/* ==========================================================================
   极悦娱乐 · 共享样式表 /assets/site.css
   深海噪点底 + 切角面板 + 等宽数据 + 双层导航
   ========================================================================== */

:root {
  --c-bg: #0B1E2D;
  --c-abyss: #06121C;
  --c-layer: #14304A;
  --c-glass: #1E4A6B;
  --c-moon: #D8E3EC;
  --c-coral: #FF6B4A;
  --c-aurora: #35E0D0;
  --c-sand: #F2A65A;
  --c-foam: #8AA3B5;
  --c-near: #030B12;

  --c-text: #C7D6E3;
  --c-text-dim: #9FB6C8;

  --font-head: "Oswald", "Archivo Narrow", "Source Han Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-body: "Source Han Sans SC", "PingFang SC", "HarmonyOS Sans SC", "Microsoft YaHei", system-ui, sans-serif;
  --font-mono: "JetBrains Mono", "IBM Plex Mono", ui-monospace, SFMono-Regular, monospace;

  --wrap: 1240px;
  --gut: clamp(16px, 4vw, 44px);
  --line: rgba(30, 74, 107, 0.78);
  --line-soft: rgba(138, 163, 181, 0.22);
  --t: 0.42s cubic-bezier(0.22, 0.61, 0.36, 1);
  --cut: 20px;
}

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: 120px;
}

body {
  margin: 0;
  min-height: 100%;
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.75;
  letter-spacing: 0.01em;
  color: var(--c-text);
  background-color: var(--c-bg);
  background-image:
    radial-gradient(rgba(216, 227, 236, 0.035) 1px, transparent 1px),
    radial-gradient(1200px 700px at 78% -10%, rgba(30, 74, 107, 0.55), transparent 70%),
    radial-gradient(900px 620px at 6% 6%, rgba(53, 224, 208, 0.07), transparent 65%);
  background-size: 3px 3px, auto, auto;
  background-repeat: repeat, no-repeat, no-repeat;
  background-attachment: fixed, fixed, fixed;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

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

h1, h2, h3, h4, h5 {
  font-family: var(--font-head);
  font-weight: 500;
  line-height: 1.14;
  letter-spacing: 0.01em;
  color: var(--c-moon);
  margin: 0 0 0.6em;
}

p { margin: 0 0 1.1em; max-width: 38em; }

a { color: var(--c-aurora); text-decoration-thickness: 1px; text-underline-offset: 3px; }

ul, ol { margin: 0 0 1.1em; padding-left: 1.25em; }

code, kbd, .mono, [data-mono] { font-family: var(--font-mono); font-size: 0.9em; }

hr {
  border: 0;
  height: 1px;
  margin: clamp(24px, 4vw, 48px) 0;
  background: linear-gradient(90deg, var(--c-coral), rgba(30, 74, 107, 0.15) 45%, transparent);
}

button { font: inherit; color: inherit; }

:where(a, button, summary, [tabindex], input, select, textarea):focus-visible {
  outline: 2px solid var(--c-coral);
  outline-offset: 3px;
  border-radius: 2px;
}

.visually-hidden {
  position: absolute !important;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0 0 0 0);
  white-space: nowrap; border: 0;
}

/* ---------- 布局容器 ---------- */
.wrap {
  width: 100%;
  max-width: var(--wrap);
  margin-inline: auto;
  padding-inline: var(--gut);
}

.section {
  position: relative;
  padding-block: clamp(48px, 7vw, 96px);
}
.section--tight { padding-block: clamp(26px, 4vw, 52px); }
.section--abyss {
  background: linear-gradient(180deg, rgba(6, 18, 28, 0.35), rgba(6, 18, 28, 0.85));
  border-block: 1px solid rgba(30, 74, 107, 0.45);
}

.section__head { display: grid; gap: 10px; margin-bottom: clamp(22px, 3.2vw, 42px); }
.section__index {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.24em;
  text-transform: uppercase;
  color: var(--c-sand);
}
.section__title {
  font-weight: 300;
  font-size: clamp(1.85rem, 4.4vw, 3.4rem);
  letter-spacing: 0.005em;
  margin: 0;
}
.section__lead {
  margin: 0;
  max-width: 38em;
  color: var(--c-text-dim);
  font-size: 1.02rem;
}

