/* ============================================================
   百老汇牛牛CN · /assets/site.css
   共享外壳：reset / tokens / 排版 / 头部 / 页脚 / 基础组件
   ============================================================ */

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

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

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 { display: block; max-width: 100%; height: auto; }

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

a { color: inherit; }

:where(h1, h2, h3, h4, [id]) { scroll-margin-top: 5.5rem; }

/* ---------- 2. Tokens ---------- */
:root {
  --ink-900: #0B241F;
  --ink-700: #143F36;
  --ink-500: #1F5A4C;
  --copper-500: #B07B3C;
  --copper-300: #D9A566;
  --cinnabar: #B33A2B;
  --cream-100: #F4EDE0;
  --paper-50: #FBF7EF;
  --beige-200: #E7DCC8;
  --brown-900: #221C18;
  --sage-500: #6E7F76;

  --font-display: "Source Han Serif SC", "Noto Serif SC", "Songti SC", Georgia, "Times New Roman", serif;
  --font-body: "Noto Sans SC", "Source Han Sans SC", "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  --font-mono: "IBM Plex Mono", "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;

  --wrap: 1240px;
  --gutter: clamp(1rem, 4vw, 3rem);
  --notch: 14px;

  --hair-copper: 1px solid rgba(176, 123, 60, 0.34);
  --hair-light: 1px solid rgba(217, 165, 102, 0.34);

  --dur: 240ms;
  --dur-fast: 180ms;
  --ease: cubic-bezier(0.22, 0.61, 0.36, 1);
}

/* ---------- 3. Base / 中文排版 ---------- */
html { scroll-behavior: smooth; }

body {
  min-height: 100vh;
  background-color: var(--cream-100);
  background-image:
    radial-gradient(circle at 10% 4%, rgba(176, 123, 60, 0.14), transparent 42%),
    radial-gradient(circle at 92% 96%, rgba(31, 90, 76, 0.13), transparent 40%);
  background-attachment: fixed;
  color: var(--brown-900);
  font-family: var(--font-body);
  font-size: clamp(16px, 0.55vw + 14px, 17px);
  line-height: 1.75;
  letter-spacing: 0.01em;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-display);
  font-weight: 800;
  line-height: 1.14;
  letter-spacing: -0.02em;
  color: var(--ink-900);
}

h1 { font-size: clamp(2.6rem, 6vw, 5.2rem); }
h2 { font-size: clamp(1.65rem, 3vw, 2.5rem); }
h3 { font-size: clamp(1.2rem, 1.8vw, 1.55rem); }

p { max-width: 38em; }

strong { font-weight: 700; color: var(--ink-900); }

code, kbd, samp, .mono {
  font-family: var(--font-mono);
  font-size: 0.9em;
  letter-spacing: 0.02em;
}

::selection {
  background: var(--copper-300);
  color: var(--ink-900);
}

/* 焦点可见性 */
:where(a, button, summary, [tabindex]):focus-visible {
  outline: 2px solid var(--copper-300);
  outline-offset: 3px;
  border-radius: 2px;
}

.site-footer :where(a, button):focus-visible,
.site-header :where(a, button):focus-visible {
  outline-color: var(--copper-300);
  outline-offset: 3px;
}

.panel--notch :where(a, button):focus-visible { outline-offset: -4px; }

/* ---------- 4. 布局工具 ---------- */
.container {
  width: min(calc(100% - 2 * var(--gutter)), var(--wrap));
  margin-inline: auto;
}

.section { padding-block: clamp(2.5rem, 6vw, 5rem); }

.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;
}

.eyebrow {
  display: block;
  margin: 0 0 0.55rem;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 500;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--copper-500);
}

.section-rule {
  height: 1px;
  border: 0;
  margin-block: clamp(1.5rem, 4vw, 3rem);
  background-image: repeating-linear-gradient(90deg, var(--copper-500) 0 8px, transparent 8px 18px);
  opacity: 0.55;
}

.grid {
  display: grid;
  gap: clamp(1rem, 2.6vw, 2rem);
}

.grid--2 { grid-template-columns: repeat(auto-fit, minmax(min(100%, 300px), 1fr)); }
.grid--3 { grid-template-columns: repeat(auto-fit, minmax(min(100%, 240px), 1fr)); }
.grid--asym { grid-template-columns: minmax(0, 1.35fr) minmax(0, 0.8fr); }

