:root {
  --bg: #f6f7fa;
  --surface: #ffffff;
  --text: #1e2128;
  --muted: #687080;
  --line: #e4e7ed;
  --rule: #c9cfda;
  --accent: #2f5fd0;
  --accent-soft: rgba(47, 95, 208, .1);
  --serif: "Songti SC", "Noto Serif SC", "Source Han Serif SC", "Noto Serif CJK SC", SimSun, serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --mono: ui-monospace, "SFMono-Regular", "JetBrains Mono", Consolas, "Liberation Mono", monospace;
  --measure: 720px;
  --shell: 1080px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b0c0f;
    --surface: #121418;
    --text: #f2f4f8;
    --muted: #98a0ad;
    --line: #23262c;
    --rule: #3a3f47;
    --accent: #8fb0ff;
    --accent-soft: rgba(143, 176, 255, .12);
  }
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

img { max-width: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--sans);
  font-size: 15px;
  line-height: 1.75;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; text-decoration-color: var(--rule); text-underline-offset: 2px; }
a:hover { text-decoration-color: currentColor; }
a:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; border-radius: 2px; }

.shell { width: 100%; max-width: var(--shell); margin: 0 auto; padding: 0 24px; }

/* ---------- header ---------- */

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(150%) blur(10px);
  border-bottom: 1px solid var(--line);
}

.site-header .shell {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  min-height: 60px;
}

.brand {
  display: inline-flex;
  align-items: center;
  text-decoration: none;
  min-height: 44px;
}

.brand-name {
  font-family: var(--serif);
  font-size: 16px;
  font-weight: 600;
  letter-spacing: .02em;
}

.hero .mark {
  width: 64px;
  height: 64px;
  margin: 0 0 26px;
}

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

.site-nav a {
  display: inline-flex;
  align-items: center;
  min-height: 44px;
  padding: 0 10px;
  font-size: 13.5px;
  color: var(--muted);
  text-decoration: none;
}

.site-nav a:hover { color: var(--text); }
.site-nav a[aria-current="page"] { color: var(--text); }

.site-nav .lang {
  margin-left: 6px;
  padding-left: 14px;
  border-left: 1px solid var(--line);
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: .04em;
}

/* ---------- landing ---------- */

.hero { padding: 84px 0 56px; border-bottom: 1px solid var(--line); }

.eyebrow {
  margin: 0 0 22px;
  font-family: var(--mono);
  font-size: 11.5px;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--muted);
}

.hero h1 {
  margin: 0;
  font-family: var(--serif);
  font-size: clamp(38px, 6vw, 60px);
  font-weight: 600;
  line-height: 1.08;
  letter-spacing: .01em;
}

.hero .en {
  display: block;
  margin-top: 10px;
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: .22em;
  text-transform: uppercase;
  color: var(--muted);
}

.hero .lead {
  margin: 28px 0 0;
  max-width: 34em;
  font-size: 16px;
  line-height: 1.8;
}

.hero dl {
  display: grid;
  grid-template-columns: max-content 1fr;
  gap: 6px 20px;
  margin: 32px 0 0;
  font-size: 13px;
  color: var(--muted);
}

.hero dt { font-family: var(--mono); font-size: 11.5px; letter-spacing: .08em; text-transform: uppercase; }
.hero dd { margin: 0; color: var(--text); }

.section { padding: 56px 0; border-bottom: 1px solid var(--line); }

.section-title {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 16px;
  margin: 0 0 6px;
  font-family: var(--serif);
  font-size: 20px;
  font-weight: 600;
}

.section-note { margin: 0; color: var(--muted); font-size: 13.5px; }

.doc-index { margin: 26px 0 0; padding: 0; list-style: none; border-top: 1px solid var(--rule); }

.doc-index li { border-bottom: 1px solid var(--line); }

.doc-index a {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 24px;
  padding: 18px 2px;
  text-decoration: none;
  min-height: 60px;
}

.doc-index a:hover .doc-name { text-decoration: underline; text-decoration-color: var(--rule); }

.doc-name { font-size: 16px; }

.doc-meta {
  font-family: var(--mono);
  font-size: 11.5px;
  letter-spacing: .04em;
  color: var(--muted);
  white-space: nowrap;
}

.contact-line { margin: 18px 0 0; font-size: 14px; }
.contact-line .label { display: inline-block; min-width: 5.5em; color: var(--muted); font-size: 12.5px; }

