/* ============================================================
   大江体育 · 共享外壳样式 /assets/site.css
   浅色坐标纸 + 墨底指挥栏 + 赤铜编号 + 荧光绿脉冲
   ============================================================ */

/* ---------- reset ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
@media (prefers-reduced-motion: no-preference) { html { scroll-behavior: smooth; } }
body {
  margin: 0;
  background: var(--snow);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: 17px;
  line-height: 1.75;
  font-variant-numeric: tabular-nums;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
h1, h2, h3, h4, h5, p, ul, ol, figure, blockquote { margin: 0; }
ul, ol { padding: 0; list-style: none; }
a { color: inherit; text-decoration: none; }
button, input, select, textarea { font: inherit; color: inherit; }
button { background: none; border: 0; padding: 0; cursor: pointer; }
img, svg, video { display: block; max-width: 100%; }
[hidden] { display: none !important; }

/* ---------- variables ---------- */
:root {
  --snow: #EEF3F5;
  --snow-mid: #D2DDE3;
  --line: #B4C3CB;
  --copper: #B0522B;
  --copper-deep: #7A341A;
  --ink: #0D1418;
  --ink-soft: #1C272D;
  --pulse: #C8FF4D;
  --signal: #FF7A18;
  --sand: #6B5843;
  --text: #14202A;

  --font-sans: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Source Han Sans SC", "Noto Sans CJK SC", system-ui, -apple-system, "Segoe UI", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "Liberation Mono", "Courier New", monospace;

  --r-lg: 28px;
  --r-md: 20px;
  --r-sm: 12px;
  --r-pill: 999px;

  --shell: 1280px;
  --gutter: 24px;
  --bar-h: 64px;
  --bar-h-compact: 52px;
  --ease: cubic-bezier(0.22, 0.61, 0.36, 1);
  --dur: 260ms;
  --section-gap: clamp(64px, 9vw, 120px);
}

/* ---------- focus ---------- */
:focus-visible {
  outline: 2px solid var(--signal);
  outline-offset: 3px;
  border-radius: 6px;
}
.site-footer :focus-visible,
.site-header :focus-visible { outline-color: var(--pulse); }

/* ---------- skip link ---------- */
.skip-link {
  position: absolute;
  left: 16px;
  top: 8px;
  z-index: 200;
  transform: translateY(-180%);
  background: var(--pulse);
  color: var(--ink);
  padding: 10px 18px;
  border-radius: var(--r-pill);
  font-size: 14px;
  font-weight: 700;
  letter-spacing: 0.02em;
  transition: transform 200ms var(--ease);
}
.skip-link:focus-visible { transform: translateY(0); }

/* ============================================================
   HEADER · 紧凑命令栏
   ============================================================ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(13, 20, 24, 0.94);
  color: var(--snow);
  -webkit-backdrop-filter: blur(12px);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(180, 195, 203, 0.16);
  transition: background var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}
.site-header[data-scrolled] {
  background: rgba(8, 13, 16, 0.98);
  box-shadow: 0 14px 34px rgba(13, 20, 24, 0.3);
}

.command-bar { position: relative; }

.bar-inner {
  position: relative;
  max-width: var(--shell);
  margin: 0 auto;
  padding: 0 var(--gutter);
  height: var(--bar-h);
  display: flex;
  align-items: center;
  gap: 20px;
  transition: height var(--dur) var(--ease);
}
.site-header[data-scrolled] .bar-inner { height: var(--bar-h-compact); }

/* --- brand --- */
.brand-mark {
  flex: 0 0 auto;
  display: flex;
  align-items: center;
  gap: 12px;
}
.brand-rule {
  display: block;
  width: 1px;
  height: 26px;
  background: var(--line);
  flex: 0 0 auto;
}
.brand-name {
  font-size: 19px;
  font-weight: 900;
  letter-spacing: 0.04em;
  line-height: 1;
  color: #FFFFFF;
  white-space: nowrap;
}

/* --- primary nav --- */
.primary-nav { flex: 1 1 auto; min-width: 0; }
.nav-list {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 2px;
}
.nav-item { flex: 0 0 auto; }
.nav-link {
  display: inline-block;
  padding: 8px 13px;
  border-radius: var(--r-pill);
  border: 1px solid transparent;
  font-size: 13.5px;
  font-weight: 600;
  letter-spacing: 0.02em;
  line-height: 1.2;
  color: rgba(238, 243, 245, 0.72);
  transition: color 180ms var(--ease), background 180ms var(--ease), border-color 180ms var(--ease);
}
.nav-link:hover { color: #FFFFFF; background: rgba(238, 243, 245, 0.08); }
.nav-link[aria-current="page"] {
  color: var(--pulse);
  border-color: var(--pulse);
  background: rgba(200, 255, 77, 0.08);
}

