.page-about {
  --rail-w: 208px;
  --about-gap: 64px;
  background: var(--ink);
  color: var(--text);
  font-family: var(--font-sans);
  padding-bottom: 0;
}

.page-about .breadcrumbs {
  padding-top: 20px;
  padding-bottom: 6px;
  font-family: var(--font-mono);
  font-size: 13px;
}

.page-about .crumb-sep {
  color: var(--line);
  margin: 0 8px;
}

.page-about a:focus-visible,
.page-about summary:focus-visible {
  outline: 2px solid var(--blue);
  outline-offset: 2px;
}

/* ---------- 首屏 ---------- */
.page-about .about-hero {
  position: relative;
  overflow: hidden;
  margin-top: 6px;
  padding: 36px 0 48px;
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.page-about .about-hero::before {
  content: "";
  position: absolute;
  inset: 10px;
  border: 1px solid rgba(46, 74, 66, 0.5);
  pointer-events: none;
}

.page-about .about-hero::after {
  content: "";
  position: absolute;
  top: -140px;
  right: -90px;
  width: 340px;
  height: 340px;
  background: radial-gradient(circle, rgba(255, 46, 136, 0.2), transparent 66%);
  pointer-events: none;
}

.page-about .about-hero-grid {
  position: relative;
  display: grid;
  gap: 36px;
}

.page-about .about-hero-main .eyebrow {
  margin: 0;
}

.page-about h1 {
  margin: 14px 0 20px;
  font-size: clamp(31px, 7vw, 58px);
  line-height: 1.12;
  font-weight: 800;
  letter-spacing: -0.02em;
}

.page-about h1 em {
  font-style: normal;
  color: var(--magenta);
}

.page-about .about-hero .lede {
  margin: 0;
  max-width: 48ch;
  font-size: 16px;
  line-height: 1.85;
  color: var(--text-2);
}

.page-about .about-file {
  position: relative;
  border: 1px solid var(--line);
  background: var(--ink-2);
  padding: 18px 20px 8px;
}

.page-about .about-file::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0;
  width: 3px;
  height: 100%;
  background: var(--magenta);
}

.page-about .file-label {
  margin: 0;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--mint);
}

.page-about .file-list {
  margin: 10px 0 0;
  padding: 0;
}

.page-about .file-row {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 14px;
  padding: 10px 0;
  border-top: 1px solid var(--line);
}

.page-about .file-row:first-child {
  border-top: 0;
}

.page-about .file-row dt {
  font-size: 13.5px;
  color: var(--text-2);
}

.page-about .file-row dd {
  margin: 0;
  font-family: var(--font-mono);
  font-size: 14px;
  color: var(--gold);
  letter-spacing: 0.02em;
}

/* ---------- 主体骨架 ---------- */
.page-about .about-body {
  display: grid;
  gap: 28px;
  padding-top: 44px;
}

/* ---------- 左侧刻度 ---------- */
.page-about .about-rail {
  border-top: 1px solid var(--line);
  padding-top: 12px;
}

.page-about .rail-title {
  margin: 0 0 8px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.16em;
  color: var(--text-2);
}

.page-about .rail-list {
  display: flex;
  gap: 6px;
  margin: 0;
  padding: 0 0 10px;
  overflow-x: auto;
  list-style: none;
}

.page-about .rail-item {
  flex: 0 0 auto;
}

.page-about .rail-link {
  display: flex;
  flex-direction: column;
  gap: 3px;
  padding: 9px 13px;
  border: 1px solid var(--line);
  background: var(--ink-2);
  text-decoration: none;
  transition: border-color 160ms ease, background-color 160ms ease;
}

.page-about .rail-year {
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: 0.06em;
  color: var(--gold);
}

.page-about .rail-text {
  font-size: 12.5px;
  color: var(--text-2);
  white-space: nowrap;
}

.page-about .rail-link:hover,
.page-about .rail-link:focus-visible {
  border-color: var(--magenta);
  background: var(--ink-3);
}

.page-about .rail-link:hover .rail-text {
  color: var(--text);
}

/* ---------- 章节 ---------- */
.page-about .about-chapter {
  padding: 38px 0;
  border-top: 1px solid var(--line);
  scroll-margin-top: 24px;
}

.page-about .about-flow > .about-chapter:first-child {
  border-top: 0;
  padding-top: 0;
}

.page-about .chapter-head {
  display: flex;
  align-items: baseline;
  gap: 12px;
  margin-bottom: 14px;
}

