/* =========================================================
   博云体育看台 · /assets/site.css
   共享外壳：reset / 变量 / 中文排版 / 页头 / 页脚 / 基础组件
   ========================================================= */

/* ---------- 1. reset ---------- */
*,
*::before,
*::after { box-sizing: border-box; }

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  background-color: #050B1A;
}

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

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

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

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

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

table { border-collapse: collapse; }

summary { cursor: pointer; }

/* ---------- 2. 设计变量 ---------- */
:root {
  --void: #050B1A;
  --deep: #0A1730;
  --track: #122A4A;
  --grid: #1E3A5F;
  --accent: #2FF0D0;
  --accent-soft: #8FF6E4;
  --orange: #FF7A2F;
  --amber: #FFC24B;
  --text: #F2F7FF;
  --text-dim: #A7B6CC;
  --ice: #DDE9FF;

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

  --fs-1: 12px;
  --fs-2: 14px;
  --fs-3: 16px;
  --fs-4: 20px;
  --fs-5: 28px;
  --fs-6: 40px;
  --fs-7: 64px;
  --fs-8: 88px;

  --shell: 1280px;
  --gutter: 24px;
  --rail: 64px;

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

  --ease: cubic-bezier(.22, .61, .36, 1);
  --dur: .32s;
}

/* ---------- 3. 中文排版与页面底 ---------- */
body {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  background-color: var(--void);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: var(--fs-3);
  font-weight: 400;
  line-height: 1.75;
  letter-spacing: .01em;
  overflow-x: hidden;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
}

/* 蓝图网格层 */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background-image:
    linear-gradient(to right, rgba(30, 58, 95, .34) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(30, 58, 95, .34) 1px, transparent 1px);
  background-size: 96px 96px;
  opacity: .55;
}

/* 夜间灯光光斑层 */
body::after {
  content: "";
  position: fixed;
  inset: -20%;
  z-index: 0;
  pointer-events: none;
  background:
    radial-gradient(38% 30% at 14% 8%, rgba(47, 240, 208, .14), transparent 70%),
    radial-gradient(34% 28% at 88% 78%, rgba(255, 122, 47, .10), transparent 70%),
    radial-gradient(52% 42% at 72% 6%, rgba(18, 42, 74, .78), transparent 72%);
  animation: light-drift 22s ease-in-out infinite alternate;
}

@keyframes light-drift {
  from { transform: translate3d(0, 0, 0) scale(1); }
  to { transform: translate3d(-2.4%, 3%, 0) scale(1.06); }
}

main {
  position: relative;
  z-index: 1;
  flex: 1 0 auto;
}

::selection {
  background: rgba(47, 240, 208, .28);
  color: var(--text);
}

/* ---------- 4. 焦点可见 ---------- */
:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: 6px;
}

/* ---------- 5. 跳至主内容 ---------- */
.skip-link {
  position: fixed;
  top: 10px;
  left: 10px;
  z-index: 200;
  padding: 11px 20px;
  border-radius: var(--r-pill);
  background-color: var(--accent);
  color: #04211C;
  font-size: var(--fs-2);
  font-weight: 700;
  letter-spacing: .04em;
  transform: translateY(-180%);
  transition: transform .24s var(--ease);
}

.skip-link:focus {
  transform: translateY(0);
}

/* ---------- 6. 页头 ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 60;
  background-color: rgba(5, 11, 26, .96);
  background-image: linear-gradient(180deg, rgba(10, 23, 48, .97), rgba(5, 11, 26, .93));
  border-bottom: 1px solid var(--grid);
  box-shadow: 0 22px 46px -38px #000;
}

.header-shell {
  width: min(100% - var(--gutter) * 2, var(--shell));
  margin-inline: auto;
}

.header-rail {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 7px 0;
  border-bottom: 1px dashed rgba(30, 58, 95, .85);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .16em;
  text-transform: uppercase;
  color: rgba(167, 182, 204, .72);
  white-space: nowrap;
  overflow: hidden;
}

.rail-cell { flex: 0 1 auto; overflow: hidden; text-overflow: ellipsis; }

.rail-cell--mid { color: rgba(47, 240, 208, .78); }

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 32px;
  padding: 13px 0;
  min-height: 74px;
}

/* 品牌区 */
.brand {
  display: flex;
  flex-direction: column;
  gap: 2px;
  min-width: 0;
}

.brand-mark {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  min-width: 0;
}