@media (max-width: 860px) {
  .grid--asym { grid-template-columns: minmax(0, 1fr); }
}

/* ---------- 5. 跳转链接 ---------- */
.skip-link {
  position: fixed;
  top: 0.6rem;
  left: var(--gutter);
  z-index: 200;
  padding: 0.7rem 1.15rem;
  background: var(--ink-900);
  color: var(--paper-50);
  border: 1px solid var(--copper-300);
  border-radius: 2px;
  font-size: 0.9rem;
  text-decoration: none;
  transform: translateY(-180%);
  transition: transform var(--dur) var(--ease);
}

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

/* ---------- 6. 头部命令栏 ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--ink-900);
  color: var(--cream-100);
  border-bottom: 1px solid rgba(217, 165, 102, 0.34);
  box-shadow: 0 18px 34px -30px rgba(0, 0, 0, 0.9);
}

.scroll-progress {
  position: absolute;
  left: 0; right: 0; bottom: 0;
  height: 2px;
  overflow: hidden;
  pointer-events: none;
}

.scroll-progress__bar {
  display: block;
  height: 100%;
  width: 100%;
  transform: scaleX(0);
  transform-origin: 0 50%;
  background: linear-gradient(90deg, var(--copper-500), var(--copper-300));
}

.command-bar__inner {
  display: flex;
  align-items: center;
  flex-wrap: nowrap;
  gap: clamp(0.7rem, 1.8vw, 1.5rem);
  width: min(calc(100% - 2 * var(--gutter)), var(--wrap));
  margin-inline: auto;
  padding-block: 0.78rem;
}

/* 品牌 */
.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.62rem;
  flex: 0 0 auto;
  min-width: 0;
  text-decoration: none;
  color: inherit;
}

.brand__mark {
  display: grid;
  place-items: center;
  width: 2.35rem;
  height: 2.35rem;
  flex: 0 0 auto;
  background: var(--copper-300);
  color: var(--ink-900);
  font-family: var(--font-display);
  font-size: 1.12rem;
  font-weight: 800;
  line-height: 1;
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 9px), calc(100% - 9px) 100%, 0 100%);
}

.brand__text {
  display: flex;
  flex-direction: column;
  line-height: 1.18;
  min-width: 0;
}

.brand__name {
  font-family: var(--font-display);
  font-size: 1.05rem;
  font-weight: 800;
  letter-spacing: 0.01em;
  color: var(--paper-50);
  white-space: nowrap;
}

.brand__tagline {
  font-size: 0.68rem;
  letter-spacing: 0.14em;
  color: rgba(244, 237, 224, 0.6);
  white-space: nowrap;
}

/* 版本状态 */
.version-chip {
  display: none;
  align-items: center;
  gap: 0.42rem;
  flex: 0 0 auto;
  max-width: none;
  margin: 0;
  padding: 0.28rem 0.62rem;
  border: 1px dashed rgba(217, 165, 102, 0.46);
  border-radius: 999px;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.05em;
  white-space: nowrap;
  color: var(--copper-300);
}

.version-chip__dot {
  width: 0.42rem;
  height: 0.42rem;
  border-radius: 50%;
  background: var(--cinnabar);
  box-shadow: 0 0 0 3px rgba(179, 58, 43, 0.24);
}

.version-chip__label { color: rgba(244, 237, 224, 0.58); }
.version-chip__value { color: var(--paper-50); }
.version-chip__sep { color: rgba(217, 165, 102, 0.5); }
.version-chip__period { color: rgba(217, 165, 102, 0.85); }

/* 导航 */
.site-nav {
  margin-left: auto;
  min-width: 0;
}

.nav-list {
  display: flex;
  align-items: center;
  gap: 0.1rem;
  padding: 0;
  margin: 0;
  list-style: none;
}

