/* ==========================================================================
   亿博CN · /assets/site.css
   共享层：reset / 变量 / 中文排版 / 页头 / 页脚 / 通用组件 / 响应式
   ========================================================================== */

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

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

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

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

img, svg, video { max-width: 100%; height: auto; }

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

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

[hidden] { display: none !important; }

/* ---------- 2. 设计变量 ---------- */
:root {
  /* 色板 */
  --indigo-950: #0B1533;
  --indigo-850: #121F45;
  --indigo-700: #1D3266;
  --porcelain: #F7F8F2;
  --mist: #C9D1E3;
  --signal: #FF6B2C;
  --signal-soft: #FFB38A;
  --celadon: #57D6B2;
  --celadon-deep: #1F8F7A;
  --ink: #111826;

  /* 线 */
  --line-dark: rgba(201, 209, 227, 0.18);
  --line-light: rgba(17, 24, 38, 0.14);

  /* 字体 */
  --font-head: "Archivo Narrow", "Noto Sans SC", "Source Han Sans SC", "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  --font-body: "Noto Sans SC", "Source Han Sans SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, -apple-system, sans-serif;
  --font-mono: "Sarasa Mono SC", "IBM Plex Mono", "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;

  /* 尺度 */
  --maxw: 1440px;
  --gutter: clamp(18px, 4vw, 56px);
  --header-h: 76px;
  --radius-s: 8px;
  --radius-m: 16px;
  --radius-l: 28px;
  --dur: 240ms;
  --ease: cubic-bezier(0.2, 0.7, 0.3, 1);
}

/* ---------- 3. 基础与中文排版 ---------- */
body {
  min-height: 100vh;
  overflow-x: hidden;
  background: var(--indigo-950);
  color: var(--porcelain);
  font-family: var(--font-body);
  font-size: clamp(16px, 1.05vw, 17.5px);
  line-height: 1.8;
  letter-spacing: 0.005em;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

h1, h2, h3, h4 {
  font-family: var(--font-head);
  font-weight: 900;
  letter-spacing: -0.02em;
  line-height: 1.12;
  text-wrap: balance;
}

h1 { font-size: clamp(2.4rem, 5.4vw, 5rem); letter-spacing: -0.03em; line-height: 1.04; }
h2 { font-size: clamp(1.7rem, 2.7vw, 2.6rem); }
h3 { font-size: clamp(1.15rem, 1.5vw, 1.45rem); letter-spacing: -0.01em; }
h4 { font-size: clamp(1rem, 1.1vw, 1.15rem); letter-spacing: 0; }

p { margin-bottom: 1em; }
p:last-child { margin-bottom: 0; }

strong, b { font-weight: 700; }

small { font-size: 0.8em; }

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

[id] { scroll-margin-top: calc(var(--header-h) + 18px); }

:focus-visible {
  outline: 3px solid var(--celadon);
  outline-offset: 3px;
  border-radius: 4px;
}

::selection {
  background: var(--signal);
  color: var(--ink);
}

.sr-only {
  position: absolute;
  width: 1px; height: 1px;
  margin: -1px; padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}

/* ---------- 4. 布局与通用排版组件 ---------- */
.container {
  width: 100%;
  max-width: var(--maxw);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.section { padding-block: clamp(48px, 6vw, 96px); }
.section--tight { padding-block: clamp(32px, 4vw, 56px); }

.section--paper {
  background: var(--porcelain);
  color: var(--ink);
  --line-dark: var(--line-light);
  --mist: #44516b;
}

.section--deep { background: var(--indigo-850); }

.section--paper h1,
.section--paper h2,
.section--paper h3,
.section--paper h4 { color: var(--ink); }

.section--paper .eyebrow { color: var(--celadon-deep); }

.section--paper .tag {
  background: rgba(17, 24, 38, 0.06);
  border-color: rgba(17, 24, 38, 0.16);
  color: #3b4a63;
}

.section--paper .tag--celadon {
  background: rgba(31, 143, 122, 0.12);
  border-color: rgba(31, 143, 122, 0.38);
  color: #12685a;
}

