:root {
  --color-surface: #f3f1f1;
  --color-surface-alt: #ebe8e8;
  --color-surface-deep: #dfdcdc;
  --color-ink: #4f4040;
  --color-ink-soft: #786463;
  --color-ink-muted: #8b7574;
  --color-line: #d5d1d1;
  --color-primary: #df2620;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #f0d5d4;
  --color-accent: #ea1710;
  --color-accent-ink: #ffffff;
  --color-highlight: #f1cac8;
  --color-focus: #d80a03;
  --color-contrast-surface: #1a0d0d;
  --color-contrast-ink: #e7e4e4;
  --color-contrast-line: #473c3c;
  --color-contrast-accent: #f02a24;
  --overlay-scrim: linear-gradient(180deg, rgba(26, 13, 13, 0.35) 0%, rgba(26, 13, 13, 0.72) 55%, rgba(26, 13, 13, 0.92) 100%);
  --font-heading: "Kaiti SC", STKaiti, KaiTi, "Songti SC", serif;
  --font-body: "Songti SC", "PingFang SC", "Microsoft YaHei", serif;
  --font-mono: ui-monospace, Menlo, Consolas, monospace;
  --text-xs: 12.2px;
  --text-sm: 15.2px;
  --text-base: 17px;
  --text-lg: 21.2px;
  --text-xl: 26.6px;
  --text-2xl: 33.2px;
  --text-3xl: 41.5px;
  --text-4xl: 51.9px;
  --text-display: clamp(39px, 8.0vw, 102px);
  --text-figure: clamp(32px, 5.7vw, 73px);
  --weight-heading: 580;
  --weight-body: 400;
  --leading-body: 1.98;
  --leading-heading: 1.25;
  --tracking-heading: 0.021em;
  --radius-sm: 2px;
  --radius-md: 2px;
  --radius-lg: 3px;
  --radius-pill: 3px;
  --border-thin: 1px;
  --border-thick: 1px;
  --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: 960px;
  --measure: 62ch;
  --gutter: 16px;
  --section-y: 128px;
  --section-y-lg: 179px;
}

/* ========== 1. Reset ========== */
*,
*::before,
*::after { box-sizing: border-box; }

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

body {
  margin: 0;
  min-height: 100%;
  background-color: var(--color-surface);
  background-image: radial-gradient(color-mix(in srgb, var(--color-ink) 7%, transparent) 0.5px, transparent 0.6px);
  background-size: 4px 4px;
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: var(--text-base);
  font-weight: var(--weight-body);
  line-height: var(--leading-body);
  letter-spacing: 0.012em;
  -webkit-font-smoothing: antialiased;
}

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

ul,
ol {
  margin: 0;
  padding: 0;
  list-style: none;
}

button {
  font: inherit;
  color: inherit;
  background: none;
  border: 0;
  cursor: pointer;
}

table { border-collapse: collapse; }

hr {
  height: var(--border-thin);
  margin: var(--space-6) 0;
  border: 0;
  background: var(--color-line);
}

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

:focus-visible {
  outline: 2px solid var(--color-focus);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

/* ========== 2. 中文排版 ========== */
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); }

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

a {
  color: inherit;
  text-decoration: none;
}

.prose a,
.link-inline {
  border-bottom: var(--border-thin) solid color-mix(in srgb, var(--color-accent) 42%, transparent);
  transition: color 220ms ease-out, border-color 220ms ease-out;
}

.prose a:hover,
.link-inline:hover {
  color: var(--color-accent);
  border-bottom-color: currentColor;
}

.num,
.figure,
[data-num],
time {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  letter-spacing: -0.01em;
}

.micro {
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
  letter-spacing: 0.1em;
}

.prose {
  max-width: var(--measure);
  font-size: var(--text-base);
}

.prose h2 {
  margin: var(--space-8) 0 var(--space-3);
}

.prose h3 {
  margin: var(--space-6) 0 var(--space-2);
}

.prose p { margin: 0 0 var(--space-4); }

.prose ul,
.prose ol {
  margin: 0 0 var(--space-4);
  padding-left: 1.5em;
}

.prose ul { list-style: disc; }
.prose ol { list-style: decimal; }
.prose li { margin-bottom: var(--space-1); }
.prose li::marker { color: var(--color-ink-muted); }