/* --- tools --- */
.bar-tools {
  position: relative;
  flex: 0 0 auto;
  display: flex;
  align-items: center;
  gap: 10px;
}

.chip-button {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 14px;
  border-radius: var(--r-pill);
  border: 1px solid rgba(180, 195, 203, 0.35);
  background: rgba(28, 39, 45, 0.6);
  color: var(--snow);
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0.02em;
  line-height: 1.2;
  transition: border-color 180ms var(--ease), color 180ms var(--ease), background 180ms var(--ease);
}
.chip-button:hover { border-color: var(--signal); color: #FFFFFF; }
.chip-button[aria-expanded="true"] {
  border-color: var(--pulse);
  color: var(--pulse);
  background: rgba(200, 255, 77, 0.08);
}
.chip-button__label { white-space: nowrap; }
.chip-button__caret {
  width: 8px;
  height: 8px;
  flex: 0 0 auto;
  border-right: 2px solid currentColor;
  border-bottom: 2px solid currentColor;
  transform: rotate(45deg) translate(-1px, -1px);
  transition: transform 220ms var(--ease);
}
.chip-button[aria-expanded="true"] .chip-button__caret { transform: rotate(-135deg) translate(-1px, -1px); }

.round-coordinate {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 16px;
  border-radius: var(--r-pill);
  background: var(--ink-soft);
  border: 1px solid rgba(200, 255, 77, 0.35);
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: 0.04em;
  line-height: 1.2;
  color: var(--pulse);
  white-space: nowrap;
  transition: background 200ms var(--ease), transform 200ms var(--ease);
}
.round-coordinate:hover { background: #243239; transform: translateY(-1px); }
.round-coordinate::before {
  content: "";
  width: 7px;
  height: 7px;
  flex: 0 0 auto;
  border-radius: 50%;
  background: var(--pulse);
  animation: round-pulse 1.6s ease-in-out infinite;
}
@keyframes round-pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.25; }
}
.round-coordinate__key { color: rgba(238, 243, 245, 0.6); }
.round-coordinate__value { font-weight: 700; }

.nav-toggle {
  display: none;
  align-items: center;
  gap: 8px;
  padding: 8px 14px;
  border-radius: var(--r-pill);
  border: 1px solid rgba(180, 195, 203, 0.35);
  color: var(--snow);
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0.02em;
  transition: border-color 180ms var(--ease), color 180ms var(--ease);
}
.nav-toggle__bars { display: inline-flex; flex-direction: column; gap: 4px; }
.nav-toggle__bars i {
  display: block;
  width: 16px;
  height: 2px;
  background: currentColor;
  transition: transform 220ms var(--ease);
}
.nav-toggle__text { white-space: nowrap; }
.nav-toggle[aria-expanded="true"] { border-color: var(--pulse); color: var(--pulse); }
.nav-toggle[aria-expanded="true"] .nav-toggle__bars i:first-child { transform: translateY(3px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] .nav-toggle__bars i:last-child { transform: translateY(-3px) rotate(-45deg); }

/* --- field jump panel --- */
.field-panel {
  position: absolute;
  top: calc(100% + 8px);
  right: max(16px, calc((100vw - var(--shell)) / 2 + var(--gutter)));
  z-index: 110;
  width: min(340px, calc(100vw - 32px));
  padding: 18px;
  border-radius: var(--r-md);
  background: var(--ink-soft);
  border: 1px solid rgba(180, 195, 203, 0.2);
  box-shadow: 0 26px 54px rgba(5, 9, 11, 0.55);
}
.field-panel__title {
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.1em;
  color: rgba(200, 255, 77, 0.8);
  margin-bottom: 12px;
}
.field-panel__list {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 8px;
}
.field-link {
  display: block;
  padding: 10px 12px;
  border-radius: var(--r-sm);
  background: rgba(238, 243, 245, 0.05);
  border: 1px solid rgba(180, 195, 203, 0.18);
  font-size: 13.5px;
  font-weight: 600;
  color: var(--snow);
  transition: background 180ms var(--ease), border-color 180ms var(--ease), color 180ms var(--ease);
}
.field-link:hover { background: rgba(255, 122, 24, 0.14); border-color: var(--signal); color: #FFFFFF; }

