/* =========================================================
   YABO 品牌站 · 共享样式 /assets/site.css
   P0 网格底纹 → P1 画板 → P2 数据卡 → P3 浮层标签
   ========================================================= */

:root {
  --ink: #081422;
  --deck: #0E2135;
  --hull: #1A3247;
  --grid: #2C4A66;
  --cyan: #19D3E6;
  --mist: #8FE9F2;
  --amber: #F5A93F;
  --teal: #0B6E7A;
  --frost: #E9F1F7;
  --dim: #9FB3C6;
  --cold: #DDE6EE;
  --on-cyan: #04121b;

  --font-display: "Barlow Condensed", "Source Han Sans SC", "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: "JetBrains Mono", "IBM Plex Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --font-body: "Noto Sans SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;

  --r: 2px;
  --shell: 1240px;
  --gutter: clamp(18px, 4vw, 40px);
  --panel-gap: 96px;
  --ease: cubic-bezier(.2, .8, .2, 1);
}

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background-color: var(--ink);
  background-image:
    radial-gradient(1200px 620px at 82% -12%, rgba(25, 211, 230, .10), transparent 62%),
    radial-gradient(920px 520px at 4% 6%, rgba(11, 110, 122, .18), transparent 64%),
    linear-gradient(180deg, #081422 0%, #0a1a2b 46%, #07111d 100%);
  background-attachment: fixed;
  color: var(--frost);
  font-family: var(--font-body);
  font-size: 17px;
  font-weight: 400;
  line-height: 1.85;
  letter-spacing: .005em;
  min-height: 100vh;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background-image:
    repeating-linear-gradient(90deg, rgba(44, 74, 102, .30) 0 1px, transparent 1px 80px),
    repeating-linear-gradient(0deg, rgba(44, 74, 102, .20) 0 1px, transparent 1px 80px);
  opacity: .55;
}

img { max-width: 100%; display: block; border: 0; }
main { display: block; position: relative; z-index: 1; }
button { font: inherit; color: inherit; }

h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 700;
  letter-spacing: -.01em;
  line-height: 1.02;
  margin: 0 0 .55em;
  color: var(--frost);
}
h1 { font-size: clamp(38px, 6.4vw, 76px); }
h2 { font-size: clamp(26px, 3.4vw, 40px); }
h3 { font-size: clamp(19px, 2vw, 25px); letter-spacing: 0; line-height: 1.25; }
h4 { font-size: 17px; font-family: var(--font-body); font-weight: 600; line-height: 1.5; }

p { margin: 0 0 1.2em; }
p:last-child { margin-bottom: 0; }

a { color: var(--cyan); text-decoration: none; }
a:hover { color: var(--mist); }

ul, ol { margin: 0 0 1.2em; padding-left: 1.25em; }
li { margin-bottom: .4em; }

:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: 3px;
  border-radius: 1px;
}

.skip-link {
  position: absolute;
  left: 50%;
  top: -80px;
  transform: translateX(-50%);
  z-index: 200;
  padding: 10px 18px;
  background: var(--cyan);
  color: var(--on-cyan);
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: .12em;
  border-radius: var(--r);
  transition: top .18s var(--ease);
}
.skip-link:focus { top: 12px; color: var(--on-cyan); }

/* ---------- 排版工具类 ---------- */
.mono {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  letter-spacing: .06em;
}

.label {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 500;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--dim);
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 500;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--cyan);
  margin-bottom: 18px;
}
.eyebrow::before {
  content: "";
  width: 24px;
  height: 1px;
  background: var(--cyan);
}

.section-lead {
  max-width: 38em;
  color: var(--dim);
  font-size: 17px;
}

/* ---------- 布局骨架 ---------- */
.shell {
  width: 100%;
  max-width: var(--shell);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.stack {
  display: flex;
  flex-direction: column;
  gap: var(--panel-gap);
}

.grid-12 {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: 24px;
}

.split {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: 24px;
  align-items: start;
}
.split-main { grid-column: 1 / 8; min-width: 0; }
.split-side { grid-column: 9 / 13; min-width: 0; }

.channel {
  position: sticky;
  top: 104px;
}

.stagger-a { margin-inline-start: 0; }
.stagger-b { margin-inline-start: 0; }
.stagger-c { margin-inline-start: 0; }

