.page-about {
  --about-line: rgba(16, 57, 74, 0.16);
  --about-serif: var(--font-display);
  background: var(--salt-50);
  color: var(--ink-900);
  font-family: var(--font-body);
  overflow-x: hidden;
}

/* ---------- 页首信息带 ---------- */
.page-about .about-hero {
  position: relative;
  overflow: hidden;
  padding: clamp(26px, 4.5vw, 60px) 0 clamp(36px, 6vw, 76px);
  background:
    radial-gradient(110% 130% at 8% 0%, rgba(46, 124, 147, 0.42) 0%, rgba(16, 57, 74, 0) 58%),
    radial-gradient(85% 120% at 92% 8%, rgba(180, 83, 30, 0.32) 0%, rgba(180, 83, 30, 0) 62%),
    linear-gradient(165deg, #123c4c 0%, var(--lake-900) 50%, #0a2531 100%);
  color: var(--salt-50);
}

.page-about .about-hero__bg {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center 62%;
  opacity: 0.2;
  pointer-events: none;
}

.page-about .about-hero__inner {
  position: relative;
  z-index: 1;
}

.page-about .about-hero .breadcrumb {
  font-size: 12.5px;
  letter-spacing: 0.04em;
  color: rgba(250, 248, 244, 0.72);
}

.page-about .about-hero .breadcrumb a {
  color: rgba(250, 248, 244, 0.9);
  text-decoration: none;
  border-bottom: 1px solid rgba(250, 248, 244, 0.28);
  padding-bottom: 1px;
  transition: color 120ms var(--ease), border-color 120ms var(--ease);
}

.page-about .about-hero .breadcrumb a:hover,
.page-about .about-hero .breadcrumb a:focus-visible {
  color: var(--ochre-100);
  border-bottom-color: var(--ochre-100);
}

.page-about .about-hero .eyebrow {
  margin: 20px 0 10px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.18em;
  color: rgba(250, 248, 244, 0.68);
}

.page-about .about-hero h1 {
  margin: 0 0 16px;
  max-width: 22ch;
  font-family: var(--font-display);
  font-size: clamp(1.85rem, 4.2vw, 3.05rem);
  font-weight: 800;
  line-height: 1.16;
  letter-spacing: -0.015em;
  color: var(--salt-50);
}

.page-about .about-hero .lede {
  margin: 0;
  max-width: 62ch;
  font-size: clamp(1rem, 1.5vw, 1.1rem);
  line-height: 1.8;
  color: rgba(250, 248, 244, 0.86);
}

.page-about .about-facts {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px 20px;
  margin: clamp(26px, 4vw, 40px) 0 0;
  padding: 22px 0 0;
  list-style: none;
  border-top: 1px solid rgba(250, 248, 244, 0.2);
}

.page-about .about-facts__value {
  display: block;
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: clamp(1.3rem, 2.4vw, 1.7rem);
  font-weight: 700;
  line-height: 1.1;
  color: var(--salt-50);
}

.page-about .about-facts__label {
  display: block;
  margin-top: 5px;
  font-size: 12.5px;
  letter-spacing: 0.06em;
  color: rgba(250, 248, 244, 0.64);
}

/* ---------- 主体骨架 ---------- */
.page-about .about-shell {
  padding: clamp(36px, 6vw, 72px) 0 clamp(56px, 8vw, 104px);
}

.page-about .about-shell__inner {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(24px, 3vw, 40px);
}

.page-about .about-side,
.page-about .about-stream {
  min-width: 0;
}

.page-about .about-side__title {
  margin: 0 0 10px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.16em;
  color: var(--steel-500);
}

.page-about .about-side__list {
  display: flex;
  gap: 8px;
  margin: 0;
  padding: 0 0 4px;
  list-style: none;
  overflow-x: auto;
  scrollbar-width: none;
}

.page-about .about-side__list::-webkit-scrollbar {
  display: none;
}

.page-about .about-side__list a {
  display: block;
  padding: 6px 12px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--glass);
  color: var(--steel-500);
  font-size: 13px;
  line-height: 1.5;
  white-space: nowrap;
  text-decoration: none;
  transition: color 120ms var(--ease), border-color 120ms var(--ease), background 120ms var(--ease);
}

.page-about .about-side__list a:hover,
.page-about .about-side__list a:focus-visible {
  color: var(--ochre-500);
  border-color: var(--ochre-500);
  background: var(--ochre-100);
}

/* ---------- 纵向标尺与章节 ---------- */
.page-about .about-stream {
  position: relative;
}

.page-about .about-sec {
  position: relative;
}

.page-about .about-sec + .about-sec {
  margin-top: clamp(48px, 7vw, 92px);
}

.page-about .about-sec__num {
  display: block;
  margin: 0 0 10px;
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 26px;
  font-weight: 700;
  line-height: 1;
  letter-spacing: 0.02em;
  color: var(--ochre-500);
  opacity: 0.6;
}