.brand-index {
  flex: none;
  padding: 3px 9px;
  border: 1px solid rgba(47, 240, 208, .38);
  border-radius: var(--r-pill);
  background-color: rgba(47, 240, 208, .07);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .18em;
  color: var(--accent);
  line-height: 1.5;
}

.brand-name {
  font-size: clamp(20px, 2.2vw, 26px);
  font-weight: 900;
  line-height: 1.2;
  letter-spacing: -.015em;
  color: var(--text);
  white-space: nowrap;
}

.brand-descriptor {
  font-size: var(--fs-1);
  line-height: 1.6;
  letter-spacing: .06em;
  color: var(--text-dim);
}

/* 导航 */
.site-nav {
  display: flex;
  align-items: center;
  gap: 20px;
  min-width: 0;
}

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

.nav-list a {
  position: relative;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 9px 13px;
  border-radius: var(--r-pill);
  font-size: var(--fs-2);
  font-weight: 500;
  color: var(--text-dim);
  white-space: nowrap;
  transition: color var(--dur) var(--ease), background-color var(--dur) var(--ease);
}

.nav-num {
  display: inline-block;
  max-width: 0;
  overflow: hidden;
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: .1em;
  color: var(--amber);
  opacity: 0;
  transition: max-width var(--dur) var(--ease), opacity var(--dur) var(--ease);
}

.nav-list a:hover,
.nav-list a:focus-visible {
  color: var(--text);
  background-color: rgba(47, 240, 208, .08);
}

.nav-list a:hover .nav-num,
.nav-list a:focus-visible .nav-num {
  max-width: 2.6em;
  opacity: 1;
}

.nav-list a[aria-current="page"] {
  color: var(--text);
  background-color: rgba(47, 240, 208, .1);
}

.nav-list a[aria-current="page"] .nav-num {
  max-width: 2.6em;
  opacity: 1;
  color: var(--accent);
}

.nav-list a[aria-current="page"]::after {
  content: "";
  position: absolute;
  left: 13px;
  right: 13px;
  bottom: 3px;
  height: 2px;
  border-radius: 2px;
  background-color: var(--accent);
}

.nav-cta {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 20px;
  border-radius: var(--r-pill);
  background-color: var(--accent);
  color: #04211C;
  font-size: var(--fs-2);
  font-weight: 800;
  letter-spacing: .04em;
  white-space: nowrap;
  box-shadow: 0 14px 30px -18px rgba(47, 240, 208, .95);
  transition: transform var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}

.nav-cta:hover {
  transform: translateY(-1px);
  box-shadow: 0 18px 34px -16px rgba(47, 240, 208, .95);
}

/* 移动按钮 */
.nav-toggle {
  display: none;
  align-items: center;
  gap: 10px;
  padding: 10px 16px 10px 14px;
  border: 1px solid var(--grid);
  border-radius: var(--r-pill);
  background-color: rgba(18, 42, 74, .78);
  color: var(--text);
  font-size: var(--fs-1);
  font-weight: 700;
  letter-spacing: .14em;
  transition: border-color var(--dur) var(--ease), background-color var(--dur) var(--ease),
    color var(--dur) var(--ease);
}

.nav-toggle:hover {
  border-color: rgba(47, 240, 208, .5);
  background-color: rgba(47, 240, 208, .08);
}

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

.nav-toggle-bars {
  display: inline-flex;
  flex-direction: column;
  gap: 3px;
  width: 16px;
  flex: none;
}

.nav-toggle-bars i {
  display: block;
  height: 2px;
  border-radius: 2px;
  background-color: currentColor;
  transition: transform var(--dur) var(--ease), opacity var(--dur) var(--ease);
}

.nav-toggle-bars i:nth-child(2) {
  width: 70%;
  margin-left: auto;
}

.nav-toggle[aria-expanded="true"] .nav-toggle-bars i:nth-child(1) { transform: translateY(5px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] .nav-toggle-bars i:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] .nav-toggle-bars i:nth-child(3) { transform: translateY(-5px) rotate(-45deg); }

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

.header-progress__bar {
  display: block;
  width: 100%;
  height: 100%;
  transform: scaleX(0);
  transform-origin: 0 50%;
  background-image: linear-gradient(90deg, var(--accent), #7CF0FF 62%, var(--orange));
}

/* 移动遮罩 */
.nav-scrim {
  position: fixed;
  inset: 0;
  z-index: 70;
  background-color: rgba(3, 7, 16, .74);
  opacity: 0;
  visibility: hidden;
  transition: opacity .3s var(--ease), visibility .3s;
}

