:root {
  --color-surface: #fefefe;
  --color-surface-alt: #f4f4f4;
  --color-surface-deep: #e6e6e6;
  --color-ink: #323639;
  --color-ink-soft: #5b6167;
  --color-ink-muted: #777d83;
  --color-line: #d9dadb;
  --color-primary: #0876d3;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #dcebf8;
  --color-accent: #4a8301;
  --color-accent-ink: #ffffff;
  --color-highlight: #dee8d0;
  --color-focus: #478000;
  --color-contrast-surface: #121f2a;
  --color-contrast-ink: #e4e6e7;
  --color-contrast-line: #404b54;
  --color-contrast-accent: #8efd02;
  --overlay-scrim: linear-gradient(180deg, rgba(18, 31, 42, 0.35) 0%, rgba(18, 31, 42, 0.72) 55%, rgba(18, 31, 42, 0.92) 100%);
  --font-heading: "Source Han Sans SC", "Noto Sans SC", SimHei, "Microsoft YaHei", sans-serif;
  --font-body: "PingFang SC", "Microsoft YaHei", "Source Han Sans SC", sans-serif;
  --font-mono: ui-monospace, Menlo, Consolas, monospace;
  --text-xs: 10.1px;
  --text-sm: 14.3px;
  --text-base: 17px;
  --text-lg: 24.0px;
  --text-xl: 34.0px;
  --text-2xl: 48.1px;
  --text-3xl: 68.0px;
  --text-4xl: 96.1px;
  --text-display: clamp(40px, 8.2vw, 105px);
  --text-figure: clamp(33px, 5.9vw, 76px);
  --weight-heading: 895;
  --weight-body: 400;
  --leading-body: 1.76;
  --leading-heading: 1.16;
  --tracking-heading: -0.002em;
  --radius-sm: 202px;
  --radius-md: 436px;
  --radius-lg: 670px;
  --radius-pill: 999px;
  --border-thin: 2px;
  --border-thick: 2px;
  --shadow-1: none;
  --shadow-2: none;
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-6: 48px;
  --space-8: 64px;
  --container: 1220px;
  --measure: 67ch;
  --gutter: 24px;
  --section-y: 85px;
  --section-y-lg: 119px;
}

/* ============================================================
   1. 复位与中文排版骨架
   ============================================================ */
*,
*::before,
*::after { box-sizing: border-box; }

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

@media (prefers-reduced-motion: no-preference) {
  html { scroll-behavior: smooth; }
}

body {
  --header-offset: 106px;
  margin: 0;
  font-family: var(--font-body);
  font-size: var(--text-base);
  font-weight: var(--weight-body);
  line-height: var(--leading-body);
  color: var(--color-ink);
  background: var(--color-surface);
  overflow-x: hidden;
}

body.nav-open { overflow: hidden; }

h1, h2, h3, h4, h5, h6 {
  margin: 0;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
}

h1 { font-size: var(--text-3xl); }
h2 { font-size: var(--text-2xl); }
h3 { font-size: var(--text-xl); }
h4 { font-size: var(--text-lg); }
h5 { font-size: var(--text-base); font-weight: 800; }
h6 { font-size: var(--text-sm); font-weight: 800; letter-spacing: 0.06em; }

p { margin: 0 0 var(--space-3); }
p:last-child { margin-bottom: 0; }

ul, ol { margin: 0 0 var(--space-3); padding-left: 1.2em; }
li { margin-bottom: 6px; }

a {
  color: var(--color-primary);
  text-decoration-thickness: 2px;
  text-underline-offset: 3px;
}
a:hover { color: color-mix(in srgb, var(--color-primary) 72%, #000); }

strong, b { font-weight: 800; }

img, svg, video { max-width: 100%; display: block; }

hr {
  border: 0;
  border-top: var(--border-thin) solid var(--color-line);
  margin: var(--space-4) 0;
}

code, kbd, samp {
  font-family: var(--font-mono);
  font-size: 0.94em;
  background: var(--color-surface-alt);
  border: var(--border-thin) solid var(--color-line);
  padding: 1px 6px;
}

::selection {
  background: var(--color-primary);
  color: var(--color-primary-ink);
}

:focus-visible {
  outline: var(--border-thick) solid var(--color-focus);
  outline-offset: 3px;
}

/* ============================================================
   2. 布局工具
   ============================================================ */
.container {
  width: 100%;
  max-width: calc(var(--container) + var(--gutter) * 2);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.measure { max-width: var(--measure); }

