/* ==========================================================================
   B体育赛场 — 共享样式 /assets/site.css
   分区：变量 → 重置 → 基础排版 → 工具 → 按钮标签 → 头部 → 页脚 → 组件
   ========================================================================== */

/* ---------- 1. 变量 ---------- */
:root {
  --color-danxia: #9E3B27;
  --color-danxia-deep: #6B2318;
  --color-night: #101C33;
  --color-teal-deep: #0E3438;
  --color-gold: #C8912F;
  --color-sand: #E9D3A6;
  --color-cyan: #2FD4C3;
  --color-cyan-soft: #A8F0E7;
  --color-paper: #F5F0E6;
  --color-ink: #171310;
  --color-gray: #6E6459;

  --font-display: "Noto Serif SC", "Source Han Serif SC", "Songti SC", "SimSun", serif;
  --font-body: "PingFang SC", "HarmonyOS Sans", "Hiragino Sans GB", "Microsoft YaHei", system-ui, -apple-system, sans-serif;
  --font-mono: "JetBrains Mono", "IBM Plex Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;

  --page-max: 1280px;
  --gutter: clamp(20px, 4vw, 48px);
  --rail-w: 120px;

  --radius-lg: 28px;
  --radius-md: 18px;
  --radius-sm: 10px;
  --radius-pill: 999px;

  --sp-1: 24px;
  --sp-2: 48px;
  --sp-3: 96px;

  --ease: cubic-bezier(.22, .61, .36, 1);
  --shell-line: rgba(23, 19, 16, .14);
  --shell-line-light: rgba(245, 240, 230, .18);
}

/* ---------- 2. 重置 ---------- */
*,
*::before,
*::after { box-sizing: border-box; }

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: 104px;
}

body {
  margin: 0;
  background: var(--color-paper);
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: 17px;
  line-height: 1.85;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

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

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

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

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

img, svg, picture { max-width: 100%; }

[hidden] { display: none !important; }

:focus-visible {
  outline: 2px solid var(--color-night);
  outline-offset: 2px;
  box-shadow: 0 0 0 5px rgba(47, 212, 195, .55);
  border-radius: 6px;
}

/* ---------- 3. 基础排版 ---------- */
h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 900;
  line-height: 1.12;
  letter-spacing: -.01em;
}

strong, b { font-weight: 700; }

::selection {
  background: var(--color-cyan-soft);
  color: var(--color-teal-deep);
}

/* ---------- 4. 工具 ---------- */
.wrap {
  width: 100%;
  max-width: var(--page-max);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.mono {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  letter-spacing: -.01em;
}

.section { padding-block: var(--sp-2); }
.section--danxia { background: var(--color-danxia); color: var(--color-paper); }
.section--night { background: var(--color-night); color: var(--color-paper); }
.section--teal { background: var(--color-teal-deep); color: var(--color-paper); }
.section--sand { background: var(--color-sand); color: var(--color-ink); }

.section--danxia a:hover,
.section--night a:hover,
.section--teal a:hover { color: var(--color-cyan); }

.sec-label {
  display: inline-flex;
  align-items: center;
  gap: .6rem;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .2em;
  color: var(--color-danxia);
}

.sec-label::before {
  content: "";
  width: 28px;
  height: 1px;
  background: currentColor;
}

.section--danxia .sec-label,
.section--night .sec-label,
.section--teal .sec-label { color: var(--color-gold); }

.sec-title {
  font-family: var(--font-display);
  font-weight: 900;
  font-size: clamp(1.55rem, 3vw, 2rem);
  line-height: 1.16;
  letter-spacing: -.01em;
}

.sec-lede {
  max-width: 34em;
  margin-top: 14px;
  font-size: 16.5px;
  line-height: 1.85;
  opacity: .82;
}

.prose {
  max-width: 36em;
  font-size: 17px;
  line-height: 1.85;
}

.prose p + p { margin-top: 1em; }
.prose a { border-bottom: 1px solid var(--color-gold); }

.grid {
  display: grid;
  gap: clamp(16px, 2.4vw, 32px);
}

.grid--5-7 { grid-template-columns: 5fr 7fr; }
.grid--4-8 { grid-template-columns: 4fr 8fr; }
.grid--3-6-3 { grid-template-columns: 3fr 6fr 3fr; }
.grid--2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }

.stair-up { transform: translateY(-40px); }
.stair-down { transform: translateY(40px); }

.rule-diagonal {
  position: relative;
  height: 96px;
  margin: 0;
  overflow: hidden;
}