/* ---------- 面板层级 ---------- */
.panel {
  position: relative;
  background: linear-gradient(180deg, rgba(14, 33, 53, .94), rgba(10, 25, 41, .94));
  border: 1px solid var(--grid);
  border-radius: var(--r);
  padding: clamp(20px, 3vw, 38px);
  box-shadow: 0 26px 60px -42px #000;
}
.panel::after {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: inherit;
  pointer-events: none;
  box-shadow: inset 0 1px 0 rgba(233, 241, 247, .05);
}
.panel--deck {
  background: linear-gradient(180deg, rgba(26, 50, 71, .92), rgba(16, 35, 53, .94));
  border-color: #31536f;
}
.panel--chip {
  background: rgba(26, 50, 71, .55);
  border-color: #33556f;
  padding: 16px 18px;
  box-shadow: 0 14px 30px -26px #000;
}
.panel--light {
  background: linear-gradient(180deg, #e7eef4, var(--cold));
  border-color: #c2d1de;
  color: var(--ink);
}
.panel--light h1,
.panel--light h2,
.panel--light h3,
.panel--light h4 { color: var(--ink); }
.panel--light .label,
.panel--light .section-lead { color: #4a6076; }
.panel--light a { color: #0a5c68; }
.panel--light a:hover { color: #083f48; }

/* ---------- 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 12px 20px;
  background: rgba(26, 50, 71, .55);
  border: 1px solid var(--grid);
  border-radius: var(--r);
  color: var(--frost);
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 500;
  letter-spacing: .14em;
  text-transform: uppercase;
  text-decoration: none;
  cursor: pointer;
  transition: border-color .16s var(--ease), color .16s var(--ease), background .16s var(--ease);
}
.btn:hover {
  border-color: var(--cyan);
  color: var(--frost);
  background: rgba(25, 211, 230, .10);
}
.btn--primary {
  background: var(--cyan);
  border-color: var(--cyan);
  color: var(--on-cyan);
  font-weight: 600;
}
.btn--primary:hover {
  background: var(--mist);
  border-color: var(--mist);
  color: var(--on-cyan);
}
.btn--amber {
  background: rgba(245, 169, 63, .10);
  border-color: rgba(245, 169, 63, .45);
  color: var(--amber);
}
.btn--amber:hover {
  background: rgba(245, 169, 63, .18);
  border-color: var(--amber);
  color: var(--amber);
}

/* ---------- 面包屑 ---------- */
.breadcrumbs {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  margin: 0 0 26px;
  padding: 0;
  list-style: none;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .12em;
  color: var(--dim);
}
.breadcrumbs li {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin: 0;
}
.breadcrumbs li + li::before {
  content: "／";
  color: var(--grid);
}
.breadcrumbs a { color: var(--dim); }
.breadcrumbs a:hover { color: var(--cyan); }
.breadcrumbs [aria-current="page"] { color: var(--frost); }

/* ---------- 正文 ---------- */
.prose {
  max-width: 38em;
  color: var(--frost);
}
.prose > p { color: var(--frost); }
.prose h2 { margin-top: 1.6em; }
.prose h3 { margin-top: 1.4em; }
.prose ul,
.prose ol { color: var(--frost); }
.prose strong { color: var(--mist); font-weight: 600; }

/* ---------- 章节索引 ---------- */
.chapter-head {
  display: flex;
  align-items: flex-start;
  gap: 18px;
  padding-bottom: 16px;
  margin-bottom: 26px;
  border-bottom: 1px solid var(--grid);
}
.chapter-num {
  flex: none;
  min-width: 54px;
  padding-top: 5px;
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 500;
  letter-spacing: .2em;
  color: var(--cyan);
}
.chapter-title { margin: 0; }

/* ---------- 目录与分段控件 ---------- */
.toc {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 2px;
}
.toc li { margin: 0; }
.toc-link {
  display: flex;
  align-items: baseline;
  gap: 10px;
  padding: 8px 10px;
  border-left: 2px solid transparent;
  color: var(--dim);
  font-size: 15px;
  transition: color .12s var(--ease), border-color .12s var(--ease), background .12s var(--ease);
}
.toc-link:hover { color: var(--frost); background: rgba(25, 211, 230, .07); }
.toc-link.is-active {
  color: var(--amber);
  border-left-color: var(--amber);
  background: rgba(245, 169, 63, .08);
}

