:root {
  --color-surface: #f3f2f1;
  --color-surface-alt: #ebe9e8;
  --color-surface-deep: #dfdddb;
  --color-ink: #4a453a;
  --color-ink-soft: #6e6859;
  --color-ink-muted: #8c8473;
  --color-line: #d5d3d0;
  --color-primary: #85744c;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #e4e0da;
  --color-accent: #ea1310;
  --color-accent-ink: #ffffff;
  --color-highlight: #f1cac8;
  --color-focus: #d80603;
  --color-contrast-surface: #211f1a;
  --color-contrast-ink: #e7e6e4;
  --color-contrast-line: #4d4b46;
  --color-contrast-accent: #f24745;
  --overlay-scrim: linear-gradient(180deg, rgba(33, 31, 26, 0.35) 0%, rgba(33, 31, 26, 0.72) 55%, rgba(33, 31, 26, 0.92) 100%);
  --font-heading: "Songti SC", "Source Han Serif SC", "Noto Serif SC", SimSun, serif;
  --font-body: "PingFang SC", "Microsoft YaHei", "Source Han Sans SC", sans-serif;
  --font-mono: ui-monospace, Menlo, Consolas, monospace;
  --text-xs: 12.9px;
  --text-sm: 15.5px;
  --text-base: 17px;
  --text-lg: 20.4px;
  --text-xl: 24.5px;
  --text-2xl: 29.4px;
  --text-3xl: 35.3px;
  --text-4xl: 42.3px;
  --text-display: clamp(39px, 8.0vw, 103px);
  --text-figure: clamp(33px, 5.8vw, 74px);
  --weight-heading: 630;
  --weight-body: 400;
  --leading-body: 1.76;
  --leading-heading: 1.28;
  --tracking-heading: -0.007em;
  --radius-sm: 4px;
  --radius-md: 6px;
  --radius-lg: 7px;
  --radius-pill: 7px;
  --border-thin: 1px;
  --border-thick: 2px;
  --shadow-1: 0 1px 0 rgba(74, 69, 58, 0.12);
  --shadow-2: 0 2px 0 rgba(74, 69, 58, 0.18);
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-6: 48px;
  --space-8: 64px;
  --container: 1220px;
  --measure: 68ch;
  --gutter: 16px;
  --section-y: 72px;
  --section-y-lg: 101px;
}

/* ============================================================
   2. Reset
   ============================================================ */
*,
*::before,
*::after { box-sizing: border-box; }

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: 130px;
}

body {
  margin: 0;
  background-color: var(--color-surface);
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: var(--text-base);
  font-weight: var(--weight-body);
  line-height: var(--leading-body);
  overflow-wrap: break-word;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

img, svg, video, canvas { display: block; max-width: 100%; }
button, input, select, textarea { font: inherit; color: inherit; }
button { background: none; border: 0; padding: 0; }
a { color: inherit; text-decoration-color: var(--color-primary); }
h1, h2, h3, h4, h5, h6, p, figure, blockquote, dl, dd, hr { margin: 0; }
ul, ol { margin: 0; padding: 0; list-style: none; }
table { border-collapse: collapse; }
[hidden] { display: none !important; }

/* ============================================================
   3. 中文排版与标题
   ============================================================ */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
  text-wrap: balance;
}

h1 { font-size: var(--text-3xl); }
h2 { font-size: var(--text-2xl); }
h3 { font-size: var(--text-xl); }
h4 { font-size: var(--text-lg); }

p { text-wrap: pretty; }

.num,
.metric__value,
.data-table .num,
.mono {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-feature-settings: "tnum" 1;
  letter-spacing: -0.01em;
}

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

:where(a, button, [tabindex], summary):focus-visible {
  outline: var(--border-thick) solid var(--color-focus);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

/* ============================================================
   4. 布局骨架
   ============================================================ */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--space-3);
}

.container--narrow { max-width: 900px; }

.grid {
  display: grid;
  gap: var(--gutter);
}

.grid--12 { grid-template-columns: repeat(12, minmax(0, 1fr)); }

.stack { display: flex; flex-direction: column; gap: var(--space-3); }
.cluster { display: flex; flex-wrap: wrap; align-items: center; gap: var(--space-2); }
.measure { max-width: var(--measure); }

