:root {
  --color-surface: #f4f3f2;
  --color-surface-alt: #eceae9;
  --color-surface-deep: #e0dedc;
  --color-ink: #4d443c;
  --color-ink-soft: #74675d;
  --color-ink-muted: #8d7d72;
  --color-line: #d6d4d1;
  --color-primary: #9b6a45;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #e8e0da;
  --color-accent: #dc330f;
  --color-accent-ink: #ffffff;
  --color-highlight: #f0d0c9;
  --color-focus: #d32703;
  --color-contrast-surface: #171310;
  --color-contrast-ink: #e7e5e4;
  --color-contrast-line: #45413f;
  --color-contrast-accent: #ef3710;
  --overlay-scrim: linear-gradient(180deg, rgba(23, 19, 16, 0.35) 0%, rgba(23, 19, 16, 0.72) 55%, rgba(23, 19, 16, 0.92) 100%);
  --font-heading: STZhongsong, "Source Han Serif SC", "Songti SC", SimSun, serif;
  --font-body: "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: ui-monospace, Menlo, Consolas, monospace;
  --text-xs: 11.0px;
  --text-sm: 14.7px;
  --text-base: 17px;
  --text-lg: 22.7px;
  --text-xl: 30.2px;
  --text-2xl: 40.3px;
  --text-3xl: 53.7px;
  --text-4xl: 71.5px;
  --text-display: clamp(54px, 11.1vw, 142px);
  --text-figure: clamp(45px, 8.0vw, 102px);
  --weight-heading: 739;
  --weight-body: 400;
  --leading-body: 1.69;
  --leading-heading: 1.17;
  --tracking-heading: 0.015em;
  --radius-sm: 1px;
  --radius-md: 2px;
  --radius-lg: 2px;
  --radius-pill: 2px;
  --border-thin: 1px;
  --border-thick: 1px;
  --shadow-1: 0 1px 0 rgba(77, 68, 60, 0.12);
  --shadow-2: 0 2px 0 rgba(77, 68, 60, 0.18);
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-6: 48px;
  --space-8: 64px;
  --container: 1160px;
  --measure: 67ch;
  --gutter: 32px;
  --section-y: 92px;
  --section-y-lg: 129px;
}

/* ---------- reset ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body, h1, h2, h3, h4, h5, h6, p, ul, ol, dl, dd, figure, blockquote { margin: 0; }
ul, ol { padding: 0; list-style: none; }
img, svg, video { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button { font: inherit; color: inherit; background: none; border: 0; cursor: pointer; }
[hidden] { display: none !important; }
table { border-collapse: collapse; }

/* ---------- base typography ---------- */
body {
  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: 0.012em;
  -webkit-font-smoothing: antialiased;
}
h1, h2, h3, h4, h5 {
  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; }
strong { font-weight: 700; }
code, kbd, samp, .mono { font-family: var(--font-mono); font-size: 0.94em; letter-spacing: 0.04em; }

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

/* ---------- layout ---------- */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--space-3);
}
@media (min-width: 768px) {
  .container { padding-inline: var(--space-4); }
}
.section { padding-block: var(--section-y); }
.section--lg { padding-block: var(--section-y-lg); }
.section--alt { background-color: var(--color-surface-alt); }
.section--deep { background-color: var(--color-contrast-surface); color: var(--color-contrast-ink); }
.section--deep h1, .section--deep h2, .section--deep h3 { color: var(--color-contrast-ink); }

.grid {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: var(--space-4);
}
.grid > * { grid-column: 1 / -1; }
@media (min-width: 900px) {
  .grid { gap: var(--gutter); }
  .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-9 { grid-column: span 9; }
}
.stack > * + * { margin-top: var(--space-3); }
.stack--tight > * + * { margin-top: var(--space-1); }
.stack--loose > * + * { margin-top: var(--space-6); }

.section-head {
  max-width: var(--measure);
  margin-inline: auto;
  margin-bottom: var(--space-6);
  text-align: center;
}
.section-head h1, .section-head h2 { margin-top: var(--space-2); }
.kicker {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.24em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}

.prose { max-width: var(--measure); line-height: var(--leading-body); }
.prose > * + * { margin-top: var(--space-3); }
.prose h2 { margin-top: var(--space-6); }
.prose h3 { margin-top: var(--space-4); }
.prose ul, .prose ol { padding-left: var(--space-3); }
.prose ul { list-style: none; }
.prose ul li { position: relative; padding-left: var(--space-2); }
.prose ul li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.72em;
  width: 8px;
  height: 1px;
  background-color: var(--color-primary);
}
.prose ol { list-style: decimal; }