.rule-diagonal::before {
  content: "";
  position: absolute;
  left: 0;
  top: 50%;
  width: min(62%, 460px);
  height: 1px;
  background: var(--color-gold);
  transform: rotate(12deg);
  transform-origin: left center;
}

.rule-diagonal::after {
  content: "";
  position: absolute;
  left: min(62%, 460px);
  top: calc(50% - 3px);
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--color-cyan);
}

/* 左侧章节索引列 */
.rail {
  position: sticky;
  top: 112px;
  display: flex;
  flex-direction: column;
  gap: 2px;
  align-self: start;
}

.rail-link {
  display: flex;
  align-items: baseline;
  gap: .55rem;
  padding: 7px 0 7px 12px;
  border-left: 1px solid var(--shell-line);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .1em;
  color: var(--color-gray);
  transition: color .2s var(--ease), border-color .2s var(--ease);
}

.rail-link:hover { color: var(--color-danxia); }

.rail-link[aria-current="true"] {
  color: var(--color-danxia);
  border-left-color: var(--color-danxia);
  font-weight: 700;
}

/* ---------- 5. 按钮与标签 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: .55rem;
  min-height: 44px;
  padding: .62rem 1.35rem;
  border-radius: var(--radius-pill);
  font-family: var(--font-body);
  font-size: 14px;
  font-weight: 600;
  letter-spacing: .04em;
  line-height: 1;
  white-space: nowrap;
  transition: transform .2s var(--ease), background-color .2s var(--ease),
              color .2s var(--ease), border-color .2s var(--ease), box-shadow .2s var(--ease);
}

.btn--primary {
  background: var(--color-danxia);
  color: var(--color-paper);
  box-shadow: 0 8px 20px -10px rgba(158, 59, 39, .9);
}

.btn--primary:hover {
  background: var(--color-danxia-deep);
  color: var(--color-paper);
  transform: translateY(-2px);
}

.btn--ghost {
  border: 1px solid rgba(23, 19, 16, .26);
  color: var(--color-ink);
}

.btn--ghost:hover {
  border-color: var(--color-danxia);
  color: var(--color-danxia);
  transform: translateY(-2px);
}

.btn--dark {
  background: var(--color-night);
  color: var(--color-paper);
}

.btn--dark:hover {
  background: var(--color-teal-deep);
  color: var(--color-paper);
  transform: translateY(-2px);
}

.btn--cyan {
  background: var(--color-cyan);
  color: var(--color-night);
}

.btn--cyan:hover {
  background: var(--color-cyan-soft);
  color: var(--color-night);
  transform: translateY(-2px);
}

.btn--block {
  width: 100%;
}

.section--night .btn--ghost,
.section--teal .btn--ghost,
.section--danxia .btn--ghost {
  border-color: rgba(245, 240, 230, .42);
  color: var(--color-paper);
}

.section--night .btn--ghost:hover,
.section--teal .btn--ghost:hover,
.section--danxia .btn--ghost:hover {
  border-color: var(--color-cyan);
  color: var(--color-cyan);
}

.pill {
  display: inline-flex;
  align-items: center;
  gap: .45rem;
  padding: .3rem .85rem;
  border-radius: var(--radius-pill);
  background: var(--color-cyan-soft);
  color: var(--color-teal-deep);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: .08em;
  line-height: 1.5;
}

.pill--gold {
  background: var(--color-gold);
  color: var(--color-night);
}

.pill--outline {
  background: transparent;
  border: 1px solid rgba(23, 19, 16, .22);
  color: var(--color-gray);
}

.section--danxia .pill--outline,
.section--night .pill--outline,
.section--teal .pill--outline {
  border-color: rgba(245, 240, 230, .35);
  color: rgba(245, 240, 230, .8);
}

/* 面包屑 */
.breadcrumb {
  font-size: 13px;
  line-height: 1.7;
  color: var(--color-gray);
}

.breadcrumb ol {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: .35rem;
}

.breadcrumb li {
  display: inline-flex;
  align-items: center;
  gap: .35rem;
}

.breadcrumb li + li::before {
  content: "／";
  color: var(--color-gold);
}

.breadcrumb a:hover {
  color: var(--color-danxia);
  text-decoration: underline;
  text-underline-offset: 3px;
}

/* ---------- 6. 头部 ---------- */
.skip-link {
  position: fixed;
  top: 10px;
  left: 10px;
  z-index: 200;
  padding: .7rem 1.15rem;
  border-radius: var(--radius-pill);
  background: var(--color-night);
  color: var(--color-paper);
  font-size: 14px;
  font-weight: 600;
  letter-spacing: .06em;
  transform: translateY(-180%);
  transition: transform .2s var(--ease);
}