.page-grid {
  display: grid;
  grid-template-columns: minmax(0, 3fr) minmax(0, 6fr) minmax(0, 3fr);
  gap: var(--gutter);
  align-items: start;
}

.section { padding-block: var(--section-y); }
.section--lead { padding-block: var(--section-y-lg); }

.section__head {
  position: relative;
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: var(--space-1) var(--space-2);
  padding-block-end: var(--space-2);
  margin-block-end: var(--space-3);
}

.section__head::after {
  content: "";
  position: absolute;
  inset-inline: var(--space-2);
  inset-block-end: 0;
  height: var(--border-thin);
  background-color: var(--color-line);
}

.section__title { font-size: var(--text-2xl); }
.section__note {
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
}

/* ============================================================
   5. 纸张层叠：面板与错位
   ============================================================ */
.panel {
  position: relative;
  background-color: var(--color-surface);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-1);
  padding: var(--space-3);
  transition: transform 200ms ease-out, box-shadow 200ms ease-out, background-color 200ms ease-out;
}

.panel--alt { background-color: var(--color-surface-alt); }
.panel--deep { background-color: var(--color-surface-deep); }
.panel--inset { box-shadow: none; }
.panel--lift:hover { transform: translateY(-2px); box-shadow: var(--shadow-2); }

.shift-l { margin-inline-start: calc(var(--space-1) * -1); }
.shift-r { margin-inline-start: var(--space-1); }
.shift-t { margin-block-start: calc(var(--space-1) * -1); }
.shift-b { margin-block-start: var(--space-1); }

.rule-offset {
  height: var(--border-thin);
  border: 0;
  margin-block: var(--space-4);
  margin-inline: var(--space-2);
  background-color: var(--color-line);
}

/* ============================================================
   6. 贴纸标签
   ============================================================ */
.sticker {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 9px;
  border: var(--border-thin) solid color-mix(in srgb, var(--color-ink) 12%, transparent);
  border-radius: var(--radius-sm);
  background-color: var(--color-surface-deep);
  color: var(--color-ink-soft);
  font-family: var(--font-body);
  font-size: var(--text-xs);
  line-height: 1.5;
  letter-spacing: 0.08em;
  white-space: nowrap;
  text-decoration: none;
  transition: background-color 200ms ease-out, color 200ms ease-out,
              border-color 200ms ease-out, transform 200ms ease-out, box-shadow 200ms ease-out;
}

.sticker--primary {
  background-color: var(--color-primary-soft);
  color: var(--color-primary);
  border-color: color-mix(in srgb, var(--color-primary) 32%, transparent);
}

.sticker--highlight {
  background-color: var(--color-highlight);
  color: color-mix(in srgb, var(--color-accent) 62%, var(--color-ink));
  border-color: color-mix(in srgb, var(--color-accent) 22%, transparent);
}

.sticker--invert {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-color: var(--color-contrast-surface);
}

.sticker--accent {
  background-color: var(--color-accent);
  color: var(--color-accent-ink);
  border-color: var(--color-accent);
}

.sticker--tilt { transform: rotate(-1.2deg); }
.sticker--tilt-alt { transform: rotate(1deg); }

.sticker--corner {
  position: absolute;
  inset-block-start: calc(var(--space-1) * -1);
  inset-inline-end: var(--space-2);
  z-index: 3;
  box-shadow: var(--shadow-2);
}

a.sticker { box-shadow: var(--shadow-1); }

a.sticker:hover,
a.sticker:focus-visible {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-color: var(--color-contrast-surface);
  box-shadow: var(--shadow-2);
  transform: translateY(-2px) rotate(0deg);
}

/* ============================================================
   7. 按钮
   ============================================================ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 11px 20px;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  background-color: var(--color-surface);
  color: var(--color-ink);
  font-size: var(--text-sm);
  font-weight: 500;
  letter-spacing: 0.03em;
  text-decoration: none;
  cursor: pointer;
  box-shadow: var(--shadow-1);
  transition: transform 180ms ease-out, box-shadow 180ms ease-out,
              background-color 180ms ease-out, color 180ms ease-out, border-color 180ms ease-out;
}

.btn:hover { transform: translateY(-2px); box-shadow: var(--shadow-2); }

.btn--primary {
  background-color: var(--color-primary);
  color: var(--color-primary-ink);
  border-color: var(--color-primary);
}

