:root {
  --color-surface: #eeeeee;
  --color-surface-alt: #e7e6e6;
  --color-surface-deep: #dddcdb;
  --color-ink: #5d5550;
  --color-ink-soft: #726a65;
  --color-ink-muted: #867e79;
  --color-line: #d4d2d2;
  --color-primary: #897161;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #e0dcda;
  --color-accent: #8a7138;
  --color-accent-ink: #ffffff;
  --color-highlight: #dcd8cd;
  --color-focus: #806528;
  --color-contrast-surface: #181615;
  --color-contrast-ink: #e7e5e4;
  --color-contrast-line: #464443;
  --color-contrast-accent: #b69549;
  --overlay-scrim: linear-gradient(180deg, rgba(24, 22, 21, 0.35) 0%, rgba(24, 22, 21, 0.72) 55%, rgba(24, 22, 21, 0.92) 100%);
  --font-heading: "Songti SC", STSong, "Source Han Serif SC", SimSun, serif;
  --font-body: "Songti SC", STSong, "Source Han Serif SC", SimSun, 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(36px, 7.5vw, 96px);
  --text-figure: clamp(30px, 5.4vw, 69px);
  --weight-heading: 475;
  --weight-body: 400;
  --leading-body: 1.82;
  --leading-heading: 1.2;
  --tracking-heading: 0.023em;
  --radius-sm: 1px;
  --radius-md: 1px;
  --radius-lg: 1px;
  --radius-pill: 1px;
  --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: 1080px;
  --measure: 70ch;
  --gutter: 24px;
  --section-y: 113px;
  --section-y-lg: 158px;
}

/* ========== reset ========== */
*,
*::before,
*::after { box-sizing: border-box; }

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

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);
  letter-spacing: 0.01em;
  overflow-x: hidden;
}

h1, h2, h3, h4, h5, h6,
p, figure, blockquote, dl, dd, ul, ol { margin: 0; }

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);
}

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

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

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

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

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

/* ========== 骨架 ========== */
.shell {
  width: 100%;
  max-width: var(--container);
  margin: 0 auto;
  padding-left: var(--gutter);
  padding-right: var(--gutter);
}

.section { padding-top: var(--section-y); padding-bottom: var(--section-y); }
.section--lg { padding-top: var(--section-y-lg); padding-bottom: var(--section-y-lg); }
.section--tight { padding-top: var(--space-8); padding-bottom: var(--space-8); }
.section--alt { background-color: var(--color-surface-alt); }
.section--deep { background-color: var(--color-surface-deep); }
.section--contrast {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}
.section--contrast .section-head__note,
.section--contrast .lede { color: color-mix(in srgb, var(--color-contrast-ink) 78%, transparent); }
.section--contrast .section-head__index { color: var(--color-contrast-accent); }
.section--contrast :focus-visible { outline-color: var(--color-contrast-accent); }

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

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

.prose {
  max-width: var(--measure);
  line-height: 1.75;
}
.prose > * + * { margin-top: var(--space-3); }
.prose ul,
.prose ol { list-style: disc; padding-left: 1.5em; }
.prose li + li { margin-top: var(--space-1); }
.prose strong { font-weight: 600; color: var(--color-primary); }

/* ========== 标题与文字 ========== */
.display-title {
  font-family: var(--font-heading);
  font-size: var(--text-display);
  font-weight: var(--weight-heading);
  line-height: 1.05;
  letter-spacing: var(--tracking-heading);
}

.figure-num {
  font-family: var(--font-mono);
  font-size: var(--text-figure);
  font-weight: var(--weight-heading);
  line-height: 1;
  font-variant-numeric: tabular-nums;
  letter-spacing: -0.01em;
}

.num,
.data-table .num,
.stand-nav__num,
.stand-index__num,
.metric {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
}

.lede {
  max-width: var(--measure);
  font-size: var(--text-lg);
  line-height: 1.6;
  color: var(--color-ink-soft);
}

.section-head { max-width: var(--measure); }
.section-head__index {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  color: var(--color-accent);
}
.section-head__title {
  margin-top: var(--space-2);
  font-size: var(--text-2xl);
}
.section-head__note {
  margin-top: var(--space-2);
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
}

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

.col-3 { grid-column: span 3; }
.col-4 { grid-column: span 4; }
.col-5 { grid-column: span 5; }
.col-6 { grid-column: span 6; }
.col-7 { grid-column: span 7; }
.col-8 { grid-column: span 8; }
.col-9 { grid-column: span 9; }
.col-12 { grid-column: span 12; }

