/* =========================================================
   lb303利博中心 · 共享样式 /assets/site.css
   霓虹夜色：深墨底 + 荧光青 / 霓虹紫粉，仅用于边界与关键入口
   ========================================================= */

/* ---------- 1. 设计变量（定稿，原样保留） ---------- */
:root {
  --color-surface: #2c282a;
  --color-surface-alt: #3b3638;
  --color-surface-deep: #4d474a;
  --color-ink: #cfc4cb;
  --color-ink-soft: #a38f9b;
  --color-ink-muted: #8b7482;
  --color-line: #494447;
  --color-primary: #d6439c;
  --color-primary-ink: #181115;
  --color-primary-soft: #442c3a;
  --color-accent: #20dfd2;
  --color-accent-ink: #181115;
  --color-highlight: #2a4948;
  --color-focus: #14ebdd;
  --color-contrast-surface: #f3f1f2;
  --color-contrast-ink: #383336;
  --color-contrast-line: #cac7c9;
  --color-contrast-accent: #117871;
  --overlay-scrim: linear-gradient(180deg, rgba(243, 241, 242, 0.35) 0%, rgba(243, 241, 242, 0.72) 55%, rgba(243, 241, 242, 0.92) 100%);
  --font-heading: "PingFang SC", "HarmonyOS Sans SC", "Microsoft YaHei", "Source Han Sans SC", sans-serif;
  --font-body: "PingFang SC", "HarmonyOS Sans SC", "Microsoft YaHei", "Source Han Sans SC", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --text-xs: 10.1px;
  --text-sm: 14.3px;
  --text-base: 17px;
  --text-lg: 24.0px;
  --text-xl: 34.0px;
  --text-2xl: 48.1px;
  --text-3xl: 68.0px;
  --text-4xl: 96.1px;
  --text-display: clamp(43px, 8.9vw, 114px);
  --text-figure: clamp(36px, 6.4vw, 82px);
  --weight-heading: 731;
  --weight-body: 400;
  --leading-body: 1.71;
  --leading-heading: 1.29;
  --tracking-heading: -0.004em;
  --radius-sm: 8px;
  --radius-md: 8px;
  --radius-lg: 8px;
  --radius-pill: 999px;
  --border-thin: 1px;
  --border-thick: 2px;
  --shadow-1: 0 0 0 1px rgba(32, 223, 210, 0.35);
  --shadow-2: 0 0 28px rgba(32, 223, 210, 0.35);
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-6: 48px;
  --space-8: 64px;
  --container: 1140px;
  --measure: 72ch;
  --gutter: 32px;
  --section-y: 95px;
  --section-y-lg: 133px;
}

/* ---------- 2. Reset 与基础 ---------- */
*, *::before, *::after { box-sizing: border-box; }

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

body {
  margin: 0;
  background-color: var(--color-surface);
  background-image:
    radial-gradient(68% 44% at 4% -6%, color-mix(in srgb, var(--color-accent) 9%, transparent), transparent 68%),
    radial-gradient(54% 42% at 104% 8%, color-mix(in srgb, var(--color-primary) 13%, transparent), transparent 70%);
  background-repeat: no-repeat;
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: var(--text-base);
  font-weight: var(--weight-body);
  line-height: var(--leading-body);
  -webkit-font-smoothing: antialiased;
}

img, svg, video { display: block; max-width: 100%; height: auto; }
button, input, select, textarea { font: inherit; color: inherit; }
ul, ol { margin: 0; padding: 0; list-style: none; }
p { margin: 0 0 var(--space-2); }
p:last-child { margin-bottom: 0; }
hr { border: 0; border-top: var(--border-thin) solid var(--color-line); margin: var(--space-4) 0; }