.btn--invert {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-color: var(--color-contrast-surface);
}

.btn--ghost {
  background-color: transparent;
  box-shadow: none;
}

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

/* ============================================================
   8. 面包屑
   ============================================================ */
.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 6px;
  font-size: var(--text-xs);
  letter-spacing: 0.04em;
  color: var(--color-ink-muted);
}

.breadcrumb li {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

.breadcrumb li + li::before {
  content: "/";
  color: var(--color-line);
}

.breadcrumb a {
  color: var(--color-ink-soft);
  text-decoration: none;
}

.breadcrumb a:hover { text-decoration: underline; }
.breadcrumb [aria-current="page"] { color: var(--color-ink); }

/* ============================================================
   9. 正文容器
   ============================================================ */
.prose {
  max-width: var(--measure);
  color: var(--color-ink);
}

.prose > * + * { margin-block-start: var(--space-3); }
.prose h2 { margin-block-start: var(--space-6); font-size: var(--text-2xl); }
.prose h3 { margin-block-start: var(--space-4); font-size: var(--text-xl); }
.prose ul,
.prose ol { padding-inline-start: 1.5em; }
.prose ul { list-style: square; }
.prose ol { list-style: decimal; }
.prose li + li { margin-block-start: 6px; }
.prose strong { font-weight: 600; }
.prose a {
  text-decoration-line: underline;
  text-decoration-thickness: 2px;
  text-decoration-color: var(--color-primary);
  text-underline-offset: 4px;
}
.prose a:hover { background-color: var(--color-primary-soft); }

/* ============================================================
   10. 图片容器与展签
   ============================================================ */
.figure {
  position: relative;
  margin: 0;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-lg);
  background-color: var(--color-contrast-surface);
  overflow: hidden;
  box-shadow: var(--shadow-2);
}

.figure__media {
  display: block;
  width: 100%;
  aspect-ratio: 16 / 10;
  object-fit: cover;
  background-color: var(--color-contrast-surface);
  filter: saturate(0.86) contrast(1.06);
}

.figure__scrim {
  position: absolute;
  inset: 0;
  background-image: var(--overlay-scrim);
  pointer-events: none;
}

.figure__caption {
  position: absolute;
  inset-inline-start: var(--space-2);
  inset-block-end: var(--space-2);
  max-width: calc(100% - var(--space-4));
  padding: 6px 10px;
  border-radius: var(--radius-sm);
  background-color: var(--color-surface);
  color: var(--color-ink);
  font-size: var(--text-xs);
  line-height: 1.55;
  letter-spacing: 0.04em;
  box-shadow: var(--shadow-2);
}

.figure__caption--corner {
  inset-inline-start: auto;
  inset-block-end: auto;
  inset-inline-end: var(--space-2);
  inset-block-start: var(--space-2);
}

.figure__caption em {
  font-style: normal;
  color: var(--color-ink-muted);
  margin-inline-start: 6px;
}

/* ============================================================
   11. 索引轨 / 数据舞台 / 术语卡
   ============================================================ */
.rail {
  position: relative;
  padding-inline-end: var(--space-2);
  border-inline-end: var(--border-thin) solid var(--color-line);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
}

.rail__title {
  font-family: var(--font-heading);
  font-size: var(--text-base);
  font-weight: var(--weight-heading);
  letter-spacing: 0;
  color: var(--color-ink);
  margin-block-end: var(--space-2);
}

.stage {
  position: relative;
  padding: var(--space-4) var(--space-3);
  border: var(--border-thin) solid var(--color-contrast-surface);
  border-radius: var(--radius-lg);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}

.stage h2,
.stage h3,
.stage h4 { color: var(--color-contrast-ink); }

.stage a { color: var(--color-contrast-ink); }

.stage__rule {
  height: var(--border-thin);
  border: 0;
  margin-block: var(--space-3);
  margin-inline: var(--space-2);
  background-color: var(--color-contrast-line);
}

.term-card {
  position: relative;
  padding: var(--space-2);
  border: var(--border-thin) solid color-mix(in srgb, var(--color-accent) 20%, transparent);
  border-radius: var(--radius-md);
  background-color: var(--color-highlight);
  color: color-mix(in srgb, var(--color-accent) 32%, var(--color-ink));
  box-shadow: var(--shadow-2);
  font-size: var(--text-sm);
  line-height: 1.7;
}