.nav-item { flex: 0 0 auto; }

.nav-link {
  position: relative;
  display: inline-flex;
  align-items: baseline;
  gap: 0.38rem;
  padding: 0.5rem 0.66rem;
  border-radius: 2px;
  font-size: 0.9rem;
  color: rgba(244, 237, 224, 0.82);
  text-decoration: none;
  transition: color var(--dur-fast) var(--ease), background-color var(--dur-fast) var(--ease);
}

.nav-index {
  font-family: var(--font-mono);
  font-size: 0.62rem;
  letter-spacing: 0.06em;
  color: var(--copper-500);
  transition: color var(--dur-fast) var(--ease);
}

.nav-link:hover {
  color: var(--paper-50);
  background: rgba(217, 165, 102, 0.13);
}

.nav-link:hover .nav-index { color: var(--copper-300); }

.nav-link[aria-current="page"] {
  color: var(--paper-50);
  background: rgba(176, 123, 60, 0.22);
}

.nav-link[aria-current="page"] .nav-index { color: var(--copper-300); }

.nav-link[aria-current="page"]::after {
  content: "";
  position: absolute;
  left: 0.66rem;
  right: 0.66rem;
  bottom: 0.12rem;
  height: 2px;
  background: var(--copper-300);
}

/* 头部 CTA */
.header__cta {
  flex: 0 0 auto;
  padding: 0.55rem 0.95rem;
  font-size: 0.85rem;
}

/* 移动端开关 */
.nav-toggle {
  display: none;
  align-items: center;
  gap: 0.45rem;
  margin-left: auto;
  padding: 0.45rem 0.7rem;
  background: transparent;
  border: 1px solid rgba(217, 165, 102, 0.5);
  border-radius: 2px;
  color: var(--cream-100);
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.12em;
  cursor: pointer;
  transition: background-color var(--dur-fast) var(--ease), border-color var(--dur-fast) var(--ease);
}

.nav-toggle:hover { background: rgba(217, 165, 102, 0.14); }

.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: 2px;
  background: var(--copper-300);
  transition: transform var(--dur) var(--ease);
}

.nav-toggle__bars::before { top: 0; }
.nav-toggle__bars::after { bottom: 0; }

.nav-toggle[aria-expanded="true"] .nav-toggle__bars::before { transform: translateY(4px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] .nav-toggle__bars::after { transform: translateY(-4px) rotate(-45deg); }

/* ---------- 7. 页脚 ---------- */
.site-footer {
  position: relative;
  margin-top: clamp(3.5rem, 8vw, 6.5rem);
  background: var(--ink-900);
  color: var(--cream-100);
  border-top: 1px solid rgba(217, 165, 102, 0.4);
}

.footer__perf {
  height: 0;
  border-top: 1px dashed rgba(217, 165, 102, 0.36);
  margin-inline: var(--gutter);
}

.footer__inner {
  padding-block: clamp(2.2rem, 5vw, 3.6rem) clamp(1.2rem, 3vw, 2rem);
}

.footer__top {
  display: grid;
  grid-template-columns: minmax(0, 1.15fr) minmax(0, 0.85fr);
  gap: clamp(1.6rem, 4vw, 3.5rem);
  align-items: start;
}

.footer__eyebrow {
  max-width: none;
  margin: 0 0 0.5rem;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--copper-300);
}

.footer__wordmark {
  max-width: none;
  margin: 0 0 0.6rem;
  font-family: var(--font-display);
  font-size: clamp(1.9rem, 3.4vw, 2.7rem);
  font-weight: 800;
  line-height: 1.1;
  letter-spacing: -0.02em;
  color: var(--paper-50);
}

.footer__wordmark-en {
  margin-left: 0.4rem;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 500;
  letter-spacing: 0.18em;
  color: var(--copper-300);
  vertical-align: super;
}

.footer__note {
  max-width: 30em;
  margin: 0 0 1.15rem;
  font-size: 0.92rem;
  line-height: 1.7;
  color: rgba(244, 237, 224, 0.72);
}

/* 票根联络卡 */
.footer__stub {
  position: relative;
  background: var(--paper-50);
  color: var(--brown-900);
  border: 1px solid var(--copper-300);
  padding: clamp(1.05rem, 2.2vw, 1.5rem) clamp(1rem, 2.2vw, 1.5rem) clamp(1.05rem, 2.2vw, 1.5rem) clamp(1.6rem, 3vw, 2.1rem);
}

