.page-about {
  --rail-w: 15rem;
  --about-rail-line: var(--hair);
}

/* ---------- 首屏 ---------- */
.page-about .about-mast {
  padding-block: clamp(1.75rem, 4vw, 2.75rem) clamp(2rem, 5vw, 3.25rem);
  background:
    linear-gradient(180deg, rgba(19, 88, 255, .045), rgba(19, 88, 255, 0) 60%),
    var(--paper);
  border-bottom: var(--hairline);
}

.page-about .breadcrumbs ol {
  display: flex;
  flex-wrap: wrap;
  gap: .45rem;
  align-items: center;
  list-style: none;
  margin: 0 0 clamp(1.25rem, 3vw, 2rem);
  padding: 0;
  font-family: var(--font-mono);
  font-size: .72rem;
  letter-spacing: .08em;
  color: var(--brick);
}

.page-about .breadcrumbs li + li::before {
  content: "/";
  margin-right: .45rem;
  color: var(--hair);
}

.page-about .breadcrumbs a {
  color: var(--brick);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color var(--dur) var(--ease), border-color var(--dur) var(--ease);
}

.page-about .breadcrumbs a:hover,
.page-about .breadcrumbs a:focus-visible {
  color: var(--blue);
  border-bottom-color: var(--blue);
}

.page-about .mast-grid {
  display: grid;
  gap: 1.5rem;
}

@media (min-width: 880px) {
  .page-about .mast-grid {
    grid-template-columns: 13rem minmax(0, 1fr);
    gap: 3.25rem;
    align-items: start;
  }
}

.page-about .mast-meta {
  border-left: 3px solid var(--blue);
  padding-left: 1rem;
  display: flex;
  flex-direction: column;
  gap: .4rem;
}

.page-about .mast-code,
.page-about .mast-season,
.page-about .mast-note {
  font-family: var(--font-mono);
  font-size: .72rem;
  letter-spacing: .1em;
  line-height: 1.6;
  margin: 0;
  color: var(--brick);
  text-transform: uppercase;
}

.page-about .mast-season {
  color: var(--orange);
}

.page-about .mast-note {
  margin-top: .5rem;
  padding-top: .5rem;
  border-top: var(--hairline);
  text-transform: none;
  letter-spacing: .04em;
  font-size: .72rem;
  color: var(--bronze);
}

.page-about .mast-body h1 {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(1.9rem, 6.4vw, 3.7rem);
  line-height: 1.05;
  letter-spacing: -.01em;
  color: var(--ink);
  margin: 0 0 1.1rem;
  max-width: 20ch;
}

.page-about .mast-body .lede {
  font-size: clamp(1rem, 1.55vw, 1.12rem);
  line-height: 1.8;
  color: var(--brick);
  max-width: 40em;
  margin: 0;
}

.page-about .mast-stats {
  margin: clamp(1.75rem, 4vw, 2.5rem) 0 0;
  padding-top: clamp(1.25rem, 3vw, 1.75rem);
  border-top: var(--hairline);
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1.25rem 1rem;
}

@media (min-width: 720px) {
  .page-about .mast-stats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
    gap: 1.5rem;
  }
}

.page-about .mast-stat {
  margin: 0;
  padding-left: .85rem;
  border-left: 2px solid var(--hair);
}

.page-about .mast-stat:nth-child(1) { border-left-color: var(--blue); }
.page-about .mast-stat:nth-child(2) { border-left-color: var(--bronze); }
.page-about .mast-stat:nth-child(3) { border-left-color: var(--orange); }
.page-about .mast-stat:nth-child(4) { border-left-color: var(--lime); }

.page-about .mast-stat dt {
  font-family: var(--font-mono);
  font-size: .68rem;
  letter-spacing: .12em;
  text-transform: uppercase;
  color: var(--brick);
  margin-bottom: .35rem;
}

.page-about .mast-stat dd {
  margin: 0;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: clamp(1.6rem, 4.2vw, 2.3rem);
  line-height: 1;
  color: var(--ink);
  font-variant-numeric: tabular-nums;
}

.page-about .mast-stat .stat-unit {
  font-family: var(--font-body);
  font-size: .78rem;
  font-weight: 400;
  letter-spacing: 0;
  color: var(--brick);
  margin-left: .3rem;
}

/* ---------- 登记簿结构 ---------- */
.page-about .registry {
  display: grid;
  gap: 1.75rem;
  padding-block: clamp(2rem, 5vw, 3.5rem) clamp(3rem, 7vw, 5rem);
}

@media (min-width: 920px) {
  .page-about .registry {
    grid-template-columns: var(--rail-w) minmax(0, 1fr);
    gap: 3.5rem;
    align-items: start;
  }

  .page-about .registry-rail {
    position: sticky;
    top: 5.5rem;
    align-self: start;
    max-height: calc(100vh - 7rem);
    overflow-y: auto;
  }
}