/* ---------- 跳转链接 ---------- */
.skip-link {
  position: absolute;
  top: -80px;
  left: 12px;
  z-index: 200;
  padding: 10px 20px;
  font-family: var(--font-head);
  font-size: 0.86rem;
  letter-spacing: 0.08em;
  color: #08151F;
  background: var(--c-coral);
  text-decoration: none;
  clip-path: polygon(0 0, calc(100% - 10px) 0, 100% 10px, 100% 100%, 10px 100%, 0 calc(100% - 10px));
  transition: top 0.22s ease;
}
.skip-link:focus { top: 12px; }

/* ---------- 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.45em;
  padding: 0.62em 1.25em;
  font-family: var(--font-head);
  font-size: 0.85rem;
  font-weight: 600;
  letter-spacing: 0.07em;
  color: var(--c-moon);
  background: transparent;
  border: 1px solid var(--line);
  text-decoration: none;
  cursor: pointer;
  clip-path: polygon(0 0, calc(100% - 10px) 0, 100% 10px, 100% 100%, 10px 100%, 0 calc(100% - 10px));
  transition: background var(--t), color var(--t), border-color var(--t), transform var(--t);
}
.btn:hover { transform: translateY(-1px); }
.btn--primary {
  color: #08151F;
  background: var(--c-coral);
  border-color: var(--c-coral);
  font-weight: 700;
}
.btn--primary:hover { background: #FF8365; border-color: #FF8365; }
.btn--ghost {
  color: var(--c-aurora);
  border-color: rgba(53, 224, 208, 0.5);
  background: rgba(53, 224, 208, 0.05);
}
.btn--ghost:hover { background: rgba(53, 224, 208, 0.14); color: var(--c-moon); }
.btn--block { width: 100%; }

/* ---------- 标签牌 ---------- */
.tag {
  display: inline-flex;
  align-items: center;
  gap: 0.45em;
  padding: 0.26em 0.7em;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--c-aurora);
  background: rgba(53, 224, 208, 0.08);
  box-shadow: inset 0 0 0 1px rgba(53, 224, 208, 0.35);
}
.tag--index {
  color: var(--c-sand);
  background: rgba(242, 166, 90, 0.08);
  box-shadow: inset 0 0 0 1px rgba(242, 166, 90, 0.35);
}
.tag--coral {
  color: var(--c-coral);
  background: rgba(255, 107, 74, 0.09);
  box-shadow: inset 0 0 0 1px rgba(255, 107, 74, 0.4);
}

/* ---------- 页头 ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 60;
  background: linear-gradient(180deg, rgba(6, 18, 28, 0.97), rgba(11, 30, 45, 0.95));
  border-bottom: 1px solid rgba(30, 74, 107, 0.6);
  backdrop-filter: blur(10px);
}

.header-top__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding-block: 12px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
  color: var(--c-moon);
  min-width: 0;
}
.brand__mark {
  display: grid;
  place-items: center;
  flex: none;
  width: 42px;
  height: 42px;
  font-family: var(--font-mono);
  font-size: 0.9rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--c-coral);
  background: linear-gradient(150deg, rgba(255, 107, 74, 0.18), rgba(53, 224, 208, 0.08));
  box-shadow: inset 0 0 0 1px rgba(255, 107, 74, 0.5);
  clip-path: polygon(0 0, calc(100% - 12px) 0, 100% 12px, 100% 100%, 12px 100%, 0 calc(100% - 12px));
}
.brand__text { display: grid; min-width: 0; }
.brand__name {
  font-family: var(--font-head);
  font-size: 1.16rem;
  font-weight: 600;
  letter-spacing: 0.09em;
  line-height: 1.25;
  color: var(--c-moon);
}
.brand__sub {
  font-family: var(--font-mono);
  font-size: 0.66rem;
  letter-spacing: 0.14em;
  color: var(--c-foam);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.header-top__aside { display: flex; align-items: center; gap: 14px; }

