.page-about {
  --about-measure: 620px;
  --about-block: 56px;
  max-width: var(--max);
  margin-inline: auto;
  padding: 20px var(--gutter) 72px;
}

/* ---------- 首屏 ---------- */
.page-about .about-hero {
  padding-bottom: 28px;
}

.page-about .about-hero .kicker {
  margin: 0;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--cyan);
}

.page-about .about-hero h1 {
  margin: 10px 0 0;
  font-size: clamp(34px, 10vw, 58px);
  font-weight: 900;
  line-height: 1.05;
  letter-spacing: -0.02em;
  color: var(--ink);
}

.page-about .about-hero .lede {
  margin: 18px 0 0;
  max-width: 50ch;
  font-size: 17px;
  line-height: 1.85;
  color: var(--soft);
}

.page-about .about-facts {
  list-style: none;
  margin: 30px 0 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  background: var(--line-strong);
  border: 1px solid var(--line-strong);
}

.page-about .about-facts li {
  background: var(--bg);
  padding: 16px 14px 18px;
}

.page-about .fact-num {
  display: block;
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: clamp(24px, 6.4vw, 36px);
  font-weight: 700;
  line-height: 1.05;
  letter-spacing: -0.03em;
  color: var(--gold);
}

.page-about .fact-label {
  display: block;
  margin-top: 8px;
  font-size: 12px;
  line-height: 1.6;
  letter-spacing: 0.04em;
  color: var(--soft);
}

/* ---------- 章节索引 ---------- */
.page-about .about-toc {
  margin-top: 34px;
  padding-top: 14px;
  border-top: 1px solid var(--line);
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(132px, 1fr));
  gap: 6px;
}

.page-about .about-toc a {
  display: flex;
  align-items: baseline;
  gap: 8px;
  padding: 9px 10px;
  border: 1px solid transparent;
  color: var(--soft);
  text-decoration: none;
  font-size: 14px;
  line-height: 1.5;
  transition: color 180ms var(--ease), border-color 180ms var(--ease), background-color 180ms var(--ease);
}

.page-about .about-toc a:hover,
.page-about .about-toc a:focus-visible {
  color: var(--ink);
  border-color: var(--line-strong);
  background: var(--panel);
}

.page-about .about-toc a.is-active,
.page-about .about-toc a[aria-current="true"] {
  color: var(--ink);
  border-color: var(--line-strong);
  background: var(--panel-2);
}

.page-about .about-toc a.is-active .toc-num,
.page-about .about-toc a[aria-current="true"] .toc-num {
  color: var(--cyan);
}

.page-about .toc-num {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--ice);
}

/* ---------- 大编号章节 ---------- */
.page-about .about-chapter {
  margin-top: var(--about-block);
  padding-top: 26px;
  border-top: 1px solid var(--line);
}

.page-about .about-chapter .chapter-num {
  display: block;
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: clamp(30px, 8vw, 46px);
  font-weight: 700;
  line-height: 1;
  letter-spacing: -0.04em;
  color: var(--ice);
}

.page-about .about-chapter .chapter-title {
  margin: 8px 0 0;
  font-size: clamp(21px, 5.2vw, 30px);
  font-weight: 800;
  line-height: 1.25;
  letter-spacing: -0.02em;
  color: var(--ink);
}

.page-about .about-chapter .chapter-body {
  margin-top: 18px;
  max-width: var(--about-measure);
  font-size: 17px;
  line-height: 1.85;
  color: var(--ink);
}

.page-about .about-chapter .chapter-body > p {
  margin: 0 0 16px;
}

.page-about .about-chapter .chapter-body > p:last-child {
  margin-bottom: 0;
}

.page-about .about-chapter .chapter-body.has-aside {
  max-width: none;
}

.page-about .about-link {
  color: var(--ice);
  text-decoration: none;
  border-bottom: 1px solid var(--line-strong);
  padding-bottom: 2px;
  transition: color 180ms var(--ease), border-color 180ms var(--ease);
}

.page-about .about-link:hover,
.page-about .about-link:focus-visible {
  color: var(--gold);
  border-color: var(--gold);
}

/* ---------- 图文分栏 ---------- */
.page-about .about-split {
  display: grid;
  gap: 26px;
}

.page-about .about-figure {
  margin: 0;
}

.page-about .about-figure .media-frame {
  border: 1px solid var(--line);
  background: var(--panel-2);
  overflow: hidden;
}

.page-about .about-figure .media-frame img {
  display: block;
  width: 100%;
  height: auto;
  object-fit: cover;
}

.page-about .about-figure .media-caption {
  margin-top: 10px;
  font-size: 12.5px;
  line-height: 1.7;
  color: var(--muted);
}

.page-about .flow-figure,
.page-about .tl-figure {
  margin: 26px 0 22px;
}

/* ---------- 时间线 ---------- */
.page-about .timeline {
  list-style: none;
  margin: 26px 0 0;
  padding: 0;
}

.page-about .tl-item {
  position: relative;
  padding: 0 0 26px 26px;
  border-left: 1px solid var(--line-strong);
  transition: border-color 200ms var(--ease);
}

.page-about .tl-item:last-child {
  padding-bottom: 0;
  border-left-color: transparent;
}

