.page-about {
  --about-rail: 112px;
  --about-measure: 68ch;
  --about-pad: clamp(22px, 5vw, 56px);
  background:
    linear-gradient(to right, rgba(143, 166, 184, 0.045) 1px, transparent 1px) 0 0 / 64px 64px,
    var(--ink);
  color: var(--mist);
  overflow-x: clip;
  padding-bottom: clamp(48px, 8vw, 96px);
}

.page-about img {
  max-width: 100%;
  height: auto;
}

.page-about .about-link {
  color: var(--cyan);
  text-decoration: none;
  border-bottom: 1px solid var(--cyan-line);
  transition: border-color 140ms var(--ease), color 140ms var(--ease);
}

.page-about .about-link:hover,
.page-about .about-link:focus-visible {
  color: var(--gold);
  border-bottom-color: var(--gold);
}

/* 首屏 */
.page-about .about-hero {
  position: relative;
  padding: clamp(18px, 3.5vw, 34px) 0 clamp(34px, 6vw, 64px);
}

.page-about .hero-grid {
  display: grid;
  gap: clamp(24px, 5vw, 48px);
  align-items: start;
}

.page-about .hero-kicker {
  margin: 0;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.3em;
  text-transform: uppercase;
  color: var(--cyan);
}

.page-about .hero-copy h1 {
  margin: 12px 0 20px;
  font-size: clamp(2rem, 7vw, 4.1rem);
  line-height: 1.05;
  letter-spacing: 0.01em;
  font-weight: 800;
  text-wrap: balance;
}

.page-about .hero-lead {
  margin: 0;
  max-width: 56ch;
  font-size: clamp(1rem, 1.9vw, 1.125rem);
  line-height: 1.85;
  color: rgba(234, 242, 247, 0.82);
}

.page-about .stats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin-top: clamp(22px, 4vw, 32px);
  background: var(--line);
  border: 1px solid var(--line);
}

.page-about .stat {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 14px 16px;
  background: var(--ink-2);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 10px), calc(100% - 10px) 100%, 0 100%);
}

.page-about .stat-num {
  font-family: var(--mono);
  font-size: clamp(1.3rem, 3vw, 1.65rem);
  line-height: 1;
  color: var(--gold);
}

.page-about .stat-label {
  font-size: 12px;
  letter-spacing: 0.04em;
  color: var(--slate);
}

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

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

.page-about .hero-figure img {
  aspect-ratio: 3 / 4;
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 42px), calc(100% - 42px) 100%, 0 100%);
}

.page-about .about-figure figcaption {
  margin-top: 10px;
  font-family: var(--mono);
  font-size: 11px;
  line-height: 1.6;
  letter-spacing: 0.06em;
  color: var(--slate);
}

/* 章节索引条 */
.page-about .chapter-nav {
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  background: rgba(12, 31, 49, 0.72);
}

.page-about .chapter-nav-inner {
  display: flex;
  gap: 4px;
  overflow-x: auto;
  padding: 8px 0;
  scrollbar-width: thin;
}

.page-about .chapter-nav a {
  flex: 0 0 auto;
  display: inline-flex;
  align-items: baseline;
  gap: 7px;
  padding: 8px 12px;
  font-size: 13px;
  color: var(--slate);
  text-decoration: none;
  border: 1px solid transparent;
  transition: color 140ms var(--ease), border-color 140ms var(--ease), background 140ms var(--ease);
}

.page-about .chapter-nav a:hover,
.page-about .chapter-nav a:focus-visible {
  color: var(--mist);
  background: var(--steel);
  border-color: var(--cyan-line);
}

.page-about .cn-idx {
  font-family: var(--mono);
  font-size: 11px;
  color: var(--orange);
}

/* 章节骨架 */
.page-about .chapter {
  display: grid;
  gap: 14px;
  padding: clamp(38px, 6.5vw, 76px) 0;
  border-bottom: 1px solid var(--line);
}

.page-about .chapter:last-of-type {
  border-bottom: 0;
}

.page-about .chapter-rail {
  display: flex;
  align-items: baseline;
  gap: 12px;
}

.page-about .chapter-idx {
  font-family: var(--mono);
  font-size: 2rem;
  line-height: 1;
  font-weight: 700;
  color: var(--cyan);
}

.page-about .chapter-anno {
  display: none;
}

.page-about .chapter-body {
  max-width: var(--about-measure);
}

.page-about .chapter-body h2 {
  margin: 0 0 18px;
  padding-left: 14px;
  border-left: 3px solid var(--cyan);
  font-size: clamp(1.4rem, 4.2vw, 2rem);
  line-height: 1.28;
  letter-spacing: 0.01em;
  text-wrap: balance;
}