.page-about .registry-rail .toc-title {
  font-family: var(--font-mono);
  font-size: .68rem;
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--brick);
  margin: 0 0 .9rem;
  padding-left: 1rem;
}

.page-about .registry-rail .toc-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
}

.page-about .registry-rail .toc-link {
  display: flex;
  gap: .6rem;
  align-items: baseline;
  padding: .55rem .6rem .55rem 1rem;
  border-left: 3px solid var(--hair);
  font-size: .84rem;
  line-height: 1.45;
  color: var(--brick);
  text-decoration: none;
  transition: color var(--dur) var(--ease), border-color var(--dur) var(--ease), background-color var(--dur) var(--ease);
}

.page-about .registry-rail .toc-link .toc-num {
  font-family: var(--font-mono);
  font-size: .68rem;
  letter-spacing: .08em;
  color: var(--hair);
  transition: color var(--dur) var(--ease);
}

.page-about .registry-rail .toc-link:hover,
.page-about .registry-rail .toc-link:focus-visible {
  color: var(--ink);
  border-left-color: var(--blue);
}

.page-about .registry-rail .toc-link[aria-current="true"],
.page-about .registry-rail .toc-link.is-active {
  color: var(--blue);
  border-left-color: var(--blue);
  background: rgba(19, 88, 255, .05);
}

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

/* ---------- 章节通用 ---------- */
.page-about .reg-section {
  padding-block: clamp(1.75rem, 4vw, 2.75rem);
  border-top: var(--hairline);
}

.page-about .reg-section:first-child {
  border-top: 0;
  padding-top: 0;
}

.page-about .reg-head {
  display: flex;
  flex-direction: column;
  gap: .6rem;
  margin-bottom: clamp(1.25rem, 3vw, 1.75rem);
}

@media (min-width: 720px) {
  .page-about .reg-head {
    flex-direction: row;
    align-items: baseline;
    gap: 1.25rem;
  }
}

.page-about .reg-index {
  font-family: var(--font-mono);
  font-size: .74rem;
  letter-spacing: .16em;
  color: var(--blue);
  border: 1px solid var(--blue);
  padding: .15rem .5rem;
  line-height: 1.4;
  flex-shrink: 0;
}

.page-about .reg-head h2 {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: clamp(1.3rem, 3.1vw, 2.05rem);
  line-height: 1.22;
  letter-spacing: -.005em;
  color: var(--ink);
  margin: 0;
  max-width: 26ch;
}

.page-about .reg-lead {
  font-size: 1.02rem;
  line-height: 1.8;
  color: var(--ink);
  max-width: 34em;
  margin: 0 0 1.25rem;
  border-left: 3px solid var(--bronze);
  padding-left: 1rem;
}

/* 长短交错：把导语窗口拉窄 */
.page-about .reg-lead-window {
  max-width: 26em;
}

.page-about .reg-flow-text p,
.page-about .cert-text p,
.page-about .region-text p,
.page-about .team-pair p {
  font-size: .98rem;
  line-height: 1.85;
  color: var(--brick);
  max-width: 36em;
  margin: 0 0 1rem;
}

.page-about .reg-flow-text p:last-child,
.page-about .cert-text p:last-child,
.page-about .region-text p:last-child,
.page-about .team-pair p:last-child {
  margin-bottom: 0;
}

/* ---------- 01 起点 ---------- */
.page-about .reg-flow {
  display: grid;
  gap: 1.5rem;
}

@media (min-width: 880px) {
  .page-about .reg-flow {
    grid-template-columns: minmax(0, 1fr) minmax(0, 1.05fr);
    gap: 2.5rem;
    align-items: start;
  }

  .page-about .reg-flow .about-figure {
    margin-top: -.75rem;
  }
}

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

.page-about .about-figure .media {
  overflow: hidden;
  border: var(--hairline);
  background: var(--brick);
}

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

.page-about .media--wide img { aspect-ratio: 14 / 9; }
.page-about .media--report img { aspect-ratio: 3 / 2; }
.page-about .media--square img { aspect-ratio: 16 / 9; }

.page-about .media-cap {
  font-family: var(--font-mono);
  font-size: .7rem;
  letter-spacing: .06em;
  color: var(--brick);
  padding-top: .6rem;
  border-top: 1px solid var(--paper-line);
  margin-top: .6rem;
}

.page-about .about-figure--inset {
  max-width: 42rem;
  margin-top: clamp(1.75rem, 4vw, 2.5rem);
}

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

/* ---------- 02 时间线节点 ---------- */
.page-about .node-stack {
  display: flex;
  flex-direction: column;
  border-top: var(--hairline);
}