.segmented {
  display: inline-flex;
  gap: 2px;
  padding: 3px;
  background: rgba(8, 20, 34, .8);
  border: 1px solid var(--grid);
  border-radius: var(--r);
}
.segmented [data-seg] {
  padding: 7px 14px;
  background: transparent;
  border: 0;
  border-radius: var(--r);
  color: var(--dim);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .14em;
  text-transform: uppercase;
  cursor: pointer;
  transition: background .14s var(--ease), color .14s var(--ease);
}
.segmented [data-seg]:hover { color: var(--frost); }
.segmented [data-seg][aria-selected="true"] {
  background: var(--cyan);
  color: var(--on-cyan);
  font-weight: 600;
}
[data-seg-panel][hidden] { display: none; }

/* ---------- 数据条 ---------- */
.meter {
  height: 6px;
  background: rgba(44, 74, 102, .55);
  border-radius: 1px;
  overflow: hidden;
}
.meter-fill {
  display: block;
  height: 100%;
  width: 0;
  background: linear-gradient(90deg, var(--teal), var(--cyan));
  border-radius: 1px;
  transition: width .6s var(--ease);
}
.meter--amber .meter-fill { background: linear-gradient(90deg, #8a5a17, var(--amber)); }

/* ---------- 图片容器基座 ---------- */
.media-frame {
  position: relative;
  display: block;
  overflow: hidden;
  margin: 0;
  aspect-ratio: 16 / 10;
  background: linear-gradient(135deg, #0E2135 0%, #123b4c 60%, #0B6E7A 130%);
  border: 1px solid var(--grid);
  border-radius: var(--r);
}
.media-frame img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  filter: saturate(.9) brightness(.92);
}
.media-frame::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 1;
  pointer-events: none;
  background-image:
    repeating-linear-gradient(90deg, rgba(8, 20, 34, .35) 0 1px, transparent 1px 56px),
    repeating-linear-gradient(0deg, rgba(8, 20, 34, .35) 0 1px, transparent 1px 56px),
    linear-gradient(160deg, transparent 46%, rgba(25, 211, 230, .35) 50%, transparent 54%);
}
.media-frame figcaption {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 2;
  padding: 12px 14px;
  background: linear-gradient(180deg, transparent, rgba(8, 20, 34, .92));
  color: var(--dim);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .12em;
}
.media-frame--wide { aspect-ratio: 21 / 9; }
.media-frame--tall { aspect-ratio: 4 / 5; }
.media-frame--square { aspect-ratio: 1 / 1; }

/* ---------- 入场显现 ---------- */
[data-reveal] {
  opacity: 0;
  transform: translateY(12px);
  transition: opacity .18s var(--ease), transform .18s var(--ease);
}
[data-reveal].is-in {
  opacity: 1;
  transform: none;
}
.reveal-group > [data-reveal]:nth-child(2) { transition-delay: .06s; }
.reveal-group > [data-reveal]:nth-child(3) { transition-delay: .12s; }
.reveal-group > [data-reveal]:nth-child(4) { transition-delay: .18s; }

/* =========================================================
   头部
   ========================================================= */
.site-header {
  position: sticky;
  top: 0;
  z-index: 80;
  padding: 14px var(--gutter) 0;
  background: linear-gradient(180deg, rgba(8, 20, 34, .96) 0%, rgba(8, 20, 34, .72) 58%, rgba(8, 20, 34, 0) 100%);
}
.header-shell {
  max-width: var(--shell);
  margin-inline: auto;
}

.header-rail {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 0 6px 9px;
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 500;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--dim);
  overflow: hidden;
  max-height: 40px;
  transition: max-height .22s var(--ease), opacity .18s var(--ease), padding .22s var(--ease);
}
.rail-mono { color: var(--frost); white-space: nowrap; }
.rail-line {
  flex: 1 1 auto;
  height: 1px;
  min-width: 24px;
  background: var(--grid);
}
.rail-note { white-space: nowrap; }
.rail-status {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  color: var(--cyan);
  white-space: nowrap;
}
.rail-dot {
  width: 6px;
  height: 6px;
  background: var(--cyan);
  box-shadow: 0 0 0 3px rgba(25, 211, 230, .16);
  animation: yabo-breathe 3.2s ease-in-out infinite;
}