/* ---------- header ---------- */
.skip-link {
  position: absolute;
  left: var(--space-3);
  top: -100px;
  z-index: 200;
  padding: 10px 16px;
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  border-radius: var(--radius-sm);
  transition: top 0.18s ease;
}
.skip-link:focus { top: var(--space-2); }

.site-header {
  position: sticky;
  top: 0;
  z-index: 80;
  background-color: var(--color-surface);
  border-bottom: 1px solid var(--color-line);
  transition: background-color 0.24s ease, border-color 0.24s ease, color 0.24s ease;
}
.site-header__bar {
  display: grid;
  grid-template-columns: 1fr auto;
  align-items: center;
  gap: var(--space-2);
  padding-block: var(--space-2);
}
.site-header__meta {
  border-top: 1px solid var(--color-line);
  padding-block: 6px;
  transition: border-color 0.24s ease;
}

.brand { display: inline-flex; flex-direction: column; gap: 2px; min-width: 0; }
.brand__mark {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-lg);
  line-height: 1.1;
  letter-spacing: 0.1em;
  color: var(--color-ink);
}
.brand__tagline {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: var(--color-ink-muted);
}
.site-header__utility {
  display: none;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
  text-align: right;
}
.archive-stamp {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  color: var(--color-ink-muted);
}
.archive-stamp::before {
  content: "";
  flex: none;
  width: 8px;
  height: 8px;
  background-color: var(--color-accent);
  border-radius: var(--radius-sm);
}

.nav-toggle {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: 9px 12px;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-sm);
  background-color: var(--color-surface);
  color: var(--color-ink-soft);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  transition: border-color 0.18s ease, color 0.18s ease;
}
.nav-toggle:hover { border-color: var(--color-primary); color: var(--color-ink); }
.nav-toggle__bars {
  display: block;
  width: 16px;
  height: 2px;
  background-color: currentColor;
  box-shadow: 0 -5px 0 currentColor, 0 5px 0 currentColor;
  margin-block: 5px;
}

.site-nav { display: none; }
.site-nav[data-open="true"] {
  display: block;
  grid-column: 1 / -1;
  margin-top: var(--space-1);
  padding-top: var(--space-2);
  border-top: 3px double var(--color-line);
}
.site-nav__list { display: flex; flex-direction: column; gap: 2px; }
.site-nav__link {
  display: block;
  padding: 10px 0 10px var(--space-2);
  border-left: 2px solid transparent;
  font-size: var(--text-sm);
  letter-spacing: 0.06em;
  color: var(--color-ink-soft);
  transition: color 0.18s ease, border-color 0.18s ease;
}
.site-nav__link:hover { color: var(--color-ink); }
.site-nav__link[aria-current="page"] {
  color: var(--color-ink);
  border-left-color: var(--color-accent);
  background-color: var(--color-primary-soft);
}

@media (min-width: 960px) {
  .site-header__bar {
    grid-template-columns: auto 1fr auto;
    gap: var(--space-6);
  }
  .brand { grid-column: 1; }
  .site-header__utility { display: block; grid-column: 2; }
  .nav-toggle { display: none; }
  .site-nav { display: block; grid-column: 3; }
  .site-nav[data-open="true"] {
    grid-column: 3;
    margin-top: 0;
    padding-top: 0;
    border-top: 0;
  }
  .site-nav__list { flex-direction: row; gap: var(--space-4); }
  .site-nav__link {
    position: relative;
    padding: 6px 0;
    border-left: 0;
    background-color: transparent;
    font-size: var(--text-sm);
  }
  .site-nav__link[aria-current="page"] { background-color: transparent; }
  .site-nav__link::after {
    content: "";
    position: absolute;
    left: 0;
    right: 0;
    bottom: -2px;
    height: 2px;
    background-color: var(--color-accent);
    transform: scaleX(0);
    transform-origin: left center;
    transition: transform 0.18s ease;
  }
  .site-nav__link:hover::after,
  .site-nav__link[aria-current="page"]::after { transform: scaleX(1); }
}

/* overlay state: 首屏叠加态 */
.site-header[data-state="overlay"] {
  background-color: transparent;
  border-color: transparent;
}
.site-header[data-state="overlay"] .brand__mark,
.site-header[data-state="overlay"] .site-nav__link,
.site-header[data-state="overlay"] .nav-toggle { color: var(--color-contrast-ink); }
.site-header[data-state="overlay"] .brand__tagline,
.site-header[data-state="overlay"] .site-header__utility,
.site-header[data-state="overlay"] .archive-stamp { color: var(--color-contrast-ink); }
.site-header[data-state="overlay"] .site-header__meta { border-color: var(--color-contrast-line); }
.site-header[data-state="overlay"] .nav-toggle {
  border-color: var(--color-contrast-line);
  background-color: transparent;
}
.site-header[data-state="overlay"] .site-nav__link[aria-current="page"] {
  background-color: transparent;
  border-left-color: var(--color-contrast-accent);
}
.site-header[data-state="overlay"] .site-nav__link::after { background-color: var(--color-contrast-accent); }

