrap;
}

.trust-label {
    font-size: 0.85rem;
    opacity: 0.8;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    font-weight: 600;
}

.trust-logos {
    display: flex;
    gap: var(--space-lg);
    font-size: 1.5rem;
}

.hero-content h1 {
    font-size: clamp(2.5rem, 5vw, 4rem);
    margin-bottom: 0.25rem;
    font-weight: 800;
    letter-spacing: -0.02em;
    text-shadow: 0 2px 20px rgba(0, 0, 0, 0.15);
}

.hero-content h2 {
    font-size: clamp(1.5rem, 3vw, 2.2rem);
    margin-bottom: var(--space-xl);
    font-weight: 400;
    opacity: 0.9;
}

.tagline {
    font-size: 1.2rem;
    margin-bottom: var(--space-sm);
    opacity: 0.95;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.tagline-zh {
    font-size: 1rem;
    margin-bottom: var(--space-xl);
    opacity: 0.8;
}

.cta-buttons {
    display: flex;
    gap: var(--space-md);
    justify-content: center;
    flex-wrap: wrap;
    margin-bottom: var(--space-2xl);
}

/* Buttons */
.btn {
    padding: 0.875rem 1.75rem;
    border-radius: 30px;
    text-decoration: none;
    font-weight: 600;
    font-size: 0.95rem;
    transition: all var(--transition);
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    border: 2px solid transparent;
    cursor: pointer;
    line-height: 1.4;
}

.btn.secondary {
    background: transparent;
    color: white;
    border-color: rgba(255, 255, 255, 0.6);
}

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

.btn-block {
    display: flex;
    width: 100%;
    justify-content: center;
}

/* Hero Stats */
.hero-stats {
    display: flex;
    justify-content: center;
    gap: var(--space-2xl);
    flex-wrap: wrap;
    margin-top: var(--space-xl);
}

.hero-stat {
    text-align: center;
}

.hero-number {
    display: block;
    font-size: 1.5rem;
    font-weight: 700;
    opacity: 0.95;
}

.hero-label {
    font-size: 0.8rem;
    opacity: 0.7;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

/* ===== Sections ===== */
section {
    padding: var(--space-3xl) var(--space-xl);
}

.section-container {
    max-width: var(--max-width);
    margin: 0 auto;
}

.section-container > h2 {
    font-size: 2.2rem;
    color: var(--primary);
    margin-bottom: var(--space-sm);
    font-weight: 700;
}

.section-container > h3 {
    font-size: 1.4rem;
    color: var(--text-light);
    margin-bottom: var(--space-xl);
    font-weight: 500;
}

.section-subtitle {
    font-size: 1.05rem;
    color: var(--text-light);
    margin-bottom: var(--space-2xl);
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.section-subtitle-zh {
    font-size: 0.95rem;
    color: var(--text-muted);
    margin-bottom: var(--space-2xl);
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

/* ===== Services ===== */
.services {
    background: var(--bg-light);
}

.services-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--space-xl);
}

.service-card {
    background: var(--surface);
    padding: var(--space-xl);
    border-radius: var(--radius-lg);
    box-shadow: 0 4px 20px var(--shadow);
    transition: transform var(--transition), box-shadow var(--transition);
    border: 1px solid var(--border);
}

.service-card:hover {
    transform: translateY(-6px);
    box-shadow: 0 12px 40px var(--shadow-lg);
}

.service-card:focus-within {
    outline: 2px solid var(--primary);
    outline-offset: 2px;
}

.service-icon {
    font-size: 2.5rem;
    margin-bottom: var(--space-md);
}

.service-card h3 {
    font-size: 1.3rem;
    color: var(--text);
    margin-bottom: var(--space-xs);
}

.service-card h4 {
    font-size: 1rem;
    color: var(--primary);
    margin-bottom: var(--space-md);
    font-weight: 500;
}

.service-card p {
    color: var(--text-light);
    font-size: 0.9rem;
    line-height: 1.8;
    margin-bottom: var(--space-sm);
}

/* ===== About ===== */
.about {
    background: var(--bg-light);
}

.about-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-3xl);
    align-items: center;
}

.about-text p {
    font-size: 1.05rem;
    color: var(--text);
    margin-bottom: var(--space-md);
    line-height: 1.8;
}

