/* ===========================================
   北欧极简 — Scandinavian Clean
   亮色基底 × 冷蓝强调 × 精准排版
   =========================================== */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=Noto+Sans+SC:wght@400;500;600;700&family=JetBrains+Mono:wght@400;500&display=swap');

:root {
    --bg-primary: #FAFAFA;
    --bg-surface: #FFFFFF;
    --bg-subtle: #F0F2F5;
    --bg-hover: #E8EBF0;

    --text-primary: #1A1A2E;
    --text-body: #4A4A5A;
    --text-muted: #8E8E9A;
    --text-light: #B0B0BC;

    --accent: #2563EB;
    --accent-hover: #1D4ED8;
    --accent-soft: rgba(37,99,235,0.08);
    --accent-border: rgba(37,99,235,0.2);

    --success: #059669;
    --success-soft: rgba(5,150,105,0.08);

    --border: #E5E7EB;
    --border-strong: #D1D5DB;

    --shadow-sm: 0 1px 2px rgba(0,0,0,0.04);
    --shadow-md: 0 4px 12px rgba(0,0,0,0.06);
    --shadow-lg: 0 8px 30px rgba(0,0,0,0.08);

    --font-heading: 'Inter','Noto Sans SC',-apple-system,BlinkMacSystemFont,'Segoe UI',sans-serif;
    --font-body: 'Inter','Noto Sans SC',-apple-system,BlinkMacSystemFont,'Segoe UI',sans-serif;
    --font-mono: 'JetBrains Mono','Courier New',monospace;

    --space-xs: 8px;
    --space-sm: 16px;
    --space-md: 24px;
    --space-lg: 40px;
    --space-xl: 64px;
    --space-2xl: 96px;
    --space-3xl: 128px;

    --radius-sm: 4px;
    --radius-md: 6px;
    --radius-lg: 8px;
    --radius-xl: 12px;

    --max-width: 1200px;
}

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

html {
    font-size: 16px;
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-body);
    background: var(--bg-primary);
    color: var(--text-body);
    line-height: 1.6;
    overflow-x: hidden;
}

[data-zh][data-en] { visibility: hidden; }
body.lang-ready [data-zh][data-en] { visibility: visible; }

a { color: inherit; text-decoration: none; transition: color 0.2s ease; }
img { max-width: 100%; display: block; }
ul, ol { list-style: none; }

h1,h2,h3,h4,h5,h6 {
    font-family: var(--font-heading);
    font-weight: 700;
    line-height: 1.3;
    color: var(--text-primary);
}

/* ========= Navigation ========= */
header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(255,255,255,0.92);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
}

.main-nav { height: 60px; }

.nav-container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 var(--space-md);
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo a {
    display: flex;
    align-items: center;
    gap: 10px;
}

.logo img {
    height: 26px;
    width: auto;
}

.logo-brand {
    font-family: var(--font-heading);
    font-size: 18px;
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: 0.02em;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 4px;
}

.nav-links a {
    padding: 6px 14px;
    font-size: 14px;
    font-weight: 500;
    color: var(--text-muted);
    border-radius: var(--radius-md);
    transition: color 0.2s ease, background 0.2s ease;
}

.nav-links a:hover {
    color: var(--text-primary);
    background: var(--bg-subtle);
}

.nav-links a.active {
    color: var(--accent);
    background: var(--accent-soft);
}

.nav-right { display: flex; align-items: center; gap: 12px; }

.language-switch { position: relative; }

.dropdown-trigger {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 5px 10px;
    font-size: 13px;
    color: var(--text-muted);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: color 0.2s ease, border-color 0.2s ease;
}

.dropdown-trigger:hover {
    color: var(--text-body);
    border-color: var(--border-strong);
}

.dropdown-content {
    position: absolute;
    top: calc(100% + 6px);
    right: 0;
    min-width: 130px;
    background: var(--bg-surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-4px);
    transition: opacity 0.2s ease, visibility 0.2s ease, transform 0.2s ease;
    z-index: 100;
}

.dropdown:hover .dropdown-content {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.dropdown-content a {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 9px 14px;
    font-size: 13px;
    color: var(--text-body);
    transition: background 0.15s ease;
}

.dropdown-content a:first-child { border-radius: var(--radius-lg) var(--radius-lg) 0 0; }
.dropdown-content a:last-child { border-radius: 0 0 var(--radius-lg) var(--radius-lg); }
.dropdown-content a:hover { background: var(--bg-subtle); }
.dropdown-content a.active { color: var(--accent); font-weight: 500; }

.lang-code {
    font-size: 11px;
    color: var(--text-light);
    font-family: var(--font-mono);
}

/* ========= Buttons ========= */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 22px;
    font-size: 14px;
    font-weight: 500;
    font-family: var(--font-body);
    border-radius: var(--radius-md);
    border: 1px solid transparent;
    cursor: pointer;
    transition: all 0.2s ease;
    white-space: nowrap;
}