.section--paper .tag--signal {
  background: rgba(255, 107, 44, 0.14);
  border-color: rgba(255, 107, 44, 0.42);
  color: #a83c0b;
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  margin: 0 0 14px;
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--celadon);
}

.eyebrow::before {
  content: "";
  width: 22px;
  height: 2px;
  border-radius: 2px;
  background: currentColor;
}

.grid {
  display: grid;
  gap: clamp(16px, 2vw, 28px);
}

.grid--2 { grid-template-columns: repeat(auto-fit, minmax(min(100%, 320px), 1fr)); }
.grid--3 { grid-template-columns: repeat(auto-fit, minmax(min(100%, 250px), 1fr)); }

.prose { max-width: 72ch; }
.prose p { margin-bottom: 1em; }
.prose h2, .prose h3 { margin-top: 1.6em; }
.prose ul, .prose ol { margin: 0 0 1em; padding-left: 1.25em; }
.prose ul[class], .prose ol[class] { padding-left: 0; }
.prose li { margin: 0.35em 0; }
.prose a {
  text-decoration: underline;
  text-decoration-color: var(--signal);
  text-decoration-thickness: 2px;
  text-underline-offset: 3px;
}
.prose a:hover { text-decoration-color: var(--celadon); }

/* ---------- 5. 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: 13px 26px;
  border: 1px solid transparent;
  border-radius: 999px;
  font-family: var(--font-body);
  font-size: 15px;
  font-weight: 700;
  line-height: 1;
  cursor: pointer;
  transition: background var(--dur) var(--ease), color var(--dur) var(--ease),
              border-color var(--dur) var(--ease), transform var(--dur) var(--ease);
}

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

.btn--signal { background: var(--signal); color: var(--ink); }
.btn--signal:hover { background: var(--signal-soft); }

.btn--ghost { background: transparent; border-color: var(--line-dark); color: var(--porcelain); }
.btn--ghost:hover { border-color: var(--celadon); color: var(--celadon); }

.btn--paper { background: var(--indigo-950); color: var(--porcelain); }
.btn--paper:hover { background: var(--indigo-700); }

.btn--small {
  padding: 9px 18px;
  font-family: var(--font-mono);
  font-size: 12.5px;
  font-weight: 600;
  letter-spacing: 0.04em;
}

/* ---------- 6. 卡片、标签、索引带、面包屑 ---------- */
.panel {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 12px;
  padding: clamp(20px, 2.4vw, 32px);
  background: var(--indigo-850);
  border: 1px solid var(--line-dark);
  border-radius: var(--radius-m);
  transition: border-color var(--dur) var(--ease), background var(--dur) var(--ease);
}

.panel:hover { border-color: rgba(87, 214, 178, 0.45); }

.panel--paper {
  background: var(--porcelain);
  color: var(--ink);
  border-color: var(--line-light);
}

.panel--paper:hover { border-color: rgba(31, 143, 122, 0.5); }

.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 10px;
  border: 1px solid var(--line-dark);
  border-radius: 999px;
  background: rgba(201, 209, 227, 0.1);
  color: var(--mist);
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.05em;
  line-height: 1.5;
}

.tag--celadon {
  background: rgba(87, 214, 178, 0.14);
  border-color: rgba(87, 214, 178, 0.42);
  color: var(--celadon);
}

.tag--signal {
  background: rgba(255, 107, 44, 0.14);
  border-color: rgba(255, 107, 44, 0.42);
  color: var(--signal-soft);
}

.index-strip {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 180px), 1fr));
  margin: 0;
  padding: 0;
  list-style: none;
  border-top: 1px solid var(--line-dark);
  border-bottom: 1px solid var(--line-dark);
}

.index-strip__item {
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding: clamp(14px, 2vw, 22px);
  border-inline-end: 1px solid var(--line-dark);
}

.index-strip__item:last-child { border-inline-end: 0; }

.index-strip__num {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  color: var(--signal-soft);
}

.index-strip__label {
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.03em;
  color: var(--porcelain);
}

.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 6px;
  margin: 0;
  padding: 0;
  list-style: none;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.04em;
  color: var(--mist);
}