.page-about .about-node {
  border-bottom: var(--hairline);
  border-left: 3px solid var(--hair);
  background: transparent;
  transition: border-color var(--dur) var(--ease), background-color var(--dur) var(--ease);
}

.page-about .about-node--build { border-left-color: var(--brick); }
.page-about .about-node--cert { border-left-color: var(--bronze); }
.page-about .about-node--record { border-left-color: var(--blue); }
.page-about .about-node--season { border-left-color: var(--orange); }

.page-about .about-node[open] {
  background: rgba(19, 88, 255, .035);
}

.page-about .about-node > summary {
  display: grid;
  grid-template-columns: 5.5rem minmax(0, 1fr) 1.5rem;
  align-items: center;
  gap: .85rem;
  padding: .95rem 1rem .95rem .9rem;
  cursor: pointer;
  list-style: none;
}

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

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

.page-about .node-num {
  font-family: var(--font-mono);
  font-size: .74rem;
  letter-spacing: .08em;
  color: var(--brick);
  white-space: nowrap;
}

.page-about .about-node[open] .node-num {
  color: var(--blue);
}

.page-about .node-title {
  font-size: .98rem;
  font-weight: 600;
  line-height: 1.5;
  color: var(--ink);
}

.page-about .node-mark {
  position: relative;
  width: 1.1rem;
  height: 1.1rem;
  justify-self: end;
  flex-shrink: 0;
}

.page-about .node-mark::before,
.page-about .node-mark::after {
  content: "";
  position: absolute;
  background: var(--brick);
  transition: transform var(--dur) var(--ease), background-color var(--dur) var(--ease);
}

.page-about .node-mark::before {
  left: 0;
  right: 0;
  top: 50%;
  height: 1.5px;
  transform: translateY(-50%);
}

.page-about .node-mark::after {
  top: 0;
  bottom: 0;
  left: 50%;
  width: 1.5px;
  transform: translateX(-50%);
}

.page-about .about-node[open] .node-mark::after {
  transform: translateX(-50%) scaleY(0);
}

.page-about .about-node[open] .node-mark::before {
  background: var(--blue);
}

.page-about .node-body {
  padding: 0 1.25rem 1.25rem 7.25rem;
}

.page-about .node-body p {
  font-size: .94rem;
  line-height: 1.85;
  color: var(--brick);
  max-width: 38em;
  margin: 0;
}

@media (max-width: 620px) {
  .page-about .about-node > summary {
    grid-template-columns: minmax(0, 1fr) 1.4rem;
    grid-template-areas:
      "num mark"
      "title title";
    row-gap: .3rem;
    padding: .9rem .85rem;
  }

  .page-about .node-num { grid-area: num; }
  .page-about .node-title { grid-area: title; }
  .page-about .node-mark { grid-area: mark; }

  .page-about .node-body {
    padding: 0 .9rem 1.1rem .9rem;
  }
}

/* ---------- 03 资质认证 ---------- */
.page-about .reg-section--cert {
  background:
    linear-gradient(135deg, rgba(46, 110, 96, .06), rgba(46, 110, 96, 0) 55%);
}

.page-about .cert-layout {
  display: grid;
  gap: 1.75rem;
}

@media (min-width: 880px) {
  .page-about .cert-layout {
    grid-template-columns: minmax(0, 1fr) minmax(0, 1.1fr);
    gap: 3rem;
    align-items: start;
  }
}

.page-about .cert-badges {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 1rem;
}

@media (min-width: 560px) {
  .page-about .cert-badges {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

.page-about .cert-item {
  border: var(--hairline);
  border-top: 3px solid var(--bronze);
  padding: 1.1rem .9rem 1rem;
  background: var(--paper);
  transition: transform var(--dur) var(--ease), box-shadow var(--dur) var(--ease), border-top-color var(--dur) var(--ease);
  cursor: default;
}

.page-about .cert-item:hover,
.page-about .cert-item:focus-within {
  transform: translateY(-3px);
  box-shadow: 0 6px 18px rgba(14, 17, 20, .08);
  border-top-color: var(--blue);
}

.page-about .cert-item:focus-visible {
  outline: 2px solid var(--blue);
  outline-offset: 2px;
}

.page-about .cert-badge {
  display: block;
  width: 4.5rem;
  height: 4.5rem;
  color: var(--brick);
  margin-bottom: .75rem;
}

.page-about .cert-name {
  font-size: .92rem;
  font-weight: 700;
  color: var(--ink);
  margin: 0 0 .35rem;
  line-height: 1.45;
}

.page-about .cert-detail {
  font-size: .82rem;
  line-height: 1.7;
  color: var(--brick);
  margin: 0;
  max-height: 0;
  overflow: hidden;
  opacity: 0;
  transition: max-height 280ms var(--ease), opacity 220ms var(--ease);
}

.page-about .cert-item:hover .cert-detail,
.page-about .cert-item:focus-within .cert-detail {
  max-height: 8rem;
  opacity: 1;
}