.page-about .about-sec__title {
  margin: 0 0 14px;
  font-family: var(--font-display);
  font-size: clamp(1.4rem, 2.6vw, 1.9rem);
  font-weight: 800;
  line-height: 1.25;
  letter-spacing: -0.01em;
  color: var(--lake-900);
}

.page-about .about-sec__lead {
  margin: 0 0 20px;
  padding-left: 15px;
  border-left: 3px solid var(--ochre-500);
  font-size: 16.5px;
  line-height: 1.75;
  color: var(--ink-900);
}

.page-about .about-sec__lead strong {
  font-weight: 700;
}

.page-about .about-sec__body p {
  margin: 0 0 1.2em;
  max-width: 68ch;
  font-size: 16px;
  line-height: 1.78;
  color: var(--ink-900);
}

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

.page-about .about-sec__body a {
  color: var(--lake-600);
  text-decoration: underline;
  text-underline-offset: 3px;
  text-decoration-color: rgba(46, 124, 147, 0.35);
  transition: color 120ms var(--ease), text-decoration-color 120ms var(--ease);
}

.page-about .about-sec__body a:hover,
.page-about .about-sec__body a:focus-visible {
  color: var(--ochre-500);
  text-decoration-color: var(--ochre-500);
}

/* ---------- 配图 ---------- */
.page-about .about-figure {
  margin: 26px 0;
}

.page-about .about-figure img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  border-radius: var(--radius);
  object-fit: cover;
  background: var(--ochre-100);
}

.page-about .about-figure figcaption {
  margin-top: 9px;
  font-size: 12.5px;
  line-height: 1.7;
  color: var(--steel-500);
}

/* ---------- 四档卡片 ---------- */
.page-about .tier-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 14px;
  margin: 24px 0 24px;
}

.page-about .tier-card {
  position: relative;
  padding: 18px 16px 20px 20px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--paper);
  transition: border-color 120ms var(--ease), box-shadow 120ms var(--ease), transform 120ms var(--ease);
}

.page-about .tier-card::before {
  content: "";
  position: absolute;
  left: 0;
  top: 16px;
  width: 3px;
  height: 24px;
  border-radius: 0 2px 2px 0;
  background: var(--steel-500);
}

.page-about .tier--a::before { background: var(--fern-700); }
.page-about .tier--b::before { background: var(--lake-600); }
.page-about .tier--c::before { background: var(--ochre-500); }
.page-about .tier--d::before { background: var(--clay-700); }

.page-about .tier-card:hover,
.page-about .tier-card:focus-visible {
  border-color: var(--ochre-500);
  box-shadow: 0 8px 22px rgba(16, 57, 74, 0.1);
  transform: translateY(-2px);
  outline: none;
}

.page-about .tier-card:focus-visible {
  box-shadow: 0 0 0 2px var(--ochre-500);
}

.page-about .tier-card__badge {
  margin: 0 0 10px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  color: var(--steel-500);
}

.page-about .tier-card__num {
  margin: 0 0 8px;
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 32px;
  font-weight: 700;
  line-height: 1;
  color: var(--ink-900);
}

.page-about .tier-card__num small {
  margin-left: 5px;
  font-size: 12.5px;
  font-weight: 500;
  letter-spacing: 0;
  color: var(--steel-500);
}

.page-about .tier-card__mat {
  margin: 0 0 9px;
  font-size: 14px;
  font-weight: 600;
  line-height: 1.55;
  color: var(--lake-900);
}

.page-about .tier-card__case {
  margin: 0;
  font-size: 13.5px;
  line-height: 1.72;
  color: var(--steel-500);
}

/* ---------- 交期状态列表 ---------- */
.page-about .about-status {
  margin: 24px 0;
  padding: 0;
  list-style: none;
  border-top: 1px solid var(--line);
}

.page-about .about-status li {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 8px 14px;
  padding: 15px 2px;
  border-bottom: 1px solid var(--line);
  transition: background 120ms var(--ease);
}

.page-about .about-status li:hover {
  background: var(--ochre-100);
}

.page-about .about-status .status {
  display: inline-block;
  padding: 3px 10px;
  border-radius: 999px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  line-height: 1.5;
  letter-spacing: 0.08em;
}

.page-about .about-status__code {
  font-size: 14px;
  font-weight: 600;
  color: var(--ink-900);
  letter-spacing: 0.02em;
}

.page-about .about-status__note {
  flex: 1 1 260px;
  min-width: 0;
  margin: 0;
  font-size: 13.5px;
  line-height: 1.7;
  color: var(--steel-500);
}

/* ---------- 玻璃旁注 ---------- */
.page-about .about-note {
  margin: 26px 0 0;
  padding: 16px 18px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--glass);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

