.page-about {
  --about-cut: 18px;
  --about-marker: 44px;
}

/* ============ 首屏框景 ============ */
.page-about .about-hero {
  padding: calc(var(--header-h) + clamp(18px, 4vw, 40px)) 0 clamp(28px, 5vw, 56px);
}

.page-about .hero-frame {
  position: relative;
  padding: clamp(26px, 5vw, 60px) clamp(18px, 4vw, 54px) clamp(22px, 4vw, 44px);
  background: var(--frame-grad);
  border: 1px solid var(--line-strong);
  clip-path: polygon(
    0 var(--cut), var(--cut) 0,
    100% 0, 100% calc(100% - var(--cut)),
    calc(100% - var(--cut)) 100%, 0 100%
  );
  overflow: hidden;
}

.page-about .hero-frame::before {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  width: min(320px, 60%);
  height: 200px;
  background: radial-gradient(circle at 100% 0, rgba(56, 207, 224, .26), transparent 68%);
  pointer-events: none;
}

.page-about .hero-ticks {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  height: 9px;
  background-image: repeating-linear-gradient(90deg, var(--line-strong) 0 1px, transparent 1px 30px);
  opacity: .75;
  pointer-events: none;
}

.page-about .hero-frame > * {
  position: relative;
  z-index: 1;
}

.page-about h1 {
  margin: 14px 0 0;
  font-family: var(--font-display);
  font-weight: 900;
  font-size: clamp(30px, 7vw, 62px);
  line-height: 1.12;
  letter-spacing: .04em;
  color: var(--star);
}

.page-about .hero-lead {
  margin-top: clamp(16px, 3vw, 24px);
  max-width: 62ch;
}

.page-about .hero-metrics {
  list-style: none;
  margin: clamp(24px, 4vw, 40px) 0 0;
  padding: clamp(18px, 3vw, 28px) 0 0;
  border-top: 1px solid var(--line);
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: clamp(18px, 3vw, 28px) 20px;
}

.page-about .metric-value {
  display: block;
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: clamp(26px, 5.4vw, 44px);
  line-height: 1;
  letter-spacing: -.02em;
  color: var(--star);
}

.page-about .metric.is-hot .metric-value {
  color: var(--orange-lit);
  text-shadow: 0 0 24px rgba(244, 87, 28, .35);
}

.page-about .metric .unit {
  font-size: .42em;
  margin-left: .2em;
  color: var(--mist);
  letter-spacing: 0;
}

.page-about .metric-label {
  display: block;
  margin-top: 10px;
  font-size: 13px;
  line-height: 1.55;
  color: var(--mist);
}

/* ============ 时间线骨架 ============ */
.page-about .timeline-section {
  padding-top: clamp(28px, 5vw, 56px);
}

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

.page-about .timeline::before {
  content: "";
  position: absolute;
  left: calc(var(--about-marker) / 2);
  top: 10px;
  bottom: 8px;
  width: 1px;
  background: linear-gradient(180deg, var(--orange) 0%, rgba(56, 207, 224, .55) 38%, rgba(147, 162, 194, .22) 100%);
}

.page-about .tl-item {
  position: relative;
  display: grid;
  grid-template-columns: var(--about-marker) minmax(0, 1fr);
  gap: 0 16px;
  padding-bottom: clamp(38px, 7vw, 76px);
}

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

.page-about .tl-num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: var(--about-marker);
  height: var(--about-marker);
  background: var(--abyss);
  border: 1px solid var(--line-strong);
  border-radius: 50%;
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: .06em;
  color: var(--mist);
  transition: color .3s var(--ease), border-color .3s var(--ease), box-shadow .3s var(--ease);
}

.page-about .tl-item:hover .tl-num,
.page-about .tl-item:focus-within .tl-num {
  color: var(--orange-lit);
  border-color: var(--orange);
  box-shadow: 0 0 0 5px rgba(244, 87, 28, .13);
}

.page-about .node-tip {
  display: none;
}

.page-about .tl-body {
  min-width: 0;
}

.page-about .tl-head {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 6px 14px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--line);
  margin-bottom: clamp(16px, 3vw, 26px);
}

.page-about .tl-head .chapter-title {
  margin: 0;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(21px, 4.4vw, 30px);
  letter-spacing: .04em;
  line-height: 1.3;
  color: var(--star);
}

.page-about .chapter-sub {
  margin: 0;
  font-family: var(--font-serif);
  font-size: 13px;
  letter-spacing: .16em;
  text-transform: uppercase;
  color: var(--glacier);
  padding-left: 12px;
  border-left: 2px solid var(--orange);
}