.skip-link:focus,
.skip-link:focus-visible {
  transform: translateY(0);
  color: var(--color-paper);
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 60;
  background: var(--color-paper);
  border-bottom: 1px solid var(--shell-line);
  transition: background-color .3s var(--ease), box-shadow .3s var(--ease);
}

.site-header[data-condensed] {
  background: rgba(245, 240, 230, .97);
  box-shadow: 0 14px 34px -26px rgba(23, 19, 16, .85);
}

.header-shell {
  width: 100%;
  max-width: var(--page-max);
  margin-inline: auto;
  padding: 14px var(--gutter);
  min-height: 78px;
  display: flex;
  align-items: center;
  gap: clamp(12px, 2vw, 30px);
  transition: min-height .28s var(--ease), padding .28s var(--ease);
}

.site-header[data-condensed] .header-shell {
  min-height: 56px;
  padding-block: 8px;
}

/* 品牌 */
.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  flex: 0 0 auto;
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 42px;
  height: 42px;
  border-radius: 14px;
  background: linear-gradient(135deg, var(--color-danxia) 0 62%, var(--color-danxia-deep) 62% 100%);
  color: var(--color-paper);
  font-family: var(--font-display);
  font-weight: 900;
  font-size: 23px;
  line-height: 1;
  transition: width .28s var(--ease), height .28s var(--ease),
              font-size .28s var(--ease), border-radius .28s var(--ease);
}

.site-header[data-condensed] .brand-mark {
  width: 34px;
  height: 34px;
  border-radius: 11px;
  font-size: 19px;
}

.brand-text {
  display: flex;
  flex-direction: column;
  line-height: 1.15;
}

.brand-name {
  font-family: var(--font-display);
  font-weight: 900;
  font-size: 19px;
  letter-spacing: .01em;
  color: var(--color-ink);
}

.brand-sub {
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: .22em;
  color: var(--color-gray);
}

.site-header[data-condensed] .brand-sub { display: none; }

/* 导航 */
.site-nav {
  flex: 1 1 auto;
  display: flex;
  justify-content: flex-end;
}

.nav-list {
  display: flex;
  align-items: center;
  gap: 2px;
}

.nav-item { display: block; }

.nav-link {
  position: relative;
  display: inline-flex;
  align-items: center;
  gap: .45em;
  min-height: 44px;
  padding: 10px 12px;
  border-radius: var(--radius-pill);
  font-size: 14px;
  font-weight: 500;
  letter-spacing: .06em;
  line-height: 1.2;
  color: var(--color-ink);
  transition: color .18s var(--ease), background-color .18s var(--ease);
}

.nav-index {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .04em;
  color: var(--color-gold);
  transition: color .18s var(--ease);
}

.nav-label { white-space: nowrap; }

.nav-link::after {
  content: "";
  position: absolute;
  left: 12px;
  right: 12px;
  bottom: 6px;
  height: 2px;
  border-radius: 2px;
  background: var(--color-danxia);
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform .24s var(--ease);
}

.nav-link:hover { color: var(--color-danxia); }
.nav-link:hover::after { transform: scaleX(1); }

.nav-link[aria-current="page"] {
  color: var(--color-danxia);
  font-weight: 700;
}

.nav-link[aria-current="page"] .nav-index { color: var(--color-danxia); }

.nav-link[aria-current="page"]::after { transform: scaleX(1); }

/* 收拢态当前章节 */
.header-current {
  display: none;
  align-items: center;
  gap: .5rem;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .12em;
  color: var(--color-gray);
  white-space: nowrap;
  max-width: 12em;
  overflow: hidden;
  text-overflow: ellipsis;
}

.header-current::before {
  content: "";
  flex: 0 0 auto;
  width: 18px;
  height: 1px;
  background: var(--color-gold);
}

.site-header[data-condensed] .header-current { display: inline-flex; }

/* 操作区 */
.header-actions {
  display: flex;
  align-items: center;
  gap: 10px;
  flex: 0 0 auto;
  margin-left: auto;
}

.header-entry,
.header-cta { white-space: nowrap; }

/* 移动端开关 */
.nav-toggle {
  display: none;
  align-items: center;
  gap: 9px;
  min-width: 44px;
  min-height: 44px;
  padding: 0 15px;
  border-radius: var(--radius-pill);
  border: 1px solid rgba(23, 19, 16, .24);
  font-size: 13px;
  font-weight: 600;
  letter-spacing: .1em;
  transition: background-color .2s var(--ease), color .2s var(--ease),
              border-color .2s var(--ease);
}