.term-card__term {
  display: block;
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  color: var(--color-ink);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 5px;
  margin-block-end: 6px;
}

.term-card__body { margin-block-end: var(--space-2); }

.term-card__foot {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-1);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
}

.term-card__foot button {
  padding: 4px 9px;
  border: var(--border-thin) solid color-mix(in srgb, var(--color-accent) 26%, transparent);
  border-radius: var(--radius-sm);
  background-color: var(--color-surface);
  color: var(--color-ink-soft);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  cursor: pointer;
  transition: background-color 180ms ease-out, color 180ms ease-out, transform 180ms ease-out;
}

.term-card__foot button:hover { transform: translateY(-2px); }

.term-card__foot button[data-copied] {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-color: var(--color-contrast-surface);
}

/* ============================================================
   12. 指标、反色块、横条、对照表
   ============================================================ */
.metric { display: flex; flex-direction: column; gap: 2px; }

.metric__value {
  font-size: var(--text-xl);
  color: var(--color-ink);
}

.metric__label {
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
}

.invert-block {
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-size: var(--text-sm);
}

.invert-block a { color: var(--color-contrast-ink); }

.stripe {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-1) var(--space-3);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-sm);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
}

.stripe__tag {
  padding: 3px 8px;
  border-radius: var(--radius-sm);
  background-color: var(--color-contrast-accent);
  color: var(--color-contrast-ink);
}

.data-table {
  width: 100%;
  font-size: var(--text-sm);
}

.data-table th,
.data-table td {
  padding: 10px var(--space-2);
  border-block-end: var(--border-thin) solid var(--color-line);
  text-align: start;
  vertical-align: top;
}

.data-table th {
  background-color: var(--color-surface-deep);
  color: var(--color-ink-soft);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.08em;
}

.data-table tbody tr:nth-child(even) { background-color: var(--color-surface-alt); }

.data-table .num {
  text-align: end;
  font-size: var(--text-base);
  color: var(--color-ink);
}

.stage .data-table th {
  background-color: color-mix(in srgb, var(--color-contrast-ink) 12%, transparent);
  color: var(--color-contrast-ink);
}

.stage .data-table td {
  border-block-end-color: var(--color-contrast-line);
  color: var(--color-contrast-ink);
}

.stage .data-table tbody tr:nth-child(even) {
  background-color: color-mix(in srgb, var(--color-contrast-ink) 4%, transparent);
}

.stage .data-table .num { color: var(--color-contrast-ink); }

/* ============================================================
   13. 旁注
   ============================================================ */
.marginalia {
  position: relative;
  display: inline-block;
}

.marginalia__trigger {
  text-decoration: underline;
  text-decoration-style: dotted;
  text-decoration-thickness: 1px;
  text-decoration-color: var(--color-ink-muted);
  text-underline-offset: 4px;
  cursor: help;
}

.marginalia__body {
  position: absolute;
  inset-inline-start: 0;
  inset-block-start: calc(100% + 6px);
  z-index: 20;
  width: max-content;
  max-width: min(272px, 78vw);
  padding: 10px 12px;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  background-color: var(--color-surface);
  color: var(--color-ink-soft);
  font-size: var(--text-xs);
  line-height: 1.65;
  letter-spacing: 0.02em;
  box-shadow: var(--shadow-2);
  opacity: 0;
  visibility: hidden;
  transform: translateY(-4px);
  transition: opacity 180ms ease-out, transform 180ms ease-out, visibility 180ms;
}

.marginalia:hover .marginalia__body,
.marginalia:focus-within .marginalia__body {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

/* ============================================================
   14. 站点头部
   ============================================================ */
.skip-link {
  position: absolute;
  inset-inline-start: var(--space-2);
  inset-block-start: 0;
  z-index: 200;
  padding: 10px 16px;
  border-radius: 0 0 var(--radius-sm) var(--radius-sm);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-size: var(--text-sm);
  text-decoration: none;
  transform: translateY(-130%);
  transition: transform 180ms ease-out;
}

.skip-link:focus { transform: translateY(0); }

.site-header {
  position: sticky;
  inset-block-start: 0;
  z-index: 90;
  background-color: var(--color-surface);
  border-block-end: var(--border-thin) solid var(--color-line);
  box-shadow: var(--shadow-1);
}