.chip {
  display: inline-flex;
  align-items: center;
  padding: 0.32em 0.75em;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.14em;
  color: var(--c-aurora);
  background: rgba(53, 224, 208, 0.06);
  box-shadow: inset 0 0 0 1px rgba(53, 224, 208, 0.3);
  white-space: nowrap;
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: 10px;
  padding: 0.52em 0.85em;
  font-family: var(--font-head);
  font-size: 0.78rem;
  letter-spacing: 0.14em;
  color: var(--c-moon);
  background: transparent;
  border: 1px solid var(--line);
  cursor: pointer;
}
.nav-toggle__bars {
  position: relative;
  display: block;
  width: 20px;
  height: 2px;
  background: currentColor;
  transition: background 0.2s ease;
}
.nav-toggle__bars::before,
.nav-toggle__bars::after {
  content: "";
  position: absolute;
  left: 0;
  width: 20px;
  height: 2px;
  background: currentColor;
  transition: transform 0.25s ease;
}
.nav-toggle__bars::before { top: -6px; }
.nav-toggle__bars::after { top: 6px; }
[data-nav-toggle][aria-expanded="true"] .nav-toggle__bars { background: transparent; }
[data-nav-toggle][aria-expanded="true"] .nav-toggle__bars::before { transform: translateY(6px) rotate(45deg); }
[data-nav-toggle][aria-expanded="true"] .nav-toggle__bars::after { transform: translateY(-6px) rotate(-45deg); }

.header-nav {
  background: linear-gradient(90deg, rgba(20, 48, 74, 0.55), rgba(6, 18, 28, 0.5));
  border-top: 1px solid rgba(30, 74, 107, 0.45);
}
.header-nav__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
}
.nav-list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 2px;
  margin: 0;
  padding: 0;
  list-style: none;
}
.nav-link {
  position: relative;
  display: block;
  padding: 0.92em 0.95em;
  font-family: var(--font-head);
  font-size: 0.9rem;
  font-weight: 500;
  letter-spacing: 0.1em;
  color: #A9C0D2;
  text-decoration: none;
  transition: color var(--t);
}
.nav-link::after {
  content: "";
  position: absolute;
  left: 0.95em;
  right: 0.95em;
  bottom: 0.42em;
  height: 2px;
  background: var(--c-coral);
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform 0.3s ease;
}
.nav-link:hover { color: var(--c-moon); }
.nav-link:hover::after { transform: scaleX(1); }
.nav-link[aria-current="page"] { color: var(--c-coral); }
.nav-link[aria-current="page"]::after { transform: scaleX(1); }

.header-nav__meta {
  font-family: var(--font-mono);
  font-size: 0.66rem;
  letter-spacing: 0.18em;
  color: rgba(138, 163, 181, 0.75);
  white-space: nowrap;
}

/* ---------- 页脚 ---------- */
.site-footer {
  position: relative;
  margin-top: clamp(56px, 9vw, 120px);
  background: linear-gradient(180deg, rgba(6, 18, 28, 0.6), var(--c-abyss) 42%, var(--c-near));
  border-top: 1px solid rgba(30, 74, 107, 0.55);
}
.site-footer::before {
  content: "";
  position: absolute;
  top: -1px;
  left: 0;
  width: min(38%, 460px);
  height: 2px;
  background: linear-gradient(90deg, var(--c-coral), var(--c-aurora) 62%, transparent);
}

.footer-top {
  display: grid;
  grid-template-columns: minmax(230px, 1.5fr) repeat(3, minmax(140px, 1fr));
  gap: clamp(24px, 3.6vw, 56px);
  padding-block: clamp(42px, 6vw, 76px) clamp(26px, 3.5vw, 42px);
}

.footer-brand__mark {
  display: grid;
  place-items: center;
  width: 38px;
  height: 38px;
  margin-bottom: 14px;
  font-family: var(--font-mono);
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--c-aurora);
  box-shadow: inset 0 0 0 1px rgba(53, 224, 208, 0.45);
  clip-path: polygon(0 0, calc(100% - 11px) 0, 100% 11px, 100% 100%, 11px 100%, 0 calc(100% - 11px));
}
.footer-brand__name {
  margin: 0 0 8px;
  font-family: var(--font-head);
  font-size: 1.35rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  color: var(--c-moon);
}
.footer-brand__line {
  margin: 0;
  max-width: 24em;
  font-size: 0.86rem;
  color: var(--c-foam);
}