.nav-toggle-bar {
  position: relative;
  display: block;
  width: 16px;
  height: 2px;
  border-radius: 2px;
  background: currentColor;
  transition: background-color .2s var(--ease);
}

.nav-toggle-bar::before,
.nav-toggle-bar::after {
  content: "";
  position: absolute;
  left: 0;
  width: 16px;
  height: 2px;
  border-radius: 2px;
  background: currentColor;
  transition: transform .24s var(--ease), top .24s var(--ease);
}

.nav-toggle-bar::before { top: -5px; }
.nav-toggle-bar::after { top: 5px; }

.site-header[data-open] .nav-toggle {
  background: var(--color-cyan);
  border-color: var(--color-cyan);
  color: var(--color-night);
}

.site-header[data-open] .nav-toggle-bar { background: transparent; }
.site-header[data-open] .nav-toggle-bar::before { top: 0; transform: rotate(45deg); }
.site-header[data-open] .nav-toggle-bar::after { top: 0; transform: rotate(-45deg); }

/* 滚动进度 */
.header-progress {
  position: absolute;
  left: 0;
  right: 0;
  bottom: -1px;
  height: 2px;
  pointer-events: none;
}

.header-progress-bar {
  display: block;
  width: 0;
  height: 100%;
  background: linear-gradient(90deg, var(--color-danxia) 0%, var(--color-gold) 58%, var(--color-cyan) 100%);
  transition: width .12s linear;
}

/* 返回顶部 */
.back-top {
  position: fixed;
  right: clamp(16px, 3vw, 32px);
  bottom: clamp(16px, 3vw, 32px);
  z-index: 80;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  min-height: 44px;
  padding: 0 18px;
  border-radius: var(--radius-pill);
  background: var(--color-night);
  color: var(--color-paper);
  font-size: 13px;
  font-weight: 600;
  letter-spacing: .08em;
  box-shadow: 0 14px 30px -14px rgba(16, 28, 51, .85);
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  pointer-events: none;
  transition: opacity .24s var(--ease), transform .24s var(--ease),
              visibility .24s, background-color .18s var(--ease);
}

.back-top[data-visible] {
  opacity: 1;
  visibility: visible;
  transform: none;
  pointer-events: auto;
}

.back-top:hover { background: var(--color-danxia); }

.back-top-icon {
  font-family: var(--font-mono);
  font-size: 15px;
  color: var(--color-cyan);
}

.back-top-label { white-space: nowrap; }

/* ---------- 7. 页脚 ---------- */
.site-footer {
  background: var(--color-danxia-deep);
  color: var(--color-paper);
  padding-block: clamp(48px, 6vw, 88px) 0;
}

.footer-shell {
  width: 100%;
  max-width: var(--page-max);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.footer-top {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1.75fr);
  gap: clamp(32px, 5vw, 72px);
  padding-bottom: clamp(28px, 4vw, 48px);
  border-bottom: 1px solid var(--shell-line-light);
}

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

.footer-brand-link {
  display: inline-flex;
  align-items: center;
  gap: 12px;
}

.footer-mark {
  display: grid;
  place-items: center;
  width: 44px;
  height: 44px;
  border-radius: 14px;
  background: linear-gradient(135deg, var(--color-gold) 0 60%, #8F6519 60% 100%);
  color: var(--color-night);
  font-family: var(--font-display);
  font-weight: 900;
  font-size: 23px;
  line-height: 1;
}

.footer-name {
  font-family: var(--font-display);
  font-weight: 900;
  font-size: 22px;
  color: var(--color-paper);
}

.footer-tagline {
  margin-top: 12px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .22em;
  color: rgba(245, 240, 230, .62);
}

.footer-cta { margin-top: 22px; }

.footer-nav {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 24px;
}

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

.footer-col-title {
  margin-bottom: 14px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  font-weight: 600;
  letter-spacing: .22em;
  color: var(--color-gold);
}

.footer-list li + li { margin-top: 8px; }

.footer-list a {
  display: inline-block;
  padding-block: 3px;
  font-size: 15px;
  line-height: 1.7;
  color: rgba(245, 240, 230, .82);
  transition: color .18s var(--ease);
}