.page-about .prose p {
  margin: 0 0 14px;
  color: var(--body-ink);
}

.page-about .prose a,
.page-about .tl-note a {
  color: var(--orange-lit);
  text-decoration: none;
  border-bottom: 1px dashed rgba(255, 138, 61, .5);
}

.page-about .prose a:hover,
.page-about .tl-note a:hover {
  color: var(--star);
  border-bottom-color: var(--star);
}

.page-about .tl-intro {
  margin-bottom: clamp(16px, 3vw, 24px);
}

.page-about .tl-note {
  margin: 16px 0 0;
  font-size: 13px;
  line-height: 1.7;
  color: var(--mist);
}

/* 图文分栏 */
.page-about .tl-split {
  display: grid;
  gap: clamp(18px, 3vw, 30px);
}

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

.page-about .figure-media {
  overflow: hidden;
  border: 1px solid var(--line);
  background: var(--frame-grad);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 14px), calc(100% - 14px) 100%, 0 100%);
}

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

.page-about .figure-caption {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  margin-top: 10px;
  font-size: 12px;
  line-height: 1.6;
  color: var(--mist);
}

.page-about .figure-band {
  margin-bottom: clamp(20px, 3vw, 32px);
}

/* ============ 分工表 ============ */
.page-about .duty-table {
  width: 100%;
  min-width: 560px;
  border-collapse: collapse;
  background: var(--plateau);
}

.page-about .duty-table caption {
  caption-side: top;
  text-align: left;
  padding: 0 0 12px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .2em;
  color: var(--butter);
}

.page-about .duty-table th,
.page-about .duty-table td {
  padding: 15px 16px;
  text-align: left;
  vertical-align: top;
  font-size: 14px;
  line-height: 1.7;
  color: var(--body-ink);
  border-bottom: 1px solid var(--line);
}

.page-about .duty-table thead th {
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: .22em;
  text-transform: uppercase;
  color: var(--glacier);
  border-bottom: 1px solid var(--line-strong);
  white-space: nowrap;
}

.page-about .duty-table tbody th {
  color: var(--star);
  font-weight: 700;
  white-space: nowrap;
}

.page-about .duty-table tbody tr:hover td,
.page-about .duty-table tbody tr:hover th {
  background: rgba(26, 39, 80, .55);
}

.page-about .duty-table .num {
  color: var(--orange-lit);
  font-weight: 700;
}

.page-about .table-scroll {
  border: 1px solid var(--line);
  background: var(--plateau);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 16px), calc(100% - 16px) 100%, 0 100%);
}

/* ============ 引文 ============ */
.page-about .pullquote {
  margin: clamp(20px, 3vw, 30px) 0 0;
  padding: 6px 0 6px 20px;
  border-left: 2px solid var(--orange);
  font-family: var(--font-serif);
  font-size: clamp(16px, 2.6vw, 20px);
  line-height: 1.75;
  color: var(--star);
}

/* ============ 四条方法（折叠） ============ */
.page-about .method-list {
  display: grid;
  gap: 12px;
}

.page-about .method {
  background: var(--plateau);
  border: 1px solid var(--line);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 14px), calc(100% - 14px) 100%, 0 100%);
  transition: border-color .3s var(--ease);
}

.page-about .method:hover {
  border-color: var(--line-strong);
}

.page-about .method > summary {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 6px 14px;
  padding: 17px 20px;
  cursor: pointer;
  list-style: none;
  transition: background .3s var(--ease);
}

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

.page-about .method > summary::after {
  content: "展开";
  margin-left: auto;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .18em;
  color: var(--glacier);
}

.page-about .method[open] > summary::after {
  content: "收起";
  color: var(--orange-lit);
}

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

.page-about .method-key {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .16em;
  color: var(--orange);
  padding: 3px 9px;
  border: 1px solid rgba(244, 87, 28, .45);
  border-radius: var(--pill);
  white-space: nowrap;
}

.page-about .method-sum {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: clamp(15px, 3.2vw, 17px);
  line-height: 1.5;
  color: var(--star);
}

.page-about .method-body {
  padding: 15px 20px 19px;
}

.page-about .method-body p {
  margin: 0;
  font-size: 14px;
  line-height: 1.8;
  color: var(--body-ink);
}

.page-about .method-body a {
  color: var(--orange-lit);
  text-decoration: none;
  border-bottom: 1px dashed rgba(255, 138, 61, .5);
}

/* ============ 阶段区 ============ */
.page-about .stage-section {
  position: relative;
  overflow: hidden;
  padding-top: clamp(40px, 7vw, 80px);
}

.page-about .stage-bg {
  position: absolute;
  inset: 0;
  z-index: 0;
}

.page-about .stage-bg img {
  width: 100%;
  height: 100%;
  max-width: 100%;
  object-fit: cover;
  opacity: .2;
}