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

:focus-visible {
  outline: var(--border-thick) solid var(--color-focus);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color 0.2s ease, border-color 0.2s ease;
}
a:hover { color: color-mix(in srgb, var(--color-accent) 68%, var(--color-contrast-surface)); }

h1, h2, h3, h4, h5 {
  margin: 0 0 var(--space-2);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: color-mix(in srgb, var(--color-ink) 72%, var(--color-contrast-surface));
}
h1 { font-size: var(--text-2xl); }
h2 { font-size: var(--text-xl); }
h3 { font-size: var(--text-lg); }
h4 { font-size: var(--text-base); }
h5 { font-size: var(--text-sm); }

.skip-link {
  position: absolute;
  left: var(--space-3);
  top: -120px;
  z-index: 200;
  padding: 10px 18px;
  border-radius: var(--radius-sm);
  background-color: var(--color-accent);
  color: var(--color-accent-ink);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  box-shadow: var(--shadow-2);
  transition: top 0.2s ease;
}
.skip-link:focus { top: var(--space-2); color: var(--color-accent-ink); }

/* ---------- 3. 布局原语 ---------- */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--space-3);
}

.grid {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: var(--gutter);
}
.grid--tight { gap: var(--space-2); }
.span-3 { grid-column: span 3; }
.span-4 { grid-column: span 4; }
.span-5 { grid-column: span 5; }
.span-6 { grid-column: span 6; }
.span-7 { grid-column: span 7; }
.span-8 { grid-column: span 8; }
.span-9 { grid-column: span 9; }
.span-10 { grid-column: span 10; }
.span-12 { grid-column: span 12; }

.section {
  position: relative;
  padding-block: var(--section-y);
  border-top: var(--border-thin) solid var(--color-line);
}
.section--hero { padding-block: var(--section-y-lg); }
.section--alt { background-color: var(--color-surface-alt); }
.section--deep { background-color: var(--color-surface-deep); }
.section--flush { border-top: 0; }

.section__head {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: var(--space-1) var(--space-3);
  margin-bottom: var(--space-6);
}
.section__index {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.16em;
  color: var(--color-primary);
}
.section-title {
  margin: 0;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-xl);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: color-mix(in srgb, var(--color-ink) 72%, var(--color-contrast-surface));
}

.rule { border-top: var(--border-thin) solid var(--color-line); margin-block: var(--space-4); }

/* ---------- 4. 文本元素 ---------- */
.display {
  margin: 0 0 var(--space-3);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-display);
  line-height: 1.02;
  letter-spacing: -0.02em;
  color: color-mix(in srgb, var(--color-ink) 66%, var(--color-contrast-surface));
}
.figure-number {
  display: block;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-figure);
  line-height: 1;
  color: var(--color-primary);
}
.lede {
  max-width: 56ch;
  font-size: var(--text-lg);
  line-height: 1.5;
  color: var(--color-ink);
}
.note {
  max-width: 60ch;
  padding-left: var(--space-2);
  border-left: var(--border-thick) solid var(--color-primary);
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
}
.mark {
  padding: 0 4px;
  border-radius: 4px;
  background-color: color-mix(in srgb, var(--color-accent) 18%, transparent);
  color: var(--color-ink);
}
.u {
  text-decoration: underline;
  text-decoration-color: var(--color-primary);
  text-decoration-thickness: var(--border-thick);
  text-underline-offset: 4px;
}
.mono, code, kbd {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
}
code {
  padding: 1px 6px;
  border-radius: var(--radius-sm);
  background-color: color-mix(in srgb, var(--color-surface-deep) 70%, transparent);
  color: var(--color-accent);
}

.prose { max-width: var(--measure); }
.prose > * + * { margin-top: var(--space-3); }
.prose h2, .prose h3 { margin-top: var(--space-6); }
.prose ul li {
  position: relative;
  padding-left: var(--space-3);
  margin-bottom: 6px;
}
.prose ul li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.75em;
  width: 8px;
  height: var(--border-thick);
  background-color: var(--color-accent);
}
.prose ol { counter-reset: item; }
.prose ol li {
  position: relative;
  padding-left: var(--space-4);
  margin-bottom: 6px;
  counter-increment: item;
}
.prose ol li::before {
  content: counter(item, decimal-leading-zero);
  position: absolute;
  left: 0;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--color-primary);
}