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

.footer-meta {
  display: grid;
  gap: 8px;
  padding-block: 26px;
  border-bottom: 1px solid var(--shell-line-light);
  font-size: 14px;
  line-height: 1.85;
  color: rgba(245, 240, 230, .76);
}

.footer-strong {
  color: var(--color-paper);
  font-weight: 600;
}

.footer-note {
  font-size: 13px;
  color: rgba(245, 240, 230, .58);
}

.footer-legal {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 10px 28px;
  padding-block: 22px 30px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .06em;
  color: rgba(245, 240, 230, .58);
}

.footer-legal-item { margin: 0; }

/* ---------- 8. 通用内容组件 ---------- */
.card {
  background: var(--color-sand);
  color: var(--color-ink);
  border-radius: var(--radius-lg);
  padding: clamp(20px, 3vw, 32px);
  transition: transform .24s var(--ease), box-shadow .24s var(--ease);
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: 0 20px 38px -22px rgba(23, 19, 16, .55);
}

.section--danxia .card,
.section--night .card,
.section--teal .card {
  background: rgba(233, 211, 166, .13);
  color: var(--color-paper);
}

.card-title {
  font-family: var(--font-display);
  font-weight: 900;
  font-size: 20px;
  line-height: 1.3;
}

.score-card {
  border-radius: var(--radius-lg);
  background: var(--color-night);
  color: var(--color-paper);
  padding: clamp(20px, 3vw, 32px);
  box-shadow: 0 30px 56px -30px rgba(16, 28, 51, .8);
}

.score-num {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-weight: 700;
  font-size: clamp(2.4rem, 5vw, 3.25rem);
  line-height: 1.04;
  letter-spacing: -.02em;
  color: var(--color-paper);
}

.score-num--lg { font-size: clamp(3.2rem, 7vw, 5rem); }
.score-num--sm { font-size: clamp(1.5rem, 2.6vw, 2rem); }

.stat {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 14px 0;
  border-top: 1px solid rgba(245, 240, 230, .2);
}

.section--sand .stat,
.card .stat { border-top-color: rgba(23, 19, 16, .16); }

.stat-value {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 1.6rem;
  font-weight: 700;
  line-height: 1.1;
  color: var(--color-cyan);
}

.card .stat-value,
.section--sand .stat-value { color: var(--color-danxia); }

.stat-label {
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: .16em;
  opacity: .7;
}

/* 主客场切换 */
.switch {
  display: inline-flex;
  gap: 4px;
  padding: 4px;
  border-radius: var(--radius-pill);
  background: rgba(23, 19, 16, .08);
}

.section--night .switch,
.section--teal .switch,
.section--danxia .switch,
.score-card .switch { background: rgba(245, 240, 230, .14); }

.switch-option {
  min-height: 40px;
  padding: 0 20px;
  border-radius: var(--radius-pill);
  font-size: 14px;
  font-weight: 600;
  letter-spacing: .06em;
  color: var(--color-gray);
  transition: background-color .2s var(--ease), color .2s var(--ease);
}

.section--night .switch-option,
.section--teal .switch-option,
.section--danxia .switch-option,
.score-card .switch-option { color: rgba(245, 240, 230, .72); }

.switch-option[aria-pressed="true"] {
  background: var(--color-night);
  color: var(--color-paper);
  box-shadow: 0 8px 18px -12px rgba(16, 28, 51, .9);
}

.section--night .switch-option[aria-pressed="true"],
.section--teal .switch-option[aria-pressed="true"],
.section--danxia .switch-option[aria-pressed="true"],
.score-card .switch-option[aria-pressed="true"] {
  background: var(--color-cyan);
  color: var(--color-night);
}

/* 图片容器 */
.media-frame {
  position: relative;
  display: block;
  overflow: hidden;
  isolation: isolate;
  border-radius: var(--radius-lg);
  aspect-ratio: 16 / 10;
  background: linear-gradient(150deg, var(--color-night) 0%, var(--color-teal-deep) 58%, var(--color-danxia-deep) 100%);
}

.media-frame > img,
.media-frame > picture,
.media-frame > picture > img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.media-frame::after {
  content: "";
  position: absolute;
  inset: 0;
  pointer-events: none;
  background: radial-gradient(120% 100% at 25% 8%, rgba(9, 12, 18, 0) 42%, rgba(9, 12, 18, .58) 100%);
}

.media-frame--wide { aspect-ratio: 16 / 9; }
.media-frame--tall { aspect-ratio: 3 / 4; }
.media-frame--square { aspect-ratio: 1 / 1; }