.site-header[data-collapsed] .header-rail {
  max-height: 0;
  opacity: 0;
  padding-bottom: 0;
}

.nav-capsule {
  position: relative;
  display: flex;
  align-items: center;
  gap: 16px;
  min-height: 64px;
  padding: 10px 12px 10px 16px;
  background: linear-gradient(180deg, rgba(22, 47, 71, .96), rgba(14, 33, 53, .97));
  border: 1px solid var(--grid);
  border-radius: var(--r);
  box-shadow: 0 22px 46px -30px #000, inset 0 1px 0 rgba(233, 241, 247, .06);
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
  transition: min-height .22s var(--ease), padding .22s var(--ease);
}
.nav-capsule::before {
  content: "";
  position: absolute;
  left: 0;
  top: 14px;
  bottom: 14px;
  width: 2px;
  background: linear-gradient(180deg, var(--cyan), transparent);
}
.site-header[data-collapsed] .nav-capsule {
  min-height: 52px;
  padding: 6px 10px 6px 16px;
}

.capsule-progress {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  height: 2px;
  overflow: hidden;
  background: rgba(44, 74, 102, .45);
  pointer-events: none;
}
.capsule-fill {
  display: block;
  height: 100%;
  width: 0;
  background: linear-gradient(90deg, var(--teal), var(--cyan) 70%, var(--amber));
  transition: width .12s linear;
}

/* 品牌 */
.brand {
  display: inline-flex;
  align-items: center;
  gap: 11px;
  padding: 2px 4px;
  color: var(--frost);
  text-decoration: none;
  flex: none;
}
.brand:hover { color: var(--frost); }
.brand-glyph {
  position: relative;
  display: block;
  width: 22px;
  height: 22px;
  border: 1px solid var(--cyan);
  background: rgba(25, 211, 230, .08);
}
.brand-glyph::before {
  content: "";
  position: absolute;
  inset: 5px;
  background: var(--cyan);
}
.brand-glyph::after {
  content: "";
  position: absolute;
  left: 5px;
  right: 5px;
  bottom: -4px;
  height: 2px;
  background: var(--amber);
}
.brand-text {
  display: flex;
  flex-direction: column;
  line-height: 1.05;
}
.brand-name {
  font-family: var(--font-display);
  font-size: 21px;
  font-weight: 700;
  letter-spacing: .1em;
  color: var(--frost);
}
.brand-sub {
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: .26em;
  text-transform: uppercase;
  color: var(--dim);
  transition: opacity .18s var(--ease);
}
.site-header[data-collapsed] .brand-sub { opacity: .55; }

.nav-current {
  display: none;
  padding: 5px 10px;
  border: 1px solid rgba(245, 169, 63, .38);
  background: rgba(245, 169, 63, .08);
  color: var(--amber);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .16em;
  white-space: nowrap;
}

/* 导航 */
.site-nav {
  display: flex;
  align-items: center;
  gap: 2px;
  margin-inline-start: auto;
}
.site-nav a {
  position: relative;
  display: inline-block;
  padding: 8px 11px;
  color: var(--dim);
  font-size: 14px;
  letter-spacing: .02em;
  text-decoration: none;
  white-space: nowrap;
  transition: color .16s var(--ease), background .16s var(--ease);
}
.site-nav a:hover {
  color: var(--frost);
  background: rgba(25, 211, 230, .08);
}
.site-nav a[aria-current="page"] { color: var(--frost); }
.site-nav a[aria-current="page"]::after {
  content: "";
  position: absolute;
  left: 11px;
  right: 11px;
  bottom: 1px;
  height: 2px;
  background: var(--cyan);
}

/* 通道按钮 */
.nav-cta {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  flex: none;
  padding: 10px 16px;
  background: var(--cyan);
  border: 1px solid var(--cyan);
  border-radius: var(--r);
  color: var(--on-cyan);
  font-size: 14px;
  font-weight: 600;
  letter-spacing: .04em;
  text-decoration: none;
  white-space: nowrap;
  transition: background .16s var(--ease), border-color .16s var(--ease);
}
.nav-cta:hover {
  background: var(--mist);
  border-color: var(--mist);
  color: var(--on-cyan);
}
.nav-cta-mark {
  width: 8px;
  height: 8px;
  background: var(--on-cyan);
  animation: yabo-breathe 3.2s ease-in-out infinite;
}