.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 10px;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-pill);
  background-color: color-mix(in srgb, var(--color-surface-deep) 55%, transparent);
  color: var(--color-ink-soft);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  line-height: 1.6;
}
.tag--accent {
  color: var(--color-accent);
  border-color: color-mix(in srgb, var(--color-accent) 45%, transparent);
  background-color: color-mix(in srgb, var(--color-accent) 8%, transparent);
}
.tag--primary {
  color: var(--color-primary);
  border-color: color-mix(in srgb, var(--color-primary) 50%, transparent);
  background-color: color-mix(in srgb, var(--color-primary) 12%, transparent);
}

/* ---------- 5. 按钮与入口块 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-1);
  padding: 10px 18px;
  border: var(--border-thin) solid transparent;
  border-radius: var(--radius-pill);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.06em;
  line-height: 1.4;
  text-decoration: none;
  cursor: pointer;
  transition: background-color 0.2s ease, color 0.2s ease, box-shadow 0.25s ease, transform 0.2s ease, border-color 0.2s ease;
}
.btn--primary {
  background-color: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
  box-shadow: 0 0 0 1px color-mix(in srgb, var(--color-primary) 35%, transparent), 0 0 22px color-mix(in srgb, var(--color-primary) 32%, transparent);
}
.btn--primary:hover {
  background-color: color-mix(in srgb, var(--color-primary) 86%, var(--color-contrast-surface));
  color: var(--color-primary-ink);
  box-shadow: 0 0 0 1px color-mix(in srgb, var(--color-primary) 55%, transparent), 0 0 32px color-mix(in srgb, var(--color-primary) 48%, transparent);
  transform: translateY(-1px);
}
.btn--ghost {
  background-color: transparent;
  border-color: color-mix(in srgb, var(--color-accent) 55%, transparent);
  color: var(--color-accent);
  box-shadow: var(--shadow-1);
}
.btn--ghost:hover {
  background-color: color-mix(in srgb, var(--color-accent) 14%, transparent);
  color: var(--color-accent);
  box-shadow: var(--shadow-2);
}
.btn--sm { padding: 6px 14px; font-size: var(--text-xs); letter-spacing: 0.1em; }
.btn--block { width: 100%; }

.quick-chip {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 13px;
  border: var(--border-thin) solid color-mix(in srgb, var(--color-accent) 38%, transparent);
  border-radius: var(--radius-pill);
  background-color: color-mix(in srgb, var(--color-accent) 7%, transparent);
  color: var(--color-accent);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  white-space: nowrap;
  transition: background-color 0.2s ease, color 0.2s ease, box-shadow 0.25s ease, border-color 0.2s ease;
}
.quick-chip::before { content: "→"; font-size: var(--text-xs); opacity: 0.75; }
.quick-chip:hover,
.quick-chip:focus-visible {
  background-color: var(--color-accent);
  border-color: var(--color-accent);
  color: var(--color-accent-ink);
  box-shadow: var(--shadow-2);
}
.quick-chip--alt {
  border-color: color-mix(in srgb, var(--color-primary) 50%, transparent);
  background-color: color-mix(in srgb, var(--color-primary) 12%, transparent);
  color: var(--color-primary);
}
.quick-chip--alt:hover,
.quick-chip--alt:focus-visible {
  background-color: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
  box-shadow: 0 0 26px color-mix(in srgb, var(--color-primary) 45%, transparent);
}