.footer__stub::before,
.footer__stub::after {
  content: "";
  position: absolute;
  top: 50%;
  width: 18px;
  height: 18px;
  margin-top: -9px;
  border-radius: 50%;
  background: var(--ink-900);
  border: 1px solid rgba(217, 165, 102, 0.45);
}

.footer__stub::before { left: -10px; }
.footer__stub::after { right: -10px; }

.footer__stub-title {
  max-width: none;
  margin: 0 0 0.85rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px dashed rgba(176, 123, 60, 0.5);
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--copper-500);
}

.footer__contact {
  display: grid;
  gap: 0.5rem;
  padding: 0;
  margin: 0;
  list-style: none;
}

.footer__contact-item {
  display: grid;
  grid-template-columns: 4.6rem minmax(0, 1fr) auto;
  gap: 0.55rem;
  align-items: baseline;
  padding-bottom: 0.45rem;
  border-bottom: 1px dashed rgba(176, 123, 60, 0.36);
}

.footer__contact-item:last-child { border-bottom: 0; padding-bottom: 0; }

.footer__contact-label {
  font-family: var(--font-mono);
  font-size: 0.66rem;
  letter-spacing: 0.1em;
  color: var(--sage-500);
}

.footer__contact-value {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  line-height: 1.55;
  color: var(--ink-900);
  overflow-wrap: anywhere;
}

.footer__status {
  max-width: none;
  margin: 0.7rem 0 0;
  min-height: 1.1em;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.06em;
  color: var(--ink-500);
}

/* 复制按钮 */
.copy-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.25rem;
  padding: 0.16rem 0.45rem;
  background: transparent;
  border: 1px dashed rgba(176, 123, 60, 0.72);
  border-radius: 2px;
  color: var(--ink-500);
  font-family: var(--font-mono);
  font-size: 0.64rem;
  letter-spacing: 0.08em;
  cursor: pointer;
  transition: background-color var(--dur-fast) var(--ease), color var(--dur-fast) var(--ease), border-color var(--dur-fast) var(--ease);
}

.copy-btn:hover {
  background: var(--ink-500);
  border-color: var(--ink-500);
  color: var(--paper-50);
}

.copy-btn.is-copied {
  background: var(--ink-700);
  border-color: var(--ink-700);
  border-style: solid;
  color: var(--paper-50);
}

/* 页脚索引列 */
.footer__columns {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: clamp(1.2rem, 3vw, 2.5rem);
  margin-top: clamp(2rem, 4.5vw, 3.2rem);
  padding-top: clamp(1.4rem, 3vw, 2rem);
  border-top: 1px dashed rgba(217, 165, 102, 0.3);
}

.footer__heading {
  max-width: none;
  margin: 0 0 0.7rem;
  font-family: var(--font-display);
  font-size: 0.98rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--paper-50);
}

.footer__list {
  display: grid;
  gap: 0.38rem;
  padding: 0;
  margin: 0;
  list-style: none;
}

.footer__link {
  display: inline-block;
  font-size: 0.88rem;
  color: rgba(244, 237, 224, 0.72);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color var(--dur-fast) var(--ease), border-color var(--dur-fast) var(--ease);
}

.footer__link:hover {
  color: var(--paper-50);
  border-bottom-color: var(--copper-300);
}

.footer__bottom {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.6rem 1.5rem;
  margin-top: clamp(1.8rem, 4vw, 2.8rem);
  padding-top: clamp(0.9rem, 2vw, 1.2rem);
  border-top: 1px solid rgba(217, 165, 102, 0.24);
}

.footer__icp,
.footer__legal,
.footer__copy {
  max-width: none;
  margin: 0;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.06em;
  color: rgba(244, 237, 224, 0.56);
}

.footer__icp { color: var(--copper-300); }

/* ---------- 8. 通用按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.45rem;
  padding: 0.64rem 1.12rem;
  border: 1px solid transparent;
  border-radius: 2px;
  background: transparent;
  font-family: var(--font-body);
  font-size: 0.875rem;
  font-weight: 600;
  line-height: 1.3;
  letter-spacing: 0.03em;
  text-decoration: none;
  cursor: pointer;
  transition: background-color var(--dur-fast) var(--ease), color var(--dur-fast) var(--ease), border-color var(--dur-fast) var(--ease), transform var(--dur-fast) var(--ease);
}

