/* ==========================================================================
   亚博注册站 · 全站共享样式 /assets/site.css
   深夜体育屏气质：深蓝夜空 + 荧光青行动 + 暖橙高亮
   ========================================================================== */

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--topbar-h) + 14px);
}

body,
h1, h2, h3, h4, h5, h6,
p, ul, ol, li, figure, blockquote, fieldset, legend {
  margin: 0;
}

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

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

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

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

/* ---------- 2. 设计变量 ---------- */
:root {
  /* 色彩 */
  --night: #070B1A;
  --deep: #0C1226;
  --track: #111A36;
  --cyan: #00E5FF;
  --mint: #2AF5C8;
  --orange: #FF8A2A;
  --amber: #FFB347;
  --ink: #F4F7FF;
  --muted: #9AA8C7;
  --line: #1E2A4A;
  --paper: #E8EDF7;
  --danger: #FF5C7A;

  /* 结构 */
  --rail-w: 264px;
  --topbar-h: 60px;
  --wrap: 1180px;

  /* 字体 */
  --font-head: "Barlow Condensed", "Oswald", "Noto Sans SC", "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  --font-body: "Inter", "Noto Sans SC", "PingFang SC", "Microsoft YaHei", system-ui, -apple-system, sans-serif;
  --font-mono: "JetBrains Mono", "Roboto Mono", ui-monospace, SFMono-Regular, Consolas, monospace;

  /* 字号阶梯 */
  --step-hero: clamp(44px, 7.4vw, 92px);
  --step-h1: clamp(34px, 4.6vw, 62px);
  --step-h2: clamp(24px, 2.8vw, 36px);
  --step-h3: clamp(18px, 1.9vw, 22px);

  /* 间距 */
  --sp-block: clamp(46px, 7vw, 96px);
  --sp-gap: clamp(16px, 2.4vw, 28px);

  --ease: cubic-bezier(.22, .8, .24, 1);
}

/* ---------- 3. 基础排版 ---------- */
body {
  padding-top: var(--topbar-h);
  background-color: var(--night);
  background-image:
    radial-gradient(1100px 560px at 88% -12%, rgba(0, 229, 255, .10), transparent 62%),
    radial-gradient(820px 480px at 4% 6%, rgba(255, 138, 42, .08), transparent 64%);
  background-repeat: no-repeat;
  color: var(--ink);
  font-family: var(--font-body);
  font-size: 16px;
  font-weight: 400;
  line-height: 1.78;
  letter-spacing: .002em;
  min-height: 100vh;
}

body.nav-locked { overflow: hidden; }

h1, h2, h3, h4, .display {
  font-family: var(--font-head);
  font-weight: 800;
  line-height: 1.02;
  letter-spacing: -.02em;
  color: var(--ink);
}

h1 { font-size: var(--step-h1); }
h2 { font-size: var(--step-h2); }
h3 { font-size: var(--step-h3); }
h4 { font-size: 18px; font-weight: 700; letter-spacing: 0; }

.display {
  font-size: var(--step-hero);
  line-height: .96;
  letter-spacing: -.03em;
}

p { text-wrap: pretty; }

a {
  color: var(--cyan);
  text-decoration: none;
  transition: color .18s var(--ease), border-color .18s var(--ease);
}

a:hover { color: var(--mint); }

strong { color: var(--ink); font-weight: 700; }

small { font-size: 13px; color: var(--muted); }

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

::selection { background: rgba(0, 229, 255, .32); color: #fff; }

/* ---------- 4. 工具类 ---------- */
.sr-only {
  position: absolute;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

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

.center { text-align: center; }

.rule {
  height: 1px;
  background: var(--line);
  border: 0;
  margin: clamp(24px, 4vw, 44px) 0;
}

/* ---------- 5. Skip link ---------- */
.skip-link {
  position: fixed;
  top: 10px;
  left: 10px;
  z-index: 300;
  transform: translateY(-180%);
  padding: 10px 16px;
  background: var(--cyan);
  color: #04121A;
  font-family: var(--font-head);
  font-size: 14px;
  font-weight: 800;
  letter-spacing: .06em;
  border-radius: 2px;
  transition: transform .2s var(--ease);
}