.band { padding-block: var(--section-y); }
.band--lg { padding-block: var(--section-y-lg); }
.band--tight { padding-block: var(--space-6); }

.band--alt { background: var(--color-surface-alt); }
.band--deep { background: var(--color-surface-deep); }

.band--contrast {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}
.band--contrast h1,
.band--contrast h2,
.band--contrast h3,
.band--contrast h4,
.band--contrast h5 { color: var(--color-contrast-ink); }
.band--contrast a { color: var(--color-contrast-accent); }

.band--primary {
  background: var(--color-primary);
  color: var(--color-primary-ink);
}
.band--primary h1,
.band--primary h2,
.band--primary h3,
.band--primary h4 { color: var(--color-primary-ink); }
.band--primary a { color: var(--color-primary-ink); }

.band--accent {
  background: var(--color-accent);
  color: var(--color-accent-ink);
}
.band--accent h1,
.band--accent h2,
.band--accent h3,
.band--accent h4 { color: var(--color-accent-ink); }
.band--accent a { color: var(--color-accent-ink); }

.grid { display: grid; gap: var(--gutter); }
.grid--2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid--3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.grid--7 { grid-template-columns: repeat(7, minmax(0, 1fr)); }

.split {
  display: grid;
  grid-template-columns: minmax(0, 4fr) minmax(0, 8fr);
  gap: var(--space-6);
  align-items: start;
}

.split--flip {
  grid-template-columns: minmax(0, 8fr) minmax(0, 4fr);
}

.stack > * + * { margin-top: var(--space-3); }
.stack--tight > * + * { margin-top: var(--space-1); }
.stack--wide > * + * { margin-top: var(--space-4); }

/* ============================================================
   3. 排版组件
   ============================================================ */
.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  font-family: var(--font-heading);
  font-weight: 800;
  font-size: var(--text-xs);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--color-primary-ink);
  background: var(--color-primary);
  padding: 6px 14px;
  border-radius: var(--radius-sm);
  margin-bottom: var(--space-2);
}

.eyebrow--accent { background: var(--color-accent); color: var(--color-accent-ink); }
.eyebrow--contrast {
  background: transparent;
  color: var(--color-contrast-accent);
  border: var(--border-thin) solid var(--color-contrast-line);
}

.u-display {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-display);
  line-height: 0.96;
  letter-spacing: -0.03em;
  margin: 0;
}

.u-figure {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-figure);
  line-height: 0.94;
  letter-spacing: -0.03em;
}

.num,
.num-lg {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-feature-settings: "tnum" 1;
  letter-spacing: -0.02em;
}

.num-lg { font-size: var(--text-lg); font-weight: 700; }

.lede {
  font-size: var(--text-lg);
  line-height: 1.5;
  color: var(--color-ink-soft);
  max-width: var(--measure);
}

.meta {
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
  letter-spacing: 0.01em;
}

.rule {
  height: 0;
  border: 0;
  border-top: var(--border-thin) solid var(--color-line);
  margin: var(--space-3) 0;
}

.band--contrast .rule { border-top-color: var(--color-contrast-line); }

.hl {
  background: var(--color-highlight);
  padding: 0 6px;
  border-radius: 3px;
}

/* 深色带内的数字高亮：唯一用途 */
.on-contrast-figure {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  color: var(--color-contrast-accent);
  font-weight: 700;
}

/* ============================================================
   4. 几何元素
   ============================================================ */
.disc {
  display: block;
  width: 64px;
  height: 64px;
  border-radius: var(--radius-lg);
  background: var(--color-primary);
  flex: 0 0 auto;
}

.disc--accent { background: var(--color-accent); }
.disc--contrast { background: var(--color-contrast-surface); }
.disc--outline {
  background: transparent;
  border: var(--border-thick) solid currentColor;
}

.disc--num {
  display: grid;
  place-items: center;
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: var(--text-lg);
  color: var(--color-primary-ink);
}

.semi {
  display: block;
  width: 96px;
  height: 48px;
  border-radius: var(--radius-lg) var(--radius-lg) 0 0;
  background: var(--color-accent);
}

.geo-bar {
  display: block;
  height: 10px;
  width: 100%;
  background: linear-gradient(
    90deg,
    var(--color-primary) 0 34%,
    var(--color-accent) 34% 67%,
    var(--color-contrast-surface) 67% 100%
  );
}