/* ========== 按钮 ========== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: 10px var(--space-3);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  background-color: transparent;
  color: var(--color-ink);
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  letter-spacing: 0.06em;
  transition: color 180ms ease-out, border-color 180ms ease-out, background-color 180ms ease-out;
}
.btn:hover { color: var(--color-primary); border-color: var(--color-primary); }

.btn--solid {
  background-color: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
}
.btn--solid:hover {
  background-color: color-mix(in srgb, var(--color-primary) 84%, var(--color-contrast-surface));
  border-color: color-mix(in srgb, var(--color-primary) 84%, var(--color-contrast-surface));
  color: var(--color-primary-ink);
}

.btn--quiet {
  border-color: transparent;
  padding-left: 0;
  padding-right: 0;
  border-bottom: var(--border-thin) solid var(--color-accent);
  border-radius: 0;
}
.btn--quiet:hover { color: var(--color-accent); border-bottom-color: var(--color-accent); }

.section--contrast .btn { color: var(--color-contrast-ink); border-color: var(--color-contrast-line); }
.section--contrast .btn:hover { color: var(--color-contrast-accent); border-color: var(--color-contrast-accent); }
.section--contrast .btn--quiet { border-color: transparent; border-bottom-color: var(--color-contrast-accent); }

/* ========== 强调 ========== */
.keyword {
  border-bottom: var(--border-thin) solid color-mix(in srgb, var(--color-accent) 45%, transparent);
  padding-bottom: 1px;
  transition: border-color 180ms ease-out;
}
.keyword:hover { border-bottom-color: var(--color-accent); }
.section--contrast .keyword { border-bottom-color: color-mix(in srgb, var(--color-contrast-accent) 55%, transparent); }
.section--contrast .keyword:hover { border-bottom-color: var(--color-contrast-accent); }

.mark {
  background-color: var(--color-highlight);
  color: var(--color-ink);
  padding: 0 4px;
}

/* ========== 面包屑 ========== */
.breadcrumb { padding-top: var(--space-4); }
.breadcrumb__list {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: var(--space-1) var(--space-2);
  list-style: none;
  padding: 0;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
  letter-spacing: 0.06em;
}
.breadcrumb__item { display: inline-flex; align-items: baseline; gap: var(--space-2); }
.breadcrumb__item + .breadcrumb__item::before {
  content: "/";
  color: var(--color-line);
}
.breadcrumb__link { color: var(--color-ink-soft); }
.breadcrumb__link:hover { color: var(--color-primary); }

/* ========== 图录 ========== */
.media {
  position: relative;
  display: block;
  overflow: hidden;
  border-radius: var(--radius-sm);
  background-color: var(--color-surface-deep);
}
.media--3x2 { aspect-ratio: 3 / 2; }
.media--16x9 { aspect-ratio: 16 / 9; }
.media--1x1 { aspect-ratio: 1 / 1; }

.media__img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  border-radius: inherit;
}

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

.media__label {
  position: absolute;
  left: var(--space-3);
  right: var(--space-3);
  bottom: var(--space-3);
  color: var(--color-contrast-ink);
  font-size: var(--text-sm);
  letter-spacing: 0.04em;
}

.media__caption {
  margin-top: var(--space-1);
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
  letter-spacing: 0.04em;
}

.figure-rail {
  display: flex;
  gap: var(--space-3);
  overflow-x: auto;
  scroll-snap-type: x mandatory;
  padding-bottom: var(--space-2);
  scrollbar-width: none;
}
.figure-rail::-webkit-scrollbar { display: none; }
.figure-rail__item {
  flex: 0 0 clamp(220px, 52%, 320px);
  scroll-snap-align: start;
}

/* ========== 数据表 ========== */
.data-table {
  width: 100%;
  border-collapse: collapse;
  font-size: var(--text-sm);
}
.data-table caption {
  text-align: left;
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
  padding-bottom: var(--space-2);
  letter-spacing: 0.06em;
}
.data-table th,
.data-table td {
  text-align: left;
  padding: var(--space-2) var(--space-3);
  border-bottom: var(--border-thin) solid var(--color-line);
  vertical-align: baseline;
}
.data-table thead th {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: var(--color-ink-soft);
}
.data-table tbody tr:nth-child(even) { background-color: var(--color-surface-deep); }