.skip-link:focus { transform: none; color: #04121A; }

/* ---------- 6. 头部外壳 ---------- */
.site-header {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 80;
}

/* 6.1 移动顶栏 */
.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  height: var(--topbar-h);
  padding: 0 14px 0 16px;
  background: rgba(7, 11, 26, .94);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(10px);
}

.topbar__brand {
  display: flex;
  align-items: baseline;
  gap: 8px;
  min-width: 0;
}

.topbar__mark {
  font-family: var(--font-head);
  font-size: 21px;
  font-weight: 800;
  letter-spacing: .1em;
  color: var(--cyan);
}

.topbar__name {
  font-size: 14px;
  font-weight: 600;
  color: var(--ink);
  white-space: nowrap;
}

.nav-toggle {
  position: relative;
  display: inline-flex;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 46px;
  height: 40px;
  padding: 0 11px;
  background: var(--track);
  border: 1px solid var(--line);
  border-radius: 2px;
  cursor: pointer;
  transition: border-color .2s var(--ease), background .2s var(--ease);
}

.nav-toggle span {
  display: block;
  height: 2px;
  background: var(--ink);
  transition: transform .26s var(--ease), opacity .2s var(--ease);
}

.nav-toggle:hover { border-color: var(--cyan); }
.nav-toggle:hover span { background: var(--cyan); }

.site-header[data-open] .nav-toggle span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.site-header[data-open] .nav-toggle span:nth-child(2) { opacity: 0; }
.site-header[data-open] .nav-toggle span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* 6.2 遮罩 */
.nav-scrim {
  position: fixed;
  inset: 0;
  z-index: 85;
  background: rgba(4, 7, 18, .7);
  opacity: 0;
  visibility: hidden;
  transition: opacity .26s var(--ease), visibility .26s var(--ease);
}

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

/* 6.3 轨道导航 */
.rail {
  position: fixed;
  top: 0; left: 0; bottom: 0;
  z-index: 90;
  width: min(86vw, 306px);
  display: flex;
  flex-direction: column;
  gap: 18px;
  padding: 22px 18px 24px;
  overflow-y: auto;
  background: linear-gradient(180deg, var(--deep) 0%, var(--night) 100%);
  border-right: 1px solid var(--line);
  transform: translateX(-103%);
  visibility: hidden;
  transition: transform .3s var(--ease), visibility .3s var(--ease);
}

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

.rail__brand {
  display: block;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--line);
  color: var(--ink);
}

.rail__mark {
  display: inline-block;
  font-family: var(--font-head);
  font-size: 32px;
  font-weight: 800;
  line-height: 1;
  letter-spacing: .1em;
  color: var(--cyan);
}

.rail__name {
  display: block;
  margin-top: 8px;
  font-size: 15px;
  font-weight: 700;
  letter-spacing: .05em;
  color: var(--ink);
}

.rail__tag {
  display: block;
  margin-top: 8px;
  font-size: 12px;
  line-height: 1.65;
  color: var(--muted);
}

.rail__nav { flex: 1 1 auto; }

.rail__navtitle {
  margin-bottom: 10px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .2em;
  text-transform: uppercase;
  color: var(--muted);
}

.rail__list {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.rail__item { list-style: none; }

.rail__link {
  position: relative;
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 11px 10px 11px 12px;
  border-left: 2px solid transparent;
  border-radius: 2px;
  color: var(--muted);
  font-size: 14px;
  font-weight: 600;
  line-height: 1.4;
  transition: color .18s var(--ease), background .18s var(--ease), border-color .18s var(--ease);
}

.rail__link:hover {
  color: var(--ink);
  background: var(--track);
}

.rail__link[aria-current="page"] {
  color: var(--ink);
  border-left-color: var(--cyan);
  background: linear-gradient(90deg, rgba(0, 229, 255, .18), rgba(0, 229, 255, 0));
}

