.page-about {
  display: block;
  background: var(--paper);
  color: var(--ink);
  padding-bottom: clamp(52px, 8vw, 120px);
}

/* ---------- 首屏 ---------- */

.page-about .about-hero {
  padding-top: clamp(24px, 4vw, 52px);
}

.page-about .about-hero .eyebrow {
  margin: 0;
  color: var(--scale);
}

.page-about .about-hero .display-title {
  margin: 14px 0 0;
  font-family: var(--font-display);
  font-weight: 200;
  font-size: clamp(42px, 8.2vw, 104px);
  line-height: 0.98;
  letter-spacing: -0.025em;
  color: var(--ink);
}

.page-about .about-hero .lede {
  max-width: 62ch;
  margin: clamp(18px, 2.6vw, 28px) 0 0;
  font-family: var(--font-body);
  font-size: clamp(16px, 1.1vw, 17.5px);
  line-height: 1.95;
  color: var(--ink);
}

.page-about .about-hero .stat-band {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px 20px;
  margin-top: clamp(26px, 3.6vw, 44px);
  padding: 18px 0 20px;
  border-top: 1px solid var(--ink);
  border-bottom: 1px solid var(--hairline);
}

.page-about .about-hero .stat-item {
  display: grid;
  gap: 5px;
  min-width: 0;
}

.page-about .about-hero .stat-value {
  font-family: var(--font-mono);
  font-size: clamp(24px, 3.2vw, 36px);
  font-weight: 600;
  line-height: 1;
  letter-spacing: -0.01em;
  font-variant-numeric: tabular-nums;
  color: var(--ink);
}

.page-about .about-hero .stat-label {
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.12em;
  line-height: 1.7;
  color: var(--scale);
}

/* ---------- 主体骨架：旁注轨道 + 正文 ---------- */

.page-about .about-body {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(20px, 4vw, 40px);
  margin-top: clamp(34px, 5.5vw, 70px);
}

.page-about .about-rail {
  min-width: 0;
}

.page-about .rail-title {
  margin: 0 0 10px;
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--scale);
}

.page-about .rail-index {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  gap: 6px;
  overflow-x: auto;
  scrollbar-width: none;
  -webkit-overflow-scrolling: touch;
}

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

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

.page-about .rail-link {
  display: flex;
  align-items: baseline;
  gap: 7px;
  padding: 6px 10px 10px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  color: var(--scale);
  text-decoration: none;
  white-space: nowrap;
  border-bottom: 2px solid var(--hairline-soft);
  transition: color var(--speed) ease, border-color var(--speed) ease;
}

.page-about .rail-link:hover {
  color: var(--ink);
  border-bottom-color: var(--lava);
}

.page-about .rail-link:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 2px;
}

.page-about .rail-num {
  font-size: 10px;
  color: var(--lava);
}

.page-about .about-main {
  min-width: 0;
}

/* ---------- 章节 ---------- */

.page-about .about-section {
  padding: clamp(26px, 3.4vw, 42px) 0;
}

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

.page-about .about-split {
  height: 1px;
  background: var(--grid);
  opacity: 0.45;
  transform: skewY(-0.7deg);
  transform-origin: left center;
}

.page-about .sec-head {
  display: flex;
  align-items: baseline;
  flex-wrap: wrap;
  gap: 12px;
  margin-bottom: clamp(16px, 2.2vw, 24px);
}

.page-about .sec-num {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.18em;
  font-variant-numeric: tabular-nums;
  color: var(--lava);
}

.page-about .sec-title {
  margin: 0;
  font-family: var(--font-head);
  font-weight: 800;
  font-size: clamp(20px, 2.5vw, 30px);
  line-height: 1.28;
  letter-spacing: -0.01em;
  min-width: 0;
}

.page-about .about-text p {
  max-width: 68ch;
  margin: 0 0 1.05em;
  font-family: var(--font-body);
  font-size: clamp(16px, 1.05vw, 17.5px);
  line-height: 1.95;
  color: var(--ink);
}

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

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

.page-about .about-text a:hover {
  color: var(--lava);
}

/* ---------- 归档方法 ---------- */

.page-about .method-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(22px, 3vw, 34px);
  align-items: start;
}

.page-about .figure-storage {
  margin: 0;
  min-width: 0;
}

.page-about .figure-storage .media-frame,
.page-about .figure-ring .media-frame,
.page-about .figure-wide .media-frame {
  overflow: hidden;
  background: var(--room);
}