.nav-scrim[data-open] {
  opacity: 1;
  visibility: visible;
}

/* ---------- 7. 页脚 ---------- */
.site-footer {
  position: relative;
  z-index: 1;
  margin-top: auto;
  background-color: var(--void);
  background-image: linear-gradient(180deg, var(--void), var(--deep) 46%, #03070F);
  border-top: 1px solid var(--grid);
  color: var(--text-dim);
}

.footer-ice {
  position: relative;
  height: 56px;
  overflow: hidden;
}

.footer-ice svg {
  width: 100%;
  height: 100%;
}

.ice-line {
  fill: none;
  stroke-linecap: round;
}

.ice-line--a { stroke: rgba(47, 240, 208, .45); stroke-width: 1.4; }
.ice-line--b { stroke: rgba(221, 233, 255, .18); stroke-width: 1; }
.ice-line--c { stroke: rgba(47, 240, 208, .18); stroke-width: 1; stroke-dasharray: 4 7; }

.footer-shell {
  width: min(100% - var(--gutter) * 2, var(--shell));
  margin-inline: auto;
}

.footer-main {
  display: grid;
  grid-template-columns: minmax(0, 1.5fr) repeat(3, minmax(0, .85fr)) minmax(0, 1.35fr);
  gap: 44px 32px;
  padding: 52px 0 40px;
}

.footer-brand {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 16px;
  min-width: 0;
}

.footer-brandline {
  font-family: var(--font-mono);
  font-size: var(--fs-2);
  line-height: 1.6;
  letter-spacing: .03em;
  color: var(--text);
}

.footer-note {
  max-width: 34ch;
  font-size: 13px;
  line-height: 1.9;
  color: var(--text-dim);
}

.footer-old {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  padding: 9px 18px;
  border: 1px solid rgba(47, 240, 208, .42);
  border-radius: var(--r-pill);
  background-color: rgba(47, 240, 208, .07);
  color: var(--accent);
  font-size: var(--fs-2);
  font-weight: 700;
  transition: background-color var(--dur) var(--ease), border-color var(--dur) var(--ease),
    transform var(--dur) var(--ease);
}

.footer-old:hover {
  background-color: rgba(47, 240, 208, .16);
  border-color: var(--accent);
  transform: translateY(-1px);
}

.footer-old__dot {
  width: 7px;
  height: 7px;
  flex: none;
  border-radius: 50%;
  background-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(47, 240, 208, .16);
}

.footer-col {
  display: flex;
  flex-direction: column;
  gap: 14px;
  min-width: 0;
}

.footer-col__title {
  display: flex;
  align-items: center;
  gap: 8px;
  padding-bottom: 10px;
  border-bottom: 1px dashed rgba(30, 58, 95, .95);
  font-size: var(--fs-1);
  font-weight: 700;
  letter-spacing: .16em;
  color: var(--text);
}

.footer-col__title::before {
  content: "";
  width: 6px;
  height: 6px;
  flex: none;
  border-radius: 2px;
  background-color: var(--amber);
}

.footer-list {
  display: flex;
  flex-direction: column;
  gap: 11px;
}

.footer-list a {
  position: relative;
  display: inline-block;
  padding-left: 0;
  font-size: var(--fs-2);
  color: var(--text-dim);
  transition: color var(--dur) var(--ease), padding-left var(--dur) var(--ease);
}

.footer-list a::before {
  content: "";
  position: absolute;
  left: 0;
  top: 50%;
  width: 0;
  height: 1px;
  background-color: var(--accent);
  transition: width var(--dur) var(--ease);
}

.footer-list a:hover {
  color: var(--text);
  padding-left: 15px;
}

.footer-list a:hover::before { width: 10px; }

.footer-contact {
  display: flex;
  flex-direction: column;
  gap: 14px;
  min-width: 0;
}

.contact-list {
  display: flex;
  flex-direction: column;
  gap: 13px;
}

.contact-list li {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.contact-key {
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: .2em;
  color: rgba(47, 240, 208, .85);
}

.contact-val {
  font-size: 13px;
  line-height: 1.75;
  color: var(--text-dim);
  word-break: break-word;
}

.footer-base {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  padding: 20px 0 34px;
  border-top: 1px solid rgba(30, 58, 95, .9);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .1em;
  color: rgba(167, 182, 204, .62);
}