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

.btn--copper {
  background: var(--copper-500);
  border-color: var(--copper-300);
  color: #1A130E;
}

.btn--copper:hover { background: var(--copper-300); }

.btn--primary {
  background: var(--ink-500);
  border-color: rgba(217, 165, 102, 0.45);
  color: var(--paper-50);
}

.btn--primary:hover { background: var(--ink-700); }

.btn--ghost {
  border-color: rgba(11, 36, 31, 0.35);
  color: var(--ink-900);
}

.btn--ghost:hover {
  background: rgba(11, 36, 31, 0.06);
  border-color: var(--ink-900);
}

.btn--ghost-light {
  border-color: rgba(217, 165, 102, 0.55);
  color: var(--cream-100);
}

.btn--ghost-light:hover {
  background: rgba(217, 165, 102, 0.15);
  color: var(--paper-50);
}

/* ---------- 9. 基础组件 ---------- */
/* 面包屑 */
.breadcrumb { padding-block: 0.9rem; }

.breadcrumb__list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.45rem;
  padding: 0;
  margin: 0;
  list-style: none;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.1em;
  color: var(--sage-500);
}

.breadcrumb__link {
  color: var(--ink-500);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: border-color var(--dur-fast) var(--ease);
}

.breadcrumb__link:hover { border-bottom-color: var(--copper-500); }

.breadcrumb__sep { color: var(--copper-500); }

/* 阅读列 */
.prose {
  max-width: 36em;
  font-size: 1.02rem;
  line-height: 1.8;
}

.prose > * + * { margin-top: 1.1em; }

.prose h2 { margin-top: 2.1em; }

.prose h3 { margin-top: 1.7em; }

.prose ul,
.prose ol {
  padding-left: 1.25em;
  list-style: revert;
}

.prose li + li { margin-top: 0.4em; }

.prose a {
  color: var(--ink-500);
  text-decoration: underline;
  text-decoration-color: var(--copper-300);
  text-underline-offset: 3px;
}

.prose a:hover { color: var(--ink-900); }

.prose blockquote {
  padding: 0.9rem 1.1rem;
  border-left: 3px solid var(--copper-500);
  background: rgba(231, 220, 200, 0.55);
  font-family: var(--font-display);
  font-size: 1.05rem;
  color: var(--ink-700);
}

.prose code {
  padding: 0.1em 0.35em;
  background: var(--beige-200);
  border-radius: 2px;
  color: var(--ink-700);
}

/* 面板 */
.panel {
  background: var(--paper-50);
  border: var(--hair-copper);
  border-radius: 2px;
  padding: clamp(1.1rem, 2.4vw, 1.9rem);
}

.panel--notch {
  clip-path: polygon(
    var(--notch) 0,
    100% 0,
    100% calc(100% - var(--notch)),
    calc(100% - var(--notch)) 100%,
    0 100%,
    0 var(--notch)
  );
}

.panel--dark {
  background: var(--ink-900);
  border-color: rgba(217, 165, 102, 0.4);
  color: var(--cream-100);
}

.panel--dark h2,
.panel--dark h3 { color: var(--paper-50); }

/* 标签 / 票根签 */
.tag {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.28rem 0.62rem;
  border: 1px dashed rgba(176, 123, 60, 0.6);
  border-radius: 999px;
  background: rgba(231, 220, 200, 0.42);
  color: var(--ink-700);
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.08em;
  cursor: pointer;
  transition: background-color var(--dur-fast) var(--ease), color var(--dur-fast) var(--ease), border-color var(--dur-fast) var(--ease);
}

.tag:hover { border-color: var(--copper-500); }

.tag[aria-pressed="true"],
.tag.is-active {
  background: var(--ink-500);
  border-color: var(--ink-500);
  border-style: solid;
  color: var(--paper-50);
}