.page-about .figure-storage .media-frame {
  clip-path: polygon(0 0, calc(100% - 26px) 0, 100% 26px, 100% 100%, 26px 100%, 0 calc(100% - 26px));
}

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

.page-about .media-caption {
  margin-top: 10px;
  font-family: var(--font-mono);
  font-size: 11px;
  line-height: 1.7;
  letter-spacing: 0.04em;
  color: var(--scale);
}

.page-about .code-diagram {
  display: block;
  width: 100%;
  max-width: 620px;
  height: auto;
  margin: clamp(18px, 2.6vw, 28px) 0 0;
}

.page-about .figure-ring {
  margin: clamp(26px, 3.4vw, 40px) 0 0;
}

.page-about .figure-ring .media-frame {
  max-width: 620px;
  margin: 0 auto;
  background: var(--board);
  clip-path: polygon(0 0, calc(100% - 22px) 0, 100% 22px, 100% 100%, 22px 100%, 0 calc(100% - 22px));
}

.page-about .figure-ring .media-caption {
  max-width: 620px;
  margin-left: auto;
  margin-right: auto;
}

/* ---------- 指标定义 ---------- */

.page-about .figure-wide {
  margin: 0 0 clamp(22px, 3vw, 32px);
}

.page-about .figure-wide .media-frame {
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 30px), calc(100% - 30px) 100%, 0 100%);
}

.page-about .metric-list {
  list-style: none;
  margin: clamp(20px, 2.6vw, 30px) 0 0;
  padding: 0;
  border-top: 2px solid var(--ink);
}

.page-about .metric-item {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 8px;
  padding: 20px 0;
  border-bottom: 1px solid var(--hairline);
}

.page-about .metric-value {
  font-family: var(--font-mono);
  font-size: clamp(28px, 3.6vw, 44px);
  font-weight: 600;
  line-height: 1;
  letter-spacing: -0.02em;
  font-variant-numeric: tabular-nums;
  color: var(--turf);
}

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

.page-about .metric-name {
  margin: 0 0 8px;
  font-family: var(--font-head);
  font-weight: 800;
  font-size: 15px;
  letter-spacing: 0.02em;
  color: var(--ink);
}

.page-about .metric-desc {
  margin: 0;
  max-width: 58ch;
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.9;
  color: var(--ink);
}

.page-about .term {
  margin-top: clamp(18px, 2.4vw, 26px);
  border-top: 1px solid var(--hairline);
}

.page-about .term-summary {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 15px 0;
  cursor: pointer;
  list-style: none;
  font-family: var(--font-head);
  font-weight: 700;
  font-size: 15px;
  line-height: 1.6;
  color: var(--ink);
}

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

.page-about .term-summary::before {
  content: "+";
  flex: 0 0 auto;
  width: 14px;
  font-family: var(--font-mono);
  font-size: 16px;
  line-height: 1;
  color: var(--lava);
}

.page-about .term[open] .term-summary::before {
  content: "–";
}

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

.page-about .term-body {
  padding: 0 0 18px 24px;
}

.page-about .term-body p {
  margin: 0;
  max-width: 62ch;
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.9;
  color: var(--ink);
}

/* ---------- 时间线 ---------- */

.page-about .timeline {
  list-style: none;
  position: relative;
  margin: clamp(22px, 3vw, 34px) 0 0;
  padding: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 26px;
}

.page-about .timeline::after {
  content: "";
  position: absolute;
  left: 4px;
  top: 8px;
  bottom: 8px;
  width: 1px;
  background: var(--hairline);
}

.page-about .tl-node {
  position: relative;
  padding-left: 22px;
  min-width: 0;
}

.page-about .tl-mark {
  position: absolute;
  left: 0;
  top: 5px;
  width: 10px;
  height: 10px;
  background: var(--turf);
  transform: rotate(45deg);
}

.page-about .tl-phase {
  display: block;
  margin-bottom: 8px;
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--lava);
}

.page-about .tl-title {
  margin: 0 0 8px;
  font-family: var(--font-head);
  font-weight: 800;
  font-size: clamp(17px, 1.7vw, 21px);
  line-height: 1.35;
  letter-spacing: -0.01em;
  color: var(--ink);
}

.page-about .tl-body {
  margin: 0;
  max-width: 52ch;
  font-family: var(--font-body);
  font-size: 15.5px;
  line-height: 1.9;
  color: var(--ink);
}

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

/* ---------- 分工 ---------- */

.page-about .role-list {
  list-style: none;
  margin: clamp(20px, 2.6vw, 28px) 0 0;
  padding: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 14px;
}