.rail__index {
  flex: 0 0 auto;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .06em;
  color: var(--muted);
}

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

.rail__label { min-width: 0; }

.rail__foot {
  margin-top: auto;
  display: grid;
  gap: 10px;
  padding-top: 18px;
  border-top: 1px solid var(--line);
}

.rail__cta { width: 100%; }

.rail__meta {
  font-family: var(--font-mono);
  font-size: 11px;
  line-height: 1.7;
  color: var(--muted);
  word-break: break-all;
}

/* ---------- 7. 页脚 ---------- */
.site-footer {
  position: relative;
  margin-top: var(--sp-block);
  background: var(--deep);
  border-top: 1px solid var(--line);
}

.footer__stripe {
  height: 6px;
  background-image:
    repeating-linear-gradient(115deg, var(--cyan) 0 14px, transparent 14px 30px),
    linear-gradient(90deg, rgba(255, 138, 42, .9), rgba(0, 229, 255, .25));
}

.footer__inner {
  max-width: var(--wrap);
  margin: 0 auto;
  padding: clamp(34px, 5vw, 64px) clamp(18px, 4vw, 40px) 26px;
}

.footer__grid {
  display: grid;
  gap: clamp(26px, 3vw, 44px);
  grid-template-columns: 1fr;
}

.footer__brandmark {
  display: block;
  font-family: var(--font-head);
  font-size: 26px;
  font-weight: 800;
  letter-spacing: .02em;
  color: var(--ink);
}

.footer__brandsub {
  display: block;
  margin-top: 6px;
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 400;
  letter-spacing: .14em;
  color: var(--cyan);
}

.footer__tagline {
  margin-top: 14px;
  max-width: 34ch;
  font-size: 14px;
  line-height: 1.75;
  color: var(--muted);
}

.footer__tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 16px;
}

.footer__title {
  display: flex;
  align-items: center;
  gap: 9px;
  margin-bottom: 14px;
  font-family: var(--font-head);
  font-size: 15px;
  font-weight: 800;
  letter-spacing: .1em;
  color: var(--ink);
}

.footer__title::before {
  content: "";
  width: 14px;
  height: 2px;
  background: var(--cyan);
}

.footer__list { display: grid; gap: 2px; }

.footer__link {
  display: inline-block;
  padding: 5px 0;
  border-bottom: 1px solid transparent;
  font-size: 14px;
  color: var(--muted);
}

.footer__link:hover {
  color: var(--cyan);
  border-bottom-color: rgba(0, 229, 255, .55);
}

.footer__col--contact .footer__list { gap: 12px; }

.footer__contact { display: grid; gap: 3px; }

.footer__label {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--muted);
}

.footer__text {
  font-size: 14px;
  line-height: 1.72;
  color: var(--ink);
  word-break: break-all;
}

.footer__note {
  margin-top: 14px;
  max-width: 40ch;
  font-size: 12px;
  line-height: 1.75;
  color: var(--muted);
}

.footer__bottom {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 22px;
  margin-top: clamp(28px, 4vw, 46px);
  padding-top: 18px;
  border-top: 1px solid var(--line);
  font-size: 13px;
  color: var(--muted);
}

.footer__legal {
  font-size: 12px;
  letter-spacing: .06em;
  color: var(--amber);
}

.footer__meta { color: var(--muted); }

/* ---------- 8. 通用按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 20px;
  background: var(--track);
  border: 1px solid var(--line);
  border-radius: 2px;
  color: var(--ink);
  font-family: var(--font-head);
  font-size: 15px;
  font-weight: 700;
  letter-spacing: .05em;
  line-height: 1.2;
  cursor: pointer;
  transition: transform .2s var(--ease), box-shadow .25s var(--ease),
              border-color .2s var(--ease), background .2s var(--ease), color .2s var(--ease);
}

.btn:hover {
  color: var(--ink);
  border-color: var(--cyan);
  transform: translateY(-1px);
  box-shadow: 0 0 0 1px rgba(0, 229, 255, .38), 0 10px 26px -14px rgba(0, 229, 255, .8);
}