/* 图片容器基座（页面阶段放置真实图片） */
.media-frame {
  position: relative;
  display: block;
  overflow: hidden;
  aspect-ratio: 16 / 10;
  background: var(--beige-200);
  border: var(--hair-copper);
  border-radius: 2px;
}

.media-frame--wide { aspect-ratio: 21 / 9; }
.media-frame--tall { aspect-ratio: 3 / 4; }

.media-frame img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  filter: saturate(0.92) contrast(1.03);
}

.media-frame::after {
  content: "";
  position: absolute;
  inset: 0;
  pointer-events: none;
  background-image:
    linear-gradient(180deg, rgba(176, 123, 60, 0.1), transparent 34%, rgba(11, 36, 31, 0.16)),
    repeating-linear-gradient(0deg, rgba(34, 28, 24, 0.05) 0 1px, transparent 1px 3px);
}

.media-frame__caption {
  margin-top: 0.55rem;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.06em;
  color: var(--sage-500);
}

/* 返回顶部（由 site.js 注入） */
.to-top {
  position: fixed;
  right: clamp(0.9rem, 3vw, 2rem);
  bottom: clamp(0.9rem, 3vw, 2rem);
  z-index: 90;
  display: grid;
  place-items: center;
  width: 2.9rem;
  height: 2.9rem;
  padding: 0;
  background: var(--ink-900);
  border: 1px solid rgba(217, 165, 102, 0.55);
  border-radius: 2px;
  color: var(--copper-300);
  font-family: var(--font-mono);
  font-size: 1rem;
  line-height: 1;
  cursor: pointer;
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--dur) var(--ease), transform var(--dur) var(--ease), background-color var(--dur-fast) var(--ease);
}

.to-top[data-visible] {
  opacity: 1;
  pointer-events: auto;
}

.to-top:hover {
  background: var(--ink-700);
  transform: translateY(-2px);
}

/* ---------- 10. 进场动效 ---------- */
html.js [data-reveal] {
  opacity: 0;
  transform: translateY(12px);
  transition: opacity var(--dur) var(--ease), transform var(--dur) var(--ease);
}

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

/* ---------- 11. 响应式 ---------- */
@media (min-width: 1180px) {
  .version-chip { display: inline-flex; }
}

@media (max-width: 1080px) {
  .nav-link { padding-inline: 0.5rem; font-size: 0.86rem; }
  .nav-index { display: none; }
}

@media (max-width: 900px) {
  .nav-toggle { display: inline-flex; }
  .header__cta { display: none; }
  .version-chip { display: none; }

  .site-nav {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    margin: 0;
    display: none;
    max-height: calc(100vh - 4rem);
    overflow-y: auto;
    background: var(--ink-700);
    border-top: 1px solid rgba(217, 165, 102, 0.32);
    border-bottom: 1px solid rgba(217, 165, 102, 0.32);
    box-shadow: 0 26px 44px -30px rgba(0, 0, 0, 0.95);
  }

  .site-nav[data-open] { display: block; }

  .nav-list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: 0.4rem var(--gutter) 1.1rem;
  }

  .nav-item { border-bottom: 1px dashed rgba(217, 165, 102, 0.22); }
  .nav-item:last-child { border-bottom: 0; }

  .nav-link {
    width: 100%;
    padding: 0.85rem 0.15rem;
    font-size: 1rem;
  }

  .nav-index { display: inline; }

  .nav-link[aria-current="page"]::after {
    left: 0.15rem;
    right: auto;
    width: 30px;
    bottom: 0.55rem;
  }

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

@media (max-width: 640px) {
  .brand__tagline { display: none; }
  .footer__columns { grid-template-columns: minmax(0, 1fr); }
  .footer__bottom { flex-direction: column; align-items: flex-start; }
  .footer__contact-item { grid-template-columns: minmax(0, 1fr) auto; }
  .footer__contact-label { grid-column: 1 / -1; }
}

@media (max-width: 420px) {
  .nav-toggle__text { display: none; }
  .footer__stub { padding-left: 1.1rem; }
  .footer__stub::before { display: none; }
}

/* ---------- 12. 降低动态偏好 & 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;
    scroll-behavior: auto !important;
  }

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

  .to-top:hover { transform: none; }
}

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

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