/* ---------- document pages ---------- */

.doc-shell { padding: 44px 0 72px; }

.doc {
  max-width: var(--measure);
  margin: 0 auto;
}

.doc-head { margin: 0 0 30px; }

.doc-head .crumb {
  margin: 0 0 18px;
  font-family: var(--mono);
  font-size: 11.5px;
  letter-spacing: .12em;
  text-transform: uppercase;
  color: var(--muted);
}

.doc-head .doc-nav { display: flex; flex-wrap: wrap; gap: 8px 18px; padding: 14px 0 0; border-top: 1px solid var(--line); font-size: 13px; }
.doc-head .doc-nav a { color: var(--muted); text-decoration: none; }
.doc-head .doc-nav a:hover { color: var(--text); }

.doc h1 { font-family: var(--serif); font-size: 30px; line-height: 1.3; font-weight: 600; margin: 0 0 10px; letter-spacing: .01em; }
.doc .meta { color: var(--muted); font-size: 12.5px; line-height: 1.75; margin: 0; padding-bottom: 20px; border-bottom: 1px solid var(--line); }
.doc h2 { font-size: 16.5px; line-height: 1.5; font-weight: 650; margin: 38px 0 10px; }
.doc h3 { font-size: 14.5px; font-weight: 600; margin: 24px 0 6px; }
.doc p { margin: 10px 0; }
.doc ul, .doc ol { margin: 10px 0; padding-left: 1.35em; }
.doc li { margin: 6px 0; }
.doc strong { font-weight: 600; }

.doc .summary {
  margin: 24px 0 4px;
  padding: 2px 0 2px 14px;
  border-left: 2px solid var(--rule);
  font-size: 14.5px;
  line-height: 1.8;
}

.doc .summary strong {
  display: block;
  margin-bottom: 4px;
  font-size: 11.5px;
  font-weight: 600;
  letter-spacing: .14em;
  color: var(--muted);
  text-transform: uppercase;
}

.doc .summary strong + br { display: none; }

.doc .table-wrap {
  overflow-x: auto;
  margin: 18px 0 6px;
  border-top: 1px solid var(--rule);
  border-bottom: 1px solid var(--rule);
  -webkit-overflow-scrolling: touch;
}

.doc table { border-collapse: collapse; width: 100%; min-width: 560px; font-size: 13px; line-height: 1.65; }
.doc th, .doc td { border: 0; border-bottom: 1px solid var(--line); padding: 9px 12px 9px 0; text-align: left; vertical-align: top; }
.doc tr:last-child td { border-bottom: 0; }
.doc th { font-size: 12px; font-weight: 600; color: var(--muted); border-bottom: 1px solid var(--rule); }
.doc th:not(:first-child), .doc td:not(:first-child) { padding-left: 12px; }
.doc .url { color: var(--muted); font-size: 11.5px; word-break: break-all; }
.doc .note { margin: 32px 0 0; color: var(--muted); font-size: 12.5px; line-height: 1.75; }
.doc .footer { margin-top: 36px; padding-top: 14px; border-top: 1px solid var(--line); color: var(--muted); font-size: 12px; line-height: 1.7; }

/* ---------- footer ---------- */

.site-footer { padding: 36px 0 44px; color: var(--muted); font-size: 12.5px; }

.site-footer .rows { display: flex; flex-wrap: wrap; align-items: center; gap: 8px 22px; }

.site-footer a { color: var(--muted); text-decoration: none; }
.site-footer a:hover { color: var(--text); text-decoration: underline; text-decoration-color: var(--rule); }

.site-footer .license { display: inline-flex; align-items: center; gap: 7px; min-height: 32px; }
.site-footer .license img { width: 14px; height: 14px; opacity: .75; }
.site-footer .sep { color: var(--rule); }
.site-footer .rows + .rows { margin-top: 10px; }

@media (max-width: 640px) {
  .shell { padding: 0 18px; }
  .hero { padding: 48px 0 40px; }
  .hero .mark { width: 52px; height: 52px; margin-bottom: 22px; }
  .hero dl { grid-template-columns: 1fr; gap: 2px; }
  .hero dd + dt { margin-top: 10px; }
  .section { padding: 40px 0; }
  .doc-shell { padding: 28px 0 56px; }
  .doc h1 { font-size: 25px; }
  .doc h2 { font-size: 16px; margin-top: 32px; }
  body { font-size: 14.5px; }
  .brand-name { font-size: 15px; }
  .site-nav a:not(.lang) { display: none; }
  .site-nav .lang { margin-left: 0; padding-left: 0; border-left: 0; font-size: 12.5px; }
  .doc-index a { flex-direction: column; gap: 4px; }
}

@media (prefers-reduced-motion: reduce) {
  * { scroll-behavior: auto !important; }
}