:root {
  --ink: #111827;
  --body: #374151;
  --muted: #5f6b7a;
  --subtle: #64748b;
  --line: #e5e7eb;
  --soft: #f8fafc;
  --white: #fff;
  --accent: #4f46e5;
  --accent-strong: #4338ca;
  --tint: #eef2ff;
  --tint-soft: #f5f7ff;
  --nav-gradient: linear-gradient(135deg, #3563f4, #5b3df5);
  --cta-gradient: linear-gradient(135deg, #172554, #4f46e5 60%, #7c3aed);
  --shadow: 0 18px 55px rgba(15, 23, 42, .09);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; color: var(--body); background: var(--white); font-family: Arial, Helvetica, sans-serif; -webkit-font-smoothing: antialiased; }
body[data-lang="en"] .zh, body[data-lang="zh"] .en { display: none !important; }
a { color: inherit; }
.skip-link { position: fixed; top: -80px; left: 16px; z-index: 100; padding: 12px 16px; border-radius: 8px; color: #fff; background: #111827; }
.skip-link:focus { top: 12px; }
.site-header { position: sticky; top: 0; z-index: 50; border-bottom: 1px solid var(--line); background: #fff; }
.nav-shell { display: flex; align-items: center; justify-content: space-between; gap: 16px; width: 100%; max-width: 1280px; margin: 0 auto; padding: 16px 24px; }
.nav-left, .brand, .primary-nav, .nav-actions { display: flex; align-items: center; }
.nav-left { min-width: 0; }
.brand { gap: 12px; color: var(--ink); font-size: 20px; font-weight: 700; line-height: 28px; text-decoration: none; white-space: nowrap; }
.brand img { width: 32px; height: auto; }
.primary-nav { gap: 20px; margin-left: 24px; }
.primary-nav a { color: #4b5563; font-size: 14px; line-height: 20px; text-decoration: none; white-space: nowrap; }
.primary-nav a:hover, .site-footer a:hover { color: var(--accent); }
.nav-actions { gap: 12px; }
.action, .lang-button, .menu-button { border: 0; font: 500 14px/20px Arial, Helvetica, sans-serif; text-decoration: none; white-space: nowrap; cursor: pointer; }
.action { padding: 8px 16px; border-radius: 8px; }
.action-outline { border: 1px solid #d1d5db; background: #fff; }
.action-online { display: flex; align-items: center; gap: 4px; border-radius: 999px; color: #fff; background: #000; }
.action-login, .lang-button { display: flex; align-items: center; gap: 8px; }
.lang-wrap { position: relative; }
.lang-button { padding: 8px 12px; border-radius: 8px; color: #111827; background: #f3f4f6; }
.lang-menu { position: absolute; top: 44px; right: 0; display: none; min-width: 140px; padding: 5px; border: 1px solid var(--line); border-radius: 8px; background: #fff; box-shadow: var(--shadow); }
.lang-menu.open { display: block; }
.lang-option { width: 100%; height: 36px; padding: 0 16px; border: 0; border-radius: 6px; background: #fff; text-align: left; cursor: pointer; }
.lang-option[aria-selected="true"] { color: var(--accent-strong); background: var(--tint); font-weight: 700; }
.menu-button { display: none; align-items: center; justify-content: center; width: 40px; height: 40px; border: 1px solid #d1d5db; border-radius: 8px; background: #fff; }
.mobile-panel { display: none; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 10px; padding: 18px 24px 22px; border-top: 1px solid var(--line); background: #fff; }
.mobile-panel.open { display: grid; }
.mobile-panel a, .mobile-panel button { padding: 10px 12px; border: 1px solid var(--line); border-radius: 8px; color: #374151; background: #fff; font: 500 14px/20px Arial, Helvetica, sans-serif; text-align: left; text-decoration: none; }
.container { width: min(1180px, calc(100% - 48px)); margin: 0 auto; }
.breadcrumbs { display: flex; align-items: center; gap: 10px; overflow-x: auto; padding-top: 28px; padding-bottom: 12px; color: var(--subtle); font-size: 15px; white-space: nowrap; }
.breadcrumbs a { color: var(--subtle); text-decoration: underline; text-underline-offset: 3px; }
.hero { padding: 18px 0 44px; text-align: center; }
.eyebrow { display: inline-flex; padding: 7px 10px; border-radius: 999px; color: var(--accent-strong); background: var(--tint); font-size: 12px; font-weight: 700; letter-spacing: .07em; text-transform: uppercase; }