.page-about .stage-section::after {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 1;
  background: linear-gradient(180deg, var(--abyss) 0%, rgba(6, 11, 24, .7) 42%, var(--abyss) 100%);
  pointer-events: none;
}

.page-about .stage-section > .wrap {
  position: relative;
  z-index: 2;
}

.page-about .stage-stack {
  display: grid;
  gap: clamp(16px, 3vw, 22px);
}

.page-about .stage-card {
  position: relative;
  padding: clamp(20px, 3.6vw, 30px);
  background: rgba(14, 23, 48, .86);
  border: 1px solid var(--line);
  border-left: 3px solid var(--orange);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 20px), calc(100% - 20px) 100%, 0 100%);
  transition: transform .4s var(--ease), border-color .4s var(--ease);
}

.page-about .stage-card:nth-child(odd) {
  transform: rotate(-.8deg);
}

.page-about .stage-card:nth-child(even) {
  transform: rotate(1deg) translateX(4px);
}

.page-about .stage-card:hover {
  transform: rotate(0deg) translateY(-4px);
  border-color: var(--line-strong);
}

.page-about .stage-year {
  margin: 0;
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: .24em;
  color: var(--butter);
}

.page-about .stage-title {
  margin: 10px 0 0;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(18px, 3.8vw, 23px);
  letter-spacing: .04em;
  line-height: 1.35;
  color: var(--star);
}

.page-about .stage-text {
  margin: 10px 0 0;
  font-size: 14px;
  line-height: 1.8;
  color: var(--body-ink);
}

/* ============ 收尾 ============ */
.page-about .about-next {
  padding-top: clamp(36px, 6vw, 72px);
}

.page-about .next-panel {
  padding: clamp(24px, 4.5vw, 48px);
  background: var(--plateau);
  border: 1px solid var(--line-strong);
}

.page-about .next-title {
  margin: 0;
  font-family: var(--font-display);
  font-weight: 900;
  font-size: clamp(22px, 4.6vw, 34px);
  letter-spacing: .05em;
  line-height: 1.25;
  color: var(--star);
}

.page-about .next-text {
  margin: 14px 0 0;
  max-width: 62ch;
  font-size: 15px;
  line-height: 1.85;
  color: var(--body-ink);
}

.page-about .next-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: clamp(20px, 3vw, 28px);
}

/* ============ 断点：桌面 ============ */
@media (min-width: 900px) {
  .page-about {
    --about-marker: 68px;
  }

  .page-about .timeline::before {
    left: calc(var(--about-marker) / 2);
  }

  .page-about .tl-item {
    gap: 0 34px;
  }

  .page-about .tl-num {
    font-size: 16px;
    border-radius: 18px;
    border-color: var(--line-strong);
  }

  .page-about .node-tip {
    display: block;
    position: absolute;
    left: calc(100% + 14px);
    top: 50%;
    transform: translateY(-50%) translateX(-6px);
    padding: 6px 12px;
    max-width: 200px;
    background: var(--indigo);
    border: 1px solid var(--line-strong);
    border-radius: var(--pill);
    font-size: 12px;
    line-height: 1.4;
    color: var(--star);
    white-space: nowrap;
    opacity: 0;
    pointer-events: none;
    transition: opacity .3s var(--ease), transform .3s var(--ease);
    z-index: 3;
  }

  .page-about .tl-item:hover .node-tip,
  .page-about .tl-item:focus-within .node-tip {
    opacity: 1;
    transform: translateY(-50%) translateX(0);
  }

  .page-about .tl-split {
    grid-template-columns: minmax(0, 1.05fr) minmax(0, 1fr);
    align-items: start;
  }

  .page-about .stage-stack {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: clamp(18px, 2.6vw, 30px);
  }

  .page-about .stage-card:nth-child(even) {
    transform: rotate(1deg) translateX(0) translateY(22px);
  }

  .page-about .stage-card:hover {
    transform: rotate(0deg) translateY(16px);
  }

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

@media (min-width: 1180px) {
  .page-about .hero-lead {
    font-size: 18px;
  }

  .page-about .duty-table th,
  .page-about .duty-table td {
    padding: 17px 20px;
  }
}

/* ============ 降低动效偏好 ============ */
@media (prefers-reduced-motion: reduce) {
  .page-about .stage-card,
  .page-about .stage-card:nth-child(odd),
  .page-about .stage-card:nth-child(even),
  .page-about .tl-num,
  .page-about .node-tip {
    transition: none;
  }

  .page-about .stage-card,
  .page-about .stage-card:nth-child(odd),
  .page-about .stage-card:nth-child(even),
  .page-about .stage-card:hover {
    transform: none;
  }
}