@media (hover: none) {
  .page-about .cert-detail {
    max-height: 8rem;
    opacity: 1;
  }
}

/* ---------- 04 团队 ---------- */
.page-about .team-list {
  list-style: none;
  margin: 0 0 1.75rem;
  padding: 0;
  border-top: var(--hairline);
}

.page-about .team-row {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: .35rem;
  padding: 1rem 0 1rem 1rem;
  border-bottom: var(--hairline);
  border-left: 3px solid var(--hair);
}

.page-about .team-row:nth-child(1) { border-left-color: var(--blue); }
.page-about .team-row:nth-child(2) { border-left-color: var(--orange); }
.page-about .team-row:nth-child(3) { border-left-color: var(--bronze); }
.page-about .team-row:nth-child(4) { border-left-color: var(--brick); }

@media (min-width: 720px) {
  .page-about .team-row {
    grid-template-columns: 4.5rem 9rem minmax(0, 1fr);
    align-items: baseline;
    gap: 1.25rem;
  }
}

.page-about .team-num {
  font-family: var(--font-mono);
  font-size: 1.7rem;
  font-weight: 700;
  letter-spacing: -.02em;
  color: var(--ink);
  line-height: 1;
  font-variant-numeric: tabular-nums;
}

.page-about .team-role {
  font-size: .96rem;
  font-weight: 700;
  color: var(--ink);
  line-height: 1.5;
}

.page-about .team-desc {
  font-size: .9rem;
  line-height: 1.8;
  color: var(--brick);
  max-width: 40em;
}

.page-about .team-pair {
  display: grid;
  gap: 1rem;
}

@media (min-width: 760px) {
  .page-about .team-pair {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 2rem;
    max-width: 62em;
  }
}

.page-about .team-pair p:last-child {
  border-left: 3px solid var(--blue);
  padding-left: 1rem;
}

/* ---------- 05 服务区域 ---------- */
.page-about .reg-section--region {
  position: relative;
  overflow: hidden;
}

.page-about .reg-section--region::before {
  content: "";
  position: absolute;
  inset: 0 0 auto 0;
  height: 4px;
  background: linear-gradient(90deg, var(--blue) 0 34%, var(--bronze) 34% 62%, var(--orange) 62% 82%, var(--lime) 82% 100%);
  opacity: .9;
}

.page-about .region-grid {
  display: grid;
  gap: 1.75rem;
}

@media (min-width: 900px) {
  .page-about .region-grid {
    grid-template-columns: minmax(0, 1.15fr) minmax(0, 1fr);
    gap: 3rem;
    align-items: start;
  }
}

/* ---------- 06 质量改进 ---------- */
.page-about .loop-list {
  list-style: none;
  margin: 0 0 2rem;
  padding: 0;
  display: grid;
  gap: 0;
  counter-reset: loop;
}

@media (min-width: 800px) {
  .page-about .loop-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    column-gap: 2.5rem;
  }
}

.page-about .loop-item {
  padding: 1.15rem 0 1.25rem 1rem;
  border-top: var(--hairline);
  border-left: 3px solid var(--hair);
  position: relative;
}

.page-about .loop-item:nth-child(1) { border-left-color: var(--blue); }
.page-about .loop-item:nth-child(2) { border-left-color: var(--bronze); }
.page-about .loop-item:nth-child(3) { border-left-color: var(--orange); }
.page-about .loop-item:nth-child(4) { border-left-color: var(--brick); }

.page-about .loop-num {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: .7rem;
  letter-spacing: .12em;
  color: var(--paper);
  background: var(--brick);
  padding: .12rem .48rem;
  margin: 0 0 .6rem;
}

.page-about .loop-item h3 {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1.08rem;
  line-height: 1.4;
  color: var(--ink);
  margin: 0 0 .5rem;
}

.page-about .loop-item p:last-child {
  font-size: .92rem;
  line-height: 1.82;
  color: var(--brick);
  margin: 0;
  max-width: 34em;
}

.page-about .reg-cta {
  border-top: var(--hairline);
  padding-top: 1.5rem;
  display: flex;
  flex-direction: column;
  gap: 1.1rem;
}

.page-about .reg-cta > p {
  font-size: .95rem;
  line-height: 1.8;
  color: var(--brick);
  max-width: 34em;
  margin: 0;
}

.page-about .cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: .75rem;
}

@media (prefers-reduced-motion: reduce) {
  .page-about .cert-item,
  .page-about .about-node,
  .page-about .registry-rail .toc-link,
  .page-about .node-mark::before,
  .page-about .node-mark::after,
  .page-about .cert-detail {
    transition-duration: 0ms;
  }

  .page-about .cert-item:hover,
  .page-about .cert-item:focus-within {
    transform: none;
  }
}