/* ---------- footer ---------- */
.site-footer {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  padding-block: var(--section-y-lg) var(--space-6);
}
.footer-inner { display: block; }
.footer-brand {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.24em;
  text-transform: uppercase;
  color: var(--color-contrast-accent);
  margin-bottom: var(--space-6);
}
.footer-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-6);
  margin-bottom: var(--space-8);
}
@media (min-width: 640px) {
  .footer-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (min-width: 960px) {
  .footer-grid { grid-template-columns: repeat(4, minmax(0, 1fr)); gap: var(--gutter); }
}
.footer-col__title {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.2em;
  color: color-mix(in srgb, var(--color-contrast-ink) 62%, transparent);
  padding-bottom: var(--space-1);
  border-bottom: 3px double var(--color-contrast-line);
  margin-bottom: var(--space-2);
}
.footer-links { display: flex; flex-direction: column; gap: 10px; }
.footer-links li { font-size: var(--text-sm); color: color-mix(in srgb, var(--color-contrast-ink) 88%, transparent); }
.footer-links a {
  display: inline-block;
  border-bottom: 1px solid transparent;
  transition: color 0.18s ease, border-color 0.18s ease;
}
.footer-links a:hover { color: var(--color-contrast-accent); border-bottom-color: var(--color-contrast-accent); }
.footer-contact .footer-links li { font-size: var(--text-sm); line-height: 1.6; word-break: break-word; }

.footer-bigtype {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-3xl);
  line-height: 1.05;
  letter-spacing: 0.08em;
  text-align: center;
  color: var(--color-contrast-ink);
  padding-block: var(--space-6);
  border-top: 1px solid var(--color-contrast-line);
}
.footer-bigtype__alt { color: var(--color-contrast-accent); }
@media (min-width: 768px) {
  .footer-bigtype { font-size: calc(var(--text-4xl) * 1.3); letter-spacing: 0.06em; padding-block: var(--space-8); }
}

.footer-ticket {
  border: 3px double var(--color-contrast-line);
  border-radius: var(--radius-sm);
  padding: var(--space-3) var(--space-4);
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
  margin-top: var(--space-6);
}
.footer-ticket__line {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.06em;
  line-height: 1.8;
  color: color-mix(in srgb, var(--color-contrast-ink) 74%, transparent);
}
.footer-ticket__line a { border-bottom: 1px solid var(--color-contrast-line); }
.footer-ticket__line a:hover { color: var(--color-contrast-accent); border-bottom-color: var(--color-contrast-accent); }

/* ---------- components ---------- */
.num-tag {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: 3px 8px;
  border: 3px double var(--color-line);
  border-radius: var(--radius-sm);
  background-color: var(--color-surface);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
  white-space: nowrap;
}
.num-tag--accent { color: var(--color-accent); border-color: var(--color-accent); background-color: var(--color-surface); }
.num-tag--solid { background-color: var(--color-primary); border-color: var(--color-primary); color: var(--color-primary-ink); }

.stamp {
  display: inline-block;
  padding: 4px 10px;
  background-color: var(--color-primary);
  color: var(--color-primary-ink);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  border-radius: var(--radius-sm);
}
.stamp--accent { background-color: var(--color-accent); color: var(--color-accent-ink); }

.ticket {
  border: 3px double var(--color-line);
  border-radius: var(--radius-sm);
  background-color: var(--color-surface);
  padding: var(--space-3) var(--space-4);
}
.ticket--alt { background-color: var(--color-surface-alt); }

.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: 12px 22px;
  border: 1px solid var(--color-ink);
  border-radius: var(--radius-sm);
  background-color: transparent;
  color: var(--color-ink);
  font-size: var(--text-sm);
  letter-spacing: 0.1em;
  transition: background-color 0.18s ease, color 0.18s ease, border-color 0.18s ease;
}
.btn:hover { background-color: var(--color-primary-soft); }
.btn--primary {
  background-color: var(--color-accent);
  border-color: var(--color-accent);
  color: var(--color-accent-ink);
}
.btn--primary:hover { background-color: var(--color-focus); border-color: var(--color-focus); }
.btn--ghost { border-color: var(--color-line); color: var(--color-ink-soft); }
.btn--ghost:hover { border-color: var(--color-primary); color: var(--color-ink); }