.ticks {
  height: 14px;
  background-image: repeating-linear-gradient(
    90deg,
    var(--color-line) 0 2px,
    transparent 2px 14px
  );
  border-top: var(--border-thin) solid var(--color-line);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.band--contrast .ticks {
  background-image: repeating-linear-gradient(
    90deg,
    var(--color-contrast-line) 0 2px,
    transparent 2px 14px
  );
  border-color: var(--color-contrast-line);
}

/* ============================================================
   5. 按钮、标签、徽标
   ============================================================ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: 14px 26px;
  border: var(--border-thick) solid transparent;
  border-radius: var(--radius-pill);
  background: var(--color-surface-alt);
  color: var(--color-ink);
  font-family: var(--font-heading);
  font-weight: 800;
  font-size: var(--text-sm);
  letter-spacing: 0.02em;
  line-height: 1.2;
  text-decoration: none;
  cursor: pointer;
  transition: background-color 180ms ease, color 180ms ease, border-color 180ms ease;
}

.btn:hover { color: var(--color-ink); }

.btn--primary {
  background: var(--color-primary);
  color: var(--color-primary-ink);
  border-color: var(--color-primary);
}
.btn--primary:hover {
  background: color-mix(in srgb, var(--color-primary) 74%, #000);
  border-color: color-mix(in srgb, var(--color-primary) 74%, #000);
  color: var(--color-primary-ink);
}

.btn--accent {
  background: var(--color-accent);
  color: var(--color-accent-ink);
  border-color: var(--color-accent);
}
.btn--accent:hover {
  background: color-mix(in srgb, var(--color-accent) 76%, #000);
  border-color: color-mix(in srgb, var(--color-accent) 76%, #000);
  color: var(--color-accent-ink);
}

.btn--contrast {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-color: var(--color-contrast-line);
}
.btn--contrast:hover {
  background: color-mix(in srgb, var(--color-contrast-surface) 78%, var(--color-contrast-accent));
  color: var(--color-contrast-ink);
}

.btn--ghost {
  background: transparent;
  color: var(--color-ink);
  border-color: var(--color-line);
}
.btn--ghost:hover {
  background: var(--color-primary-soft);
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.btn--block { width: 100%; }

.btn[disabled],
.btn[aria-disabled="true"] {
  opacity: 0.5;
  cursor: not-allowed;
}

.pill,
.chip,
.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 14px;
  border-radius: var(--radius-sm);
  font-size: var(--text-xs);
  font-weight: 800;
  font-family: var(--font-heading);
  letter-spacing: 0.06em;
  line-height: 1.7;
  background: var(--color-surface-deep);
  color: var(--color-ink-soft);
  border: var(--border-thin) solid transparent;
}

.pill--primary { background: var(--color-primary-soft); color: color-mix(in srgb, var(--color-primary) 82%, #000); }
.pill--accent { background: var(--color-highlight); color: color-mix(in srgb, var(--color-accent) 82%, #000); }
.pill--contrast { background: var(--color-contrast-surface); color: var(--color-contrast-ink); }

.tag {
  border-radius: var(--radius-pill);
  border-color: var(--color-line);
  background: transparent;
  cursor: pointer;
  transition: background-color 160ms ease, color 160ms ease, border-color 160ms ease;
}
.tag:hover { background: var(--color-primary-soft); border-color: var(--color-primary); }
.tag[aria-pressed="true"],
.tag.is-active {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
}

.version-chip {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 14px;
  border: var(--border-thin) solid var(--color-contrast-line);
  border-radius: var(--radius-pill);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 700;
  letter-spacing: 0.04em;
  color: var(--color-contrast-accent);
  white-space: nowrap;
}

.season-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 700;
  letter-spacing: 0.06em;
  color: var(--color-contrast-accent);
}

.season-badge::before {
  content: "";
  width: 8px;
  height: 8px;
  border-radius: var(--radius-pill);
  background: var(--color-contrast-accent);
  flex: 0 0 auto;
}

/* ============================================================
   6. 资料卡 / 面板 / 图框
   ============================================================ */
.card,
.panel {
  position: relative;
  background: var(--color-surface);
  border: var(--border-thin) solid var(--color-line);
  border-radius: 0;
  padding: var(--space-3);
}

.card--flat { background: var(--color-surface-alt); }
.card--tint { background: var(--color-primary-soft); border-color: color-mix(in srgb, var(--color-primary) 30%, var(--color-line)); }
.card--leaf { background: var(--color-highlight); border-color: color-mix(in srgb, var(--color-accent) 26%, var(--color-line)); }