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

.breadcrumb__item + .breadcrumb__item::before {
  content: "/";
  color: rgba(201, 209, 227, 0.45);
}

.breadcrumb__link { color: var(--mist); transition: color var(--dur) var(--ease); }
.breadcrumb__link:hover { color: var(--celadon); }
.breadcrumb__current { color: var(--porcelain); }

/* ---------- 7. 图片 / 视觉容器基础规则 ---------- */
.media {
  position: relative;
  display: block;
  overflow: hidden;
  isolation: isolate;
  border-radius: var(--radius-m);
  background: var(--indigo-700);
}

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

.media--16x9 { aspect-ratio: 16 / 9; }
.media--4x3  { aspect-ratio: 4 / 3; }
.media--1x1  { aspect-ratio: 1 / 1; }
.media--tall { aspect-ratio: 3 / 4; }

.media--placeholder { background: var(--indigo-850); }

.media--placeholder::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 0;
  background:
    radial-gradient(115% 85% at 12% 8%, rgba(87, 214, 178, 0.34), transparent 58%),
    radial-gradient(95% 80% at 88% 92%, rgba(255, 107, 44, 0.3), transparent 60%),
    repeating-linear-gradient(90deg, rgba(247, 248, 242, 0.06) 0 1px, transparent 1px 72px);
}

.media--placeholder::after {
  content: "";
  position: absolute;
  right: 12%;
  bottom: 12%;
  width: 38%;
  aspect-ratio: 1 / 1;
  border: 1px solid rgba(247, 248, 242, 0.28);
  border-radius: 56% 44% 52% 48% / 48% 56% 44% 52%;
}

.media__caption {
  position: absolute;
  left: 0; right: 0; bottom: 0;
  z-index: 2;
  padding: 16px 16px 14px;
  background: linear-gradient(0deg, rgba(11, 21, 51, 0.92), rgba(11, 21, 51, 0));
  color: var(--porcelain);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.04em;
}

/* ---------- 8. 筛选组件 ---------- */
.filter-bar {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 0 0 clamp(18px, 2.5vw, 28px);
  padding: 0;
  list-style: none;
}

.filter-btn {
  padding: 9px 16px;
  border: 1px solid var(--line-dark);
  border-radius: 999px;
  background: transparent;
  color: var(--mist);
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: 0.04em;
  cursor: pointer;
  transition: color var(--dur) var(--ease), border-color var(--dur) var(--ease),
              background var(--dur) var(--ease);
}

.filter-btn:hover { color: var(--porcelain); border-color: var(--celadon); }

.filter-btn[aria-pressed="true"] {
  background: var(--celadon);
  border-color: var(--celadon);
  color: var(--indigo-950);
  font-weight: 700;
}

.filter-empty {
  margin-top: 20px;
  padding: 18px 22px;
  border: 1px dashed rgba(255, 107, 44, 0.5);
  border-radius: var(--radius-m);
  color: var(--signal-soft);
  font-family: var(--font-mono);
  font-size: 13px;
}

/* ---------- 9. 页头 ---------- */
.skip-link {
  position: fixed;
  top: -120px;
  left: var(--gutter);
  z-index: 300;
  padding: 10px 18px;
  border-radius: 0 0 10px 10px;
  background: var(--signal);
  color: var(--ink);
  font-weight: 700;
  font-size: 14px;
  transition: top var(--dur) var(--ease);
}

.skip-link:focus { top: 0; }

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: transparent;
  border-bottom: 1px solid transparent;
  transition: background var(--dur) var(--ease),
              border-color var(--dur) var(--ease),
              box-shadow var(--dur) var(--ease);
}

.site-header::before {
  content: "";
  position: absolute;
  inset: 0;
  pointer-events: none;
  background: linear-gradient(180deg, rgba(11, 21, 51, 0.92), rgba(11, 21, 51, 0));
  transition: opacity var(--dur) var(--ease);
}

.site-header[data-scrolled]::before { opacity: 0; }

.site-header[data-scrolled],
.site-header[data-open] {
  background: var(--indigo-950);
  border-bottom-color: var(--line-dark);
  box-shadow: 0 18px 40px -26px rgba(0, 0, 0, 0.9);
}