.btn i { font-size: 12px; transition: transform 0.2s ease; }
.btn:hover i { transform: translateX(2px); }

.btn-primary {
    background: var(--accent);
    color: #fff;
    border-color: var(--accent);
}

.btn-primary:hover {
    background: var(--accent-hover);
    border-color: var(--accent-hover);
    box-shadow: 0 2px 8px rgba(37,99,235,0.2);
}

.btn-secondary {
    background: var(--bg-surface);
    color: var(--text-body);
    border-color: var(--border-strong);
}

.btn-secondary:hover {
    color: var(--text-primary);
    border-color: var(--text-muted);
    background: var(--bg-subtle);
}

.btn-large { padding: 12px 28px; font-size: 15px; }

/* ========= Breadcrumb ========= */
.page-breadcrumb {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 13px;
    color: var(--text-light);
    margin-bottom: var(--space-md);
}

.page-breadcrumb a { color: var(--text-muted); }
.page-breadcrumb a:hover { color: var(--accent); }
.page-breadcrumb i { font-size: 9px; }

/* ========= Section headings ========= */
.section-eyebrow {
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--accent);
    margin-bottom: 8px;
}

.section-title {
    font-size: clamp(28px, 3.5vw, 40px);
    color: var(--text-primary);
    margin-bottom: 12px;
}

.section-description {
    font-size: 16px;
    color: var(--text-muted);
    max-width: 560px;
    line-height: 1.7;
}

/* ========= Footer ========= */
footer {
    background: var(--bg-subtle);
    border-top: 1px solid var(--border);
    padding: var(--space-xl) 0 var(--space-lg);
}

.footer-container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 var(--space-md);
}

.footer-main {
    display: grid;
    grid-template-columns: 1.5fr 1fr 1fr 1fr;
    gap: var(--space-lg);
    padding-bottom: var(--space-lg);
    border-bottom: 1px solid var(--border);
}

.footer-logo {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-bottom: var(--space-sm);
}

.footer-logo img { height: 22px; }

.footer-logo-text {
    font-family: var(--font-heading);
    font-size: 16px;
    font-weight: 700;
    color: var(--text-primary);
}

.footer-description {
    font-size: 13px;
    color: var(--text-muted);
    line-height: 1.7;
    max-width: 260px;
}

.footer-group-title {
    font-size: 11px;
    font-weight: 600;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    color: var(--text-light);
    margin-bottom: var(--space-sm);
    padding-bottom: 8px;
    border-bottom: 1px solid var(--border);
}

.footer-links-list { display: flex; flex-direction: column; gap: 8px; }

.footer-links-list a {
    font-size: 13px;
    color: var(--text-muted);
    transition: color 0.2s ease;
}

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

.footer-contact-item {
    font-size: 13px;
    color: var(--text-muted);
    line-height: 1.5;
}

.footer-contact-item strong {
    color: var(--text-light);
    font-weight: 500;
    font-size: 11px;
    letter-spacing: 0.04em;
}

.footer-bottom {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-top: var(--space-md);
}

.footer-copyright p {
    font-size: 12px;
    color: var(--text-light);
}

.footer-social { display: flex; gap: 8px; }

.footer-social-link {
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    color: var(--text-light);
    font-size: 14px;
    transition: all 0.2s ease;
}

.footer-social-link:hover {
    color: var(--accent);
    border-color: var(--accent-border);
    background: var(--accent-soft);
}

/* ========= Mobile nav ========= */
.mobile-menu-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    padding: 8px;
    background: none;
    border: none;
    cursor: pointer;
}

.mobile-menu-toggle span {
    width: 20px;
    height: 2px;
    background: var(--text-body);
    border-radius: 1px;
    transition: all 0.2s ease;
}

.mobile-menu-toggle.active span:nth-child(1) { transform: rotate(45deg) translate(5px, 5px); }
.mobile-menu-toggle.active span:nth-child(2) { opacity: 0; }
.mobile-menu-toggle.active span:nth-child(3) { transform: rotate(-45deg) translate(5px, -5px); }

/* ========= Responsive ========= */
@media (max-width: 900px) {
    .nav-links { display: none; }
    .nav-links.active {
        display: flex;
        flex-direction: column;
        position: absolute;
        top: 60px;
        left: 0;
        right: 0;
        background: var(--bg-surface);
        border-bottom: 1px solid var(--border);
        padding: var(--space-sm);
        box-shadow: var(--shadow-md);
    }
    .mobile-menu-toggle { display: flex; }
    .footer-main { grid-template-columns: 1fr 1fr; gap: var(--space-md); }
}

@media (max-width: 600px) {
    .footer-main { grid-template-columns: 1fr; }
    .footer-bottom { flex-direction: column; gap: var(--space-sm); text-align: center; }
}