.hero h1 { max-width: 980px; margin: 18px auto 14px; color: var(--ink); font-size: 50px; line-height: 1.1; letter-spacing: -.045em; }
.lead { max-width: 850px; margin: 0 auto; font-size: 19px; line-height: 1.65; }
.meta { display: flex; justify-content: center; flex-wrap: wrap; gap: 18px; margin-top: 18px; color: var(--subtle); font-size: 14px; }
.review-note { color: #92400e; }
.hero figure { margin: 34px 0 0; }
.hero img { display: block; width: 100%; aspect-ratio: 1.78; border: 1px solid var(--line); border-radius: 18px; object-fit: cover; box-shadow: var(--shadow); }
figcaption { margin-top: 10px; color: var(--subtle); font-size: 13px; line-height: 1.55; }
.article-layout { display: grid; grid-template-columns: minmax(0, 860px) 260px; gap: 58px; padding: 26px 0 82px; }
.article { min-width: 0; }
.article section { padding: 42px 0; border-top: 1px solid var(--line); }
.article section:first-child { padding-top: 10px; border-top: 0; }
.article h2 { margin: 0 0 18px; color: var(--ink); font-size: 30px; line-height: 1.25; letter-spacing: -.025em; }
.article p, .article li { font-size: 17px; line-height: 1.72; }
.article p { margin: 0 0 18px; }
.article li + li { margin-top: 8px; }
.article a { color: var(--accent); text-decoration: underline; text-underline-offset: 3px; }
.quick-answer { padding: 22px 24px; border-left: 4px solid var(--accent); border-radius: 0 12px 12px 0; background: var(--tint); }
.quick-answer p:last-child { margin-bottom: 0; }
.callout { margin: 22px 0; padding: 22px 24px; border: 1px solid #c7d2fe; border-radius: 14px; background: var(--tint-soft); }
.cards { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; margin: 22px 0; }
.card { padding: 22px; border: 1px solid var(--line); border-left: 4px solid var(--accent); border-radius: 4px 14px 14px 4px; background: #fff; }
.card strong { display: block; margin-bottom: 8px; color: var(--ink); font-size: 17px; }
.card p { margin: 0; font-size: 15px; line-height: 1.6; }
.metric-strip { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 12px; margin: 22px 0; }
.metric { padding: 18px; border: 1px solid var(--line); border-radius: 14px; background: #fff; }
.metric b { display: block; margin-bottom: 6px; color: var(--accent); font-size: 22px; }
.metric span { display: block; color: var(--muted); font-size: 13px; line-height: 1.45; }
.table-wrap { overflow-x: auto; margin: 22px 0; border: 1px solid var(--line); border-radius: 14px; }
.table-wrap table { width: 100%; min-width: 690px; border-collapse: collapse; }
.table-wrap th, .table-wrap td { padding: 15px 16px; border-bottom: 1px solid var(--line); font-size: 15px; line-height: 1.55; text-align: left; vertical-align: top; }
.table-wrap th { color: var(--ink); background: var(--soft); font-size: 13px; letter-spacing: .04em; text-transform: uppercase; }
.table-wrap tr:last-child td { border-bottom: 0; }
.steps { margin: 22px 0; padding: 0; list-style: none; counter-reset: step; }
.steps li { position: relative; margin: 0 0 14px; padding: 20px 22px 20px 64px; border: 1px solid var(--line); border-radius: 14px; background: #fff; }
.steps li::before { position: absolute; top: 20px; left: 20px; display: grid; place-items: center; width: 30px; height: 30px; border-radius: 9px; color: #fff; background: var(--nav-gradient); font: 700 14px Arial; counter-increment: step; content: counter(step); }
.steps strong { color: var(--ink); }
.code-block { overflow-x: auto; margin: 22px 0; padding: 18px 20px; border-radius: 12px; color: #e5e7eb; background: #111827; font: 14px/1.65 Consolas, Monaco, monospace; }
.download-box { margin: 24px 0; padding: 26px; border: 1px solid #c7d2fe; border-radius: 16px; background: linear-gradient(135deg, #eef2ff, #faf5ff); }
.download-box > strong { display: block; margin-bottom: 10px; color: var(--ink); font-size: 18px; }
