:root {
  --color-surface: #fcfcfc;
  --color-surface-alt: #f3f3f3;
  --color-surface-deep: #e6e7e7;
  --color-ink: #444b50;
  --color-ink-soft: #697178;
  --color-ink-muted: #788187;
  --color-line: #dbdcdd;
  --color-primary: #3c7ba9;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #e1eaf0;
  --color-accent: #d52b2a;
  --color-accent-ink: #ffffff;
  --color-highlight: #f5d6d6;
  --color-focus: #e11e1e;
  --color-contrast-surface: #101418;
  --color-contrast-ink: #e4e6e7;
  --color-contrast-line: #3f4246;
  --color-contrast-accent: #db4d4c;
  --overlay-scrim: linear-gradient(180deg, rgba(16, 20, 24, 0.35) 0%, rgba(16, 20, 24, 0.72) 55%, rgba(16, 20, 24, 0.92) 100%);
  --font-heading: ui-monospace, SFMono-Regular, Menlo, Consolas, "PingFang SC", monospace;
  --font-body: "PingFang SC", "Microsoft YaHei", "Source Han Sans SC", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --text-xs: 12.2px;
  --text-sm: 14.6px;
  --text-base: 16px;
  --text-lg: 19.2px;
  --text-xl: 23.0px;
  --text-2xl: 27.6px;
  --text-3xl: 33.2px;
  --text-4xl: 39.8px;
  --text-display: clamp(34px, 5.7vw, 73px);
  --text-figure: clamp(28px, 4.1vw, 53px);
  --weight-heading: 697;
  --weight-body: 400;
  --leading-body: 1.84;
  --leading-heading: 1.28;
  --tracking-heading: -0.004em;
  --radius-sm: 2px;
  --radius-md: 2px;
  --radius-lg: 2px;
  --radius-pill: 2px;
  --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: 1300px;
  --measure: 75ch;
  --gutter: 32px;
  --section-y: 85px;
  --section-y-lg: 119px;
}

/* ============================================================
   /assets/site.css · 千亿球友会 共享样式
   技术文档气质：浅灰长文 + 深色框景 + 等宽索引轨道
   ============================================================ */

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: 118px;
}

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);
}

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);
}

p { margin: 0; }

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

a {
  color: var(--color-primary);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
  text-underline-offset: 3px;
}

button, input, select, textarea { font: inherit; color: inherit; }

button {
  background: none;
  border: 0;
  padding: 0;
}

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

table { border-collapse: collapse; width: 100%; }

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

strong, b { font-weight: var(--weight-heading); color: var(--color-ink); }

code, kbd, samp, .mono { font-family: var(--font-mono); font-size: 0.94em; }

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

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

/* ---------- layout ---------- */
.container {
  width: 100%;
  max-width: var(--container);
  margin: 0 auto;
  padding-left: 20px;
  padding-right: 20px;
}

@media (min-width: 720px) {
  .container { padding-left: var(--gutter); padding-right: var(--gutter); }
}

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

.section { padding: var(--section-y) 0; }
.section--lg { padding: var(--section-y-lg) 0; }
.section--flush { padding-top: 0; }

.grid-12 {
  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; }

@media (max-width: 1023px) {
  .grid-12 { gap: var(--space-4); }
  .col-3, .col-4, .col-5 { grid-column: span 6; }
  .col-6, .col-7, .col-8, .col-9 { grid-column: span 12; }
}

@media (max-width: 719px) {
  .grid-12 { gap: var(--space-3); }
  .col-3, .col-4, .col-5, .col-6, .col-7, .col-8, .col-9 { grid-column: span 12; }
}

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

.guide-line {
  height: 1px;
  margin: var(--space-6) 0;
  background-color: var(--color-line);
  border: 0;
}

.guide-line--slant {
  position: relative;
  height: var(--space-6);
  margin: var(--space-6) 0;
  background: none;
  overflow: hidden;
}