.em-link {
  color: var(--color-ink);
  border-bottom: 1px solid var(--color-accent);
  transition: background-color 0.18s ease;
}
.em-link:hover { background-color: var(--color-highlight); }
.mark { background-color: var(--color-highlight); padding: 0 2px; }

.key-figure {
  font-family: var(--font-mono);
  font-size: var(--text-xl);
  letter-spacing: 0.02em;
  color: var(--color-ink);
  line-height: 1.1;
}

.breadcrumb {
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
  margin-bottom: var(--space-4);
}
.breadcrumb__list { display: flex; flex-wrap: wrap; align-items: center; gap: 10px; }
.breadcrumb__list li { display: inline-flex; align-items: center; gap: 10px; }
.breadcrumb__list li + li::before {
  content: "/";
  color: var(--color-line);
  font-family: var(--font-mono);
}
.breadcrumb a { border-bottom: 1px solid var(--color-line); }
.breadcrumb a:hover { color: var(--color-accent); border-bottom-color: var(--color-accent); }

.data-table { width: 100%; font-size: var(--text-sm); text-align: left; }
.data-table th {
  padding: var(--space-1) var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 400;
  letter-spacing: 0.14em;
  color: var(--color-ink-muted);
  border-bottom: 3px double var(--color-line);
  white-space: nowrap;
}
.data-table td {
  padding: var(--space-2);
  border-bottom: 1px solid var(--color-line);
  vertical-align: top;
  line-height: 1.6;
}
.data-table tbody tr:nth-child(even) { background-color: var(--color-surface-alt); }
.data-table tbody tr:hover { background-color: var(--color-primary-soft); }

.figure { display: block; }
.figure__media {
  position: relative;
  overflow: hidden;
  border-radius: var(--radius-md);
  background-color: var(--color-surface-deep);
  aspect-ratio: 16 / 10;
}
.figure__media img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  filter: sepia(0.22) saturate(0.82) contrast(1.02);
}
.figure__media::after {
  content: "";
  position: absolute;
  inset: 0;
  background-color: var(--color-primary);
  opacity: 0.2;
  mix-blend-mode: multiply;
  pointer-events: none;
}
.figure__overlay {
  position: absolute;
  inset: 0;
  z-index: 1;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  gap: var(--space-1);
  padding: var(--space-4);
  background: var(--overlay-scrim);
  color: var(--color-contrast-ink);
}
.figure__overlay h3, .figure__overlay p { color: var(--color-contrast-ink); }
.figure__caption {
  margin-top: var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
}

.toc { font-size: var(--text-sm); }
.toc__list { display: flex; flex-direction: column; }
.toc__list a {
  display: block;
  padding: 7px 0 7px var(--space-2);
  border-left: 2px solid var(--color-line);
  color: var(--color-ink-soft);
  transition: color 0.18s ease, border-color 0.18s ease;
}
.toc__list a:hover { color: var(--color-ink); }
.toc__list a[aria-current="true"] {
  color: var(--color-ink);
  border-left-color: var(--color-accent);
  background-color: var(--color-primary-soft);
}

.filter-bar { display: flex; flex-wrap: wrap; gap: var(--space-1); }
.filter-chip {
  padding: 6px 12px;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-sm);
  background-color: var(--color-surface);
  color: var(--color-ink-soft);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  transition: background-color 0.18s ease, color 0.18s ease, border-color 0.18s ease;
}
.filter-chip:hover { border-color: var(--color-primary); color: var(--color-ink); }
.filter-chip[aria-pressed="true"] {
  background-color: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
}
.filter-empty {
  padding: var(--space-4);
  border: 3px double var(--color-line);
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: var(--color-ink-muted);
  text-align: center;
}

[data-copy].is-copied { color: var(--color-accent); border-color: var(--color-accent); }

/* ---------- js injected ---------- */
.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  z-index: 120;
  width: 100%;
  height: 2px;
  background-color: var(--color-accent);
  transform: scaleX(0);
  transform-origin: left center;
  pointer-events: none;
}
.to-top {
  position: fixed;
  right: var(--space-4);
  bottom: var(--space-4);
  z-index: 110;
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: 10px 14px;
  border: 3px double var(--color-contrast-line);
  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: 0.12em;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.2s ease, visibility 0.2s ease, background-color 0.2s ease;
}
.to-top[data-visible="true"] { opacity: 1; visibility: visible; }
.to-top:hover { background-color: var(--color-accent); border-color: var(--color-accent); color: var(--color-accent-ink); }

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