.card__head {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
  padding-bottom: var(--space-2);
  margin-bottom: var(--space-2);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.card__head h3,
.card__head h4 { flex: 1 1 auto; min-width: 0; margin: 0; }

.card__index {
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: var(--text-sm);
  color: var(--color-primary);
  flex: 0 0 auto;
}

.card__body { color: var(--color-ink-soft); }

.card__foot {
  margin-top: var(--space-3);
  padding-top: var(--space-2);
  border-top: var(--border-thin) solid var(--color-line);
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-2);
}

.band--contrast .card,
.band--contrast .panel {
  background: color-mix(in srgb, var(--color-contrast-surface) 86%, var(--color-contrast-ink));
  border-color: var(--color-contrast-line);
  color: var(--color-contrast-ink);
}
.band--contrast .card__head,
.band--contrast .card__foot { border-color: var(--color-contrast-line); }
.band--contrast .card__body { color: color-mix(in srgb, var(--color-contrast-ink) 82%, transparent); }
.band--contrast .card__index { color: var(--color-contrast-accent); }

/* 图框：图像像贴在纸面上的资料卡 */
.figure {
  margin: 0;
  border: var(--border-thin) solid var(--color-line);
  background: var(--color-surface);
  padding: var(--space-2);
}

.figure--tight { padding: 0; }

.figure__media {
  position: relative;
  display: block;
  width: 100%;
  aspect-ratio: 16 / 9;
  overflow: hidden;
  background: var(--color-surface-deep);
}

.figure__media--tall { aspect-ratio: 4 / 5; }
.figure__media--wide { aspect-ratio: 21 / 9; }
.figure__media--square { aspect-ratio: 1 / 1; }

.figure__media img { width: 100%; height: 100%; object-fit: cover; }

.figure__slot {
  display: grid;
  place-items: center;
  width: 100%;
  height: 100%;
  min-height: 120px;
  background:
    repeating-linear-gradient(135deg,
      var(--color-surface-alt) 0 12px,
      var(--color-surface-deep) 12px 24px);
  font-size: var(--text-xs);
  letter-spacing: 0.2em;
  color: var(--color-ink-muted);
  text-transform: uppercase;
}

.figure__overlay {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  gap: 6px;
  padding: var(--space-3);
  background: var(--overlay-scrim);
  color: var(--color-contrast-ink);
}
.figure__overlay h3,
.figure__overlay h4 { color: var(--color-contrast-ink); }
.figure__overlay .num,
.figure__overlay .on-contrast-figure { color: var(--color-contrast-accent); }

.figure__caption {
  padding: var(--space-2) 4px 0;
  font-size: var(--text-xs);
  line-height: 1.6;
  color: var(--color-ink-muted);
}

.figure--offset { margin-left: calc(var(--space-6) * -1); }

/* ============================================================
   7. 数据表
   ============================================================ */
.data-table {
  width: 100%;
  border-collapse: collapse;
  border: var(--border-thin) solid var(--color-line);
  font-size: var(--text-sm);
}

.data-table caption {
  caption-side: top;
  text-align: left;
  padding-bottom: var(--space-2);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-lg);
  color: var(--color-ink);
}

.data-table th,
.data-table td {
  padding: 12px var(--space-2);
  text-align: left;
  border-bottom: var(--border-thin) solid var(--color-line);
  vertical-align: top;
}

.data-table thead th {
  background: var(--color-surface-deep);
  font-family: var(--font-heading);
  font-weight: 800;
  font-size: var(--text-sm);
  letter-spacing: 0.04em;
  color: var(--color-ink);
}

.data-table tbody tr:nth-child(even) { background: var(--color-surface-alt); }
.data-table tbody tr:last-child td { border-bottom: 0; }
.data-table .num { text-align: right; white-space: nowrap; }
.data-table .num--hero { font-size: var(--text-lg); font-weight: 700; color: var(--color-primary); }

.band--contrast .data-table { border-color: var(--color-contrast-line); color: var(--color-contrast-ink); }
.band--contrast .data-table caption { color: var(--color-contrast-ink); }
.band--contrast .data-table th,
.band--contrast .data-table td { border-bottom-color: var(--color-contrast-line); }
.band--contrast .data-table thead th {
  background: color-mix(in srgb, var(--color-contrast-surface) 70%, var(--color-contrast-ink));
  color: var(--color-contrast-ink);
}
.band--contrast .data-table tbody tr:nth-child(even) {
  background: color-mix(in srgb, var(--color-contrast-surface) 88%, var(--color-contrast-ink));
}
.band--contrast .data-table .num--hero { color: var(--color-contrast-accent); }