/* ---------- 6. 页头 ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 80;
  background-color: color-mix(in srgb, var(--color-surface) 88%, transparent);
  -webkit-backdrop-filter: blur(16px) saturate(140%);
  backdrop-filter: blur(16px) saturate(140%);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.scroll-progress {
  position: absolute;
  left: 0;
  right: 0;
  bottom: calc(-1 * var(--border-thin));
  height: var(--border-thick);
  overflow: hidden;
  background-color: color-mix(in srgb, var(--color-line) 55%, transparent);
  pointer-events: none;
}
.scroll-progress > span {
  display: block;
  width: 0;
  height: 100%;
  background-image: linear-gradient(90deg, var(--color-accent), var(--color-primary));
  box-shadow: 0 0 14px color-mix(in srgb, var(--color-accent) 55%, transparent);
  transition: width 0.15s linear;
}

.quick-band {
  background-color: color-mix(in srgb, var(--color-primary) 9%, var(--color-surface));
  border-bottom: var(--border-thin) solid var(--color-line);
}
.quick-band__inner {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  min-height: 46px;
  padding-block: var(--space-1);
  overflow-x: auto;
  overscroll-behavior-x: contain;
  scrollbar-width: none;
}
.quick-band__inner::-webkit-scrollbar { display: none; }
.quick-band__label {
  flex: none;
  padding-right: var(--space-3);
  border-right: var(--border-thin) solid var(--color-line);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
  white-space: nowrap;
}
.quick-band__links {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  margin: 0;
  padding: 0;
  list-style: none;
}

.masthead { padding-top: var(--space-3); }
.masthead__inner {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: var(--space-3);
  padding-bottom: var(--space-3);
}
.masthead__side {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  min-width: 0;
}
.masthead__side--end { justify-content: flex-end; }
.masthead__meta {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
  white-space: nowrap;
}

.brand {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
  text-align: center;
  padding-inline: var(--space-2);
}
.brand__name {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-lg);
  line-height: 1.1;
  letter-spacing: 0.06em;
  color: var(--color-ink);
  background-image: linear-gradient(96deg, var(--color-contrast-surface), var(--color-accent) 52%, var(--color-primary));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}
.brand:hover .brand__name { filter: brightness(1.12); }
@supports not ((-webkit-background-clip: text) or (background-clip: text)) {
  .brand__name { color: var(--color-accent); -webkit-text-fill-color: currentColor; }
}
.brand__tagline {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.12em;
  color: var(--color-ink-soft);
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: var(--space-1);
  padding: 8px 12px;
  border: var(--border-thin) solid color-mix(in srgb, var(--color-accent) 40%, transparent);
  border-radius: var(--radius-sm);
  background-color: color-mix(in srgb, var(--color-surface-deep) 60%, transparent);
  color: var(--color-accent);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  cursor: pointer;
  transition: background-color 0.2s ease, box-shadow 0.25s ease;
}
.nav-toggle:hover { background-color: color-mix(in srgb, var(--color-accent) 14%, transparent); }
.nav-toggle__bars {
  display: block;
  width: 16px;
  height: var(--border-thick);
  background-color: currentColor;
  box-shadow: 0 -5px 0 currentColor, 0 5px 0 currentColor;
}
.site-header[data-open] .nav-toggle { background-color: color-mix(in srgb, var(--color-primary) 22%, transparent); border-color: color-mix(in srgb, var(--color-primary) 55%, transparent); color: var(--color-primary); }

.site-nav { border-top: var(--border-thin) solid var(--color-line); }
.site-nav__list {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
  gap: var(--space-1) var(--space-4);
  padding-block: var(--space-2);
}
.site-nav__list li { display: flex; }
.site-nav__list a {
  position: relative;
  display: inline-block;
  padding: 6px 2px;
  border-bottom: var(--border-thick) solid transparent;
  border-radius: var(--radius-sm) var(--radius-sm) 0 0;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.1em;
  color: var(--color-ink-soft);
  transition: color 0.2s ease, border-color 0.2s ease, background-color 0.2s ease, text-shadow 0.25s ease;
}
.site-nav__list a:hover {
  color: var(--color-accent);
  border-bottom-color: color-mix(in srgb, var(--color-accent) 70%, transparent);
  text-shadow: 0 0 14px color-mix(in srgb, var(--color-accent) 45%, transparent);
}
.site-nav__list a[aria-current="page"] {
  padding-inline: 10px;
  color: color-mix(in srgb, var(--color-ink) 58%, var(--color-contrast-surface));
  background-color: var(--color-primary-soft);
  border-bottom-color: var(--color-primary);
  box-shadow: 0 0 18px color-mix(in srgb, var(--color-primary) 30%, transparent);
}