/* --- utility line --- */
.utility-line {
  max-height: 48px;
  overflow: hidden;
  border-top: 1px solid rgba(180, 195, 203, 0.14);
  transition: max-height 280ms var(--ease), opacity 200ms var(--ease), border-color 200ms var(--ease);
}
.site-header[data-scrolled] .utility-line {
  max-height: 0;
  opacity: 0;
  border-color: transparent;
}
.utility-line__inner {
  max-width: var(--shell);
  margin: 0 auto;
  padding: 9px var(--gutter) 10px;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px 24px;
}
.utility-line__item {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.03em;
  color: rgba(238, 243, 245, 0.55);
  white-space: nowrap;
}
.utility-line__item:first-child::before {
  content: "";
  display: inline-block;
  width: 6px;
  height: 6px;
  margin-right: 8px;
  border-radius: 50%;
  background: var(--pulse);
  vertical-align: middle;
}
.utility-line__item--muted { color: rgba(238, 243, 245, 0.34); }

/* --- scroll progress --- */
.scroll-progress {
  position: absolute;
  left: 0;
  bottom: 0;
  width: 100%;
  height: 2px;
  transform: scaleX(0);
  transform-origin: 0 50%;
  background: linear-gradient(90deg, var(--copper) 0%, var(--signal) 52%, var(--pulse) 100%);
  transition: transform 120ms linear;
}

/* ============================================================
   FOOTER · 指挥中心墨底
   ============================================================ */
.site-footer {
  background: var(--ink);
  color: var(--snow);
  padding: clamp(48px, 7vw, 84px) var(--gutter) 32px;
  font-size: 14.5px;
  line-height: 1.65;
}
.footer-inner {
  max-width: var(--shell);
  margin: 0 auto;
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(0, 1.55fr);
  gap: clamp(32px, 5vw, 72px);
  padding-bottom: 36px;
  border-bottom: 1px solid rgba(180, 195, 203, 0.16);
}
.footer-brand {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 14px;
}
.footer-brand__head { display: flex; align-items: center; gap: 12px; }
.footer-brand__name {
  font-size: clamp(24px, 2.6vw, 34px);
  font-weight: 900;
  letter-spacing: -0.01em;
  line-height: 1.1;
  color: #FFFFFF;
}
.footer-brand__id {
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: 0.06em;
  color: var(--pulse);
}
.footer-brand__data {
  max-width: 46ch;
  font-size: 14px;
  color: rgba(238, 243, 245, 0.62);
}
.footer-columns {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 28px;
}
.footer-column__title {
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.12em;
  color: rgba(200, 255, 77, 0.85);
  margin-bottom: 14px;
}
.footer-links { display: flex; flex-direction: column; gap: 10px; }
.footer-link {
  width: fit-content;
  font-size: 14.5px;
  color: rgba(238, 243, 245, 0.72);
  transition: color 180ms var(--ease);
}
.footer-link:hover {
  color: #FFFFFF;
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 4px;
}
.footer-contact {
  max-width: var(--shell);
  margin: 0 auto;
  padding-top: 26px;
  display: grid;
  grid-template-columns: minmax(0, 2fr) minmax(0, 1fr);
  gap: 12px 40px;
  align-items: start;
}
.footer-contact__item {
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.02em;
  color: rgba(238, 243, 245, 0.72);
}
.footer-contact__note {
  font-size: 13px;
  color: rgba(238, 243, 245, 0.45);
}
.footer-base {
  max-width: var(--shell);
  margin: 26px auto 0;
  padding-top: 18px;
  border-top: 1px solid rgba(180, 195, 203, 0.12);
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 10px 28px;
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: 0.03em;
  color: rgba(238, 243, 245, 0.45);
}

/* ============================================================
   通用组件
   ============================================================ */
.container,
.page-shell {
  width: 100%;
  max-width: var(--shell);
  margin: 0 auto;
  padding: 0 var(--gutter);
}
.page-shell {
  padding-top: clamp(40px, 6vw, 72px);
  padding-bottom: clamp(56px, 8vw, 104px);
}