/* ============================================================
   8. 可展开组件
   ============================================================ */
.disclosure {
  border: var(--border-thin) solid var(--color-line);
  background: var(--color-surface);
}

.disclosure + .disclosure { margin-top: -2px; }

.disclosure__trigger {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  width: 100%;
  padding: var(--space-3);
  border: 0;
  background: transparent;
  color: var(--color-ink);
  text-align: left;
  font-family: var(--font-heading);
  font-weight: 800;
  font-size: var(--text-base);
  line-height: 1.5;
  cursor: pointer;
  transition: background-color 180ms ease;
}

.disclosure__trigger:hover { background: var(--color-primary-soft); }
.disclosure__trigger[aria-expanded="true"] { background: var(--color-primary-soft); }

.disclosure.is-open > .disclosure__trigger {
  box-shadow: inset 0 0 0 var(--border-thick) var(--color-focus);
}

.disclosure__marker {
  flex: 0 0 auto;
  width: 26px;
  height: 26px;
  border-radius: var(--radius-lg);
  border: var(--border-thick) solid var(--color-primary);
  position: relative;
  margin-top: 2px;
}

.disclosure__marker::before,
.disclosure__marker::after {
  content: "";
  position: absolute;
  background: var(--color-primary);
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  transition: transform 180ms ease, opacity 180ms ease;
}
.disclosure__marker::before { width: 12px; height: 2px; }
.disclosure__marker::after { width: 2px; height: 12px; }

.disclosure__trigger[aria-expanded="true"] .disclosure__marker::after { opacity: 0; }

.disclosure__q { flex: 1 1 auto; }

.disclosure__panel {
  padding: 0 var(--space-3) var(--space-3) calc(var(--space-3) + 26px + var(--space-3));
  color: var(--color-ink-soft);
  font-size: var(--text-base);
}

.disclosure__panel[hidden] { display: none; }

.disclosure__panel > * + * { margin-top: var(--space-2); }

/* ============================================================
   9. 面包屑与目录
   ============================================================ */
.breadcrumbs {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
  margin: 0 0 var(--space-3);
  padding: 0;
  list-style: none;
  font-size: var(--text-xs);
  letter-spacing: 0.06em;
  color: var(--color-ink-muted);
}

.breadcrumbs li { margin: 0; display: inline-flex; align-items: center; gap: 10px; }
.breadcrumbs li + li::before {
  content: "/";
  color: var(--color-line);
  font-weight: 700;
}
.breadcrumbs a {
  color: inherit;
  text-decoration: none;
  border-bottom: var(--border-thin) solid var(--color-line);
  padding-bottom: 2px;
}
.breadcrumbs a:hover { color: var(--color-primary); border-color: var(--color-primary); }
.breadcrumbs [aria-current="page"] { color: var(--color-ink); font-weight: 700; }

.toc {
  position: sticky;
  top: calc(var(--header-offset) + var(--space-3));
  border: var(--border-thin) solid var(--color-line);
  background: var(--color-surface);
  padding: var(--space-3);
}

.toc__title {
  font-family: var(--font-heading);
  font-weight: 800;
  font-size: var(--text-sm);
  letter-spacing: 0.1em;
  color: var(--color-ink-muted);
  margin: 0 0 var(--space-2);
}

.toc ul { list-style: none; margin: 0; padding: 0; }
.toc li { margin: 0; }

.toc a {
  display: block;
  padding: 9px 12px 9px 16px;
  border-left: var(--border-thick) solid transparent;
  color: var(--color-ink-soft);
  font-size: var(--text-sm);
  text-decoration: none;
  transition: color 160ms ease, border-color 160ms ease, background-color 160ms ease;
}
.toc a:hover { color: var(--color-primary); background: var(--color-surface-alt); }
.toc a.is-current {
  border-left-color: var(--color-primary);
  color: var(--color-primary);
  font-weight: 800;
  background: var(--color-primary-soft);
}