.footer-copy,
.footer-icp { margin: 0; }

/* ---------- 8. 布局容器 ---------- */
.shell {
  width: min(100% - var(--gutter) * 2, var(--shell));
  margin-inline: auto;
}

.section {
  position: relative;
  padding: clamp(56px, 7vw, 96px) 0;
}

.section--tight {
  padding: clamp(34px, 4vw, 56px) 0;
}

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

/* ---------- 9. 文字索引与标题 ---------- */
.mono {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  letter-spacing: .02em;
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  font-family: var(--font-mono);
  font-size: var(--fs-1);
  line-height: 1.4;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--accent);
}

.eyebrow::before {
  content: "";
  width: 14px;
  height: 1px;
  flex: none;
  background-color: currentColor;
}

.eyebrow--amber { color: var(--amber); }
.eyebrow--orange { color: var(--orange); }
.eyebrow--dim { color: var(--text-dim); }

.section-title {
  max-width: 22ch;
  font-size: clamp(26px, 3.4vw, 40px);
  font-weight: 900;
  line-height: 1.24;
  letter-spacing: -.02em;
  color: var(--text);
}

.section-lead {
  max-width: 46ch;
  font-size: var(--fs-3);
  line-height: 1.85;
  color: var(--text-dim);
}

/* ---------- 10. 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: 14px 26px;
  border: 1px solid var(--grid);
  border-radius: var(--r-pill);
  background-color: var(--track);
  color: var(--text);
  font-size: var(--fs-2);
  font-weight: 700;
  letter-spacing: .03em;
  text-align: center;
  transition: transform var(--dur) var(--ease), background-color var(--dur) var(--ease),
    border-color var(--dur) var(--ease), color var(--dur) var(--ease),
    box-shadow var(--dur) var(--ease);
}

.btn:hover { transform: translateY(-1px); }
.btn:active { transform: translateY(1px); }

.btn--primary {
  background-color: var(--accent);
  border-color: var(--accent);
  color: #04211C;
  box-shadow: 0 16px 34px -20px rgba(47, 240, 208, .95);
}

.btn--primary:hover {
  background-color: var(--accent-soft);
  border-color: var(--accent-soft);
}

.btn--ghost {
  background-color: transparent;
  border-color: rgba(47, 240, 208, .45);
  color: var(--accent);
}

.btn--ghost:hover {
  background-color: rgba(47, 240, 208, .1);
  border-color: var(--accent);
}

.btn--orange {
  background-color: rgba(255, 122, 47, .12);
  border-color: rgba(255, 122, 47, .45);
  color: var(--orange);
}

.btn--orange:hover { background-color: rgba(255, 122, 47, .2); }

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

/* ---------- 11. 面包屑 ---------- */
.crumbs {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
  font-family: var(--font-mono);
  font-size: var(--fs-1);
  letter-spacing: .1em;
  color: var(--text-dim);
}

.crumbs li {
  display: inline-flex;
  align-items: center;
  gap: 10px;
}

.crumbs li + li::before {
  content: "/";
  color: #1E3A5F;
}

.crumbs a {
  color: var(--text-dim);
  transition: color var(--dur) var(--ease);
}

.crumbs a:hover { color: var(--accent); }

.crumbs [aria-current="page"] { color: var(--amber); }

/* ---------- 12. 卡片 ---------- */
.card {
  position: relative;
  overflow: hidden;
  padding: 24px;
  border: 1px solid var(--grid);
  border-radius: var(--r-md);
  background-color: var(--deep);
  background-image: linear-gradient(160deg, rgba(18, 42, 74, .92), rgba(10, 23, 48, .88));
}

.card--lg {
  padding: 32px;
  border-radius: var(--r-lg);
}

.card--pill { border-radius: var(--r-pill); }

.card__meta {
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-mono);
  font-size: var(--fs-1);
  letter-spacing: .1em;
  color: var(--text-dim);
}

.card__title {
  font-size: var(--fs-4);
  font-weight: 800;
  line-height: 1.45;
  color: var(--text);
}

/* ---------- 13. 标签与胶囊 ---------- */
.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 3px 10px;
  border: 1px solid rgba(255, 194, 75, .4);
  border-radius: var(--r-pill);
  background-color: rgba(255, 194, 75, .08);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .1em;
  color: var(--amber);
}

.tag--accent {
  border-color: rgba(47, 240, 208, .4);
  background-color: rgba(47, 240, 208, .08);
  color: var(--accent);
}