/* --- button --- */
.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 22px;
  border-radius: var(--r-pill);
  border: 1px solid var(--copper);
  background: var(--copper);
  color: #FFFFFF;
  font-size: 14px;
  font-weight: 700;
  letter-spacing: 0.02em;
  line-height: 1.2;
  transition: background 200ms var(--ease), border-color 200ms var(--ease), color 200ms var(--ease), transform 200ms var(--ease);
}
.button:hover { background: var(--copper-deep); border-color: var(--copper-deep); transform: translateY(-1px); }
.button--signal { background: var(--signal); border-color: var(--signal); color: #22120A; }
.button--signal:hover { background: #FF903C; border-color: #FF903C; color: #22120A; }
.button--ghost { background: transparent; border-color: var(--line); color: var(--copper-deep); }
.button--ghost:hover { background: var(--snow-mid); border-color: var(--copper); color: var(--copper-deep); }
.button--pulse { background: transparent; border-color: var(--pulse); color: var(--pulse); }
.button--pulse:hover { background: rgba(200, 255, 77, 0.12); color: var(--pulse); }

/* --- chip --- */
.chip {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 12px;
  border-radius: var(--r-pill);
  border: 1px solid transparent;
  background: var(--snow-mid);
  color: var(--copper-deep);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.05em;
  line-height: 1.5;
}
.chip--copper { background: var(--copper); color: #FFFFFF; }
.chip--pulse { background: transparent; border-color: var(--pulse); color: var(--pulse); }
.chip--signal { background: var(--signal); color: #22120A; }

/* --- breadcrumb --- */
.breadcrumb { margin-bottom: 24px; }
.breadcrumb__list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.04em;
  color: var(--sand);
}
.breadcrumb__item { display: inline-flex; align-items: center; }
.breadcrumb__item::after { content: "/"; margin-left: 8px; color: var(--line); }
.breadcrumb__item:last-child::after { content: none; }
.breadcrumb__link {
  color: var(--sand);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}
.breadcrumb__link:hover { color: var(--copper-deep); }
.breadcrumb__current { color: var(--text); font-weight: 700; }

/* --- grid --- */
.grid { display: grid; gap: var(--gutter); }
.grid--12 { grid-template-columns: repeat(12, minmax(0, 1fr)); }
.col-4 { grid-column: span 4; }
.col-5 { grid-column: span 5; }
.col-7 { grid-column: span 7; }
.col-8 { grid-column: span 8; }
.col-12 { grid-column: span 12; }

/* --- section head --- */
.section-head {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  align-items: baseline;
  gap: 6px 20px;
  margin-bottom: 28px;
}
.section-head__number {
  font-family: var(--font-mono);
  font-size: clamp(38px, 6vw, 72px);
  font-weight: 700;
  line-height: 0.9;
  letter-spacing: -0.02em;
  color: var(--copper);
}
.section-head__title {
  font-size: clamp(24px, 3vw, 40px);
  font-weight: 900;
  letter-spacing: -0.02em;
  line-height: 1.15;
  color: var(--text);
}
.section-head__note {
  grid-column: 2;
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.03em;
  color: var(--sand);
}

/* --- index rail --- */
.index-rail {
  position: sticky;
  top: calc(var(--bar-h-compact) + 24px);
  align-self: start;
}
.index-rail__title {
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.12em;
  color: var(--copper);
  margin-bottom: 14px;
}
.index-rail__list { display: flex; flex-direction: column; gap: 2px; }
.index-link {
  display: flex;
  gap: 10px;
  padding: 9px 12px;
  border-radius: var(--r-sm);
  border-left: 1px solid var(--line);
  font-size: 14px;
  color: var(--text);
  transition: background 180ms var(--ease), color 180ms var(--ease), border-color 180ms var(--ease);
}
.index-link:hover { background: var(--snow-mid); border-color: var(--copper); }
.index-link[aria-current="true"] { background: var(--copper); border-color: var(--copper); color: #FFFFFF; }