.btn--primary {
  background: var(--cyan);
  border-color: var(--cyan);
  color: #04121A;
}

.btn--primary:hover {
  background: #5CF0FF;
  border-color: #5CF0FF;
  color: #04121A;
}

.btn--accent {
  background: var(--orange);
  border-color: var(--orange);
  color: #1A0C02;
}

.btn--accent:hover {
  background: var(--amber);
  border-color: var(--amber);
  color: #1A0C02;
  box-shadow: 0 0 0 1px rgba(255, 138, 42, .5), 0 10px 26px -14px rgba(255, 138, 42, .9);
}

.btn--ghost { background: transparent; }

.btn--sm {
  padding: 8px 14px;
  font-size: 13px;
}

/* ---------- 9. 标签 ---------- */
.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 10px;
  background: var(--track);
  border: 1px solid var(--line);
  border-radius: 2px;
  color: var(--muted);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .08em;
  line-height: 1.5;
  white-space: nowrap;
}

.tag--cyan {
  color: var(--cyan);
  border-color: rgba(0, 229, 255, .45);
  background: rgba(0, 229, 255, .09);
}

.tag--orange {
  color: var(--amber);
  border-color: rgba(255, 138, 42, .5);
  background: rgba(255, 138, 42, .1);
}

.tag--green {
  color: var(--mint);
  border-color: rgba(42, 245, 200, .45);
  background: rgba(42, 245, 200, .09);
}

/* ---------- 10. 面包屑 ---------- */
.breadcrumb {
  font-size: 13px;
  color: var(--muted);
}

.breadcrumb__list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 6px;
}

.breadcrumb__item {
  display: flex;
  align-items: center;
  gap: 6px;
}

.breadcrumb__item + .breadcrumb__item::before {
  content: "/";
  color: var(--line);
}

.breadcrumb__link { color: var(--muted); }
.breadcrumb__link:hover { color: var(--cyan); }

.breadcrumb__current {
  color: var(--ink);
  font-weight: 600;
}

/* ---------- 11. 容器与分区节奏 ---------- */
.page-shell {
  max-width: var(--wrap);
  margin: 0 auto;
  padding: 0 clamp(18px, 4vw, 40px);
}

.section {
  position: relative;
  padding: var(--sp-block) 0;
}

.section--tight { padding: clamp(28px, 3.4vw, 48px) 0; }

.section--deep {
  background: var(--deep);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.section--track {
  background: var(--track);
  border-top: 1px solid var(--line);
}

.section__head {
  max-width: 62ch;
  margin-bottom: clamp(20px, 3vw, 36px);
}

.section__label {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 12px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--cyan);
}

.section__label::before {
  content: "";
  width: 22px;
  height: 2px;
  background: var(--cyan);
}

.section__title { font-size: var(--step-h2); }

.section__sub {
  margin-top: 12px;
  font-size: 16px;
  line-height: 1.8;
  color: var(--muted);
}

.lede {
  max-width: 64ch;
  font-size: clamp(17px, 1.6vw, 20px);
  line-height: 1.8;
  color: var(--muted);
}

.prose {
  max-width: 68ch;
  font-size: 17px;
  line-height: 1.85;
  color: #DCE4F7;
}

.prose h2 {
  margin: 1.6em 0 .5em;
  font-size: var(--step-h3);
}

.prose h3 {
  margin: 1.4em 0 .4em;
  font-size: 18px;
  letter-spacing: 0;
}

.prose p + p { margin-top: 1em; }

.prose ul,
.prose ol {
  margin: 1em 0;
  padding-left: 1.4em;
  list-style: disc;
}

.prose ol { list-style: decimal; }

.prose li + li { margin-top: .4em; }

.prose a {
  color: var(--cyan);
  border-bottom: 1px solid rgba(0, 229, 255, .45);
}

.prose a:hover { border-bottom-color: var(--mint); }

.prose blockquote {
  margin: 1.4em 0;
  padding: 12px 0 12px 18px;
  border-left: 3px solid var(--orange);
  color: var(--muted);
}