/* 移动导航按钮 */
.nav-toggle {
  display: none;
  align-items: center;
  gap: 9px;
  margin-inline-start: auto;
  padding: 9px 12px;
  background: rgba(26, 50, 71, .7);
  border: 1px solid var(--grid);
  border-radius: var(--r);
  color: var(--frost);
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 500;
  letter-spacing: .18em;
  text-transform: uppercase;
  cursor: pointer;
}
.nav-toggle:hover { border-color: var(--cyan); }
.nav-toggle-bars {
  position: relative;
  display: block;
  width: 16px;
  height: 10px;
}
.nav-toggle-bars::before,
.nav-toggle-bars::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  height: 1.5px;
  background: currentColor;
  transition: transform .18s var(--ease);
}
.nav-toggle-bars::before { top: 0; }
.nav-toggle-bars::after { bottom: 0; }
.site-header[data-open] .nav-toggle-bars::before { transform: translateY(4.25px) rotate(45deg); }
.site-header[data-open] .nav-toggle-bars::after { transform: translateY(-4.25px) rotate(-45deg); }

@keyframes yabo-breathe {
  0%, 100% { opacity: .6; }
  50% { opacity: 1; }
}

/* =========================================================
   页脚
   ========================================================= */
.site-footer {
  position: relative;
  z-index: 1;
  margin-top: var(--panel-gap);
  padding: 0 0 28px;
  background: linear-gradient(180deg, rgba(6, 16, 28, 0) 0%, rgba(6, 16, 28, .92) 22%, #060f1b 100%);
  border-top: 1px solid var(--grid);
}
.footer-shell {
  max-width: var(--shell);
  margin-inline: auto;
  padding: 56px var(--gutter) 0;
}

.footer-top {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: 32px;
}
.footer-ident { grid-column: 1 / 6; min-width: 0; }
.footer-nav { grid-column: 7 / 13; min-width: 0; }

.brand--footer { padding: 0; margin-bottom: 16px; }
.brand--footer .brand-name { font-size: 24px; }

.footer-tag {
  margin: 0 0 22px;
  color: var(--dim);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .16em;
  text-transform: uppercase;
}
.footer-meta {
  display: grid;
  gap: 8px;
  padding-top: 18px;
  border-top: 1px solid var(--grid);
}
.meta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 4px 12px;
  align-items: baseline;
}
.meta-key {
  flex: none;
  min-width: 62px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--cyan);
}
.meta-val {
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: .04em;
  color: var(--frost);
  word-break: break-word;
}

.footer-nav {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 28px;
}
.footer-col-title {
  display: flex;
  align-items: center;
  gap: 8px;
  margin: 0 0 14px;
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 500;
  letter-spacing: .2em;
  text-transform: uppercase;
  color: var(--cyan);
}
.footer-col-title::before {
  content: "";
  width: 6px;
  height: 6px;
  background: var(--amber);
}
.footer-links {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 2px;
}
.footer-links li { margin: 0; }
.footer-links a {
  display: inline-block;
  padding: 5px 0;
  color: var(--dim);
  font-size: 15px;
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color .16s var(--ease), border-color .16s var(--ease);
}
.footer-links a:hover {
  color: var(--frost);
  border-bottom-color: var(--cyan);
}

.footer-note {
  margin: 40px 0 0;
  padding-left: 14px;
  max-width: 68ch;
  border-left: 2px solid rgba(245, 169, 63, .55);
  color: var(--dim);
  font-size: 14px;
  line-height: 1.75;
}

.footer-base {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px 26px;
  margin-top: 30px;
  padding-top: 20px;
  border-top: 1px solid var(--grid);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .1em;
  color: var(--dim);
}
.footer-copy { color: var(--frost); }
.footer-icp { color: var(--dim); }
.footer-addr { color: var(--dim); }