.header-inner {
  position: relative;
  z-index: 1;
  display: flex;
  align-items: center;
  gap: clamp(14px, 2vw, 36px);
  width: 100%;
  max-width: var(--maxw);
  min-height: var(--header-h);
  margin-inline: auto;
  padding: 12px var(--gutter);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  margin-inline-end: auto;
  flex: 0 0 auto;
}

.brand-mark {
  position: relative;
  flex: 0 0 auto;
  width: 36px;
  height: 36px;
  border-radius: 11px;
  background: var(--signal);
  box-shadow: inset 0 0 0 1px rgba(17, 24, 38, 0.28);
}

.brand-mark::before {
  content: "";
  position: absolute;
  top: 9px;
  left: 9px;
  right: 9px;
  height: 5px;
  border-radius: 2px;
  background: var(--indigo-950);
}

.brand-mark::after {
  content: "";
  position: absolute;
  left: 9px;
  right: 18px;
  bottom: 9px;
  height: 5px;
  border-radius: 2px;
  background: var(--indigo-950);
}

.brand-text {
  display: flex;
  flex-direction: column;
  line-height: 1.18;
}

.brand-name {
  font-family: var(--font-head);
  font-weight: 900;
  font-size: 20px;
  letter-spacing: 0.01em;
  color: var(--porcelain);
}

.brand-tagline {
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.08em;
  color: var(--mist);
}

.primary-nav { flex: 0 1 auto; }

.nav-list {
  display: flex;
  align-items: center;
  gap: clamp(12px, 1.6vw, 28px);
  margin: 0;
  padding: 0;
  list-style: none;
}

.nav-link {
  position: relative;
  display: inline-block;
  padding: 8px 0;
  font-size: 15px;
  font-weight: 600;
  letter-spacing: 0.01em;
  color: rgba(247, 248, 242, 0.82);
  white-space: nowrap;
  transition: color var(--dur) var(--ease);
}

.nav-link::after {
  content: "";
  position: absolute;
  left: 0; right: 0; bottom: 1px;
  height: 2px;
  border-radius: 2px;
  background: var(--celadon);
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform var(--dur) var(--ease), background var(--dur) var(--ease);
}

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

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

.header-tools {
  display: flex;
  align-items: center;
  gap: 8px;
  flex: 0 0 auto;
}

.tool-link {
  padding: 7px 12px;
  border: 1px solid var(--line-dark);
  border-radius: 999px;
  color: var(--mist);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.04em;
  line-height: 1.4;
  white-space: nowrap;
  transition: color var(--dur) var(--ease), border-color var(--dur) var(--ease),
              background var(--dur) var(--ease);
}

.tool-link:hover {
  color: var(--porcelain);
  border-color: var(--celadon);
  background: rgba(87, 214, 178, 0.12);
}

.tool-link--accent {
  background: var(--signal);
  border-color: var(--signal);
  color: var(--ink);
  font-weight: 700;
}

.tool-link--accent:hover {
  background: var(--signal-soft);
  border-color: var(--signal-soft);
  color: var(--ink);
}

.nav-toggle {
  display: none;
  position: relative;
  width: 46px;
  height: 42px;
  padding: 0;
  border: 1px solid var(--line-dark);
  border-radius: 12px;
  background: rgba(18, 31, 69, 0.72);
  cursor: pointer;
  transition: border-color var(--dur) var(--ease), background var(--dur) var(--ease);
}

.nav-toggle:hover { border-color: var(--celadon); }

.nav-toggle-bar {
  position: absolute;
  left: 50%;
  width: 18px;
  height: 2px;
  border-radius: 2px;
  background: var(--porcelain);
  transform: translateX(-50%);
  transition: top var(--dur) var(--ease), transform var(--dur) var(--ease),
              opacity 160ms linear;
}

.nav-toggle-bar:nth-child(1) { top: 15px; }
.nav-toggle-bar:nth-child(2) { top: 20px; }
.nav-toggle-bar:nth-child(3) { top: 25px; }

.site-header[data-open] .nav-toggle-bar:nth-child(1) {
  top: 20px;
  transform: translateX(-50%) rotate(45deg);
}