.page-about .chapter-code {
  flex: 0 0 auto;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--magenta);
}

.page-about .chapter-title {
  margin: 0;
  font-size: clamp(21px, 3.6vw, 30px);
  line-height: 1.35;
  font-weight: 800;
  letter-spacing: -0.01em;
}

.page-about .chapter-lead {
  margin: 0 0 18px;
  padding-left: 14px;
  border-left: 2px solid var(--gold);
  font-size: 17px;
  line-height: 1.7;
  color: var(--mint);
}

.page-about .chapter-p {
  margin: 0 0 16px;
  max-width: 62ch;
  font-size: 15.5px;
  line-height: 1.85;
  color: var(--text-2);
}

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

.page-about .chapter-p a {
  color: var(--mint);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}

.page-about .chapter-p a:hover {
  color: var(--gold);
}

/* ---------- 图文分栏 ---------- */
.page-about .chapter-split {
  display: grid;
  gap: 22px;
  margin-top: 6px;
}

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

.page-about .about-figure--wide {
  margin: 22px 0 26px;
}

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

.page-about .about-figure figcaption {
  margin-top: 8px;
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.7;
  color: var(--text-2);
}

/* ---------- 折叠面板 ---------- */
.page-about .about-fold {
  margin-top: 22px;
  border: 1px solid var(--line);
  background: var(--ink-2);
}

.page-about .about-fold summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  padding: 13px 16px;
  cursor: pointer;
  list-style: none;
  font-size: 14.5px;
  font-weight: 600;
  color: var(--text);
}

.page-about .about-fold summary::-webkit-details-marker {
  display: none;
}

.page-about .about-fold summary::after {
  content: "+";
  font-family: var(--font-mono);
  font-size: 18px;
  line-height: 1;
  color: var(--magenta);
}

.page-about .about-fold[open] summary::after {
  content: "−";
}

.page-about .about-fold[open] summary {
  border-bottom: 1px solid var(--line);
}

.page-about .fold-body {
  padding: 14px 16px 16px;
}

.page-about .fold-body p {
  margin: 0;
  font-size: 14.5px;
  line-height: 1.85;
  color: var(--text-2);
}

.page-about .fold-body a {
  color: var(--mint);
  text-decoration: underline;
  text-underline-offset: 3px;
}

.page-about .fold-body a:hover {
  color: var(--gold);
}

/* ---------- 数字带 ---------- */
.page-about .stat-strip {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: 0 0 24px;
  background: var(--line);
  border: 1px solid var(--line);
}

.page-about .stat {
  background: var(--ink-2);
  padding: 16px 14px 18px;
}

.page-about .stat-num {
  display: block;
  font-family: var(--font-mono);
  font-size: clamp(38px, 8vw, 76px);
  line-height: 1;
  letter-spacing: -0.04em;
  color: var(--gold);
}

.page-about .stat-cap {
  display: block;
  margin-top: 10px;
  font-size: 12.5px;
  line-height: 1.6;
  color: var(--text-2);
}

/* ---------- 小组列表 ---------- */
.page-about .group-list {
  display: grid;
  gap: 1px;
  margin: 22px 0 24px;
  padding: 0;
  list-style: none;
  background: var(--line);
  border: 1px solid var(--line);
}

.page-about .group-item {
  background: var(--ink-2);
  padding: 16px 16px 18px;
  transition: background-color 160ms ease;
}

.page-about .group-item:hover {
  background: var(--ink-3);
}

.page-about .group-code {
  display: block;
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.14em;
  color: var(--blue);
}

.page-about .group-name {
  margin: 8px 0 6px;
  font-size: 16px;
  font-weight: 700;
  color: var(--text);
}

.page-about .group-desc {
  margin: 0;
  font-size: 14px;
  line-height: 1.8;
  color: var(--text-2);
}

/* ---------- 联系清单 ---------- */
.page-about .contact-list {
  margin: 22px 0 18px;
  padding: 0;
  border-top: 1px solid var(--line);
}

.page-about .contact-row {
  display: flex;
  flex-direction: column;
  gap: 3px;
  padding: 11px 0;
  border-bottom: 1px solid var(--line);
}

.page-about .contact-key {
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.14em;
  color: var(--mint);
}

.page-about .contact-val {
  margin: 0;
  font-size: 14.5px;
  line-height: 1.7;
  color: var(--text);
  word-break: break-word;
}