/* --- card --- */
.card {
  background: #FFFFFF;
  border: 1px solid var(--line);
  border-radius: var(--r-md);
  padding: 24px;
  transition: border-color 240ms var(--ease), transform 240ms var(--ease);
}
.card:hover { border-color: var(--copper); transform: translateY(-2px); }
.card__title {
  font-size: 20px;
  font-weight: 900;
  letter-spacing: -0.01em;
  line-height: 1.3;
  margin-bottom: 8px;
}
.card__body { max-width: 60ch; font-size: 16px; color: var(--text); }
.card--dark { background: var(--ink); border-color: rgba(180, 195, 203, 0.18); color: var(--snow); }
.card--dark:hover { border-color: rgba(200, 255, 77, 0.5); }
.card--dark .card__title { color: #FFFFFF; }
.card--dark .card__body { color: rgba(238, 243, 245, 0.75); }
.card--copper { background: var(--copper); border-color: var(--copper); color: #FFFFFF; }
.card--copper .card__title { color: #FFFFFF; }
.card--copper .card__body { color: rgba(255, 255, 255, 0.86); }
.card--bleed { margin-right: calc(-1 * clamp(0px, 2vw, 48px)); }

/* --- legend --- */
.legend {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 20px;
  padding: 14px 16px;
  border-radius: var(--r-sm);
  background: var(--snow-mid);
  font-size: 13px;
  color: var(--sand);
}
.legend__item { display: inline-flex; align-items: center; gap: 8px; }
.legend__swatch {
  width: 14px;
  height: 3px;
  border-radius: 2px;
  background: var(--copper);
  flex: 0 0 auto;
}
.legend__swatch--pulse { background: var(--pulse); }
.legend__swatch--signal { background: var(--signal); }

/* --- media frame --- */
.media-frame {
  position: relative;
  width: 100%;
  aspect-ratio: 16 / 9;
  overflow: hidden;
  border-radius: var(--r-lg);
  background: var(--snow-mid);
}
.media-frame--tall { aspect-ratio: 4 / 5; }
.media-frame--wide { aspect-ratio: 21 / 9; }
.media-frame img,
.media-frame video { width: 100%; height: 100%; object-fit: cover; }
.media-frame::after {
  content: "";
  position: absolute;
  inset: 0;
  pointer-events: none;
  background: linear-gradient(180deg, rgba(13, 20, 24, 0) 42%, rgba(13, 20, 24, 0.62) 100%);
}
.media-frame__caption {
  position: absolute;
  left: 18px;
  right: 18px;
  bottom: 16px;
  z-index: 1;
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: 0.03em;
  color: #FFFFFF;
  text-shadow: 0 1px 14px rgba(0, 0, 0, 0.65);
}

/* --- round axis --- */
.round-axis {
  position: relative;
  overflow-x: auto;
  overflow-y: hidden;
  scroll-snap-type: x proximity;
  padding: 6px 0 14px;
  -webkit-overflow-scrolling: touch;
  -webkit-mask-image: linear-gradient(90deg, transparent 0, #000 26px, #000 calc(100% - 26px), transparent 100%);
  mask-image: linear-gradient(90deg, transparent 0, #000 26px, #000 calc(100% - 26px), transparent 100%);
}
.round-axis__track { position: relative; display: flex; min-width: max-content; }
.round-axis__track::before {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  top: 37px;
  height: 1px;
  background: var(--line);
}
.round-axis__cell {
  position: relative;
  flex: 0 0 auto;
  width: 104px;
  padding: 0 8px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
  text-align: center;
  scroll-snap-align: center;
}
.round-axis__label {
  height: 26px;
  display: flex;
  align-items: center;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.04em;
  color: var(--sand);
}
.round-axis__mark {
  position: relative;
  z-index: 1;
  flex: 0 0 auto;
  width: 11px;
  height: 11px;
  border-radius: 50%;
  background: var(--snow);
  border: 2px solid var(--copper);
}
.round-axis__cell[data-current] .round-axis__mark {
  background: var(--pulse);
  border-color: var(--pulse);
  box-shadow: 0 0 0 4px rgba(200, 255, 77, 0.2);
}
.round-axis__score {
  margin-top: 6px;
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--text);
  white-space: nowrap;
}

/* --- fold --- */
.fold {
  border: 1px solid var(--line);
  border-radius: var(--r-md);
  background: #FFFFFF;
  overflow: hidden;
}
.fold + .fold { margin-top: 12px; }
.fold-head {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 16px 20px;
  text-align: left;
  font-size: 16px;
  font-weight: 700;
  color: var(--text);
  background: #FFFFFF;
  transition: background 200ms var(--ease), color 200ms var(--ease);
}
.fold-head:hover { background: var(--snow); }
.fold[data-open] .fold-head { background: var(--snow-mid); }
.fold-head__arrow {
  flex: 0 0 auto;
  width: 9px;
  height: 9px;
  border-right: 2px solid var(--copper);
  border-bottom: 2px solid var(--copper);
  transform: rotate(45deg);
  transition: transform 240ms var(--ease);
}
.fold[data-open] .fold-head__arrow { transform: rotate(-135deg); }
.fold-panel { overflow: hidden; transition: height 260ms var(--ease); }
.fold-panel__inner {
  margin-left: 20px;
  padding: 0 20px 20px 16px;
  border-left: 3px solid transparent;
  font-size: 16px;
  color: var(--text);
}
.fold[data-open] .fold-panel__inner { border-left-color: var(--pulse); }