.tag--orange {
  border-color: rgba(255, 122, 47, .45);
  background-color: rgba(255, 122, 47, .1);
  color: var(--orange);
}

.chip-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.chip {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 16px;
  border: 1px solid var(--grid);
  border-radius: var(--r-pill);
  background-color: rgba(18, 42, 74, .62);
  color: var(--text-dim);
  font-size: var(--fs-2);
  transition: color var(--dur) var(--ease), border-color var(--dur) var(--ease),
    background-color var(--dur) var(--ease);
}

.chip:hover {
  color: var(--text);
  border-color: rgba(47, 240, 208, .5);
}

.chip[aria-pressed="true"],
.chip[data-active] {
  background-color: var(--accent);
  border-color: var(--accent);
  color: #04211C;
  font-weight: 700;
}

/* ---------- 14. 可展开内容组 ---------- */
.fold {
  overflow: hidden;
  border: 1px solid var(--grid);
  border-radius: var(--r-md);
  background-color: rgba(10, 23, 48, .62);
}

.fold + .fold { margin-top: 12px; }

.fold summary {
  display: flex;
  align-items: flex-start;
  gap: 16px;
  padding: 18px 22px;
  list-style: none;
  font-size: var(--fs-3);
  font-weight: 700;
  line-height: 1.6;
  color: var(--text);
  transition: background-color var(--dur) var(--ease);
}

.fold summary::-webkit-details-marker { display: none; }

.fold summary::after {
  content: "+";
  margin-left: auto;
  flex: none;
  font-family: var(--font-mono);
  font-size: var(--fs-4);
  line-height: 1;
  color: var(--accent);
  transition: transform var(--dur) var(--ease);
}

.fold[open] summary::after { transform: rotate(45deg); }
.fold summary:hover { background-color: rgba(47, 240, 208, .06); }

.fold__idx {
  flex: none;
  padding-top: 4px;
  font-family: var(--font-mono);
  font-size: var(--fs-1);
  letter-spacing: .12em;
  color: var(--text-dim);
  transition: color var(--dur) var(--ease);
}

.fold[open] .fold__idx { color: var(--accent); }

.fold__body {
  padding: 0 22px 20px;
  font-size: var(--fs-3);
  line-height: 1.85;
  color: var(--text-dim);
}

/* ---------- 15. 数据块 ---------- */
.stat {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.stat__value {
  font-family: var(--font-mono);
  font-size: clamp(34px, 5vw, 64px);
  font-weight: 700;
  line-height: 1;
  letter-spacing: -.02em;
  color: var(--accent);
}

.stat__unit {
  font-family: var(--font-mono);
  font-size: var(--fs-2);
  color: var(--text-dim);
}

.stat__label {
  font-size: 13px;
  line-height: 1.7;
  color: var(--text-dim);
}

/* ---------- 16. 图片容器 ---------- */
.media {
  position: relative;
  overflow: hidden;
  border: 1px solid var(--grid);
  border-radius: var(--r-md);
  background-color: var(--track);
  background-image: linear-gradient(135deg, rgba(18, 42, 74, .95), rgba(5, 11, 26, .95));
  isolation: isolate;
}

.media > img,
.media > svg,
.media > video {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.media--21x9 { aspect-ratio: 21 / 9; }
.media--16x9 { aspect-ratio: 16 / 9; }
.media--4x3 { aspect-ratio: 4 / 3; }
.media--1x1 { aspect-ratio: 1 / 1; }
.media--3x4 { aspect-ratio: 3 / 4; }
.media--free { aspect-ratio: auto; }

.media__ph {
  position: absolute;
  inset: 0;
  z-index: 0;
  background-image: repeating-linear-gradient(135deg, rgba(30, 58, 95, .4) 0 2px, transparent 2px 14px);
}

.media__grid {
  position: absolute;
  inset: 0;
  z-index: 1;
  pointer-events: none;
  background-image:
    linear-gradient(to right, rgba(47, 240, 208, .12) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(47, 240, 208, .12) 1px, transparent 1px);
  background-size: 48px 48px;
  opacity: .7;
}

.media__tag {
  position: absolute;
  top: 14px;
  left: 14px;
  z-index: 2;
}

.media__caption {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 2;
  padding: 36px 18px 14px;
  font-size: 13px;
  line-height: 1.65;
  color: var(--ice);
  background-image: linear-gradient(180deg, transparent, rgba(5, 11, 26, .9));
}