.lede {
  max-width: var(--measure);
  font-size: var(--text-lg);
  line-height: 1.82;
  color: var(--color-ink-soft);
}

.display {
  font-family: var(--font-heading);
  font-size: var(--text-display);
  font-weight: var(--weight-heading);
  line-height: 1.06;
  letter-spacing: 0.005em;
  color: var(--color-ink);
}

.figure {
  display: block;
  font-size: var(--text-figure);
  font-weight: 500;
  line-height: 1;
  color: var(--color-ink);
}

.figure--mark { color: var(--color-primary); }

.figure__unit {
  margin-left: 6px;
  font-family: var(--font-body);
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
  letter-spacing: 0.04em;
}

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

.shell--wide { max-width: calc(var(--container) + 160px); }

.page { display: block; }

#main-content { display: block; }

.band { padding-block: var(--section-y); }
.band--lg { padding-block: var(--section-y-lg); }
.band--alt { background: var(--color-surface-alt); }
.band--deep { background: var(--color-surface-deep); }

.band--shift { position: relative; }

.band--shift::before,
.band--shift::after {
  content: "";
  position: absolute;
  left: 0;
  height: var(--border-thin);
  background: var(--color-line);
}

.band--shift::before { top: 0; width: 38%; }
.band--shift::after { bottom: 0; left: auto; right: 0; width: 62%; }

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

.grid--2 { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: var(--space-4); }
.grid--3 { grid-template-columns: repeat(3, minmax(0, 1fr)); gap: var(--space-4); }

.span-3 { grid-column: span 3; }
.span-4 { grid-column: span 4; }
.span-6 { grid-column: span 6; }
.span-8 { grid-column: span 8; }
.span-12 { grid-column: span 12; }

.pair {
  position: relative;
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: var(--space-6);
}

.pair::before {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  left: 50%;
  width: var(--border-thin);
  background: var(--color-line);
}

.pair__side { min-width: 0; }
.pair__side--right { text-align: right; }

.rule {
  height: var(--border-thin);
  margin: 0;
  border: 0;
  background: var(--color-line);
}

.rule--short { width: 34%; }
.rule--push { width: 61%; margin-left: 22%; }
.rule--mark { width: 48px; height: 2px; background: var(--color-primary); }

.rule--tick {
  height: 9px;
  background-color: transparent;
  background-image: repeating-linear-gradient(90deg, var(--color-line) 0 1px, transparent 1px 12px);
}

.marked {
  position: relative;
  padding-left: var(--space-3);
}

.marked::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.35em;
  bottom: 0.35em;
  width: 2px;
  background: var(--color-primary);
}

.marked--soft::before { background: var(--color-line); }

/* ========== 4. 页头 ========== */
.skip-link {
  position: absolute;
  left: var(--space-3);
  top: -120px;
  z-index: 90;
  padding: 10px var(--space-3);
  font-size: var(--text-sm);
  color: var(--color-ink);
  background: var(--color-surface-deep);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  transition: top 180ms ease-out;
}

.skip-link:focus { top: var(--space-2); }

.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 2px;
  background: var(--color-primary);
  transform: scaleX(0);
  transform-origin: 0 50%;
  opacity: 0;
  z-index: 80;
  pointer-events: none;
  transition: opacity 300ms ease-out;
}

.scroll-progress[data-active] { opacity: 0.92; }

.masthead {
  position: relative;
  z-index: 40;
  background: var(--color-surface);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.masthead__inner {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  min-height: 102px;
}

.masthead__rail {
  position: relative;
  flex: 1 1 auto;
  min-width: var(--space-6);
  height: var(--border-thin);
  background: var(--color-line);
}

.masthead__rail::before {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  top: -4px;
  height: 9px;
  background-image: repeating-linear-gradient(90deg, var(--color-line) 0 1px, transparent 1px 14px);
}

.masthead__rail::after {
  content: "";
  position: absolute;
  right: 0;
  bottom: -3px;
  width: var(--border-thin);
  height: 7px;
  background: var(--color-line);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  flex: 0 0 auto;
}

.brand__mark {
  display: grid;
  place-items: center;
  width: 42px;
  height: 42px;
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  line-height: 1;
  color: var(--color-ink);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  background: var(--color-surface-alt);
}