/* ---------- 12. 栅格 ---------- */
.grid {
  display: grid;
  gap: var(--sp-gap);
  grid-template-columns: 1fr;
}

/* ---------- 13. 面板与纸张叠层 ---------- */
.panel {
  position: relative;
  padding: clamp(18px, 2.4vw, 26px);
  background: var(--deep);
  border: 1px solid var(--line);
  border-radius: 2px;
  transition: border-color .22s var(--ease), transform .22s var(--ease);
}

.panel:hover { border-color: rgba(0, 229, 255, .4); }

.panel__head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 12px;
}

.panel__title {
  font-family: var(--font-head);
  font-size: 18px;
  font-weight: 700;
  letter-spacing: .02em;
  line-height: 1.3;
}

.panel__body {
  font-size: 15px;
  line-height: 1.78;
  color: var(--muted);
}

.paper {
  position: relative;
  padding: clamp(20px, 3vw, 34px);
  background: var(--deep);
  border: 1px solid var(--line);
  border-radius: 2px;
}

.paper--stack::before,
.paper--stack::after {
  content: "";
  position: absolute;
  inset: 0;
  z-index: -1;
  background: var(--deep);
  border: 1px solid var(--line);
  border-radius: 2px;
}

.paper--stack::before { transform: translate(6px, 6px); }
.paper--stack::after { transform: translate(12px, 12px); opacity: .5; }

/* ---------- 14. 可展开内容组 ---------- */
.accordion { border-top: 1px solid var(--line); }

.accordion__item { border-bottom: 1px solid var(--line); }

.accordion__heading {
  margin: 0;
  font-size: inherit;
  font-weight: inherit;
}

.accordion__btn {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  width: 100%;
  padding: 18px 4px;
  background: transparent;
  border: 0;
  color: var(--ink);
  font-family: var(--font-head);
  font-size: clamp(17px, 1.8vw, 21px);
  font-weight: 700;
  letter-spacing: 0;
  line-height: 1.45;
  text-align: left;
  cursor: pointer;
  transition: color .2s var(--ease);
}

.accordion__btn:hover { color: var(--cyan); }

.accordion__icon {
  position: relative;
  flex: 0 0 18px;
  width: 18px;
  height: 18px;
}

.accordion__icon::before,
.accordion__icon::after {
  content: "";
  position: absolute;
  background: var(--cyan);
  transition: transform .26s var(--ease), opacity .2s var(--ease);
}

.accordion__icon::before { left: 0; top: 8px; width: 18px; height: 2px; }
.accordion__icon::after { left: 8px; top: 0; width: 2px; height: 18px; }

.accordion__item[data-open] .accordion__btn { color: var(--cyan); }
.accordion__item[data-open] .accordion__icon::after { transform: scaleY(0); }

.accordion__panel {
  max-width: 72ch;
  padding: 0 4px 20px;
  font-size: 16px;
  line-height: 1.85;
  color: var(--muted);
}

.accordion__panel[hidden] { display: none; }

/* ---------- 15. 赛事条带（横向滚动） ---------- */
.band {
  display: flex;
  gap: 14px;
  padding: 6px 2px 16px;
  overflow-x: auto;
  scroll-snap-type: x proximity;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: thin;
  scrollbar-color: var(--line) transparent;
}

.band::-webkit-scrollbar { height: 6px; }
.band::-webkit-scrollbar-track { background: rgba(30, 42, 74, .4); }
.band::-webkit-scrollbar-thumb { background: var(--line); }

.band__item {
  flex: 0 0 auto;
  min-width: 232px;
  padding: 14px 16px;
  background: var(--track);
  border: 1px solid var(--line);
  border-left: 3px solid var(--orange);
  border-radius: 2px;
  scroll-snap-align: start;
}

.band__time {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .1em;
  color: var(--amber);
}

.band__title {
  margin-top: 6px;
  font-family: var(--font-head);
  font-size: 18px;
  font-weight: 700;
  line-height: 1.3;
}