.page-about .role-item {
  min-width: 0;
  padding: 18px 22px 20px 20px;
  background: var(--board);
  clip-path: polygon(0 0, calc(100% - 20px) 0, 100% 20px, 100% 100%, 0 100%);
}

.page-about .role-name {
  display: block;
  margin-bottom: 8px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.16em;
  color: var(--turf);
}

.page-about .role-desc {
  margin: 0;
  font-family: var(--font-body);
  font-size: 15.5px;
  line-height: 1.9;
  color: var(--ink);
}

/* ---------- 口径承诺 ---------- */

.page-about .about-commit {
  margin-top: clamp(26px, 3.6vw, 44px);
  padding: clamp(26px, 3.6vw, 46px) clamp(20px, 3vw, 44px) clamp(28px, 3.8vw, 48px);
  background: var(--ink);
  color: var(--paper);
  clip-path: polygon(0 0, calc(100% - 34px) 0, 100% 34px, 100% 100%, 0 100%);
}

.page-about .about-commit .sec-num {
  color: var(--signal);
}

.page-about .about-commit .sec-title {
  color: var(--paper);
}

.page-about .commit-lede,
.page-about .commit-foot {
  max-width: 64ch;
  margin: 0;
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.95;
  color: rgba(242, 239, 232, 0.86);
}

.page-about .commit-foot {
  margin-top: clamp(16px, 2.2vw, 22px);
  font-size: 15px;
  color: rgba(242, 239, 232, 0.72);
}

.page-about .commit-list {
  list-style: none;
  margin: clamp(16px, 2.4vw, 24px) 0 0;
  padding: 0;
  display: grid;
  gap: 10px;
}

.page-about .commit-list li {
  position: relative;
  padding-left: 22px;
  font-family: var(--font-body);
  font-size: 15.5px;
  line-height: 1.9;
  color: rgba(242, 239, 232, 0.9);
}

.page-about .commit-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.78em;
  width: 9px;
  height: 2px;
  background: var(--signal);
}

.page-about .about-commit .commit-action {
  display: inline-block;
  margin-top: clamp(20px, 2.6vw, 28px);
  background: var(--signal);
  color: var(--ink);
  border-color: var(--signal);
}

.page-about .about-commit .commit-action:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 3px;
}

/* ---------- 响应式 ---------- */

@media (min-width: 720px) {
  .page-about .about-hero .stat-band {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .page-about .metric-item {
    grid-template-columns: minmax(150px, 190px) minmax(0, 1fr);
    gap: 26px;
    align-items: start;
  }

  .page-about .role-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 16px;
    align-items: start;
  }

  .page-about .role-item:nth-child(even) {
    margin-top: 16px;
  }
}

@media (min-width: 900px) {
  .page-about .method-grid {
    grid-template-columns: minmax(0, 1.1fr) minmax(0, 0.9fr);
    gap: clamp(28px, 3.4vw, 44px);
  }

  .page-about .timeline {
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 0;
    padding-top: 2px;
  }

  .page-about .timeline::after {
    display: none;
  }

  .page-about .timeline::before {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--ink);
  }

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

  .page-about .tl-mark {
    top: -5px;
    left: 0;
  }

  .page-about .figure-wide .media-frame {
    max-width: 1040px;
  }
}

@media (min-width: 960px) {
  .page-about .about-body {
    grid-template-columns: var(--rail-w) minmax(0, 1fr);
    gap: clamp(34px, 4.6vw, 76px);
    align-items: start;
  }

  .page-about .about-rail {
    position: sticky;
    top: 104px;
  }

  .page-about .rail-title {
    margin-bottom: 12px;
  }

  .page-about .rail-index {
    display: block;
    overflow: visible;
    padding: 0;
    border-left: 1px solid var(--hairline);
  }

  .page-about .rail-link {
    display: block;
    padding: 10px 0 10px 14px;
    margin-left: -1px;
    border-bottom: none;
    border-left: 2px solid transparent;
    white-space: normal;
    letter-spacing: 0.04em;
  }

  .page-about .rail-link:hover {
    border-bottom-color: transparent;
    border-left-color: var(--lava);
  }

  .page-about .rail-num {
    display: block;
    margin-bottom: 3px;
    letter-spacing: 0.16em;
  }

  .page-about .rail-text {
    display: block;
    font-family: var(--font-head);
    font-weight: 500;
    font-size: 12px;
    letter-spacing: 0.02em;
    line-height: 1.5;
  }
}

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