.brand__text {
  display: grid;
  gap: 2px;
}

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

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

.nav {
  display: flex;
  flex: 0 0 auto;
}

.nav__list {
  display: flex;
  align-items: center;
  gap: var(--space-4);
}

.nav__item { display: block; }

.nav__link {
  position: relative;
  display: inline-block;
  padding: 6px 0 6px var(--space-2);
  font-family: var(--font-heading);
  font-size: var(--text-base);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink-soft);
  transition: color 220ms ease-out;
}

.nav__link::before {
  content: "";
  position: absolute;
  left: 0;
  top: 50%;
  width: 2px;
  height: 0;
  background: var(--color-primary);
  transform: translateY(-50%);
  transition: height 240ms ease-out;
}

.nav__link:hover { color: var(--color-ink); }
.nav__link:hover::before { height: 0.6em; }

.nav__link[aria-current="page"] {
  color: var(--color-ink);
  font-weight: var(--weight-heading);
}

.nav__link[aria-current="page"]::before { height: 1.05em; }

.nav-toggle {
  display: none;
  align-items: center;
  gap: var(--space-1);
  padding: 8px 10px;
  font-size: var(--text-xs);
  letter-spacing: 0.12em;
  color: var(--color-ink-soft);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  transition: color 220ms ease-out, border-color 220ms ease-out;
}

.nav-toggle__bars {
  display: grid;
  gap: 4px;
  width: 18px;
}

.nav-toggle__bars span {
  display: block;
  height: var(--border-thin);
  background: currentColor;
}

.nav-toggle__label { line-height: 1; }

.nav-toggle:hover { color: var(--color-ink); border-color: var(--color-ink-muted); }

.nav-toggle[aria-expanded="true"] {
  color: var(--color-primary);
  border-color: var(--color-primary);
}

/* ========== 5. 页脚 ========== */
.colophon {
  margin-top: var(--section-y);
  padding-bottom: var(--space-6);
  background: transparent;
}

.colophon__frame {
  position: relative;
  padding: var(--space-6) var(--space-4) var(--space-3);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  background: color-mix(in srgb, var(--color-surface-alt) 58%, transparent);
}

.colophon__tick {
  position: absolute;
  width: 10px;
  height: 10px;
  border: 0 solid var(--color-ink-muted);
}

.colophon__tick--tl { top: -1px; left: -1px; border-top-width: 2px; border-left-width: 2px; }
.colophon__tick--tr { top: -1px; right: -1px; border-top-width: 2px; border-right-width: 2px; }
.colophon__tick--bl { bottom: -1px; left: -1px; border-bottom-width: 2px; border-left-width: 2px; }
.colophon__tick--br { bottom: -1px; right: -1px; border-bottom-width: 2px; border-right-width: 2px; }

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

.colophon__col { min-width: 0; }

.colophon__title {
  position: relative;
  margin-bottom: var(--space-2);
  padding-left: var(--space-2);
  font-size: var(--text-base);
  color: var(--color-ink);
}

.colophon__title::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.3em;
  bottom: 0.3em;
  width: 2px;
  background: var(--color-line);
}

.colophon__line {
  margin: 0 0 var(--space-1);
  font-size: var(--text-sm);
  line-height: 1.75;
  color: var(--color-ink-soft);
}

.colophon__links {
  display: grid;
  gap: 6px;
  margin-bottom: var(--space-2);
}

.colophon__links a {
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
  border-bottom: var(--border-thin) solid transparent;
  transition: color 220ms ease-out, border-color 220ms ease-out;
}

.colophon__links a:hover {
  color: var(--color-accent);
  border-bottom-color: color-mix(in srgb, var(--color-accent) 45%, transparent);
}

.colophon__base {
  position: relative;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: var(--space-2);
  margin-top: var(--space-4);
  padding-top: var(--space-3);
  border-top: var(--border-thin) solid var(--color-line);
}

.colophon__base::before {
  content: "";
  position: absolute;
  top: -4px;
  left: 0;
  width: 120px;
  height: 9px;
  background-image: repeating-linear-gradient(90deg, var(--color-line) 0 1px, transparent 1px 12px);
}

.colophon__sign {
  margin: 0;
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  color: var(--color-ink);
}

.colophon__meta {
  margin: 0;
  font-size: var(--text-xs);
  letter-spacing: 0.05em;
  color: var(--color-ink-muted);
}