/* ---------- 7. 页脚（阶梯式） ---------- */
.site-footer {
  margin-top: var(--section-y);
  background-color: var(--color-surface);
  border-top: var(--border-thin) solid var(--color-line);
}
.footer-step { padding-block: var(--space-6); }
.footer-step--index {
  background-color: var(--color-surface-alt);
  border-bottom: var(--border-thin) solid var(--color-line);
}
.footer-step--legal { padding-block: var(--space-4); background-color: var(--color-surface); }

.footer-index {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1.1fr;
  gap: var(--space-6);
  align-items: start;
}
.footer-index__name {
  display: block;
  margin-bottom: var(--space-2);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-lg);
  line-height: 1.2;
  color: color-mix(in srgb, var(--color-ink) 72%, var(--color-contrast-surface));
}
.footer-index__note {
  margin: 0 0 var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  color: var(--color-accent);
}
.footer-index__tag {
  max-width: 36ch;
  margin: 0;
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
}

.footer-nav__title,
.footer-contact__title {
  margin: 0 0 var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}
.footer-nav__list {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 6px var(--space-3);
}
.footer-nav__list a {
  display: inline-block;
  padding: 2px 0;
  border-bottom: var(--border-thin) solid transparent;
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
}
.footer-nav__list a:hover {
  color: var(--color-accent);
  border-bottom-color: color-mix(in srgb, var(--color-accent) 60%, transparent);
}
.footer-contact__list li {
  display: flex;
  gap: var(--space-2);
  padding: 4px 0;
  border-bottom: var(--border-thin) solid color-mix(in srgb, var(--color-line) 70%, transparent);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
}
.footer-contact__list li:last-child { border-bottom: 0; }
.footer-contact__key { flex: none; color: var(--color-ink-muted); letter-spacing: 0.1em; }
.footer-contact__val { color: var(--color-ink); word-break: break-word; }

.footer-legal {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2) var(--space-4);
}
.footer-legal__links {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
}
.footer-legal__links a { color: var(--color-ink-soft); }
.footer-legal__links a:hover { color: var(--color-accent); }
.footer-legal__contact {
  flex: 1 1 340px;
  margin: 0;
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
}
.footer-legal__meta {
  margin: 0;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: var(--color-ink-muted);
}
.footer-legal__icp { color: var(--color-ink-soft); }

/* ---------- 8. 卡片 / 反色块 / 图片容器 ---------- */
.card {
  padding: var(--space-4);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-lg);
  background-color: color-mix(in srgb, var(--color-surface-deep) 55%, transparent);
  transition: border-color 0.25s ease, box-shadow 0.25s ease, transform 0.25s ease;
}
.card:hover {
  border-color: color-mix(in srgb, var(--color-accent) 45%, transparent);
  box-shadow: var(--shadow-1);
}
.card--glass {
  background-color: color-mix(in srgb, var(--color-surface-deep) 42%, transparent);
  border-color: color-mix(in srgb, var(--color-accent) 22%, var(--color-line));
  -webkit-backdrop-filter: blur(12px);
  backdrop-filter: blur(12px);
}
.card__label {
  display: block;
  margin-bottom: var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--color-primary);
}
.card__title {
  margin: 0 0 var(--space-2);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-lg);
  line-height: var(--leading-heading);
  color: color-mix(in srgb, var(--color-ink) 72%, var(--color-contrast-surface));
}
.card__text { font-size: var(--text-base); color: var(--color-ink); }
.card__meta {
  margin-top: var(--space-3);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.12em;
  color: var(--color-ink-muted);
}