.footer-col__title {
  margin: 0 0 14px;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--c-sand);
}
.footer-links { margin: 0; padding: 0; list-style: none; }
.footer-links li + li { margin-top: 9px; }
.footer-link {
  position: relative;
  display: inline-block;
  padding-left: 0;
  font-size: 0.9rem;
  color: var(--c-foam);
  text-decoration: none;
  transition: color var(--t), padding-left var(--t);
}
.footer-link::before {
  content: "";
  position: absolute;
  left: 0;
  top: 50%;
  width: 0;
  height: 1px;
  background: var(--c-coral);
  transition: width var(--t);
}
.footer-link:hover { color: var(--c-moon); padding-left: 16px; }
.footer-link:hover::before { width: 11px; }

.footer-info {
  display: grid;
  gap: 8px;
  padding-block: clamp(18px, 2.6vw, 26px);
  border-top: 1px solid rgba(30, 74, 107, 0.45);
}
.footer-info__contact {
  margin: 0;
  max-width: 78ch;
  font-family: var(--font-mono);
  font-size: 0.76rem;
  line-height: 1.9;
  letter-spacing: 0.03em;
  color: var(--c-text-dim);
}
.footer-info__note {
  margin: 0;
  max-width: 78ch;
  font-size: 0.82rem;
  color: rgba(138, 163, 181, 0.95);
}

.footer-bottom {
  background: rgba(3, 11, 18, 0.85);
  border-top: 1px solid rgba(30, 74, 107, 0.35);
}
.footer-bottom__inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  padding-block: 16px;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.08em;
  color: rgba(138, 163, 181, 0.9);
}
.footer-legal { color: var(--c-text-dim); }
.footer-copy { color: rgba(138, 163, 181, 0.85); }

/* ---------- 面包屑 ---------- */
.breadcrumb { margin: 0 0 clamp(16px, 2.2vw, 28px); }
.breadcrumb__list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5em;
  margin: 0;
  padding: 0;
  list-style: none;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.1em;
  color: var(--c-foam);
}
.breadcrumb__list li + li::before {
  content: "/";
  margin-right: 0.5em;
  color: rgba(138, 163, 181, 0.5);
}
.breadcrumb__link { color: var(--c-foam); text-decoration: none; transition: color var(--t); }
.breadcrumb__link:hover { color: var(--c-coral); }
.breadcrumb__current { color: var(--c-moon); }

/* ---------- 卡片 ---------- */
.card {
  position: relative;
  padding: clamp(18px, 2.4vw, 30px);
  background: linear-gradient(155deg, rgba(20, 48, 74, 0.88), rgba(11, 30, 45, 0.94));
  box-shadow: inset 0 0 0 1px rgba(30, 74, 107, 0.85);
  transition: transform var(--t), box-shadow var(--t);
}
.card:hover { transform: translateY(-3px); box-shadow: inset 0 0 0 1px rgba(255, 107, 74, 0.55); }
.card--cut {
  --cut: 22px;
  clip-path: polygon(0 0, calc(100% - var(--cut)) 0, 100% var(--cut), 100% 100%, var(--cut) 100%, 0 calc(100% - var(--cut)));
}
.card__title {
  margin: 0 0 0.5em;
  font-family: var(--font-head);
  font-size: 1.2rem;
  font-weight: 600;
  letter-spacing: 0.03em;
}
.card__body { margin: 0; font-size: 0.94rem; color: var(--c-text-dim); }
.card__meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6em;
  margin-bottom: 12px;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.12em;
  color: var(--c-foam);
}

/* ---------- 数据带 ---------- */
.data-band {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 1px;
  background: rgba(30, 74, 107, 0.6);
  box-shadow: inset 0 0 0 1px rgba(30, 74, 107, 0.75);
}
.data-cell { padding: 14px 18px; background: rgba(6, 18, 28, 0.78); }
.data-cell__label {
  display: block;
  margin-bottom: 4px;
  font-family: var(--font-mono);
  font-size: 0.64rem;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--c-foam);
}
.data-cell__value {
  display: block;
  font-family: var(--font-mono);
  font-size: clamp(1.25rem, 2.2vw, 1.6rem);
  font-weight: 700;
  line-height: 1.3;
  color: var(--c-aurora);
  font-variant-numeric: tabular-nums;
}
.data-cell__value--coral { color: var(--c-coral); }
.data-cell__value--sand { color: var(--c-sand); }
.data-cell__value--moon { color: var(--c-moon); }