/* ========== 6. 按钮与面包屑 ========== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: 10px var(--space-3);
  font-family: var(--font-heading);
  font-size: var(--text-base);
  line-height: 1.4;
  color: var(--color-ink);
  background: transparent;
  border: var(--border-thin) solid var(--color-ink-muted);
  border-radius: var(--radius-sm);
  transition: background-color 220ms ease-out, border-color 220ms ease-out, color 220ms ease-out;
}

.btn:hover {
  background: var(--color-surface-deep);
  border-color: var(--color-ink);
  color: var(--color-ink);
}

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

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

.btn--quiet {
  color: var(--color-ink-soft);
  border-color: var(--color-line);
}

.crumbs {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-2);
  margin: 0 0 var(--space-4);
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
}

.crumbs li { display: inline-flex; align-items: center; }

.crumbs li:not(:last-child)::after {
  content: "／";
  margin-left: var(--space-2);
  color: var(--color-line);
}

.crumbs a {
  color: var(--color-ink-soft);
  transition: color 220ms ease-out;
}

.crumbs a:hover { color: var(--color-accent); }

.tag {
  display: inline-block;
  padding: 2px 8px;
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: var(--color-ink-soft);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  background: var(--color-surface-alt);
}

.tag--mark {
  color: var(--color-primary);
  border-color: color-mix(in srgb, var(--color-primary) 45%, transparent);
  background: var(--color-primary-soft);
}

/* ========== 7. 章节构件 ========== */
.section-head {
  display: grid;
  gap: var(--space-2);
  max-width: var(--measure);
  margin-bottom: var(--space-6);
}

.section-head__kicker {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.2em;
  color: var(--color-ink-muted);
}

.section-head__title { font-size: var(--text-3xl); }
.section-head__title em { font-style: normal; color: var(--color-primary); }

.section-head__note {
  font-size: var(--text-sm);
  line-height: 1.9;
  color: var(--color-ink-soft);
}

.page-head {
  padding-block: var(--space-8) var(--space-6);
}

.page-head__title { font-size: var(--text-4xl); }
.page-head__lede { margin-top: var(--space-3); }

/* ========== 8. 数据表 ========== */
.table-wrap {
  padding-inline: var(--space-2);
  overflow-x: auto;
  overscroll-behavior-x: contain;
}

.table {
  width: 100%;
  min-width: 520px;
  font-size: var(--text-sm);
}

.table caption {
  padding-bottom: var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  text-align: left;
  color: var(--color-ink-muted);
}

.table th {
  padding: var(--space-2);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  text-align: left;
  color: var(--color-ink);
  background: var(--color-surface-deep);
  border-bottom: var(--border-thin) solid var(--color-line);
  white-space: nowrap;
}

.table td {
  padding: var(--space-2);
  color: var(--color-ink-soft);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.table .num { text-align: right; }

.table tbody tr:hover { background: var(--color-surface-alt); }
.table tbody tr.is-selected { background: var(--color-highlight); }
.table tbody tr.is-selected td { color: var(--color-ink); }

.table--key td.num--mark {
  color: var(--color-primary);
  font-weight: 500;
}

/* ========== 9. 深墨区块 ========== */
.ink-slab {
  padding-block: var(--section-y);
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}

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

.ink-slab .section-head__kicker,
.ink-slab .micro { color: color-mix(in srgb, var(--color-contrast-ink) 62%, transparent); }

.ink-slab .section-head__note,
.ink-slab p { color: color-mix(in srgb, var(--color-contrast-ink) 84%, transparent); }

.ink-slab .rule,
.ink-slab hr { background: var(--color-contrast-line); }

.ink-slab .rule--tick {
  background-color: transparent;
  background-image: repeating-linear-gradient(90deg, var(--color-contrast-line) 0 1px, transparent 1px 12px);
}

.ink-slab .rule--mark { background: var(--color-contrast-accent); }

.ink-slab .marked::before { background: var(--color-contrast-accent); }

.ink-slab .table th {
  color: var(--color-contrast-ink);
  background: transparent;
  border-bottom-color: var(--color-contrast-line);
}

.ink-slab .table td {
  color: color-mix(in srgb, var(--color-contrast-ink) 78%, transparent);
  border-bottom-color: var(--color-contrast-line);
}