/* ---------- 时间轴 ---------- */
.page-about .about-timeline {
  margin-top: 56px;
  padding: 48px 0 56px;
  border-top: 1px solid var(--line);
  background: var(--ink-2);
}

.page-about .tl-track {
  margin: 30px 0 0;
  padding: 0;
  list-style: none;
}

.page-about .tl-node {
  position: relative;
  padding: 0 0 26px 26px;
  border-left: 1px solid var(--line);
}

.page-about .tl-node:last-child {
  padding-bottom: 0;
}

.page-about .tl-dot {
  position: absolute;
  left: -6px;
  top: 5px;
  width: 11px;
  height: 11px;
  background: var(--magenta);
}

.page-about .tl-node:nth-child(2) .tl-dot {
  background: var(--blue);
}

.page-about .tl-node:nth-child(3) .tl-dot {
  background: var(--gold);
}

.page-about .tl-node:nth-child(4) .tl-dot {
  background: var(--mint);
}

.page-about .tl-year {
  display: block;
  font-family: var(--font-mono);
  font-size: 14px;
  letter-spacing: 0.08em;
  color: var(--gold);
}

.page-about .tl-name {
  display: block;
  margin-top: 6px;
  font-size: 15.5px;
  font-weight: 700;
  color: var(--text);
}

.page-about .tl-desc {
  display: block;
  margin-top: 6px;
  max-width: 34ch;
  font-size: 13.5px;
  line-height: 1.75;
  color: var(--text-2);
}

.page-about .about-cta {
  display: flex;
  flex-direction: column;
  gap: 16px;
  margin-top: 40px;
  padding-top: 24px;
  border-top: 1px solid var(--line);
}

.page-about .about-cta-text {
  margin: 0;
  font-size: 16px;
  line-height: 1.7;
  color: var(--text);
}

.page-about .about-cta-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

/* ---------- 断点 ---------- */
@media (min-width: 600px) {
  .page-about .contact-row {
    flex-direction: row;
    align-items: baseline;
    justify-content: space-between;
    gap: 24px;
  }

  .page-about .contact-key {
    flex: 0 0 96px;
  }

  .page-about .contact-val {
    text-align: right;
  }
}

@media (min-width: 760px) {
  .page-about .chapter-split {
    grid-template-columns: minmax(0, 1.12fr) minmax(0, 0.88fr);
    align-items: start;
    gap: 36px;
  }

  .page-about .chapter-split--flip > .about-figure {
    order: -1;
  }

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

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

@media (min-width: 960px) {
  .page-about .about-hero {
    padding: 52px 0 64px;
  }

  .page-about .about-hero-grid {
    grid-template-columns: minmax(0, 1fr) 288px;
    gap: 56px;
    align-items: end;
  }

  .page-about .about-body {
    grid-template-columns: var(--rail-w) minmax(0, 1fr);
    gap: var(--about-gap);
    padding-top: 60px;
  }

  .page-about .about-rail {
    position: sticky;
    top: 24px;
    align-self: start;
    border-top: 0;
    padding-top: 0;
  }

  .page-about .rail-list {
    flex-direction: column;
    gap: 0;
    overflow: visible;
    padding-bottom: 0;
  }

  .page-about .rail-link {
    flex-direction: row;
    align-items: baseline;
    gap: 12px;
    padding: 11px 0 11px 14px;
    border: 0;
    border-left: 2px solid var(--line);
    background: transparent;
  }

  .page-about .rail-link:hover,
  .page-about .rail-link:focus-visible {
    border-left-color: var(--magenta);
    background: var(--ink-2);
  }

  .page-about .about-chapter {
    padding: 52px 0;
  }

  .page-about .about-timeline {
    margin-top: 72px;
    padding: 64px 0 72px;
  }

  .page-about .tl-track {
    display: grid;
    grid-template-columns: repeat(4, minmax(0, 1fr));
    margin-top: 40px;
    border-top: 1px solid var(--line);
  }

  .page-about .tl-node {
    border-left: 0;
    padding: 30px 26px 0 0;
  }

  .page-about .tl-dot {
    left: 0;
    top: -6px;
  }

  .page-about .tl-node:nth-child(2) .tl-dot {
    left: 0;
  }

  .page-about .about-cta {
    flex-direction: row;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
  }
}

@media (min-width: 1180px) {
  .page-about .about-hero {
    padding: 60px 0 72px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .rail-link,
  .page-about .group-item {
    transition: none;
  }
}