.media-frame--bleed-left { margin-left: calc(-1 * var(--gutter)); }
.media-frame--inset-right { margin-right: calc(-1 * var(--gutter)); }

.media-caption {
  margin-top: 12px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .1em;
  color: var(--color-gray);
}

.section--danxia .media-caption,
.section--night .media-caption,
.section--teal .media-caption { color: rgba(245, 240, 230, .6); }

/* 入场显现 */
[data-reveal].is-reveal-ready {
  opacity: 0;
  transform: translateY(12px);
}

[data-reveal].is-reveal-ready.is-visible {
  opacity: 1;
  transform: none;
  transition: opacity .42s var(--ease), transform .42s var(--ease);
}

/* ---------- 9. 响应式 ---------- */
@media (max-width: 1180px) {
  .header-entry { display: none; }
}

@media (max-width: 1100px) {
  .header-current { display: none !important; }
}

@media (max-width: 980px) {
  html { scroll-padding-top: 84px; }

  .grid--5-7,
  .grid--4-8,
  .grid--3-6-3,
  .grid--2 { grid-template-columns: minmax(0, 1fr); }

  .stair-up,
  .stair-down { transform: none; }

  .rail {
    position: static;
    flex-direction: row;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 24px;
  }

  .rail-link {
    border-left: 0;
    border-radius: var(--radius-pill);
    padding: 6px 14px;
    background: rgba(23, 19, 16, .06);
  }

  .rail-link[aria-current="true"] {
    background: var(--color-danxia);
    color: var(--color-paper);
    border-left-color: transparent;
  }

  .section--night .rail-link,
  .section--teal .rail-link,
  .section--danxia .rail-link { background: rgba(245, 240, 230, .12); color: rgba(245, 240, 230, .8); }

  .section--night .rail-link[aria-current="true"],
  .section--teal .rail-link[aria-current="true"],
  .section--danxia .rail-link[aria-current="true"] {
    background: var(--color-cyan);
    color: var(--color-night);
  }

  /* 导航全屏索引层 */
  .nav-toggle { display: inline-flex; }

  .site-nav {
    position: fixed;
    inset: 0;
    z-index: 70;
    display: block;
    padding: 96px var(--gutter) 48px;
    background: var(--color-night);
    color: var(--color-paper);
    overflow-y: auto;
    overscroll-behavior: contain;
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: opacity .3s var(--ease), transform .3s var(--ease), visibility .3s;
  }

  .site-header[data-open] .site-nav {
    opacity: 1;
    visibility: visible;
    transform: none;
  }

  .nav-list {
    display: block;
  }

  .nav-item + .nav-item {
    border-top: 1px solid rgba(245, 240, 230, .12);
  }

  .nav-link {
    display: flex;
    align-items: center;
    gap: 14px;
    width: 100%;
    padding: 18px 2px;
    border-radius: 0;
    font-family: var(--font-display);
    font-weight: 900;
    font-size: clamp(1.35rem, 6vw, 1.9rem);
    letter-spacing: 0;
    color: var(--color-paper);
  }

  .nav-link::after { display: none; }

  .nav-index {
    font-size: 12px;
    letter-spacing: .2em;
    color: var(--color-gold);
  }

  .nav-link:hover,
  .nav-link[aria-current="page"] { color: var(--color-cyan); }

  .nav-link[aria-current="page"] .nav-index { color: var(--color-cyan); }

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

@media (max-width: 760px) {
  .footer-nav { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 26px 18px; }
  .footer-legal { justify-content: flex-start; }
}

@media (max-width: 640px) {
  .brand-sub { display: none; }
  .header-cta { padding: .55rem .95rem; font-size: 13px; }
  .header-shell { min-height: 66px; gap: 10px; }
  .nav-toggle-text { display: none; }
  .nav-toggle { padding: 0 13px; }
  .rule-diagonal { height: 72px; }
  .sec-lede { font-size: 16px; }
  .footer-contact { font-size: 13px; word-break: break-word; }
  .back-top { padding: 0 15px; font-size: 12px; }
}

@media (max-width: 420px) {
  .footer-nav { grid-template-columns: minmax(0, 1fr); }
}

/* ---------- 10. 动效降级 ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }

  *,
  *::before,
  *::after {
    animation-duration: .001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .001ms !important;
    scroll-behavior: auto !important;
  }

  [data-reveal],
  [data-reveal].is-reveal-ready {
    opacity: 1 !important;
    transform: none !important;
  }

  .card:hover,
  .btn:hover { transform: none; }
}