.ink-slab .table tbody tr:hover { background: color-mix(in srgb, var(--color-contrast-ink) 8%, transparent); }
.ink-slab .table tbody tr.is-selected { background: color-mix(in srgb, var(--color-contrast-accent) 18%, transparent); }

.ink-slab .table--key td.num--mark { color: var(--color-contrast-accent); }

.ink-slab__value {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-figure);
  line-height: 1;
  color: var(--color-contrast-ink);
}

.ink-slab__value--mark { color: var(--color-contrast-accent); }

/* ========== 10. 索引、折叠、矩阵、卷轴 ========== */
.entry-list {
  border-top: var(--border-thin) solid var(--color-line);
}

.entry {
  position: relative;
  display: grid;
  grid-template-columns: 92px minmax(0, 1fr) auto;
  gap: var(--space-3);
  padding: var(--space-3) 0 var(--space-3) var(--space-3);
  border-bottom: var(--border-thin) solid var(--color-line);
  transition: background-color 220ms ease-out;
}

.entry::before {
  content: "";
  position: absolute;
  left: 0;
  top: var(--space-3);
  bottom: var(--space-3);
  width: 2px;
  background: var(--color-line);
  transition: background-color 220ms ease-out;
}

.entry:hover { background: var(--color-surface-alt); }
.entry:hover::before { background: var(--color-primary); }

.entry__meta {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.04em;
  color: var(--color-ink-muted);
}

.entry__title {
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  color: var(--color-ink);
}

.entry__note {
  margin-top: 4px;
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
}

.entry__value {
  align-self: center;
  font-family: var(--font-mono);
  font-size: var(--text-xl);
  color: var(--color-ink);
}

.dossier {
  border-top: var(--border-thin) solid var(--color-line);
}

.dossier summary {
  position: relative;
  padding: var(--space-3) 0 var(--space-3) var(--space-3);
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  color: var(--color-ink);
  cursor: pointer;
  list-style: none;
}

.dossier summary::-webkit-details-marker { display: none; }

.dossier summary::before,
.dossier summary::after {
  content: "";
  position: absolute;
  left: 0;
  top: 1.55em;
  width: 11px;
  height: 1.5px;
  background: var(--color-primary);
  transform-origin: 50% 50%;
  transition: transform 240ms ease-out;
}

.dossier summary::after { transform: rotate(90deg); }
.dossier[open] summary::after { transform: rotate(0deg); }

.dossier__body {
  padding: 0 0 var(--space-4) var(--space-3);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.matrix {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 0 var(--space-4);
  border-top: var(--border-thin) solid var(--color-line);
}

.matrix__cell {
  position: relative;
  padding: var(--space-3) 0 var(--space-4);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.matrix__cell::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 12px;
  height: var(--border-thin);
  background: var(--color-ink-muted);
}

.matrix__cell h3 { font-size: var(--text-lg); }
.matrix__cell p { margin: var(--space-1) 0 0; font-size: var(--text-sm); color: var(--color-ink-soft); }

.rail-scroll {
  display: flex;
  gap: var(--space-4);
  padding-block: var(--space-2) var(--space-4);
  overflow-x: auto;
  overscroll-behavior-x: contain;
  scroll-snap-type: x proximity;
}

.rail-scroll > * {
  flex: 0 0 clamp(220px, 42vw, 300px);
  scroll-snap-align: start;
}

.rail-scroll__item {
  padding-top: var(--space-2);
  border-top: var(--border-thin) solid var(--color-line);
}

.rail-scroll__item--mark { border-top-color: var(--color-primary); }

.stat {
  display: grid;
  gap: 6px;
  padding-top: var(--space-2);
  border-top: var(--border-thin) solid var(--color-line);
}

.stat__value {
  font-family: var(--font-mono);
  font-size: var(--text-figure);
  font-weight: 500;
  line-height: 1;
  color: var(--color-ink);
}

.stat__value--mark { color: var(--color-primary); }

.stat__label {
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
}

.toc {
  border-left: var(--border-thin) solid var(--color-line);
}

.toc__link {
  display: block;
  margin-left: -1px;
  padding: 6px 0 6px var(--space-2);
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
  border-left: 2px solid transparent;
  transition: color 220ms ease-out, border-color 220ms ease-out;
}