.button { display: inline-flex; align-items: center; gap: 8px; padding: 11px 18px; border-radius: 999px; color: #fff !important; background: var(--accent); font-weight: 700; text-decoration: none !important; }
.cta { margin: 26px 0; padding: 34px; border-radius: 18px; color: #e0e7ff; background: var(--cta-gradient); }
.cta h2 { margin-bottom: 12px; color: #fff; }
.cta p { color: #e0e7ff; }
.cta a { display: inline-flex; padding: 11px 18px; border-radius: 999px; color: var(--accent-strong); background: #fff; font-weight: 700; text-decoration: none; }
.faq-item { padding: 22px 0; border-bottom: 1px solid var(--line); }
.faq-item strong { display: block; margin-bottom: 8px; color: var(--ink); font-size: 18px; }
.faq-item p { margin: 0; }
.author-box { display: flex; gap: 16px; padding: 22px; border: 1px solid var(--line); border-radius: 14px; background: var(--soft); }
.author-mark { display: grid; flex: 0 0 46px; place-items: center; height: 46px; border-radius: 12px; color: #fff; background: var(--nav-gradient); font-weight: 700; }
.author-box p { margin: 0; font-size: 14px; }
.toc { position: sticky; top: 100px; padding-left: 22px; border-left: 2px solid var(--line); }
.toc-label { margin-bottom: 10px; color: var(--subtle); font-size: 12px; font-weight: 700; letter-spacing: .1em; text-transform: uppercase; }
.toc a { display: block; padding: 5px 0; color: var(--subtle); font-size: 13px; line-height: 1.4; text-decoration: none; }
.toc a.active { color: var(--accent); font-weight: 700; }
.mobile-toc { display: none; margin: 0 0 28px; padding: 14px 16px; border: 1px solid var(--line); border-radius: 12px; }
.mobile-toc summary { color: var(--ink); font-weight: 700; cursor: pointer; }
.mobile-toc a { display: block; padding: 7px 0; color: var(--accent); }
.disclosure { padding: 16px 18px; border: 1px solid #fed7aa; border-radius: 12px; color: #7c2d12; background: #fff7ed; }
.disclosure p { margin: 0; font-size: 15px; }
.site-footer { min-height: 485px; padding: 44px 0 30px; border-top: 1px solid var(--line); background: #fff; text-align: center; }
.footer-heading { margin: 0 0 14px; color: var(--ink); font-size: 20px; font-weight: 700; }
.social-links, .footer-links, .contact-links { display: flex; flex-wrap: wrap; justify-content: center; gap: 12px 24px; }
.social-links a, .contact-links a { color: #2563eb; font-weight: 600; text-decoration: underline; text-underline-offset: 3px; }
.footer-copy { max-width: 700px; margin: 0 auto 18px; color: var(--muted); font-size: 14px; line-height: 1.6; }
.footer-links { margin: 26px 0 18px; }
.footer-links a { color: #374151; font-size: 14px; font-weight: 600; text-decoration: underline; text-underline-offset: 3px; }
.maintained, .last-updated, .copyright { margin: 8px 0; color: #5f6b7a; font-size: 14px; line-height: 1.55; }
.social-block { margin-bottom: 34px; }
@media (min-width: 1536px) { .primary-nav { gap: 24px; } }
@media (max-width: 1279.98px) {
  .primary-nav { display: none; }
  .menu-button { display: flex; }
  .article-layout { grid-template-columns: 1fr; }
  .desktop-toc { display: none; }
  .mobile-toc { display: block; }
}
@media (max-width: 767.98px) {
  .nav-shell { padding: 16px; }
  .nav-actions { gap: 8px; }
  .brand { gap: 8px; font-size: 18px; }
  .brand img { width: 28px; }
}
@media (max-width: 700px) {
  .container { width: calc(100% - 30px); }
  .mobile-panel { grid-template-columns: 1fr; }
  .hero h1 { font-size: 37px; }
  .article h2 { font-size: 26px; }
  .lead { font-size: 17px; }
  .article p, .article li { font-size: 16px; }
  .cards, .metric-strip { grid-template-columns: 1fr; }
  .hero img { border-radius: 12px; }
  .cta { padding: 26px; }
  .contact-links { flex-direction: column; }
  .site-footer { min-height: 549px; }
}
@media (max-width: 639.98px) { .nav-actions .lang-wrap, .nav-actions .action-download, .nav-actions .action-online { display: none; } }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } * { transition: none !important; } }