.site-header__top {
  border-block-end: var(--border-thin) solid var(--color-line);
}

.masthead {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  min-height: 58px;
  padding-block: 9px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: var(--color-ink);
  transition: transform 180ms ease-out;
}

.brand:hover { transform: translateY(-2px); }

.brand__mark {
  flex: none;
  display: grid;
  place-items: center;
  width: 34px;
  height: 34px;
  border-radius: var(--radius-sm);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-family: var(--font-heading);
  font-size: var(--text-base);
  font-weight: var(--weight-heading);
  box-shadow: var(--shadow-2);
}

.brand__text { display: flex; flex-direction: column; line-height: 1.15; }

.brand__name {
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  letter-spacing: var(--tracking-heading);
}

.brand__tag {
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
}

.masthead__status {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-inline-start: auto;
  font-size: var(--text-xs);
  letter-spacing: 0.04em;
  color: var(--color-ink-muted);
}

.masthead__dot {
  flex: none;
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background-color: var(--color-accent);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--color-accent) 16%, transparent);
}

.site-header__bar { position: relative; }

.nav-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-2);
  padding-block: 7px;
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  background-color: var(--color-surface-deep);
  color: var(--color-ink);
  font-size: var(--text-sm);
  letter-spacing: 0.06em;
  cursor: pointer;
  transition: background-color 180ms ease-out, transform 180ms ease-out;
}

.nav-toggle:hover { transform: translateY(-2px); }

.nav-toggle__bars {
  width: 16px;
  height: 10px;
  background-image:
    linear-gradient(var(--color-ink) 0 0),
    linear-gradient(var(--color-ink) 0 0),
    linear-gradient(var(--color-ink) 0 0);
  background-size: 100% 1.5px;
  background-position: 0 0, 0 50%, 0 100%;
  background-repeat: no-repeat;
}

.nav-toggle__label { letter-spacing: 0.08em; }

.nav { display: flex; align-items: center; }

.nav__list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 2px;
}

.nav__link {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 9px 11px;
  border-radius: var(--radius-sm);
  color: var(--color-ink-soft);
  font-size: var(--text-sm);
  letter-spacing: 0.03em;
  text-decoration: none;
  transition: color 180ms ease-out, background-color 180ms ease-out;
}

.nav__link::before {
  content: "";
  flex: none;
  width: 18px;
  height: 2px;
  border-radius: 2px;
  background-color: var(--color-primary);
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform 200ms ease-out, background-color 200ms ease-out;
}

.nav__link:hover,
.nav__link:focus-visible {
  color: var(--color-ink);
  background-color: var(--color-primary-soft);
}

.nav__link:hover::before,
.nav__link:focus-visible::before { transform: scaleX(1); }

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

.nav__link[aria-current="page"]::before { transform: scaleX(1); }

.reading-progress {
  position: absolute;
  inset-inline: 0;
  inset-block-end: -1px;
  height: 2px;
  pointer-events: none;
  overflow: hidden;
}

.reading-progress__bar {
  display: block;
  width: 100%;
  height: 100%;
  background-color: var(--color-accent);
  transform: scaleX(0);
  transform-origin: left center;
  will-change: transform;
}

/* ============================================================
   15. 站点页脚
   ============================================================ */
.site-footer {
  position: relative;
  margin-block-start: var(--section-y-lg);
  background-color: var(--color-primary);
  color: var(--color-primary-ink);
  overflow: hidden;
}

.site-footer::before {
  content: "";
  position: absolute;
  inset-inline: 0;
  inset-block-start: 0;
  height: 5px;
  background-image: repeating-linear-gradient(
    90deg,
    color-mix(in srgb, var(--color-primary-ink) 30%, transparent) 0 14px,
    transparent 14px 30px
  );
  opacity: 0.55;
}

.footer-main {
  padding-block: var(--space-8) var(--space-4);
}

.footer-kicker {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  color: color-mix(in srgb, var(--color-primary-ink) 74%, var(--color-primary));
}