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

.toc__link[aria-current="true"] {
  color: var(--color-primary);
  border-left-color: var(--color-primary);
}

/* ========== 11. 图片容器 ========== */
.media {
  position: relative;
  overflow: hidden;
  aspect-ratio: 16 / 10;
  border-radius: var(--radius-lg);
  background: var(--color-surface-deep);
}

.media--wide { aspect-ratio: 21 / 9; }
.media--tall { aspect-ratio: 4 / 5; }

.media__img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  filter: grayscale(0.75) contrast(1.04) brightness(0.98);
}

.media__overlay {
  position: absolute;
  inset: 0;
  background: var(--overlay-scrim);
}

.media__text {
  position: absolute;
  right: var(--space-3);
  bottom: var(--space-3);
  left: var(--space-3);
  color: var(--color-contrast-ink);
}

.media__text h3,
.media__text strong {
  color: var(--color-contrast-ink);
  font-family: var(--font-heading);
}

.media__text p {
  margin: 4px 0 0;
  font-size: var(--text-sm);
  color: color-mix(in srgb, var(--color-contrast-ink) 78%, transparent);
}

.media__caption {
  margin-top: var(--space-1);
  font-size: var(--text-xs);
  letter-spacing: 0.06em;
  color: var(--color-ink-muted);
}

/* ========== 12. 返回顶部与显现 ========== */
.to-top {
  position: fixed;
  right: var(--space-3);
  bottom: var(--space-3);
  z-index: 70;
  padding: 10px var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: var(--color-ink-soft);
  background: var(--color-surface);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  opacity: 0;
  visibility: hidden;
  transition: opacity 260ms ease-out, visibility 260ms ease-out, color 220ms ease-out;
}

.to-top[data-visible] { opacity: 1; visibility: visible; }
.to-top:hover { color: var(--color-primary); border-color: var(--color-primary); }

@media (prefers-reduced-motion: no-preference) {
  html.has-js [data-reveal] {
    opacity: 0;
    transform: translateY(14px);
    transition: opacity 360ms ease-out, transform 360ms ease-out;
    transition-delay: var(--reveal-delay, 0ms);
  }

  html.has-js [data-reveal][data-visible] {
    opacity: 1;
    transform: none;
  }
}

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

  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    transition-duration: 0.001ms !important;
  }

  .to-top { visibility: visible; opacity: 1; }
  .scroll-progress { transition: none; }
}

/* ========== 13. 响应式 ========== */
@media (max-width: 1023px) {
  .masthead__inner { gap: var(--space-3); }
  .nav__list { gap: var(--space-3); }
  .colophon__grid { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: var(--space-4); }
}

@media (max-width: 899px) {
  :root { --section-y: 88px; --section-y-lg: 112px; }

  .masthead__inner {
    flex-wrap: wrap;
    row-gap: var(--space-2);
    min-height: 76px;
    padding-block: var(--space-2);
  }

  .masthead__rail { min-width: var(--space-4); }

  .nav-toggle {
    display: inline-flex;
    margin-left: auto;
  }

  .nav {
    display: none;
    flex: 1 0 100%;
    width: 100%;
    padding-bottom: var(--space-2);
  }

  .nav[data-open] { display: block; }

  .nav__list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
  }

  .nav__link {
    display: block;
    width: 100%;
    padding: 12px 0 12px var(--space-3);
    border-top: var(--border-thin) solid var(--color-line);
  }

  .nav__link::before { top: 50%; }

  .pair {
    grid-template-columns: minmax(0, 1fr);
    gap: var(--space-4);
  }

  .pair::before { display: none; }
  .pair__side--right { text-align: left; }

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

  .span-3,
  .span-4,
  .span-6,
  .span-8 { grid-column: span 12; }

  .entry { grid-template-columns: minmax(0, 1fr); gap: var(--space-1); }
  .entry__value { justify-self: start; }

  .table-wrap { padding-inline: 0; }
}

@media (max-width: 639px) {
  .brand__sub { display: none; }
  .colophon__grid { grid-template-columns: minmax(0, 1fr); }
  .colophon__frame { padding: var(--space-4) var(--space-2) var(--space-2); }
  .page-head { padding-block: var(--space-6) var(--space-4); }
  :root { --text-4xl: 39px; }
}