.guide-line--slant::before {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  top: 50%;
  height: 1px;
  background-color: var(--color-line);
  transform: rotate(-2deg);
  transform-origin: left center;
}

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

/* ---------- type helpers ---------- */
.display-title {
  font-family: var(--font-heading);
  font-size: var(--text-display);
  font-weight: var(--weight-heading);
  line-height: 1.06;
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
}

.figure-number {
  font-family: var(--font-mono);
  font-size: var(--text-figure);
  font-weight: var(--weight-heading);
  line-height: 1.05;
  font-variant-numeric: tabular-nums;
  letter-spacing: -0.01em;
}

.kicker {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}

.kicker::before {
  content: "";
  width: 18px;
  height: 1px;
  background-color: var(--color-accent);
}

.mark {
  background-color: var(--color-highlight);
  color: var(--color-ink);
  padding: 0 2px;
}

.underline-accent { border-bottom: 2px solid var(--color-accent); padding-bottom: 1px; }
.underline-primary { border-bottom: var(--border-thin) solid var(--color-primary); padding-bottom: 1px; }

.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 3px 8px;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-primary);
  background-color: var(--color-primary-soft);
  border-radius: var(--radius-sm);
}

.tag--accent { color: var(--color-accent); background-color: var(--color-highlight); }

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

/* ---------- header ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 60;
  background-color: var(--color-surface);
}

.skip-link {
  position: absolute;
  left: var(--space-2);
  top: -120px;
  z-index: 120;
  padding: 10px 16px;
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  border-radius: var(--radius-sm);
  transition: top 0.12s ease-out;
}

.skip-link:focus { top: var(--space-1); text-decoration: none; }

.header-top {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}

.header-top__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2) var(--space-4);
  min-height: 42px;
  padding-top: 6px;
  padding-bottom: 6px;
}

.brand-mark {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-2);
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  color: var(--color-contrast-ink);
}

.brand-mark__name { font-weight: var(--weight-heading); letter-spacing: 0.08em; }

.brand-mark__ver {
  padding: 2px 6px;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.04em;
  color: var(--color-contrast-accent);
  border: var(--border-thin) solid var(--color-contrast-line);
  border-radius: var(--radius-sm);
}

.header-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-1) var(--space-3);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: color-mix(in srgb, var(--color-contrast-ink) 68%, var(--color-contrast-surface));
}

.header-meta .meta-link {
  color: var(--color-contrast-ink);
  border-bottom: var(--border-thin) solid var(--color-contrast-line);
}

.header-meta .meta-link:hover { border-bottom-color: var(--color-contrast-accent); text-decoration: none; }

.header-bar {
  background-color: var(--color-surface);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.header-bar__inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-2) var(--space-4);
  min-height: 58px;
}

.nav-toggle {
  order: 1;
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: 9px 12px;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-ink-soft);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: color 0.12s ease-out, border-color 0.12s ease-out;
}

.nav-toggle__bars {
  position: relative;
  width: 16px;
  height: 10px;
  border-top: var(--border-thin) solid currentColor;
  border-bottom: var(--border-thin) solid currentColor;
}

.nav-toggle__bars::before {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  top: 4px;
  border-top: var(--border-thin) solid currentColor;
}

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

.primary-nav {
  order: 4;
  flex: 1 1 100%;
  display: none;
  padding: var(--space-1) 0 var(--space-2);
}

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

.nav-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.nav-link {
  display: inline-block;
  padding: 8px 0;
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
  border-bottom: 2px solid transparent;
  transition: color 0.12s ease-out, border-color 0.12s ease-out;
}

.nav-link:hover {
  color: var(--color-ink);
  border-bottom-color: var(--color-line);
  text-decoration: none;
}

.nav-link[aria-current="page"] {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
  font-weight: var(--weight-heading);
}

.header-tools {
  order: 2;
  flex: 1 1 180px;
  min-width: 0;
  margin-left: auto;
  display: flex;
  align-items: center;
}