/* ============================================================
   10. 站点头部
   ============================================================ */
.skip-link {
  position: absolute;
  left: 50%;
  top: 0;
  z-index: 300;
  transform: translate(-50%, -160%);
  padding: 12px 24px;
  border-radius: 0 0 var(--radius-pill) var(--radius-pill);
  background: var(--color-contrast-accent);
  color: var(--color-contrast-surface);
  font-family: var(--font-heading);
  font-weight: 800;
  font-size: var(--text-sm);
  text-decoration: none;
  transition: transform 160ms ease;
}
.skip-link:focus { transform: translate(-50%, 0); color: var(--color-contrast-surface); }

.site-header {
  position: fixed;
  inset: 0 0 auto 0;
  z-index: 90;
  color: var(--color-contrast-ink);
  background: transparent;
  border-bottom: var(--border-thin) solid transparent;
  transition: background-color 200ms ease, border-color 200ms ease;
}

.site-header.is-solid {
  background: var(--color-contrast-surface);
  border-bottom-color: var(--color-contrast-line);
}

.header-shell {
  width: 100%;
  max-width: calc(var(--container) + var(--gutter) * 2);
  margin-inline: auto;
  padding: 14px var(--gutter);
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 10px 20px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  flex: 0 0 auto;
  text-decoration: none;
  color: inherit;
}

.brand:hover { color: inherit; }

.brand-mark {
  display: block;
  width: 38px;
  height: 38px;
  flex: 0 0 auto;
  border-radius: var(--radius-lg);
  background: linear-gradient(
    90deg,
    var(--color-contrast-accent) 0 50%,
    var(--color-primary) 50% 100%
  );
  box-shadow: inset 0 0 0 var(--border-thin) var(--color-contrast-surface);
}

.brand-text { display: block; min-width: 0; }

.brand-name {
  display: block;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-lg);
  line-height: 1.1;
  letter-spacing: var(--tracking-heading);
}

.brand-tagline {
  display: block;
  margin-top: 4px;
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: color-mix(in srgb, var(--color-contrast-ink) 74%, transparent);
}

.primary-nav {
  flex: 1 1 auto;
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: var(--space-2);
  min-width: 0;
}

.nav-list {
  display: flex;
  align-items: center;
  gap: 2px;
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav-list li { margin: 0; }

.nav-list a {
  display: block;
  padding: 9px 13px;
  border: var(--border-thin) solid transparent;
  border-radius: var(--radius-pill);
  color: inherit;
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: var(--text-sm);
  letter-spacing: 0.01em;
  text-decoration: none;
  white-space: nowrap;
  transition: background-color 180ms ease, color 180ms ease, border-color 180ms ease;
}

.nav-list a:hover {
  background: color-mix(in srgb, var(--color-contrast-accent) 20%, transparent);
  border-color: var(--color-contrast-accent);
  color: var(--color-contrast-ink);
}

.nav-list a[aria-current="page"] {
  background: var(--color-contrast-accent);
  border-color: var(--color-contrast-accent);
  color: var(--color-contrast-surface);
}

.nav-quick {
  display: flex;
  align-items: center;
  gap: 8px;
}

.quick-chip {
  display: inline-flex;
  align-items: center;
  padding: 6px 14px;
  border: var(--border-thin) solid var(--color-contrast-line);
  border-radius: var(--radius-pill);
  color: var(--color-contrast-ink);
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: var(--text-xs);
  letter-spacing: 0.04em;
  text-decoration: none;
  white-space: nowrap;
  transition: background-color 180ms ease, color 180ms ease, border-color 180ms ease;
}

.quick-chip:hover {
  background: var(--color-contrast-accent);
  border-color: var(--color-contrast-accent);
  color: var(--color-contrast-surface);
}

.quick-chip[aria-current="page"] {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: 10px;
  margin-left: auto;
  padding: 9px 16px;
  border: var(--border-thin) solid var(--color-contrast-line);
  border-radius: var(--radius-pill);
  background: transparent;
  color: var(--color-contrast-ink);
  font-family: var(--font-heading);
  font-weight: 800;
  font-size: var(--text-sm);
  cursor: pointer;
}

.nav-toggle-bars {
  position: relative;
  display: block;
  width: 18px;
  height: 12px;
}

.nav-toggle-bars::before,
.nav-toggle-bars::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  height: 2px;
  background: currentColor;
  transition: transform 200ms ease, top 200ms ease, bottom 200ms ease;
}
.nav-toggle-bars::before { top: 0; }
.nav-toggle-bars::after { bottom: 0; }

.site-header[data-open] .nav-toggle-bars::before { top: 5px; transform: rotate(45deg); }
.site-header[data-open] .nav-toggle-bars::after { bottom: 5px; transform: rotate(-45deg); }

