.page-about {
  --about-rail: 12.5rem;
  --about-space: clamp(1.25rem, 4vw, 3rem);
  background: var(--c-mist);
  color: var(--c-ink);
  line-height: 1.8;
  padding-bottom: clamp(2rem, 5vw, 3.5rem);
}

/* ---------- 首屏 ---------- */

.page-about .about-hero {
  position: relative;
  background: var(--c-deep);
  color: var(--c-mist);
  padding-block: clamp(2rem, 5vw, 3.25rem) clamp(2.5rem, 6vw, 4.5rem);
  border-bottom: var(--frame) solid var(--c-ink);
  overflow: hidden;
}

.page-about .about-hero::after {
  content: "";
  position: absolute;
  right: -7rem;
  bottom: -9rem;
  width: 26rem;
  height: 26rem;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(91, 192, 190, 0.3), rgba(91, 192, 190, 0) 68%);
  pointer-events: none;
}

.page-about .about-hero .breadcrumb,
.page-about .about-hero .breadcrumb a,
.page-about .about-hero .breadcrumb span {
  color: var(--c-coral-soft);
}

.page-about .about-hero__grid {
  display: grid;
  gap: clamp(1.75rem, 4vw, 3rem);
  margin-top: clamp(1.5rem, 4vw, 2.5rem);
  align-items: end;
  position: relative;
  z-index: 1;
}

.page-about .about-hero h1 {
  font-family: var(--font-head);
  font-weight: 800;
  font-size: clamp(2.1rem, 6vw, 4rem);
  line-height: 1.06;
  letter-spacing: -0.02em;
  margin: 0.55rem 0 0;
  color: var(--c-mist);
  max-width: 15em;
}

.page-about .about-hero .eyebrow {
  color: var(--c-electric);
  letter-spacing: 0.14em;
}

.page-about .about-hero .lede {
  color: rgba(244, 247, 245, 0.9);
  font-size: clamp(1rem, 1.15vw, 1.08rem);
  margin: 0;
  max-width: 34em;
}

.page-about .about-hero__facts {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.7rem 1.85rem;
  margin: 1.75rem 0 0;
  padding: 1.15rem 0 0;
  border-top: 2px solid rgba(244, 247, 245, 0.24);
}

.page-about .about-hero__facts li {
  display: flex;
  align-items: baseline;
  gap: 0.5rem;
  font-size: 0.85rem;
  color: rgba(244, 247, 245, 0.82);
}

.page-about .about-hero__facts .mono {
  font-size: 1.4rem;
  font-weight: 700;
  line-height: 1;
  color: var(--c-coral);
}

/* ---------- 布局骨架 ---------- */

.page-about .about-layout {
  display: grid;
  gap: clamp(1.75rem, 4vw, 3rem);
  padding-block: clamp(2rem, 5vw, 3.25rem) 0;
}

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

/* ---------- 章节 ---------- */

.page-about .about-section {
  scroll-margin-top: calc(var(--bar-h) + 1rem);
  padding-block: clamp(1.75rem, 4vw, 2.75rem);
  border-top: var(--frame) solid var(--c-ink);
  min-width: 0;
}

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

.page-about .about-section__head {
  margin-bottom: clamp(1.1rem, 2.5vw, 1.75rem);
}

.page-about .about-section__head .eyebrow {
  color: var(--c-channel);
  letter-spacing: 0.14em;
}

.page-about .about-section__head h2 {
  font-family: var(--font-head);
  font-weight: 800;
  font-size: clamp(1.5rem, 3.4vw, 2.35rem);
  line-height: 1.14;
  letter-spacing: -0.015em;
  margin: 0.45rem 0 0;
  max-width: 20ch;
}

.page-about .about-section p {
  font-size: clamp(0.98rem, 1.05vw, 1.0625rem);
  margin: 0 0 1em;
  max-width: 38em;
  color: var(--c-ink);
}

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

.page-about .about-figure {
  margin: clamp(1.5rem, 3vw, 2.25rem) 0 0;
}

/* ---------- 短注释块 ---------- */

.page-about .about-note {
  margin: clamp(1.25rem, 3vw, 2rem) 0;
  padding: clamp(1rem, 2.5vw, 1.5rem) clamp(1.1rem, 3vw, 1.75rem);
  border-left: 6px solid var(--c-coral);
  background: var(--c-channel);
  color: var(--c-mist);
  font-size: 0.98rem;
  line-height: 1.75;
}