.footer-wordmark {
  margin-block: var(--space-2) var(--space-2);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: clamp(calc(var(--text-4xl) * 1.05), 12.6vw, calc(var(--text-4xl) * 2.9));
  line-height: 0.94;
  letter-spacing: -0.03em;
  color: var(--color-primary-ink);
  text-shadow: 0 2px 0 color-mix(in srgb, var(--color-ink) 22%, transparent);
}

.footer-creed {
  font-size: var(--text-sm);
  letter-spacing: 0.16em;
  color: color-mix(in srgb, var(--color-primary-ink) 82%, var(--color-primary));
  margin-block-end: var(--space-4);
}

.footer-strip {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-1);
  padding-block-start: var(--space-3);
  border-block-start: var(--border-thin) solid color-mix(in srgb, var(--color-primary-ink) 26%, transparent);
}

.footer-strip__link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 7px 13px;
  border-radius: var(--radius-sm);
  background-color: var(--color-surface);
  color: var(--color-ink);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  text-decoration: none;
  box-shadow: var(--shadow-2);
  transform: rotate(-0.8deg);
  transition: transform 200ms ease-out, background-color 200ms ease-out,
              color 200ms ease-out, box-shadow 200ms ease-out;
}

.footer-strip__link:nth-child(even) { transform: rotate(0.7deg); }

.footer-strip__link:hover,
.footer-strip__link:focus-visible {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  box-shadow: var(--shadow-2);
  transform: translateY(-2px) rotate(0deg);
}

.footer-slab {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  padding-block: var(--space-2);
}

.footer-slab__inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-1) var(--space-3);
  font-size: var(--text-xs);
  letter-spacing: 0.06em;
}

.footer-slab__item {
  color: color-mix(in srgb, var(--color-contrast-ink) 82%, var(--color-contrast-surface));
}

.footer-slab__item--mono { font-family: var(--font-mono); }

.footer-slab__item--hint {
  color: var(--color-contrast-accent);
  letter-spacing: 0.08em;
}

/* ============================================================
   16. 工具类
   ============================================================ */
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}

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

/* ============================================================
   17. 响应式
   ============================================================ */
@media (max-width: 1100px) {
  .page-grid { grid-template-columns: minmax(0, 4fr) minmax(0, 8fr); }
}

@media (max-width: 1000px) {
  .masthead__status { display: none; }
  .brand { margin-inline-end: auto; }
}

@media (max-width: 899px) {
  .nav-toggle { display: inline-flex; }
  .nav { display: none; flex-basis: 100%; }
  .nav[data-open] { display: block; }
  .nav__list { flex-direction: column; align-items: stretch; gap: 0; }
  .nav__link {
    width: 100%;
    padding: 12px 10px;
    border-block-end: var(--border-thin) dashed var(--color-line);
    font-size: var(--text-base);
    border-radius: 0;
  }
  .nav__link[aria-current="page"] { background-color: var(--color-primary-soft); }
  .nav-row { padding-block: var(--space-1); }
  .page-grid { grid-template-columns: minmax(0, 1fr); }
  .rail {
    padding-inline-end: 0;
    padding-block-end: var(--space-2);
    border-inline-end: 0;
    border-block-end: var(--border-thin) solid var(--color-line);
  }
  .section { padding-block: var(--space-6); }
  .section--lead { padding-block: var(--section-y); }
  .footer-main { padding-block: var(--space-6) var(--space-3); }
}

@media (max-width: 760px) {
  .brand__tag { display: none; }
  .brand__mark { width: 30px; height: 30px; }
  .container { padding-inline: var(--space-2); }
  .footer-strip__link { transform: none; }
  .footer-strip__link:hover,
  .footer-strip__link:focus-visible { transform: translateY(-2px); }
  .footer-slab__inner { gap: 6px var(--space-2); }
}

@media (max-width: 520px) {
  .figure__caption {
    position: static;
    max-width: none;
    border-radius: 0;
    box-shadow: none;
    background-color: var(--color-surface-alt);
  }
  .figure__caption--corner { position: static; }
}

/* ============================================================
   18. 动效偏好
   ============================================================ */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }

  *,
  *::before,
  *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
  }

  .panel--lift:hover,
  .btn:hover,
  .brand:hover,
  a.sticker:hover,
  a.sticker:focus-visible,
  .footer-strip__link:hover,
  .footer-strip__link:focus-visible,
  .term-card__foot button:hover,
  .nav-toggle:hover {
    transform: none;
  }
}