.about-stats {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-xl);
}

.stat {
    text-align: center;
    padding: var(--space-xl);
    background: var(--surface);
    border-radius: var(--radius);
    border: 1px solid var(--border);
}

.stat .number {
    display: block;
    font-size: 2.5rem;
    font-weight: 800;
    color: var(--primary);
    line-height: 1.2;
}

.stat .label {
    display: block;
    font-size: 0.9rem;
    color: var(--text-light);
    margin-top: var(--space-xs);
}

.label-zh {
    font-size: 0.8rem;
    color: var(--text-muted);
}

/* ===== Resources ===== */
.resources {
    background: var(--bg);
}

.resources-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--space-xl);
}

.resource-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: var(--space-xl);
    transition: transform var(--transition), box-shadow var(--transition);
}

.resource-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 8px 30px var(--shadow);
}

.resource-icon {
    font-size: 2rem;
    margin-bottom: var(--space-md);
}

.resource-card h3 {
    font-size: 1.2rem;
    color: var(--text);
    margin-bottom: var(--space-xs);
}

.resource-card h4 {
    font-size: 1rem;
    color: var(--primary);
    margin-bottom: var(--space-md);
    font-weight: 500;
}

.resource-card p {
    font-size: 0.9rem;
    color: var(--text-light);
    line-height: 1.7;
    margin-bottom: var(--space-md);
}

.resource-meta {
    font-size: 0.8rem;
    color: var(--text-muted);
}

/* ===== Footer ===== */
.footer {
    background: var(--bg-dark);
    color: white;
    padding: var(--space-3xl) var(--space-xl) var(--space-xl);
}

.footer-content {
    max-width: var(--max-width);
    margin: 0 auto;
    display: grid;
    grid-template-columns: 1fr 2fr;
    gap: var(--space-3xl);
    margin-bottom: var(--space-2xl);
}

.footer-brand {
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
}

.footer-logo {
    margin-bottom: var(--space-sm);
}

.footer-brand span {
    font-weight: 600;
    font-size: 1rem;
}

.footer-zh {
    font-size: 0.85rem;
    opacity: 0.6;
}

.footer-links {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-xl);
}

.footer-col h4 {
    font-size: 0.85rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: var(--space-md);
    opacity: 0.7;
}

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

.footer-col li {
    margin-bottom: var(--space-sm);
}

.footer-col a {
    color: rgba(255, 255, 255, 0.7);
    text-decoration: none;
    font-size: 0.9rem;
    transition: color var(--transition);
}

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

.footer-bottom {
    max-width: var(--max-width);
    margin: 0 auto;
    padding-top: var(--space-xl);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    text-align: center;
}

.footer-bottom p {
    font-size: 0.8rem;
    opacity: 0.5;
    margin-bottom: var(--space-sm);
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
    .nav-links {
        display: none;
        position: absolute;
        top: var(--header-height);
        left: 0;
        width: 100%;
        background: var(--bg);
        flex-direction: column;
        padding: var(--space-lg);
        box-shadow: 0 10px 30px var(--shadow);
        border-bottom: 1px solid var(--border);
    }

    .nav-links.active {
        display: flex;
    }

    .menu-toggle {
        display: block;
    }

    .hero-content h1 {
        font-size: 2rem;
    }

    .hero-content h2 {
        font-size: 1.4rem;
    }

    .tagline {
        font-size: 1rem;
    }

    .hero-stats {
        gap: var(--space-lg);
    }

    .about-grid {
        grid-template-columns: 1fr;
    }

    .about-stats {
        grid-template-columns: 1fr 1fr;
    }

    .footer-content {
        grid-template-columns: 1fr;
    }

    .footer-links {
        grid-template-columns: 1fr 1fr;
    }
}

@media (max-width: 480px) {
    .about-stats {
        grid-template-columns: 1fr;
    }

    .footer-links {
        grid-template-columns: 1fr;
    }
}

/* ===== Animations ===== */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ===== Focus Styles ===== */
a:focus-visible,
button:focus-visible,
[tabindex]:focus-visible {
    outline: 2px solid var(--primary);
    outline-offset: 2px;
    border-radius: 4px;
}