/* ---------- 17. 可选章节索引带 ---------- */
.page-rail {
  position: fixed;
  top: 50%;
  right: 18px;
  z-index: 50;
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding: 12px 8px;
  border: 1px solid var(--grid);
  border-radius: var(--r-pill);
  background-color: rgba(10, 23, 48, .84);
  transform: translateY(-50%);
  opacity: 0;
  visibility: hidden;
  transition: opacity .4s var(--ease), visibility .4s;
}

.page-rail.is-pinned {
  opacity: 1;
  visibility: visible;
}

.page-rail__item {
  display: block;
  width: 34px;
  padding: 6px 0;
  border-radius: var(--r-pill);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .06em;
  text-align: center;
  color: var(--text-dim);
  transition: color var(--dur) var(--ease), background-color var(--dur) var(--ease);
}

.page-rail__item:hover {
  color: var(--text);
  background-color: rgba(47, 240, 208, .12);
}

.page-rail__item[aria-current="true"] {
  background-color: var(--accent);
  color: #04211C;
  font-weight: 700;
}

/* ---------- 18. 显现 ---------- */
.js [data-reveal] {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity .6s var(--ease), transform .6s var(--ease);
}

.js [data-reveal="in"] {
  opacity: 1;
  transform: none;
}

/* ---------- 19. 响应式 ---------- */
@media (max-width: 1200px) {
  .page-rail { display: none; }
}

@media (max-width: 1180px) {
  .brand-descriptor { display: none; }
  .site-nav { gap: 12px; }
  .nav-list a { padding: 9px 10px; }
}

@media (max-width: 1100px) {
  .footer-main {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 40px 28px;
  }
  .footer-brand,
  .footer-contact { grid-column: 1 / -1; }
  .footer-note { max-width: 46ch; }
}

@media (max-width: 1020px) {
  .nav-toggle { display: inline-flex; }

  .site-nav {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    z-index: 80;
    width: min(340px, 86vw);
    display: flex;
    flex-direction: column;
    align-items: stretch;
    gap: 10px;
    padding: 92px 22px 30px;
    background-color: var(--deep);
    background-image: linear-gradient(180deg, var(--deep), var(--void) 72%);
    border-left: 1px solid var(--grid);
    box-shadow: -34px 0 64px -42px #000;
    overflow-y: auto;
    overscroll-behavior: contain;
    transform: translate3d(103%, 0, 0);
    visibility: hidden;
    transition: transform .36s var(--ease), visibility .36s;
  }

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

  .nav-list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
  }

  .nav-list a {
    justify-content: flex-start;
    padding: 15px 12px;
    border-bottom: 1px dashed rgba(30, 58, 95, .8);
    border-radius: var(--r-sm);
    font-size: var(--fs-4);
    font-weight: 700;
    color: var(--text);
  }

  .nav-num {
    max-width: 2.6em;
    opacity: 1;
    font-size: 12px;
  }

  .nav-list a[aria-current="page"] {
    background-color: rgba(47, 240, 208, .1);
    color: var(--accent);
  }

  .nav-list a[aria-current="page"]::after { display: none; }

  .nav-cta {
    justify-content: center;
    margin-top: 18px;
    padding: 15px 22px;
    font-size: var(--fs-3);
  }

  body[data-nav-open] { overflow: hidden; }

  .header-inner { gap: 16px; }
  .header-rail { font-size: 10px; letter-spacing: .12em; }
  .rail-cell--mid { display: none; }
}

@media (max-width: 900px) {
  .grid-12 { grid-template-columns: repeat(6, minmax(0, 1fr)); }
}

@media (max-width: 640px) {
  :root { --gutter: 18px; }

  .header-inner { min-height: 66px; padding: 11px 0; }
  .brand-mark { gap: 9px; }
  .brand-index { font-size: 10px; padding: 2px 8px; letter-spacing: .14em; }

  .footer-main {
    grid-template-columns: minmax(0, 1fr);
    gap: 34px;
    padding: 40px 0 32px;
  }

  .footer-brand,
  .footer-contact { grid-column: auto; }

  .footer-base {
    flex-direction: column;
    align-items: flex-start;
    gap: 8px;
    padding: 18px 0 30px;
  }
}

@media (max-width: 560px) {
  .grid-12 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .fold summary { padding: 16px 16px; }
  .fold__body { padding: 0 16px 18px; }
}

/* ---------- 20. 降低动效 ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }

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

  body::after { animation: none; }

  .js [data-reveal] {
    opacity: 1;
    transform: none;
  }
}