.site-header[data-open] .nav-toggle-bar:nth-child(2) { opacity: 0; }

.site-header[data-open] .nav-toggle-bar:nth-child(3) {
  top: 20px;
  transform: translateX(-50%) rotate(-45deg);
}

/* ---------- 10. 页脚 ---------- */
.site-footer {
  position: relative;
  overflow: hidden;
  padding: clamp(48px, 6vw, 88px) 0 34px;
  background: var(--indigo-950);
  border-top: 1px solid var(--line-dark);
}

.site-footer::before {
  content: "";
  position: absolute;
  top: -240px;
  right: -180px;
  width: 560px;
  height: 560px;
  border-radius: 50%;
  background: radial-gradient(circle at 32% 32%, rgba(87, 214, 178, 0.18), transparent 66%);
  pointer-events: none;
}

.site-footer::after {
  content: "";
  position: absolute;
  bottom: -200px;
  left: -140px;
  width: 420px;
  height: 420px;
  border-radius: 48% 52% 44% 56% / 54% 46% 54% 46%;
  background: radial-gradient(circle at 60% 40%, rgba(255, 107, 44, 0.14), transparent 68%);
  pointer-events: none;
}

.footer-inner {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: minmax(240px, 1.05fr) minmax(0, 1.55fr);
  gap: clamp(32px, 5vw, 80px);
  width: 100%;
  max-width: var(--maxw);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.footer-lead { display: flex; flex-direction: column; align-items: flex-start; }

.footer-brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-head);
  font-weight: 900;
  font-size: clamp(1.4rem, 2vw, 1.9rem);
  letter-spacing: -0.01em;
  color: var(--porcelain);
}

.footer-brand::before {
  content: "";
  width: 14px;
  height: 14px;
  border-radius: 4px;
  background: var(--signal);
  box-shadow: 0 0 0 4px rgba(255, 107, 44, 0.16);
}

.footer-intro {
  max-width: 34ch;
  margin: 16px 0 22px;
  color: var(--mist);
  font-size: 15.5px;
  line-height: 1.85;
}

.footer-cta {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 12px 24px;
  border-radius: 999px;
  background: var(--signal);
  color: var(--ink);
  font-size: 14.5px;
  font-weight: 700;
  transition: background var(--dur) var(--ease), transform var(--dur) var(--ease);
}

.footer-cta::after {
  content: "→";
  font-family: var(--font-mono);
  transition: transform var(--dur) var(--ease);
}

.footer-cta:hover { background: var(--signal-soft); }
.footer-cta:hover::after { transform: translateX(4px); }

.footer-cols {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: clamp(20px, 3vw, 40px);
  align-content: start;
}

.footer-col-title {
  margin: 0 0 14px;
  color: var(--celadon);
  font-family: var(--font-mono);
  font-size: 11.5px;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.footer-links {
  display: grid;
  gap: 10px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.footer-links a {
  display: inline-block;
  color: rgba(247, 248, 242, 0.78);
  font-size: 14.5px;
  transition: color var(--dur) var(--ease), transform var(--dur) var(--ease);
}

.footer-links a:hover {
  color: var(--porcelain);
  transform: translateX(3px);
}

.footer-contact {
  position: relative;
  z-index: 1;
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 14px 34px;
  width: 100%;
  max-width: var(--maxw);
  margin: clamp(36px, 5vw, 60px) auto 0;
  padding: clamp(18px, 2.6vw, 26px) var(--gutter);
  border-top: 1px solid var(--line-dark);
  border-bottom: 1px solid var(--line-dark);
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--mist);
}

.footer-contact-item {
  display: inline-flex;
  align-items: baseline;
  gap: 8px;
  margin: 0;
}

.footer-contact-label {
  color: var(--celadon);
  font-size: 11px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.footer-contact-value {
  color: var(--porcelain);
  word-break: break-word;
}

.footer-legal {
  position: relative;
  z-index: 1;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 12px 28px;
  width: 100%;
  max-width: var(--maxw);
  margin-inline: auto;
  padding: 22px var(--gutter) 0;
  color: rgba(201, 209, 227, 0.68);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.03em;
}