/* ---------- 图片容器 ---------- */
.media-frame {
  position: relative;
  overflow: hidden;
  background: rgba(6, 18, 28, 0.7);
  box-shadow: inset 0 0 0 1px rgba(30, 74, 107, 0.8);
}
.media-frame__inner {
  position: relative;
  display: block;
  width: 100%;
  aspect-ratio: 16 / 10;
  background-image:
    linear-gradient(135deg, rgba(30, 74, 107, 0.55), rgba(6, 18, 28, 0.92)),
    repeating-linear-gradient(45deg, rgba(53, 224, 208, 0.06) 0 2px, transparent 2px 12px);
}
.media-frame__inner > img,
.media-frame__inner > picture > img {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.media-frame__caption {
  display: block;
  padding: 10px 14px;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.12em;
  color: var(--c-foam);
  background: rgba(6, 18, 28, 0.88);
}
.media-frame--wide .media-frame__inner { aspect-ratio: 21 / 9; }
.media-frame--tall .media-frame__inner { aspect-ratio: 4 / 5; }
.media-frame--square .media-frame__inner { aspect-ratio: 1 / 1; }

/* ---------- 章节索引（时间轴） ---------- */
.toc-rail { position: relative; padding-left: 24px; }
.toc-rail::before {
  content: "";
  position: absolute;
  left: 5px;
  top: 8px;
  bottom: 8px;
  width: 1px;
  background: linear-gradient(180deg, var(--c-coral), rgba(30, 74, 107, 0.2));
}
.toc-link {
  position: relative;
  display: block;
  padding: 0.5em 0;
  font-size: 0.9rem;
  color: #A9C0D2;
  text-decoration: none;
  transition: color var(--t), transform var(--t);
}
.toc-link::before {
  content: "";
  position: absolute;
  left: -24px;
  top: 1.05em;
  width: 9px;
  height: 9px;
  background: var(--c-bg);
  box-shadow: inset 0 0 0 1px rgba(138, 163, 181, 0.6);
  transition: background var(--t), box-shadow var(--t);
}
.toc-link:hover { color: var(--c-moon); }
.toc-link.is-active { color: var(--c-coral); transform: translateX(3px); }
.toc-link.is-active::before {
  background: var(--c-coral);
  box-shadow: 0 0 0 3px rgba(255, 107, 74, 0.16);
}

/* ---------- 折叠详情 ---------- */
.fold {
  background: rgba(6, 18, 28, 0.6);
  box-shadow: inset 0 0 0 1px rgba(30, 74, 107, 0.72);
}
.fold + .fold { margin-top: 10px; }
.fold__summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  padding: 14px 18px;
  font-family: var(--font-head);
  font-size: 1rem;
  letter-spacing: 0.03em;
  color: var(--c-moon);
  cursor: pointer;
  list-style: none;
}
.fold__summary::-webkit-details-marker { display: none; }
.fold__summary::after {
  content: "+";
  font-family: var(--font-mono);
  font-size: 1.1rem;
  line-height: 1;
  color: var(--c-coral);
}
.fold[open] .fold__summary::after { content: "–"; }
.fold[open] .fold__summary { box-shadow: inset 0 -1px 0 rgba(30, 74, 107, 0.7); }
.fold__body { padding: 14px 18px 18px; font-size: 0.94rem; color: var(--c-text-dim); }
.fold__body > :last-child { margin-bottom: 0; }

/* ---------- 表格 ---------- */
.table-scroll { overflow-x: auto; box-shadow: inset 0 0 0 1px rgba(30, 74, 107, 0.75); }
.data-table { width: 100%; border-collapse: collapse; min-width: 520px; font-size: 0.9rem; }
.data-table th,
.data-table td {
  padding: 12px 16px;
  text-align: left;
  border-bottom: 1px solid rgba(30, 74, 107, 0.55);
}
.data-table thead th {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--c-sand);
  background: rgba(6, 18, 28, 0.72);
}
.data-table tbody tr:hover { background: rgba(30, 74, 107, 0.28); }
.data-table td[data-num] { font-family: var(--font-mono); color: var(--c-aurora); font-variant-numeric: tabular-nums; }