.header-strip {
  border-top: var(--border-thin) solid transparent;
  transition: border-color 200ms ease;
}

.site-header.is-solid .header-strip { border-top-color: var(--color-contrast-line); }

.header-strip-inner {
  width: 100%;
  max-width: calc(var(--container) + var(--gutter) * 2);
  margin-inline: auto;
  padding: 6px var(--gutter) 10px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2);
}

.header-strip-note {
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: color-mix(in srgb, var(--color-contrast-ink) 66%, transparent);
}

/* ============================================================
   11. 站点页脚
   ============================================================ */
.site-footer {
  position: relative;
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-top: var(--border-thin) solid var(--color-contrast-line);
}

.footer-scallop {
  display: flex;
  justify-content: center;
  align-items: flex-end;
  gap: 0;
  padding-top: var(--space-8);
  overflow: hidden;
}

.footer-scallop span {
  display: block;
  width: 84px;
  height: 84px;
  border-radius: var(--radius-lg) var(--radius-lg) 0 0;
}

.footer-scallop span:nth-child(1) { background: var(--color-primary); }
.footer-scallop span:nth-child(2) { background: var(--color-accent); }
.footer-scallop span:nth-child(3) { background: var(--color-contrast-accent); }

.footer-shell {
  width: 100%;
  max-width: calc(var(--container) + var(--gutter) * 2);
  margin-inline: auto;
  padding: var(--space-6) var(--gutter) var(--space-6);
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1.55fr);
  gap: var(--space-6) var(--space-8);
}

.footer-lead { display: flex; flex-direction: column; gap: var(--space-3); }

.footer-brand {
  display: inline-flex;
  align-items: center;
  gap: 14px;
  color: inherit;
  text-decoration: none;
}
.footer-brand:hover { color: inherit; }

.footer-brand .brand-mark { width: 48px; height: 48px; }

.footer-brand-text { display: block; }

.footer-brand-name {
  display: block;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-lg);
  line-height: 1.1;
}

.footer-brand-line {
  display: block;
  margin-top: 4px;
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: color-mix(in srgb, var(--color-contrast-ink) 68%, transparent);
}

.footer-data-note {
  margin: 0;
  max-width: 40ch;
  font-size: var(--text-sm);
  line-height: 1.7;
  color: color-mix(in srgb, var(--color-contrast-ink) 76%, transparent);
}

.footer-nav {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: var(--space-4);
}

.footer-col-title {
  margin: 0 0 var(--space-2);
  padding-bottom: 10px;
  border-bottom: var(--border-thin) solid var(--color-contrast-line);
  font-family: var(--font-heading);
  font-weight: 800;
  font-size: var(--text-sm);
  letter-spacing: 0.12em;
  color: var(--color-contrast-accent);
}

.footer-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.footer-list li { margin: 0 0 4px; }

.footer-list a {
  display: inline-block;
  padding: 3px 0;
  color: var(--color-contrast-ink);
  font-size: var(--text-sm);
  text-decoration: none;
  border-bottom: var(--border-thin) solid transparent;
  transition: color 160ms ease, border-color 160ms ease;
}

.footer-list a:hover {
  color: var(--color-contrast-accent);
  border-bottom-color: var(--color-contrast-accent);
}

.footer-meta {
  width: 100%;
  max-width: calc(var(--container) + var(--gutter) * 2);
  margin-inline: auto;
  padding: var(--space-4) var(--gutter);
  border-top: var(--border-thin) solid var(--color-contrast-line);
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: var(--space-3);
}

.footer-meta-row { display: flex; flex-direction: column; gap: 6px; min-width: 0; }

.footer-meta-key {
  font-family: var(--font-heading);
  font-weight: 800;
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  color: color-mix(in srgb, var(--color-contrast-ink) 54%, transparent);
}

.footer-meta-val {
  font-size: var(--text-sm);
  line-height: 1.6;
  color: var(--color-contrast-ink);
  word-break: break-word;
}

.footer-base {
  width: 100%;
  max-width: calc(var(--container) + var(--gutter) * 2);
  margin-inline: auto;
  padding: var(--space-3) var(--gutter) var(--space-6);
  border-top: var(--border-thin) solid var(--color-contrast-line);
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-2) var(--space-4);
  font-size: var(--text-xs);
  letter-spacing: 0.06em;
  color: color-mix(in srgb, var(--color-contrast-ink) 66%, transparent);
}