/* ========== 折叠收纳 ========== */
.fold {
  border-top: var(--border-thin) solid var(--color-line);
}
.fold__item {
  border-bottom: var(--border-thin) solid var(--color-line);
}
.fold__summary {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
  padding: var(--space-3) 0;
  font-family: var(--font-heading);
  font-size: var(--text-base);
  color: var(--color-ink);
  cursor: pointer;
  list-style: none;
}
.fold__summary::-webkit-details-marker { display: none; }
.fold__summary::before {
  content: "+";
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--color-accent);
}
.fold__item[open] .fold__summary::before { content: "−"; }
.fold__body {
  padding-bottom: var(--space-4);
  max-width: var(--measure);
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
}

/* ========== 看台编号索引 ========== */
.stand-index {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}
.stand-index__link {
  display: inline-flex;
  align-items: baseline;
  gap: var(--space-1);
  padding: 4px var(--space-2);
  border-radius: var(--radius-sm);
  background-color: var(--color-surface-deep);
  color: var(--color-ink-soft);
  font-size: var(--text-sm);
  transition: background-color 180ms ease-out, color 180ms ease-out;
}
.stand-index__link:hover {
  background-color: var(--color-highlight);
  color: var(--color-primary);
}
.stand-index__link.is-current {
  background-color: var(--color-primary);
  color: var(--color-primary-ink);
}
.stand-index__num {
  font-size: var(--text-xs);
  opacity: 0.78;
}

/* ========== 口径注释 ========== */
.note-block {
  padding: var(--space-3);
  border-radius: var(--radius-sm);
  background-color: var(--color-primary-soft);
  color: var(--color-ink-soft);
  font-size: var(--text-sm);
  line-height: 1.75;
}
.note-block__label {
  display: block;
  margin-bottom: var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  color: var(--color-accent);
}
.section--contrast .note-block {
  background-color: color-mix(in srgb, var(--color-contrast-ink) 8%, transparent);
  color: var(--color-contrast-ink);
}

/* ========== 跳转链与进度 ========== */
.skip-link {
  position: absolute;
  top: 0;
  left: var(--space-3);
  z-index: 90;
  transform: translateY(-140%);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-sm);
  background-color: var(--color-primary);
  color: var(--color-primary-ink);
  font-size: var(--text-sm);
  transition: transform 180ms ease-out;
}
.skip-link:focus { transform: translateY(var(--space-1)); }

.read-progress {
  position: fixed;
  top: 0;
  left: 0;
  z-index: 80;
  width: 0;
  height: 2px;
  background-color: var(--color-accent);
  transition: width 120ms linear;
}

/* ========== 头部 ========== */
.site-header {
  position: relative;
  z-index: 60;
  background-color: var(--color-surface);
}

.brand-bar {
  background-color: var(--color-surface-alt);
  color: var(--color-ink-soft);
}
.brand-bar__inner {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--space-1) var(--space-3);
  padding-top: var(--space-2);
  padding-bottom: var(--space-2);
}
.brand {
  display: inline-flex;
  align-items: baseline;
  gap: var(--space-1);
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  letter-spacing: 0.1em;
  color: var(--color-primary);
}
.brand__divider { color: var(--color-line); }
.brand__sub {
  font-family: var(--font-body);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
}
.brand-bar__meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-1) var(--space-3);
  font-size: var(--text-xs);
  letter-spacing: 0.06em;
}
.meta-chip { color: var(--color-ink-soft); }
.meta-chip--quiet { font-family: var(--font-mono); color: var(--color-ink-muted); }

.stand-nav {
  position: sticky;
  top: 0;
  z-index: 60;
  background-color: var(--color-surface);
  color: var(--color-ink);
}
.stand-nav.is-stuck {
  border-bottom: var(--border-thin) solid var(--color-line);
}
.stand-nav__inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2) var(--space-4);
  padding-top: var(--space-2);
  padding-bottom: var(--space-2);
  min-height: 56px;
}
.stand-nav__list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-2) var(--space-4);
  list-style: none;
  padding: 0;
}
.stand-nav__item { display: block; }
.stand-nav__link {
  display: inline-flex;
  align-items: baseline;
  gap: var(--space-1);
  padding: 4px 0;
  font-size: var(--text-sm);
  letter-spacing: 0.06em;
  color: var(--color-ink-soft);
  transition: color 180ms ease-out;
}
.stand-nav__link:hover { color: var(--color-primary); }
.stand-nav__num {
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
  padding: 0 3px;
  border-radius: var(--radius-sm);
  transition: background-color 180ms ease-out, color 180ms ease-out;
}
.stand-nav__link:hover .stand-nav__num {
  background-color: var(--color-highlight);
  color: var(--color-primary);
}
.stand-nav__link[aria-current="page"] { color: var(--color-primary); }
.stand-nav__link[aria-current="page"] .stand-nav__num {
  background-color: var(--color-primary);
  color: var(--color-primary-ink);
}
.stand-nav__note {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-1) 0;
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  color: var(--color-primary);
}
.nav-toggle__bars {
  position: relative;
  display: block;
  width: 18px;
  height: 1px;
  background-color: currentColor;
}
.nav-toggle__bars::before,
.nav-toggle__bars::after {
  content: "";
  position: absolute;
  left: 0;
  width: 18px;
  height: 1px;
  background-color: currentColor;
}
.nav-toggle__bars::before { top: -5px; }
.nav-toggle__bars::after { top: 5px; }