.page-about .chapter-body p {
  margin: 0 0 16px;
  font-size: 1rem;
  line-height: 1.9;
  color: rgba(234, 242, 247, 0.86);
}

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

.page-about .chapter-body .section-lead {
  font-size: 1.05rem;
  color: var(--mist);
}

/* 方法论切换 */
.page-about .method-switch {
  margin: 26px 0 22px;
  display: grid;
  gap: 16px;
}

.page-about .method-radio {
  position: absolute;
  width: 1px;
  height: 1px;
  opacity: 0;
  pointer-events: none;
}

.page-about .method-tabs {
  display: inline-flex;
  gap: 6px;
  justify-self: start;
  padding: 5px;
  background: var(--ink-2);
  border: 1px solid var(--line);
  clip-path: polygon(0 0, calc(100% - 12px) 0, 100% 12px, 100% 100%, 0 100%);
}

.page-about .method-tabs label {
  cursor: pointer;
  padding: 8px 16px;
  font-size: 13px;
  letter-spacing: 0.04em;
  color: var(--slate);
  transition: background 140ms var(--ease), color 140ms var(--ease);
}

.page-about .method-tabs label:hover {
  color: var(--mist);
}

.page-about #m-before:checked ~ .method-tabs label[for="m-before"],
.page-about #m-after:checked ~ .method-tabs label[for="m-after"] {
  background: var(--cyan);
  color: var(--ink);
  font-weight: 600;
}

.page-about .method-radio:focus-visible ~ .method-tabs label {
  outline: 2px solid var(--cyan);
  outline-offset: 2px;
}

.page-about .method-panel {
  display: none;
  gap: 12px;
}

.page-about #m-before:checked ~ .method-panel--before,
.page-about #m-after:checked ~ .method-panel--after {
  display: grid;
}

.page-about .method-cell {
  padding: 16px;
  background: var(--ink-2);
  border: 1px solid var(--line);
  clip-path: polygon(0 0, calc(100% - 14px) 0, 100% 14px, 100% 100%, 0 100%);
}

.page-about .method-tag {
  display: block;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--orange);
}

.page-about .method-cell h3 {
  margin: 8px 0 6px;
  font-size: 1rem;
  line-height: 1.4;
}

.page-about .method-cell p {
  margin: 0;
  font-size: 0.92rem;
  line-height: 1.75;
  color: rgba(234, 242, 247, 0.76);
}

/* 资源整理图 */
.page-about .resource-figure {
  margin: 22px 0 24px;
}

.page-about .resource-figure img {
  aspect-ratio: 14 / 6;
  border: 1px solid var(--line);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 28px), calc(100% - 28px) 100%, 0 100%);
}

/* 时间线 */
.page-about .timeline {
  list-style: none;
  margin: 28px 0 0;
  padding: 0;
  display: grid;
  gap: 0;
}

.page-about .timeline li {
  position: relative;
  padding: 0 0 18px 26px;
}

.page-about .timeline li::before {
  content: "";
  position: absolute;
  left: 6px;
  top: 8px;
  bottom: -4px;
  width: 2px;
  background: linear-gradient(to bottom, var(--cyan-line), rgba(52, 230, 210, 0));
  transform: rotate(3deg);
  transform-origin: top center;
}

.page-about .timeline li:last-child::before {
  display: none;
}

.page-about .timeline li::after {
  content: "";
  position: absolute;
  left: 1px;
  top: 9px;
  width: 10px;
  height: 10px;
  background: var(--cyan);
  transform: rotate(45deg);
  box-shadow: 0 0 0 3px rgba(52, 230, 210, 0.14);
}

.page-about .tl-item {
  background: var(--ink-2);
  border: 1px solid var(--line);
  clip-path: polygon(0 0, calc(100% - 12px) 0, 100% 12px, 100% 100%, 0 100%);
  transition: border-color 140ms var(--ease);
}

.page-about .tl-item[open] {
  border-color: var(--cyan-line);
}

.page-about .tl-item summary {
  display: flex;
  align-items: baseline;
  gap: 10px;
  padding: 12px 16px;
  cursor: pointer;
  list-style: none;
}

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

.page-about .tl-stage {
  flex: 0 0 auto;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.06em;
  color: var(--gold);
}

.page-about .tl-name {
  font-size: 0.98rem;
  font-weight: 600;
  color: var(--mist);
}

.page-about .tl-plus {
  margin-left: auto;
  font-family: var(--mono);
  color: var(--cyan);
  transition: transform 200ms var(--ease);
}