/* ---------- 正文排版辅助 ---------- */
.prose { max-width: 38em; }
.prose p { margin-bottom: 1.25em; }
.prose h3 { margin-top: 1.8em; font-size: 1.25rem; }
.prose ul { color: var(--c-text-dim); }

.lede { font-size: clamp(1rem, 1.6vw, 1.15rem); color: var(--c-moon); }

/* ---------- 显现、进度与返回顶部 ---------- */
[data-reveal] {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 0.55s cubic-bezier(0.22, 0.61, 0.36, 1), transform 0.55s cubic-bezier(0.22, 0.61, 0.36, 1);
}
[data-reveal].is-visible { opacity: 1; transform: none; }

.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  z-index: 80;
  width: 0;
  height: 2px;
  background: linear-gradient(90deg, var(--c-coral), var(--c-aurora));
  pointer-events: none;
}

.back-to-top {
  position: fixed;
  right: clamp(14px, 3vw, 32px);
  bottom: clamp(14px, 3vw, 32px);
  z-index: 70;
  display: inline-flex;
  align-items: center;
  gap: 0.5em;
  padding: 0.7em 1.05em;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.16em;
  color: var(--c-moon);
  background: rgba(6, 18, 28, 0.94);
  border: 1px solid rgba(53, 224, 208, 0.45);
  cursor: pointer;
  opacity: 0;
  transform: translate(24px, 18px);
  pointer-events: none;
  transition: opacity var(--t), transform var(--t), color var(--t), border-color var(--t);
}
.back-to-top.is-visible { opacity: 1; transform: none; pointer-events: auto; }
.back-to-top:hover { color: var(--c-coral); border-color: var(--c-coral); }

/* ---------- 装饰细线 ---------- */
.rule-diagonal {
  height: 1px;
  border: 0;
  margin: 0;
  background: linear-gradient(90deg, transparent, rgba(30, 74, 107, 0.85) 30%, rgba(53, 224, 208, 0.5) 70%, transparent);
}

/* ---------- 响应式 ---------- */
@media (max-width: 1024px) {
  .footer-top { grid-template-columns: repeat(2, minmax(180px, 1fr)); }
  .footer-brand { grid-column: 1 / -1; }
}

@media (max-width: 900px) {
  html { scroll-padding-top: 96px; }

  .nav-toggle { display: inline-flex; }

  .header-nav { display: none; }
  .header-nav[data-open] { display: block; }
  .header-nav__inner {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    max-height: 68vh;
    overflow-y: auto;
    padding-block: 6px 18px;
  }
  .nav-list { flex-direction: column; gap: 0; }
  .nav-list li + li { border-top: 1px solid rgba(30, 74, 107, 0.42); }
  .nav-link { padding: 0.85em 0.15em; }
  .nav-link::after {
    left: 0.15em;
    right: auto;
    width: 26px;
    bottom: 0.62em;
  }
  .header-nav__meta { margin-top: 12px; padding-left: 0.15em; }
}

@media (max-width: 720px) {
  body { font-size: 15.5px; }
  .brand__sub { display: none; }
  .chip { display: none; }
  .header-top__aside { gap: 0; }
  .header-top__aside .btn { padding: 0.55em 0.9em; font-size: 0.78rem; }
  .footer-top { grid-template-columns: 1fr; gap: 26px; }
  .footer-bottom__inner { justify-content: flex-start; }
  .data-band { grid-template-columns: repeat(auto-fit, minmax(130px, 1fr)); }
  .back-to-top { padding: 0.62em 0.85em; font-size: 0.66rem; }
}

@media (max-width: 420px) {
  .brand__mark { width: 36px; height: 36px; font-size: 0.78rem; }
  .brand__name { font-size: 1.02rem; }
}

/* ---------- 动效偏好 ---------- */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }
  html { scroll-behavior: auto; }
  [data-reveal] { opacity: 1 !important; transform: none !important; }
  .back-to-top { opacity: 1; transform: none; pointer-events: auto; }
  .card:hover, .btn:hover, .toc-link.is-active { transform: none; }
}