.block-contrast {
  padding: var(--space-4);
  border: var(--border-thin) solid var(--color-contrast-line);
  border-radius: var(--radius-lg);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}
.block-contrast h2,
.block-contrast h3,
.block-contrast h4,
.block-contrast p { color: var(--color-contrast-ink); }
.block-contrast a { color: var(--color-contrast-accent); text-decoration: underline; text-underline-offset: 3px; }
.block-contrast .tag {
  border-color: var(--color-contrast-line);
  background-color: transparent;
  color: var(--color-contrast-accent);
}
.block-contrast .mono,
.block-contrast code { color: var(--color-contrast-accent); }

.figure {
  margin: 0 0 var(--space-4);
  overflow: hidden;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-lg);
  background-color: var(--color-surface-deep);
}
.figure__frame {
  position: relative;
  display: block;
  width: 100%;
  aspect-ratio: 16 / 9;
  overflow: hidden;
  background-color: var(--color-surface-deep);
  background-image:
    linear-gradient(135deg, color-mix(in srgb, var(--color-accent) 14%, transparent), transparent 58%),
    linear-gradient(315deg, color-mix(in srgb, var(--color-primary) 18%, transparent), transparent 60%);
}
.figure__frame img { width: 100%; height: 100%; object-fit: cover; }
.figure--wide .figure__frame { aspect-ratio: 21 / 9; }
.figure--tall .figure__frame { aspect-ratio: 3 / 4; }
.figure--square .figure__frame { aspect-ratio: 1 / 1; }
.figure__cap {
  padding: 10px var(--space-3);
  border-top: var(--border-thin) solid var(--color-line);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: var(--color-ink-muted);
}

.media {
  position: relative;
  overflow: hidden;
  border-radius: var(--radius-lg);
  background-color: var(--color-surface-deep);
}
.media__img { width: 100%; aspect-ratio: 16 / 9; object-fit: cover; }
.media__body {
  position: absolute;
  inset: auto 0 0 0;
  padding: var(--space-3);
  background-image: var(--overlay-scrim);
  color: var(--color-contrast-ink);
}
.media__body h3,
.media__body p { color: var(--color-contrast-ink); }
.media__body .tag { border-color: var(--color-contrast-line); background-color: transparent; color: var(--color-contrast-accent); }

/* ---------- 9. 面包屑与章节目录 ---------- */
.breadcrumb {
  padding-block: var(--space-3);
  border-bottom: var(--border-thin) solid var(--color-line);
}
.breadcrumb ol {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
}
.breadcrumb li { display: flex; align-items: center; gap: var(--space-2); color: var(--color-ink-muted); }
.breadcrumb li + li::before { content: "/"; color: var(--color-line); }
.breadcrumb a { color: var(--color-ink-soft); }
.breadcrumb a:hover { color: var(--color-accent); }
.breadcrumb [aria-current="page"] { color: var(--color-accent); }

.toc {
  position: sticky;
  top: 150px;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
}
.toc a {
  padding-left: var(--space-2);
  border-left: var(--border-thick) solid var(--color-line);
  color: var(--color-ink-muted);
  transition: color 0.2s ease, border-color 0.2s ease, text-shadow 0.25s ease;
}
.toc a:hover { color: var(--color-ink); }
.toc a[aria-current="true"] {
  border-left-color: var(--color-accent);
  color: var(--color-accent);
  text-shadow: 0 0 14px color-mix(in srgb, var(--color-accent) 40%, transparent);
}

/* ---------- 10. 动效与返回顶部 ---------- */
.reveal { transition: opacity 0.55s ease, transform 0.55s ease; }
.has-js .reveal { opacity: 0; transform: translateY(14px); }
.has-js .reveal.is-visible { opacity: 1; transform: none; }