.page-about .tl-item[open] .tl-plus {
  transform: rotate(45deg);
}

.page-about .tl-body {
  padding: 0 16px 14px;
}

.page-about .tl-body p {
  margin: 0;
  font-size: 0.93rem;
  line-height: 1.8;
  color: rgba(234, 242, 247, 0.78);
}

/* 团队 */
.page-about .team-split {
  display: grid;
  gap: 20px;
  margin: 22px 0 22px;
}

.page-about .team-figure img {
  aspect-ratio: 1 / 1;
  border: 1px solid var(--line);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 32px), calc(100% - 32px) 100%, 0 100%);
}

.page-about .roles {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px 18px;
}

.page-about .role {
  padding-top: 12px;
  border-top: 2px solid var(--steel);
}

.page-about .role h3 {
  margin: 0 0 6px;
  font-size: 0.98rem;
  color: var(--cyan);
}

.page-about .role p {
  margin: 0;
  font-size: 0.9rem;
  line-height: 1.75;
  color: rgba(234, 242, 247, 0.76);
}

/* 承诺 */
.page-about .promise-grid {
  display: grid;
  gap: 14px;
  margin-top: 24px;
}

.page-about .promise {
  padding: 18px;
  background: linear-gradient(155deg, rgba(22, 50, 74, 0.7), rgba(12, 31, 49, 0.95));
  border: 1px solid var(--line-strong);
  clip-path: polygon(0 0, calc(100% - 16px) 0, 100% 16px, 100% 100%, 0 100%);
}

.page-about .p-idx {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.18em;
  color: var(--gold);
}

.page-about .promise h3 {
  margin: 10px 0 8px;
  font-size: 1.02rem;
}

.page-about .promise p {
  margin: 0;
  font-size: 0.92rem;
  line-height: 1.8;
  color: rgba(234, 242, 247, 0.78);
}

/* 收尾 */
.page-about .closing {
  position: relative;
  margin-top: clamp(36px, 6vw, 64px);
  padding: clamp(26px, 5vw, 48px);
  background: var(--ink-2);
  border-top: 1px solid var(--line-strong);
  border-bottom: 1px solid var(--line);
  overflow: hidden;
}

.page-about .closing::before {
  content: "";
  position: absolute;
  top: -40%;
  right: -10%;
  width: 220px;
  height: 220px;
  background: var(--orange);
  opacity: 0.12;
  transform: rotate(12deg);
  pointer-events: none;
}

.page-about .closing-kicker {
  margin: 0 0 10px;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.28em;
  text-transform: uppercase;
  color: var(--cyan);
}

.page-about .closing h2 {
  margin: 0 0 12px;
  max-width: 26ch;
  font-size: clamp(1.35rem, 4vw, 2.1rem);
  line-height: 1.3;
}

.page-about .closing p {
  margin: 0;
  max-width: 56ch;
  line-height: 1.85;
  color: rgba(234, 242, 247, 0.8);
}

.page-about .closing-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 20px;
}

/* 响应式 */
@media (min-width: 720px) {
  .page-about .stats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .page-about .method-panel--before,
  .page-about #m-before:checked ~ .method-panel--before,
  .page-about #m-after:checked ~ .method-panel--after {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .page-about .promise-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .page-about .team-split {
    grid-template-columns: 260px minmax(0, 1fr);
    align-items: start;
  }
}

@media (min-width: 900px) {
  .page-about .hero-grid {
    grid-template-columns: minmax(0, 7fr) minmax(0, 4fr);
    align-items: end;
  }

  .page-about .chapter-nav {
    position: sticky;
    top: calc(var(--bar-h) + var(--ticker-h));
    z-index: 6;
    backdrop-filter: blur(6px);
  }

  .page-about .chapter-nav-inner {
    padding: 10px 0;
    gap: 6px;
  }

  .page-about .chapter {
    grid-template-columns: var(--about-rail) minmax(0, 1fr);
    gap: clamp(24px, 4vw, 56px);
  }

  .page-about .chapter-rail {
    position: sticky;
    top: calc(var(--bar-h) + var(--ticker-h) + 76px);
    flex-direction: column;
    align-items: flex-start;
    gap: 18px;
  }

  .page-about .chapter-idx {
    font-size: 3.2rem;
  }

  .page-about .chapter-anno {
    display: block;
    writing-mode: vertical-rl;
    transform: rotate(180deg);
    font-family: var(--mono);
    font-size: 11px;
    letter-spacing: 0.28em;
    text-transform: uppercase;
    color: var(--slate);
  }

  .page-about .roles {
    gap: 20px 24px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .chapter-nav a,
  .page-about .about-link,
  .page-about .method-tabs label,
  .page-about .tl-plus {
    transition: none;
  }
}