.footer-copy { margin: 0; }
.footer-icp { margin: 0; font-family: var(--font-mono); }

.footer-legal {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  list-style: none;
  margin: 0;
  margin-left: auto;
  padding: 0;
}
.footer-legal li { margin: 0; }

.footer-legal a {
  color: var(--color-contrast-ink);
  text-decoration: none;
  border-bottom: var(--border-thin) solid var(--color-contrast-line);
  padding-bottom: 2px;
}
.footer-legal a:hover {
  color: var(--color-contrast-accent);
  border-bottom-color: var(--color-contrast-accent);
}

/* ============================================================
   12. 滚动进度
   ============================================================ */
.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  z-index: 200;
  width: 100%;
  height: 3px;
  transform: scaleX(0);
  transform-origin: 0 50%;
  background: linear-gradient(
    90deg,
    var(--color-primary) 0 34%,
    var(--color-accent) 34% 67%,
    var(--color-contrast-accent) 67% 100%
  );
  pointer-events: none;
}

/* ============================================================
   13. 状态与总宽度
   ============================================================ */
main { scroll-margin-top: var(--header-offset); }

[hidden] { display: none !important; }

.is-hidden { display: none !important; }

/* ============================================================
   14. 响应式
   ============================================================ */
@media (max-width: 1180px) {
  .nav-list a { padding: 8px 10px; font-size: var(--text-xs); }
  .quick-chip { display: none; }
}

@media (max-width: 1080px) {
  body { --header-offset: 96px; }

  .nav-toggle { display: inline-flex; }

  .primary-nav {
    position: fixed;
    inset: 0 0 0 auto;
    z-index: 95;
    width: min(400px, 88vw);
    flex-direction: column;
    align-items: stretch;
    justify-content: flex-start;
    gap: var(--space-4);
    padding: calc(var(--header-offset) + var(--space-4)) var(--gutter) var(--space-6);
    background: var(--color-contrast-surface);
    border-left: var(--border-thin) solid var(--color-contrast-line);
    border-radius: var(--radius-lg) 0 0 var(--radius-lg);
    overflow-y: auto;
    transform: translateX(102%);
    transition: transform 220ms ease;
  }

  .site-header[data-open] .primary-nav { transform: translateX(0); }

  .nav-list {
    flex-direction: column;
    align-items: stretch;
    gap: 4px;
    border-top: var(--border-thin) solid var(--color-contrast-line);
    padding-top: var(--space-3);
  }

  .nav-list a {
    padding: 14px 18px;
    font-size: var(--text-lg);
    border-radius: var(--radius-pill);
  }

  .nav-quick {
    flex-direction: column;
    align-items: stretch;
    gap: 10px;
  }

  .quick-chip { display: inline-flex; justify-content: center; padding: 10px 16px; }
  .version-chip { justify-content: center; padding: 10px 16px; }

  .split,
  .split--flip { grid-template-columns: minmax(0, 1fr); }

  .toc { position: static; }

  .grid--7 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
}

@media (max-width: 880px) {
  .grid--3 { grid-template-columns: repeat(2, minmax(0, 1fr)); }

  .footer-shell { grid-template-columns: minmax(0, 1fr); }
  .footer-meta { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .figure--offset { margin-left: 0; }
}

@media (max-width: 680px) {
  body { --header-offset: 88px; }

  h1 { font-size: var(--text-2xl); }
  h2 { font-size: var(--text-xl); }

  .band { padding-block: var(--space-6); }
  .band--lg { padding-block: var(--space-8); }

  .header-shell { padding: 10px var(--gutter); gap: 8px 12px; }
  .brand-name { font-size: var(--text-base); }
  .brand-tagline { display: none; }
  .brand-mark { width: 32px; height: 32px; }

  .header-strip-inner { flex-direction: column; align-items: flex-start; gap: 4px; }
  .header-strip-note { display: none; }

  .grid--2,
  .grid--3,
  .grid--7 { grid-template-columns: minmax(0, 1fr); }

  .footer-nav { grid-template-columns: minmax(0, 1fr); gap: var(--space-3); }
  .footer-meta { grid-template-columns: minmax(0, 1fr); }
  .footer-legal { margin-left: 0; }
  .footer-scallop span { width: 62px; height: 62px; }

  .disclosure__panel { padding-left: var(--space-3); }
}

/* ============================================================
   15. 动效降级
   ============================================================ */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }
}