.site-search {
  position: relative;
  width: 100%;
  max-width: 340px;
  margin-left: auto;
}

.search-prefix {
  position: absolute;
  left: 11px;
  top: 50%;
  transform: translateY(-50%);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
  pointer-events: none;
}

.search-input {
  width: 100%;
  min-width: 0;
  padding: 9px 12px 9px 26px;
  font-size: var(--text-sm);
  color: var(--color-ink);
  background-color: var(--color-surface-alt);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
}

.search-input::placeholder { color: var(--color-ink-muted); }

.search-input:focus-visible { border-color: var(--color-primary); }

.search-panel {
  position: absolute;
  left: 0;
  right: 0;
  top: calc(100% + 6px);
  z-index: 80;
  max-height: 340px;
  overflow-y: auto;
  padding: var(--space-1);
  background-color: var(--color-surface);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  animation: qy-fade-in 0.14s ease-out;
}

.search-panel[hidden] { display: none; }

.search-panel__item {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--space-2);
  padding: 9px 10px;
  font-size: var(--text-sm);
  color: var(--color-ink);
  border-radius: var(--radius-sm);
}

.search-panel__item[hidden] { display: none; }

.search-panel__item:hover,
.search-panel__item:focus-visible {
  background-color: var(--color-primary-soft);
  text-decoration: none;
}

.search-panel__item mark {
  background-color: var(--color-highlight);
  color: var(--color-ink);
  padding: 0 1px;
}

.search-panel__hint {
  flex: none;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
  white-space: nowrap;
}

.search-panel__empty {
  padding: 10px;
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
}

.search-panel__empty[hidden] { display: none; }

.header-badge {
  position: fixed;
  right: 12px;
  bottom: 12px;
  z-index: 70;
  order: 3;
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: 9px 12px;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.02em;
  color: var(--color-contrast-ink);
  background-color: var(--color-contrast-surface);
  border: var(--border-thin) solid var(--color-contrast-line);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-1);
  transition: border-color 0.12s ease-out, color 0.12s ease-out;
}

.header-badge:hover {
  color: var(--color-contrast-ink);
  border-color: var(--color-contrast-accent);
  text-decoration: none;
}

.header-badge__dot {
  width: 6px;
  height: 6px;
  background-color: var(--color-contrast-accent);
}

.scroll-progress {
  position: absolute;
  left: 0;
  right: 0;
  bottom: -1px;
  height: 2px;
  overflow: hidden;
  pointer-events: none;
}

.scroll-progress__bar {
  display: block;
  width: 100%;
  height: 100%;
  background-color: var(--color-focus);
  transform: scaleX(0);
  transform-origin: 0 50%;
  transition: transform 0.12s linear;
}

@media (min-width: 900px) {
  .nav-toggle { display: none; }
  .primary-nav {
    order: 0;
    flex: 1 1 auto;
    display: block;
    padding: 0;
  }
  .nav-list { flex-direction: row; flex-wrap: wrap; gap: var(--space-1) var(--space-3); }
  .nav-link { padding: 18px 0; }
  .site-search { max-width: 220px; }
}

@media (min-width: 1024px) {
  .header-badge {
    position: static;
    margin-left: var(--space-1);
    transition: border-color 0.12s ease-out, color 0.12s ease-out, background-color 0.12s ease-out;
  }
  .header-badge:hover { background-color: color-mix(in srgb, var(--color-contrast-surface) 88%, var(--color-contrast-accent)); }
}

@media (min-width: 1200px) {
  .site-search { max-width: 260px; }
}

@keyframes qy-fade-in {
  from { opacity: 0; transform: translateY(-4px); }
  to { opacity: 1; transform: none; }
}

/* ---------- footer ---------- */
.site-footer {
  margin-top: var(--section-y);
  padding: var(--space-8) 0 var(--space-4);
  background-color: var(--color-surface-alt);
  border-top: var(--border-thin) solid var(--color-line);
}