/* ========== 页脚 ========== */
.site-footer {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  margin-top: var(--section-y);
}
.site-footer__inner {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--space-2) var(--space-4);
  padding-top: var(--space-4);
  padding-bottom: var(--space-4);
  font-size: var(--text-xs);
  letter-spacing: 0.06em;
}
.site-footer__brand {
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  letter-spacing: 0.1em;
  color: var(--color-contrast-ink);
}
.site-footer__year {
  margin-left: var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: color-mix(in srgb, var(--color-contrast-ink) 60%, transparent);
}
.site-footer__addr {
  color: color-mix(in srgb, var(--color-contrast-ink) 68%, transparent);
}
.site-footer__links {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-1) var(--space-3);
  list-style: none;
  padding: 0;
}
.site-footer__links a {
  color: var(--color-contrast-ink);
  border-bottom: var(--border-thin) solid var(--color-contrast-line);
  padding-bottom: 1px;
  transition: border-color 180ms ease-out, color 180ms ease-out;
}
.site-footer__links a:hover {
  color: var(--color-contrast-accent);
  border-bottom-color: var(--color-contrast-accent);
}
.site-footer__icp {
  font-family: var(--font-mono);
  color: color-mix(in srgb, var(--color-contrast-ink) 62%, transparent);
}
.site-footer :focus-visible { outline-color: var(--color-contrast-accent); }

/* ========== 滚动显现 ========== */
.reveal--pending { opacity: 0; transform: translateY(4px); }
.reveal--in {
  opacity: 1;
  transform: none;
  transition: opacity 220ms ease-out, transform 220ms ease-out;
}

/* ========== 章节目录高亮 ========== */
.section-nav a { transition: color 180ms ease-out, background-color 180ms ease-out; }
.section-nav a.is-current { color: var(--color-primary); }

/* ========== 响应式 ========== */
@media (max-width: 1080px) {
  .grid { gap: var(--space-3); }
}

@media (max-width: 860px) {
  .section { padding-top: calc(var(--section-y) * 0.55); padding-bottom: calc(var(--section-y) * 0.55); }
  .section--lg { padding-top: calc(var(--section-y-lg) * 0.5); padding-bottom: calc(var(--section-y-lg) * 0.5); }
  .section--tight { padding-top: var(--space-6); padding-bottom: var(--space-6); }

  .col-3, .col-4, .col-5, .col-6, .col-7, .col-8, .col-9 { grid-column: span 12; }

  .nav-toggle { display: inline-flex; }
  .stand-nav__inner { align-items: center; }
  .stand-nav__list {
    display: none;
    width: 100%;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    margin-top: var(--space-2);
  }
  .stand-nav[data-open] .stand-nav__list { display: flex; }
  .stand-nav__item { width: 100%; }
  .stand-nav__link {
    width: 100%;
    padding: var(--space-2) 0;
    border-top: var(--border-thin) solid var(--color-line);
  }
  .stand-nav__note { display: none; }

  .display-title { line-height: 1.1; }
  .lede { font-size: var(--text-base); }

  .site-footer { margin-top: var(--space-8); }
  .site-footer__inner { flex-direction: column; align-items: flex-start; }

  .figure-rail__item { flex-basis: min(78%, 300px); }
}

@media (max-width: 520px) {
  .brand-bar__inner { flex-direction: column; align-items: flex-start; }
  .data-table th, .data-table td { padding: var(--space-2); }
}

/* ========== 动效降级 ========== */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .read-progress { transition: none; }
  .skip-link { transition: none; }
  .btn,
  .keyword,
  .stand-nav__link,
  .stand-nav__num,
  .stand-index__link,
  .site-footer__links a,
  .section-nav a { transition: none; }
  .reveal--pending { opacity: 1; transform: none; }
  .reveal--in { transition: none; }
}