.footer-note { max-width: 62ch; margin: 0; }
.footer-legal-line { margin: 0; }

/* ---------- 11. 由 JS 注入的滚动进度与回到顶部 ---------- */
.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  z-index: 200;
  width: 100%;
  height: 3px;
  background: linear-gradient(90deg, var(--celadon), var(--signal));
  transform: scaleX(0);
  transform-origin: 0 50%;
  pointer-events: none;
}

.to-top {
  position: fixed;
  right: clamp(14px, 3vw, 28px);
  bottom: clamp(14px, 3vw, 28px);
  z-index: 150;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 46px;
  height: 46px;
  padding: 0;
  border: 1px solid var(--line-dark);
  border-radius: 50%;
  background: var(--indigo-850);
  color: var(--porcelain);
  font-family: var(--font-mono);
  font-size: 15px;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity var(--dur) var(--ease), transform var(--dur) var(--ease),
              visibility var(--dur) linear, border-color var(--dur) var(--ease);
}

.to-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: none;
}

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

/* ---------- 12. 显现（需 JS 启用，无 JS 时内容始终可见） ---------- */
html.js [data-reveal] {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity 520ms var(--ease), transform 520ms var(--ease);
}

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

/* ---------- 13. 响应式 ---------- */
@media (max-width: 1080px) {
  .brand-tagline { display: none; }
}

@media (max-width: 980px) {
  :root { --header-h: 112px; }

  .header-inner {
    display: grid;
    grid-template-columns: 1fr auto;
    grid-template-areas:
      "brand toggle"
      "tools tools";
    align-items: center;
    row-gap: 10px;
    padding: 10px var(--gutter) 12px;
  }

  .brand { grid-area: brand; margin-inline-end: 0; }
  .nav-toggle { grid-area: toggle; display: block; justify-self: end; }

  .header-tools {
    grid-area: tools;
    justify-content: space-between;
    gap: 6px;
  }

  .tool-link {
    flex: 1 1 0;
    padding: 7px 6px;
    font-size: 11.5px;
    text-align: center;
  }

  .primary-nav {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    display: none;
    background: var(--indigo-850);
    border-bottom: 1px solid var(--line-dark);
    box-shadow: 0 34px 50px -30px rgba(0, 0, 0, 0.9);
  }

  .site-header[data-open] .primary-nav {
    display: block;
    animation: navDrop var(--dur) var(--ease);
  }

  .nav-list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: 6px var(--gutter) 18px;
  }

  .nav-link {
    display: block;
    padding: 14px 0;
    font-size: 17px;
    border-bottom: 1px solid var(--line-dark);
    color: var(--pora) ;
    color: rgba(247, 248, 242, 0.86);
  }

  .nav-link::after { display: none; }
  .nav-link[aria-current="page"] { color: var(--celadon); }

  .footer-inner { grid-template-columns: 1fr; }
  .footer-lead { align-items: flex-start; }
}

@keyframes navDrop {
  from { opacity: 0; transform: translateY(-8px); }
  to   { opacity: 1; transform: none; }
}

@media (max-width: 720px) {
  .footer-cols { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .footer-legal { flex-direction: column; }
  .footer-contact { gap: 12px 22px; font-size: 12.5px; }
  .index-strip__item { border-inline-end: 0; border-bottom: 1px solid var(--line-dark); }
  .index-strip__item:last-child { border-bottom: 0; }
}

@media (max-width: 460px) {
  .footer-cols { grid-template-columns: 1fr; }
  .tool-link { font-size: 11px; letter-spacing: 0; }
  .brand-name { font-size: 18px; }
  .brand-mark { width: 32px; height: 32px; }
}

/* ---------- 14. 可访问性与打印 ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }

  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
  }

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

  .site-header[data-open] .primary-nav { animation: none; }
}

@media print {
  .site-header,
  .site-footer,
  .to-top,
  .scroll-progress,
  .filter-bar,
  .skip-link { display: none !important; }

  body { background: #fff; color: #000; }

  a { text-decoration: underline; color: #000; }

  .section,
  .panel { break-inside: avoid; }
}