.footer-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-4);
}

.footer-panel { min-width: 0; }

.footer-panel--brand {
  padding: var(--space-4) var(--space-3);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-radius: var(--radius-sm);
}

.footer-brand {
  font-family: var(--font-heading);
  font-size: var(--text-xl);
  font-weight: var(--weight-heading);
  letter-spacing: 0.06em;
  color: var(--color-contrast-ink);
}

.footer-tagline {
  margin-top: var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.02em;
  color: var(--color-contrast-accent);
}

.footer-note {
  margin-top: var(--space-2);
  font-size: var(--text-sm);
  line-height: 1.7;
  color: color-mix(in srgb, var(--color-ink) 100%, transparent);
}

.footer-panel--brand .footer-note {
  color: color-mix(in srgb, var(--color-contrast-ink) 74%, var(--color-contrast-surface));
}

.footer-icp {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-1) var(--space-2);
  margin-top: var(--space-3);
  padding-top: var(--space-2);
  border-top: var(--border-thin) solid var(--color-contrast-line);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: color-mix(in srgb, var(--color-contrast-ink) 78%, var(--color-contrast-surface));
}

.copy-btn {
  padding: 3px 8px;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-primary);
  background-color: transparent;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: color 0.12s ease-out, background-color 0.12s ease-out, border-color 0.12s ease-out;
}

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

.copy-btn.is-copied {
  color: var(--color-accent);
  border-color: var(--color-accent);
}

.footer-panel--brand .copy-btn {
  color: var(--color-contrast-ink);
  border-color: var(--color-contrast-line);
}

.footer-panel--brand .copy-btn:hover {
  color: var(--color-accent-ink);
  background-color: var(--color-contrast-accent);
  border-color: var(--color-contrast-accent);
}

.footer-title {
  font-family: var(--font-heading);
  font-size: var(--text-base);
  font-weight: var(--weight-heading);
  letter-spacing: 0.06em;
  color: var(--color-ink);
  padding-bottom: var(--space-1);
  border-bottom: var(--border-thin) solid var(--color-line);
  margin-bottom: var(--space-2);
}

.footer-list li { margin-bottom: var(--space-1); }

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

.footer-list a:hover { color: var(--color-primary); }

.footer-list--contact li {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: var(--space-2);
  align-items: baseline;
  margin-bottom: var(--space-2);
}

.footer-label {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
  white-space: nowrap;
}

.footer-value { font-size: var(--text-sm); color: var(--color-ink); }

.footer-panel--contact {
  padding: var(--space-4) var(--space-3);
  background-color: var(--color-surface);
  border-radius: var(--radius-sm);
}

.footer-bottom {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2) var(--space-4);
  margin-top: var(--space-6);
  padding-top: var(--space-3);
  border-top: var(--border-thin) solid var(--color-line);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
}

.footer-legal { display: flex; flex-wrap: wrap; gap: var(--space-3); }
.footer-legal a { color: var(--color-ink-soft); }
.footer-legal a:hover { color: var(--color-primary); }

@media (min-width: 820px) {
  .footer-grid { grid-template-columns: 1.3fr 1fr 1.4fr; gap: var(--space-4); }
  .footer-panel + .footer-panel {
    padding-left: var(--space-4);
    border-left: var(--border-thin) solid var(--color-line);
  }
}

/* ---------- buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-1);
  padding: 11px 20px;
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  font-weight: var(--weight-heading);
  letter-spacing: 0.01em;
  color: var(--color-ink);
  background-color: transparent;
  border: var(--border-thin) solid transparent;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: color 0.12s ease-out, background-color 0.12s ease-out, border-color 0.12s ease-out;
}

.btn:hover { text-decoration: none; }

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

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

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

.btn--dark:hover { border-color: var(--color-contrast-accent); }

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

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

.btn--sm { padding: 7px 14px; font-size: var(--text-xs); }

/* ---------- breadcrumbs ---------- */
.breadcrumbs {
  margin-bottom: var(--space-3);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
}