/* --- stat --- */
.stat { display: flex; flex-direction: column; gap: 4px; }
.stat__value {
  font-family: var(--font-mono);
  font-size: clamp(28px, 3.4vw, 44px);
  font-weight: 700;
  letter-spacing: 0.02em;
  line-height: 1;
  color: var(--copper);
}
.stat__label {
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.05em;
  color: var(--sand);
}
.card--dark .stat__value { color: var(--pulse); }
.card--dark .stat__label { color: rgba(238, 243, 245, 0.6); }

/* --- reveal --- */
html.js-reveal [data-reveal] {
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 420ms var(--ease) var(--reveal-delay, 0ms), transform 420ms var(--ease) var(--reveal-delay, 0ms);
}
html.js-reveal [data-reveal].is-revealed { opacity: 1; transform: none; }

/* ============================================================
   响应式
   ============================================================ */
@media (max-width: 1150px) {
  .nav-link { padding: 8px 10px; font-size: 13px; }
  .round-coordinate { padding: 8px 12px; }
}

@media (max-width: 1080px) {
  .nav-toggle { display: inline-flex; }
  .primary-nav {
    position: absolute;
    left: 0;
    right: 0;
    top: 100%;
    z-index: 105;
    display: none;
    padding: 10px 16px 18px;
    background: rgba(9, 14, 17, 0.99);
    border-bottom: 1px solid rgba(180, 195, 203, 0.16);
    -webkit-backdrop-filter: blur(12px);
    backdrop-filter: blur(12px);
  }
  .site-header[data-open] .primary-nav { display: block; animation: nav-in 220ms var(--ease); }
  @keyframes nav-in {
    from { opacity: 0; transform: translateY(-8px); }
    to { opacity: 1; transform: none; }
  }
  .nav-list { flex-direction: column; align-items: stretch; gap: 4px; }
  .nav-link { display: block; padding: 13px 16px; font-size: 15px; border-radius: var(--r-md); }
  .nav-link[aria-current="page"] { background: rgba(200, 255, 77, 0.1); }
}

@media (max-width: 900px) {
  .utility-line { display: none; }
  .footer-inner { grid-template-columns: minmax(0, 1fr); }
}

@media (max-width: 860px) {
  .grid--12 { grid-template-columns: minmax(0, 1fr); }
  .col-4, .col-5, .col-7, .col-8, .col-12 { grid-column: 1 / -1; }
  .index-rail { position: static; }
  .card--bleed { margin-right: 0; }
  .footer-contact { grid-template-columns: minmax(0, 1fr); }
}

@media (max-width: 640px) {
  :root { --gutter: 20px; --r-lg: 22px; --r-md: 18px; }
  body { font-size: 16.5px; }
  .brand-name { font-size: 17px; }
  .field-jump { padding: 8px 12px; font-size: 12.5px; }
  .round-coordinate { padding: 7px 11px; font-size: 11.5px; }
  .field-panel {
    left: 12px;
    right: 12px;
    width: auto;
    top: calc(100% + 6px);
  }
  .footer-columns { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 24px; }
  .footer-contact__item { font-size: 12.5px; }
  .section-head { gap: 4px 14px; }
}

@media (max-width: 520px) {
  .round-coordinate__key { display: none; }
  .chip-button__label { display: none; }
  .chip-button { padding: 8px 11px; }
  .footer-columns { grid-template-columns: minmax(0, 1fr); }
  .footer-base { flex-direction: column; gap: 6px; }
}

/* ============================================================
   动效降级
   ============================================================ */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
  }
  html { scroll-behavior: auto !important; }
  .round-coordinate::before { animation: none; opacity: 1; }
  html.js-reveal [data-reveal] { opacity: 1; transform: none; }
  .round-axis { scroll-snap-type: none; }
}