.to-top {
  position: fixed;
  right: var(--space-3);
  bottom: var(--space-3);
  z-index: 70;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 10px 15px;
  border: var(--border-thin) solid color-mix(in srgb, var(--color-accent) 45%, transparent);
  border-radius: var(--radius-pill);
  background-color: color-mix(in srgb, var(--color-surface-deep) 82%, transparent);
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
  color: var(--color-accent);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.12em;
  cursor: pointer;
  opacity: 0;
  transform: translateY(12px);
  pointer-events: none;
  transition: opacity 0.25s ease, transform 0.25s ease, box-shadow 0.25s ease, background-color 0.25s ease;
}
.to-top.is-shown { opacity: 1; transform: none; pointer-events: auto; }
.to-top:hover {
  background-color: color-mix(in srgb, var(--color-accent) 16%, var(--color-surface-deep));
  box-shadow: var(--shadow-2);
}
.to-top__mark { font-size: var(--text-sm); line-height: 1; }

/* ---------- 11. 响应式 ---------- */
@media (max-width: 1024px) {
  .footer-index { grid-template-columns: 1fr 1fr; gap: var(--space-4); }
  .footer-index__brand { grid-column: span 2; }
}

@media (max-width: 980px) {
  .span-3, .span-4, .span-5, .span-6 { grid-column: span 6; }
  .span-7, .span-8, .span-9, .span-10 { grid-column: span 12; }
  .toc { position: static; flex-direction: row; flex-wrap: wrap; gap: var(--space-2); }
  .toc a { border-left: 0; border-bottom: var(--border-thick) solid var(--color-line); padding-left: 0; padding-bottom: 4px; }
  .toc a[aria-current="true"] { border-left: 0; border-bottom-color: var(--color-accent); }
}

@media (max-width: 860px) {
  .nav-toggle { display: inline-flex; }
  .masthead__meta { display: none; }
  .masthead { padding-top: var(--space-2); }
  .masthead__inner { grid-template-columns: auto 1fr auto; gap: var(--space-2); padding-bottom: var(--space-2); }
  .brand { align-items: flex-start; text-align: left; padding-inline: 0; }
  .brand__tagline { letter-spacing: 0.06em; }
  .site-nav {
    max-height: 0;
    overflow: hidden;
    border-top-color: transparent;
    transition: max-height 0.32s ease, border-color 0.32s ease;
  }
  .site-header[data-open] .site-nav {
    max-height: min(70vh, 520px);
    overflow-y: auto;
    border-top-color: var(--color-line);
  }
  .site-nav__list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding-block: var(--space-2);
  }
  .site-nav__list a {
    display: block;
    padding: 12px var(--space-3);
    border-bottom: var(--border-thin) solid var(--color-line);
    border-left: var(--border-thick) solid transparent;
    border-radius: 0;
    background-color: transparent;
    color: var(--color-ink);
  }
  .site-nav__list a[aria-current="page"] {
    padding-inline: var(--space-3);
    background-color: var(--color-primary-soft);
    border-left-color: var(--color-primary);
    border-bottom-color: var(--color-line);
    box-shadow: none;
  }
}

@media (max-width: 640px) {
  .container { padding-inline: var(--space-2); }
  .span-3, .span-4, .span-5, .span-6, .span-7, .span-8, .span-9, .span-10 { grid-column: span 12; }
  .grid { gap: var(--space-3); }
  .section { padding-block: calc(var(--section-y) * 0.72); }
  .section--hero { padding-block: var(--section-y); }
  .masthead__side--end { display: none; }
  .brand__name { font-size: var(--text-base); letter-spacing: 0.04em; }
  .lede { font-size: var(--text-base); }
  .quick-band__label { display: none; }
  .footer-step { padding-block: var(--space-4); }
  .footer-index { grid-template-columns: 1fr; }
  .footer-index__brand { grid-column: span 1; }
  .footer-nav__list { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .footer-legal { flex-direction: column; align-items: flex-start; }
  .to-top { right: var(--space-2); bottom: var(--space-2); }
}

/* ---------- 12. 减少动效 ---------- */
@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;
  }
  .has-js .reveal { opacity: 1 !important; transform: none !important; }
  .to-top { transform: none; }
}