.breadcrumbs ol {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-1);
}

.breadcrumbs li { display: flex; align-items: center; gap: var(--space-1); }

.breadcrumbs li::after {
  content: "/";
  color: var(--color-line);
}

.breadcrumbs li:last-child::after { content: ""; }

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

/* ---------- doc shell / rail index ---------- */
.doc-shell {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-6);
  align-items: start;
}

@media (min-width: 1024px) {
  .doc-shell { grid-template-columns: minmax(0, 3fr) minmax(0, 9fr); }
  .doc-body { max-width: none; }
}

.doc-rail { position: relative; }

@media (min-width: 1024px) {
  .doc-rail { position: sticky; top: 132px; }
}

.rail-title {
  padding-bottom: var(--space-2);
  margin-bottom: var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.rail-list { position: relative; }

.rail-link {
  display: block;
  padding: 9px 0 9px 14px;
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
  border-left: var(--border-thin) solid var(--color-line);
  transition: color 0.12s ease-out, border-color 0.12s ease-out;
}

.rail-link:hover { color: var(--color-ink); text-decoration: none; }

.rail-link.is-active,
.rail-link[aria-current] {
  color: var(--color-primary);
  border-left-color: var(--color-primary);
  font-weight: var(--weight-heading);
}

.rail-marker {
  position: absolute;
  left: -1px;
  top: 0;
  width: 2px;
  height: 0;
  background-color: var(--color-focus);
  pointer-events: none;
  transition: transform 0.16s ease-out, height 0.16s ease-out;
}

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

.prose p { margin-bottom: var(--space-3); }

.prose h2 {
  margin: var(--space-6) 0 var(--space-2);
  font-size: var(--text-2xl);
}

.prose h3 {
  margin: var(--space-4) 0 var(--space-2);
  font-size: var(--text-xl);
}

.prose ul, .prose ol { margin: 0 0 var(--space-3); }

.prose li {
  position: relative;
  padding-left: var(--space-3);
  margin-bottom: var(--space-1);
}

.prose ul > li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.8em;
  width: 8px;
  height: 1px;
  background-color: var(--color-accent);
}

.prose ol { counter-reset: qy-item; }

.prose ol > li { counter-increment: qy-item; padding-left: var(--space-4); }

.prose ol > li::before {
  content: counter(qy-item, decimal-leading-zero);
  position: absolute;
  left: 0;
  top: 0.15em;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-accent);
}

/* ---------- steps ---------- */
.step-list { display: grid; gap: var(--space-4); }

.step {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: var(--space-3);
  align-items: start;
}

.step-badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 26px;
  height: 26px;
  padding: 0 6px;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-primary-ink);
  background-color: var(--color-ink-muted);
  border-radius: var(--radius-sm);
  transition: background-color 0.18s ease-out, color 0.18s ease-out;
}

.step.is-visible .step-badge,
.step.is-current .step-badge { background-color: var(--color-accent); }

.step__title {
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  color: var(--color-ink);
  margin-bottom: var(--space-1);
}

.step__body { max-width: var(--measure); color: var(--color-ink-soft); }

.panel--dark .step__title { color: var(--color-contrast-ink); }

.panel--dark .step-badge {
  color: var(--color-contrast-accent);
  background-color: transparent;
  border: var(--border-thin) solid var(--color-contrast-accent);
}

.panel--dark .step.is-visible .step-badge,
.panel--dark .step.is-current .step-badge {
  color: var(--color-contrast-surface);
  background-color: var(--color-contrast-accent);
}

/* ---------- expander ---------- */
.expander {
  padding: var(--space-2) 0;
  border-top: var(--border-thin) solid var(--color-line);
}

.expander:last-of-type { border-bottom: var(--border-thin) solid var(--color-line); }