.band__meta {
  margin-top: 6px;
  font-size: 13px;
  line-height: 1.7;
  color: var(--muted);
}

/* ---------- 16. 数据块 ---------- */
.stat { display: grid; gap: 4px; }

.stat__value {
  font-family: var(--font-mono);
  font-size: clamp(22px, 2.6vw, 32px);
  font-weight: 700;
  line-height: 1.1;
  color: var(--cyan);
}

.stat__label {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--muted);
}

/* ---------- 17. 图片容器基础规则（页面阶段放图） ---------- */
.media {
  position: relative;
  overflow: hidden;
  background: linear-gradient(140deg, var(--track), var(--night));
  border: 1px solid var(--line);
  border-radius: 2px;
}

.media__img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.media__tag {
  position: absolute;
  top: 12px;
  left: 12px;
  z-index: 2;
}

.media__caption {
  position: absolute;
  left: 0; right: 0; bottom: 0;
  z-index: 2;
  padding: 34px 14px 12px;
  background: linear-gradient(0deg, rgba(7, 11, 26, .94), rgba(7, 11, 26, 0));
  color: var(--ink);
  font-size: 13px;
  line-height: 1.6;
}

.media--wide { aspect-ratio: 16 / 9; }
.media--square { aspect-ratio: 1 / 1; }
.media--tall { aspect-ratio: 3 / 4; }
.media--tilt { transform: rotate(-1.2deg); }

/* ---------- 18. 脚本注入：进度条 / 回到顶部 ---------- */
.progress-bar {
  position: fixed;
  top: var(--topbar-h);
  left: 0; right: 0;
  z-index: 120;
  height: 3px;
  background: rgba(30, 42, 74, .55);
  pointer-events: none;
}

.progress-bar__fill {
  display: block;
  width: 0;
  height: 100%;
  background: linear-gradient(90deg, var(--cyan), var(--mint) 55%, var(--orange));
  transition: width .1s linear;
}

.to-top {
  position: fixed;
  right: 16px;
  bottom: 18px;
  z-index: 110;
  display: grid;
  place-items: center;
  width: 44px;
  height: 44px;
  background: var(--track);
  border: 1px solid var(--line);
  border-radius: 2px;
  color: var(--cyan);
  font-size: 17px;
  line-height: 1;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity .25s var(--ease), transform .25s var(--ease),
              visibility .25s var(--ease), border-color .2s var(--ease);
}

.to-top[data-visible="true"] {
  opacity: 1;
  visibility: visible;
  transform: none;
}

.to-top:hover { border-color: var(--cyan); }

/* ---------- 19. 显现动画 ---------- */
[data-reveal] {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity .6s var(--ease), transform .6s var(--ease);
}

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

/* ---------- 20. 响应式：平板 ---------- */
@media (min-width: 640px) {
  .grid--2,
  .grid--3,
  .grid--4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }

  .footer__grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

/* ---------- 21. 响应式：桌面（轨道导航常驻） ---------- */
@media (min-width: 1024px) {
  html { scroll-padding-top: 24px; }

  body {
    padding-top: 0;
    padding-left: var(--rail-w);
    background-attachment: fixed;
  }

  .site-header {
    right: auto;
    width: var(--rail-w);
    height: 100%;
  }

  .topbar { display: none; }

  .nav-scrim { display: none; }

  .rail {
    width: var(--rail-w);
    visibility: visible;
    transform: none;
    transition: none;
  }

  .skip-link { left: calc(var(--rail-w) + 14px); }

  .progress-bar { top: 0; left: var(--rail-w); }

  .grid--3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .grid--4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }

  .footer__grid { grid-template-columns: 1.5fr 1fr 1.1fr 1.4fr; }

  .media--tilt { transform: rotate(-1.6deg); }
}

@media (min-width: 1440px) {
  :root { --rail-w: 288px; }
  :root { --wrap: 1220px; }
}

/* ---------- 22. 减少动态效果 ---------- */
@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] {
    opacity: 1;
    transform: none;
  }
}