.page-about .about-note p {
  margin: 0;
  max-width: 42em;
}

.page-about .about-note--sand {
  background: var(--c-sand);
  color: var(--c-ink);
  border-left-color: var(--c-deep);
}

/* ---------- 年份时间线 ---------- */

.page-about .about-timeline {
  list-style: none;
  margin: clamp(1.5rem, 3vw, 2rem) 0 0;
  padding: 0;
  border: var(--frame) solid var(--c-ink);
  background: var(--c-mist);
  box-shadow: var(--shadow-hard);
}

.page-about .about-timeline__item + .about-timeline__item {
  border-top: var(--frame) solid var(--c-ink);
}

.page-about .about-node {
  display: block;
}

.page-about .about-node__head {
  display: grid;
  grid-template-columns: 4.25rem minmax(0, 1fr) auto;
  gap: 0.3rem 0.85rem;
  align-items: baseline;
  padding: clamp(0.85rem, 2vw, 1.15rem) clamp(0.9rem, 2.5vw, 1.5rem);
  background: var(--c-warm);
  cursor: pointer;
  list-style: none;
  transition: background-color 150ms ease;
}

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

.page-about .about-node__head::marker {
  content: "";
}

.page-about .about-node__head:hover {
  background: var(--c-sand);
}

.page-about .about-node__head:focus-visible {
  outline: 3px solid var(--c-coral);
  outline-offset: -3px;
}

.page-about .about-node__year {
  font-weight: 700;
  font-size: clamp(0.95rem, 2vw, 1.18rem);
  line-height: 1.2;
  color: var(--c-deep);
  letter-spacing: -0.01em;
  white-space: nowrap;
}

.page-about .about-node__title {
  font-family: var(--font-head);
  font-weight: 800;
  font-size: clamp(0.96rem, 1.6vw, 1.1rem);
  line-height: 1.45;
  color: var(--c-ink);
}

.page-about .about-node__tag {
  justify-self: end;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.1em;
  color: var(--c-slate);
  border: 2px solid currentColor;
  padding: 0.12rem 0.45rem;
  white-space: nowrap;
}

.page-about .about-node[open] > .about-node__head {
  background: var(--c-deep);
}

.page-about .about-node[open] > .about-node__head:hover {
  background: var(--c-deep);
}

.page-about .about-node[open] > .about-node__head .about-node__title {
  color: var(--c-mist);
}

.page-about .about-node[open] > .about-node__head .about-node__year {
  color: var(--c-coral);
}

.page-about .about-node[open] > .about-node__head .about-node__tag {
  color: var(--c-coral-soft);
  border-color: var(--c-coral-soft);
}

.page-about .about-node__body {
  padding: 0 clamp(0.9rem, 2.5vw, 1.5rem) clamp(1rem, 2.5vw, 1.35rem);
  background: var(--c-mist);
  border-top: 2px solid var(--c-ink);
}

.page-about .about-node__body p {
  margin: 0.9rem 0 0;
  font-size: 0.95rem;
  line-height: 1.75;
  color: var(--c-ink-soft);
  max-width: 40em;
}

/* ---------- 数字路标 ---------- */

.page-about .about-stats {
  list-style: none;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 11rem), 1fr));
  gap: 1rem;
  margin: clamp(1.5rem, 3vw, 2rem) 0;
  padding: 0;
}

.page-about .about-stat {
  border: var(--frame) solid var(--c-ink);
  background: var(--c-warm);
  padding: 0.95rem 1.05rem 1.05rem;
  box-shadow: 6px 6px 0 var(--c-channel);
}

.page-about .about-stat__num {
  display: block;
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: clamp(1.6rem, 4vw, 2.2rem);
  line-height: 1;
  letter-spacing: -0.02em;
  color: var(--c-deep);
}

.page-about .about-stat__label {
  display: block;
  margin-top: 0.5rem;
  font-size: 0.84rem;
  line-height: 1.55;
  color: var(--c-slate);
}

/* ---------- 口号 ---------- */

.page-about .about-promise-mark {
  font-family: var(--font-head);
  font-weight: 800;
  font-size: clamp(1.9rem, 6.5vw, 3.6rem);
  line-height: 1.05;
  letter-spacing: -0.02em;
  color: var(--c-deep);
  margin: 0 0 1.05rem;
  padding-left: 0.05em;
  border-left: 8px solid var(--c-coral);
  padding-left: clamp(0.6rem, 2vw, 1.1rem);
  max-width: none;
}