.page-about .about-note__title {
  margin: 0 0 8px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  color: var(--steel-500);
}

.page-about .about-note p {
  margin: 0;
  font-size: 14px;
  line-height: 1.72;
  color: var(--lake-900);
}

/* ---------- 发展节点 ---------- */
.page-about .about-timeline {
  position: relative;
  margin: 26px 0 24px;
  padding: 0 0 0 26px;
  list-style: none;
}

.page-about .about-timeline::before {
  content: "";
  position: absolute;
  left: 6px;
  top: 10px;
  bottom: 10px;
  width: 1px;
  background: var(--about-line);
}

.page-about .about-node {
  position: relative;
}

.page-about .about-node + .about-node {
  margin-top: 12px;
}

.page-about .about-node::before {
  content: "";
  position: absolute;
  left: -24px;
  top: 15px;
  width: 9px;
  height: 9px;
  box-sizing: border-box;
  border: 2px solid var(--steel-500);
  border-radius: 50%;
  background: var(--salt-50);
  transition: border-color 120ms var(--ease), background 120ms var(--ease);
}

.page-about .about-node:has(details[open])::before {
  border-color: var(--ochre-500);
  background: var(--ochre-500);
}

.page-about .about-node details {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--paper);
  overflow: hidden;
}

.page-about .about-node summary {
  display: flex;
  align-items: baseline;
  gap: 11px;
  padding: 13px 16px;
  cursor: pointer;
  list-style: none;
  font-family: var(--font-display);
  font-size: 15.5px;
  font-weight: 700;
  line-height: 1.5;
  color: var(--lake-900);
  transition: color 120ms var(--ease), background 120ms var(--ease);
}

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

.page-about .about-node summary::marker {
  content: "";
}

.page-about .about-node summary:hover {
  background: var(--ochre-100);
  color: var(--ochre-500);
}

.page-about .about-node summary:focus-visible {
  outline: 2px solid var(--ochre-500);
  outline-offset: -3px;
}

.page-about .about-node summary .is-mono {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 12.5px;
  letter-spacing: 0.08em;
  color: var(--ochre-500);
}

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

.page-about .about-node details p {
  margin: 0;
  padding: 14px 16px 16px;
  font-size: 14.5px;
  line-height: 1.78;
  color: var(--steel-500);
}

/* ---------- 桌面栅格与纵向标尺 ---------- */
@media (min-width: 720px) {
  .page-about .about-stream {
    padding-left: 34px;
  }

  .page-about .about-stream::before {
    content: "";
    position: absolute;
    left: 0;
    top: 8px;
    bottom: 8px;
    width: 1px;
    background: linear-gradient(
      180deg,
      rgba(16, 57, 74, 0) 0%,
      var(--about-line) 5%,
      var(--about-line) 95%,
      rgba(16, 57, 74, 0) 100%
    );
  }

  .page-about .about-sec::before {
    content: "";
    position: absolute;
    left: -34px;
    top: 12px;
    width: 26px;
    height: 1px;
    background: var(--ochre-500);
    opacity: 0.55;
  }

  .page-about .about-figure {
    max-width: 560px;
  }

  .page-about .about-timeline {
    padding-left: 30px;
  }

  .page-about .about-node::before {
    left: -28px;
  }
}

@media (min-width: 640px) {
  .page-about .tier-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .page-about .about-facts {
    gap: 18px 28px;
  }
}

@media (min-width: 960px) {
  .page-about .about-shell__inner {
    grid-template-columns: 190px minmax(0, 1fr);
    gap: clamp(36px, 4.5vw, 68px);
    align-items: start;
  }

  .page-about .about-side {
    position: sticky;
    top: 96px;
  }

  .page-about .about-side__title {
    margin-bottom: 14px;
  }

  .page-about .about-side__list {
    flex-direction: column;
    gap: 2px;
    padding-bottom: 0;
    overflow-x: visible;
  }

  .page-about .about-side__list a {
    padding: 8px 0 8px 12px;
    border: 0;
    border-left: 2px solid transparent;
    border-radius: 0;
    background: none;
    font-size: 13.5px;
    transition: color 120ms var(--ease), border-color 120ms var(--ease), transform 120ms var(--ease);
  }

  .page-about .about-side__list a:hover,
  .page-about .about-side__list a:focus-visible {
    background: none;
    color: var(--lake-900);
    border-left-color: var(--ochre-500);
    transform: translateX(2px);
  }

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

@media (min-width: 1120px) {
  .page-about .tier-grid {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .page-about .about-sec__lead {
    font-size: 17px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .tier-card,
  .page-about .about-side__list a,
  .page-about .about-node summary,
  .page-about .about-status li,
  .page-about .about-sec__body a {
    transition: none;
  }

  .page-about .tier-card:hover,
  .page-about .tier-card:focus-visible {
    transform: none;
  }
}
<<<END>>>