.expander__summary {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
  padding: var(--space-1) 0;
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  color: var(--color-ink);
  cursor: pointer;
  list-style: none;
}

.expander__summary::-webkit-details-marker { display: none; }

.expander__summary::before {
  content: "+";
  flex: none;
  width: 18px;
  font-family: var(--font-mono);
  font-size: var(--text-base);
  color: var(--color-primary);
}

.expander[open] > .expander__summary::before { content: "−"; color: var(--color-accent); }

.expander__summary:hover { color: var(--color-primary); }

.expander__body {
  padding: var(--space-1) 0 var(--space-3) calc(18px + var(--space-2));
  max-width: var(--measure);
  font-size: var(--text-base);
  color: var(--color-ink-soft);
}

/* ---------- figure / image containers ---------- */
.figure { margin: 0; }

.figure__frame {
  position: relative;
  overflow: hidden;
  background-color: var(--color-surface-deep);
  border-radius: var(--radius-sm);
}

.figure__frame[data-texture="grid"]::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(var(--color-line) 1px, transparent 1px),
    linear-gradient(90deg, var(--color-line) 1px, transparent 1px);
  background-size: 32px 32px;
  opacity: 0.55;
}

.figure__frame img {
  position: relative;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.figure--wide .figure__frame { aspect-ratio: 16 / 9; }
.figure--tall .figure__frame { aspect-ratio: 3 / 4; }
.figure--square .figure__frame { aspect-ratio: 1 / 1; }
.figure--band .figure__frame { aspect-ratio: 21 / 6; }

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

.figure__overlay {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  padding: var(--space-3);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.02em;
  color: var(--color-contrast-ink);
}

.figure__caption {
  margin-top: var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
}

.figure--4 { grid-column: span 4; }
.figure--5 { grid-column: span 5; }
.figure--6 { grid-column: span 6; }
.figure--7 { grid-column: span 7; }
.figure--8 { grid-column: span 8; }
.figure--12 { grid-column: span 12; }

@media (max-width: 719px) {
  .figure--4, .figure--5, .figure--6, .figure--7, .figure--8 {
    grid-column: span 12;
  }
}

/* ---------- table ---------- */
.doc-table {
  width: 100%;
  font-size: var(--text-sm);
  border-top: var(--border-thin) solid var(--color-line);
}

.doc-table caption {
  padding-bottom: var(--space-1);
  text-align: left;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
}

.doc-table th,
.doc-table td {
  padding: 11px 12px;
  text-align: left;
  vertical-align: top;
  border-bottom: var(--border-thin) solid var(--color-line);
}

.doc-table thead th {
  background-color: var(--color-surface-deep);
  font-family: var(--font-heading);
  font-size: var(--text-xs);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--color-ink);
}

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

.doc-table td.num,
.doc-table th.num { font-family: var(--font-mono); font-variant-numeric: tabular-nums; }

/* ---------- panels & cards ---------- */
.panel {
  padding: var(--space-4);
  background-color: var(--color-surface-alt);
  border-radius: var(--radius-sm);
}

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

.panel--dark {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}

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

.panel--dark p { color: color-mix(in srgb, var(--color-contrast-ink) 82%, var(--color-contrast-surface)); }

.panel--dark a { color: var(--color-contrast-accent); }

.panel--dark .rule-hair,
.panel--dark .guide-line { border-color: var(--color-contrast-line); background-color: var(--color-contrast-line); }

.card {
  padding: var(--space-3);
  background-color: var(--color-surface);
  border-radius: var(--radius-sm);
}

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

/* ---------- reveal ---------- */
.reveal {
  opacity: 0;
  transform: translateY(10px);
  transition: opacity 0.22s ease-out, transform 0.22s ease-out;
}

.reveal.is-visible { opacity: 1; transform: none; }

/* ---------- motion preferences ---------- */
@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;
  }

  .reveal { opacity: 1; transform: none; }
  .scroll-progress__bar { transition: none; }
  .rail-marker { transition: none; }
}