.page-about .tl-item::before {
  content: "";
  position: absolute;
  left: -4px;
  top: 7px;
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--bg);
  border: 1px solid var(--ice);
  transition: background-color 200ms var(--ease), box-shadow 200ms var(--ease), border-color 200ms var(--ease);
}

.page-about .tl-item.is-key::before {
  border-color: var(--gold);
}

.page-about .tl-item:hover::before,
.page-about .tl-item:focus-within::before {
  background: var(--cyan);
  border-color: var(--cyan);
  box-shadow: 0 0 0 4px rgba(53, 229, 208, 0.12);
}

.page-about .tl-year {
  margin: 0;
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 15px;
  font-weight: 700;
  letter-spacing: 0.08em;
  color: var(--ice);
}

.page-about .tl-item.is-key .tl-year {
  color: var(--gold);
}

.page-about .tl-title {
  margin: 6px 0 0;
  font-size: 17px;
  font-weight: 700;
  line-height: 1.45;
  color: var(--ink);
}

.page-about .tl-desc {
  margin: 8px 0 0;
  max-width: 46ch;
  font-size: 15px;
  line-height: 1.8;
  color: var(--soft);
}

/* ---------- 团队 ---------- */
.page-about .about-team {
  list-style: none;
  margin: 24px 0;
  padding: 0;
  display: grid;
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
}

.page-about .team-card {
  background: var(--panel-2);
  padding: 18px 16px 20px;
}

.page-about .team-num {
  display: block;
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 30px;
  font-weight: 700;
  line-height: 1;
  letter-spacing: -0.03em;
  color: var(--cyan);
}

.page-about .team-role {
  margin: 12px 0 0;
  font-size: 16px;
  font-weight: 700;
  line-height: 1.4;
  color: var(--ink);
}

.page-about .team-note {
  margin: 8px 0 0;
  font-size: 14px;
  line-height: 1.8;
  color: var(--soft);
}

/* ---------- 长期条目 ---------- */
.page-about .about-rules {
  list-style: none;
  margin: 4px 0 0;
  padding: 0;
  display: grid;
  gap: 20px;
}

.page-about .about-rules li {
  position: relative;
  padding-left: 20px;
}

.page-about .about-rules li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 9px;
  width: 7px;
  height: 7px;
  background: var(--gold);
}

.page-about .rule-title {
  margin: 0;
  font-size: 16.5px;
  font-weight: 700;
  line-height: 1.5;
  color: var(--ink);
}

.page-about .rule-text {
  margin: 6px 0 0;
  max-width: 46ch;
  font-size: 15px;
  line-height: 1.8;
  color: var(--soft);
}

/* ---------- 继续了解 ---------- */
.page-about .about-next {
  margin-top: 64px;
  padding-top: 26px;
  border-top: 1px solid var(--line-strong);
}

.page-about .about-next h2 {
  margin: 0;
  font-size: clamp(19px, 4.4vw, 24px);
  font-weight: 800;
  letter-spacing: -0.015em;
  color: var(--ink);
}

.page-about .next-links {
  list-style: none;
  margin: 20px 0 0;
  padding: 0;
  display: grid;
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
}

.page-about .next-links a {
  display: block;
  height: 100%;
  background: var(--bg);
  padding: 16px 16px 18px;
  text-decoration: none;
  color: inherit;
  transition: background-color 180ms var(--ease);
}

.page-about .next-links a:hover,
.page-about .next-links a:focus-visible {
  background: var(--panel);
}

.page-about .next-name {
  display: block;
  font-size: 16px;
  font-weight: 700;
  color: var(--ice);
}

.page-about .next-desc {
  display: block;
  margin-top: 7px;
  font-size: 14px;
  line-height: 1.75;
  color: var(--soft);
}

/* ---------- 桌面端 ---------- */
@media (min-width: 760px) {
  .page-about {
    padding-top: 28px;
    padding-bottom: 96px;
  }

  .page-about .about-facts {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .page-about .about-team {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .page-about .next-links {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (min-width: 900px) {
  .page-about .about-chapter {
    display: grid;
    grid-template-columns: 108px minmax(0, 1fr);
    column-gap: 40px;
  }

  .page-about .about-chapter .chapter-head {
    display: contents;
  }

  .page-about .about-chapter .chapter-num {
    grid-column: 1;
    grid-row: 1 / span 2;
  }

  .page-about .about-chapter .chapter-title {
    grid-column: 2;
    grid-row: 1;
    margin-top: 4px;
  }

  .page-about .about-chapter .chapter-body {
    grid-column: 2;
    grid-row: 2;
  }

  .page-about .about-split {
    grid-template-columns: minmax(0, var(--about-measure)) 250px;
    gap: 44px;
    align-items: start;
  }

  .page-about .flow-figure .media-frame,
  .page-about .tl-figure .media-frame {
    max-width: 100%;
  }

  .page-about .next-links {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

@media (min-width: 1200px) {
  .page-about {
    --about-block: 72px;
  }

  .page-about .about-split {
    grid-template-columns: minmax(0, var(--about-measure)) 300px;
    gap: 56px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about * {
    transition-duration: 1ms !important;
  }
}