/* ---------- 理由列表 ---------- */

.page-about .about-why {
  list-style: none;
  display: grid;
  gap: 1.15rem;
  margin: clamp(1.5rem, 3vw, 2rem) 0 0;
  padding: 0;
}

.page-about .about-why__item {
  border-top: var(--frame) solid var(--c-ink);
  padding-top: 0.9rem;
}

.page-about .about-why__item h3 {
  font-family: var(--font-head);
  font-weight: 800;
  font-size: 1.02rem;
  line-height: 1.4;
  margin: 0 0 0.4rem;
  color: var(--c-deep);
}

.page-about .about-why__item p {
  margin: 0;
  font-size: 0.94rem;
  line-height: 1.72;
  color: var(--c-slate);
  max-width: 32em;
}

/* ---------- 下一步 ---------- */

.page-about .about-cta {
  display: grid;
  gap: 1rem;
  margin-top: clamp(2rem, 4vw, 3rem);
  padding: clamp(1.35rem, 3.5vw, 2.1rem);
  background: var(--c-channel);
  color: var(--c-mist);
  border: var(--frame) solid var(--c-ink);
  box-shadow: var(--shadow-hard);
}

.page-about .about-cta h2 {
  font-family: var(--font-head);
  font-weight: 800;
  font-size: clamp(1.25rem, 2.6vw, 1.7rem);
  line-height: 1.2;
  margin: 0;
  color: var(--c-mist);
}

.page-about .about-cta p {
  margin: 0;
  font-size: 0.96rem;
  line-height: 1.75;
  color: rgba(244, 247, 245, 0.88);
  max-width: 40em;
}

.page-about .about-cta__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 0.35rem;
}

/* ---------- 右侧章节跟随 ---------- */

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

.page-about .about-rail__title {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.18em;
  color: var(--c-slate);
  margin: 0 0 0.8rem;
}

.page-about .about-rail .section-rail__list {
  list-style: none;
  display: grid;
  gap: 0.1rem;
  margin: 0;
  padding: 0 0 0 0.9rem;
  border-left: var(--frame) solid var(--c-ink);
}

.page-about .about-rail .section-rail__link {
  display: block;
  font-size: 0.84rem;
  line-height: 1.5;
  padding: 0.32rem 0;
  color: var(--c-slate);
  text-decoration: none;
  border-bottom: 2px solid transparent;
  transition: color 140ms ease, border-color 140ms ease;
}

.page-about .about-rail .section-rail__link:hover {
  color: var(--c-ink);
}

.page-about .about-rail .section-rail__link[aria-current="true"] {
  color: var(--c-deep);
  font-weight: 800;
  border-bottom-color: var(--c-coral);
}

/* ---------- 响应式 ---------- */

@media (min-width: 46rem) {
  .page-about .about-why {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 1.35rem 1.75rem;
  }

  .page-about .about-node__body {
    padding-left: calc(4.25rem + 0.85rem + clamp(0.9rem, 2.5vw, 1.5rem));
  }
}

@media (min-width: 62rem) {
  .page-about .about-hero__grid {
    grid-template-columns: minmax(0, 1.15fr) minmax(0, 1fr);
  }
}

@media (min-width: 68rem) {
  .page-about .about-layout {
    grid-template-columns: minmax(0, 1fr) var(--about-rail);
    column-gap: clamp(2rem, 4vw, 4rem);
    align-items: start;
  }

  .page-about .about-rail {
    position: sticky;
    top: calc(var(--bar-h) + 1.75rem);
    align-self: start;
  }
}

@media (max-width: 45.99rem) {
  .page-about .about-timeline {
    box-shadow: 5px 5px 0 var(--c-ink);
  }

  .page-about .about-stat {
    box-shadow: 5px 5px 0 var(--c-channel);
  }

  .page-about .about-rail {
    border-top: var(--frame) solid var(--c-ink);
    padding-top: 1.25rem;
  }

  .page-about .about-rail .section-rail__list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 0.15rem 1rem;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .about-node__head,
  .page-about .about-rail .section-rail__link {
    transition: none;
  }
}