/* 返回顶部 */
.to-top {
  position: fixed;
  right: 22px;
  bottom: 22px;
  z-index: 70;
  display: inline-flex;
  align-items: center;
  gap: 9px;
  padding: 10px 15px;
  background: rgba(14, 33, 53, .94);
  border: 1px solid var(--grid);
  border-radius: var(--r);
  color: var(--frost);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .16em;
  text-transform: uppercase;
  cursor: pointer;
  opacity: 0;
  transform: translateY(8px);
  pointer-events: none;
  -webkit-backdrop-filter: blur(8px);
  backdrop-filter: blur(8px);
  transition: opacity .18s var(--ease), transform .18s var(--ease), border-color .16s var(--ease);
}
.to-top:hover { border-color: var(--cyan); }
.to-top.is-on {
  opacity: 1;
  transform: none;
  pointer-events: auto;
}
.to-top-mark {
  position: relative;
  display: block;
  width: 10px;
  height: 10px;
}
.to-top-mark::before,
.to-top-mark::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  background: var(--cyan);
}
.to-top-mark::before {
  top: 0;
  height: 1.5px;
  transform: translateY(3px) rotate(-45deg);
  transform-origin: right center;
}
.to-top-mark::after {
  top: 0;
  height: 1.5px;
  transform: translateY(3px) rotate(45deg);
  transform-origin: left center;
}

/* =========================================================
   响应式
   ========================================================= */
@media (min-width: 1024px) {
  .stagger-b { margin-inline-start: 16px; }
  .stagger-c { margin-inline-start: 32px; }
  .site-header[data-collapsed] .nav-current { display: inline-block; }
}

@media (max-width: 1100px) {
  .rail-note { display: none; }
  .site-nav a { padding: 8px 9px; font-size: 13.5px; }
}

@media (max-width: 1000px) {
  .site-header { padding-top: 10px; }
  .nav-capsule { gap: 10px; min-height: 58px; }
  .site-header[data-collapsed] .nav-capsule { min-height: 54px; }
  .nav-toggle { display: inline-flex; }
  .nav-current { display: none !important; }
  .site-nav {
    position: absolute;
    top: calc(100% + 8px);
    left: 0;
    right: 0;
    z-index: 5;
    display: none;
    flex-direction: column;
    align-items: stretch;
    gap: 2px;
    margin-inline-start: 0;
    padding: 10px;
    background: linear-gradient(180deg, rgba(18, 40, 61, .99), rgba(11, 27, 43, .99));
    border: 1px solid var(--grid);
    border-radius: var(--r);
    box-shadow: 0 28px 50px -30px #000;
  }
  .site-header[data-open] .site-nav { display: flex; }
  .site-nav a {
    padding: 12px 12px;
    font-size: 15px;
    border-bottom: 1px solid rgba(44, 74, 102, .5);
  }
  .site-nav a:last-child { border-bottom: 0; }
  .site-nav a[aria-current="page"] { background: rgba(25, 211, 230, .10); }
  .site-nav a[aria-current="page"]::after { left: 0; width: 2px; top: 10px; bottom: 10px; height: auto; }
  .nav-cta { padding: 9px 13px; font-size: 13px; }
}

@media (max-width: 980px) {
  .split-main,
  .split-side { grid-column: 1 / -1; }
  .channel { position: static; top: auto; }
  .footer-ident { grid-column: 1 / -1; }
  .footer-nav { grid-column: 1 / -1; }
}

@media (max-width: 720px) {
  body { font-size: 16px; }
  :root { --panel-gap: 64px; }
  .header-rail { font-size: 10px; letter-spacing: .14em; }
  .nav-capsule { padding: 8px 10px 8px 12px; }
  .brand-name { font-size: 18px; }
  .brand-sub { letter-spacing: .2em; }
  .nav-cta { display: none; }
  .footer-nav { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 24px; }
  .footer-base { gap: 6px 18px; font-size: 11px; }
  .to-top { right: 14px; bottom: 14px; padding: 9px 12px; }
  .to-top-text { display: none; }
  .to-top { border-radius: 999px; width: 44px; height: 44px; justify-content: center; padding: 0; }
}

@media (max-width: 420px) {
  .nav-toggle-text { display: none; }
  .footer-nav { grid-template-columns: 1fr; }
}

/* =========================================================
   可访问性与动效偏好
   ========================================================= */
@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;
  }
  .rail-dot,
  .nav-cta-mark { animation: none; opacity: 1; }
}