.page-about {
  --about-rail-w: 12.5rem;
  --about-gap: clamp(1.5rem, 4vw, 3.25rem);
}

/* ---------- 首屏 ---------- */
.page-about .about-hero__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: clamp(1.5rem, 4vw, 2.75rem);
  align-items: end;
  padding-block: 1rem clamp(1.5rem, 4vw, 2.5rem);
}

.page-about .about-hero__title {
  font-family: var(--font-heading);
  font-size: clamp(2.1rem, 5.6vw, 4.2rem);
  line-height: 1.04;
  letter-spacing: -0.01em;
  margin: 0.6rem 0 0;
  max-width: 18ch;
}

.page-about .about-hero__lede {
  margin: 1.1rem 0 0;
  max-width: 40ch;
}

.page-about .about-hero__stats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: 0;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}

.page-about .about-hero__stat {
  background: var(--ink-800);
  padding: 0.85rem 1rem 1rem;
}

.page-about .about-hero__stat dt {
  font-size: 0.75rem;
  letter-spacing: 0.08em;
  color: var(--text-2);
}

.page-about .about-hero__stat dd {
  margin: 0.4rem 0 0;
  font-family: var(--font-data);
  font-size: 1.35rem;
  line-height: 1.2;
  color: var(--text-1);
}

.page-about .about-hero__figure {
  margin-block: clamp(0.5rem, 2vw, 1.25rem) clamp(1.5rem, 4vw, 3rem);
}

/* ---------- 主体：左轨道 + 右长文 ---------- */
.page-about .about-body {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--about-gap);
  padding-block: clamp(1.5rem, 5vw, 3.5rem) clamp(3rem, 8vw, 6rem);
  align-items: start;
}

.page-about .about-rail {
  border-bottom: 1px solid var(--line);
  padding-bottom: 0.75rem;
}

.page-about .about-rail__title {
  margin: 0 0 0.6rem;
  color: var(--text-2);
}

.page-about .about-rail__list {
  display: flex;
  gap: 0.4rem;
  margin: 0;
  padding: 0 0 0.25rem;
  list-style: none;
  overflow-x: auto;
  scrollbar-width: thin;
}

.page-about .about-rail__item {
  flex: 0 0 auto;
}

.page-about .about-rail__link {
  display: block;
  padding: 0.5rem 0.7rem;
  border-left: 2px solid transparent;
  border-radius: 0 var(--radius) var(--radius) 0;
  color: var(--text-2);
  text-decoration: none;
  transition: color 150ms var(--ease), background-color 150ms var(--ease), border-color 150ms var(--ease);
}

.page-about .about-rail__link:hover,
.page-about .about-rail__link:focus-visible {
  color: var(--text-1);
  background: var(--glass);
}

.page-about .about-rail__link:focus-visible {
  outline: 2px solid var(--flag-blue);
  outline-offset: 1px;
}

.page-about .about-rail__link.is-active {
  color: var(--text-1);
  background: var(--glass);
  border-left-color: var(--flag-blue);
}

.page-about .about-rail__year {
  display: block;
  font-size: 0.8125rem;
  letter-spacing: 0.06em;
  color: var(--flag-blue);
}

.page-about .about-rail__label {
  display: block;
  margin-top: 0.1rem;
  font-size: 0.875rem;
  white-space: nowrap;
}

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

/* ---------- 章节 ---------- */
.page-about .about-stage {
  scroll-margin-top: calc(var(--header-h) + 1.25rem);
}

.page-about .about-stage + .about-stage {
  margin-top: clamp(2.5rem, 7vw, 5rem);
  padding-top: clamp(2rem, 5vw, 3.5rem);
  border-top: 1px solid var(--line);
}

.page-about .about-stage__head {
  margin-bottom: 1.25rem;
}

.page-about .about-stage__head h2 {
  font-family: var(--font-heading);
  font-size: clamp(1.55rem, 3.6vw, 2.35rem);
  line-height: 1.14;
  letter-spacing: -0.005em;
  margin: 0.4rem 0 0;
  max-width: 22ch;
}

.page-about .yt-prose {
  max-width: 37em;
  margin: 0 0 1.4rem;
  line-height: 1.8;
  color: var(--text-2);
}

.page-about .yt-prose a,
.page-about .about-stage__foot a {
  color: var(--flag-blue);
  text-decoration: none;
  border-bottom: 1px solid rgba(58, 143, 224, 0.45);
}

.page-about .yt-prose a:hover,
.page-about .about-stage__foot a:hover {
  border-bottom-color: var(--flag-blue);
}

.page-about .about-stage__foot {
  margin: 1.25rem 0 0;
  font-size: 0.9375rem;
  color: var(--text-2);
}

.page-about .about-stage__figure {
  margin: 1.75rem 0 0;
}

/* ---------- 时间线 ---------- */
.page-about .about-timeline {
  list-style: none;
  margin: 0;
  padding: 0 0 0 1.35rem;
  border-left: 1px solid var(--line);
}

.page-about .about-timeline__item {
  position: relative;
  padding-bottom: 1.6rem;
}

.page-about .about-timeline__item:last-child {
  padding-bottom: 0;
}

.page-about .about-timeline__item::before {
  content: "";
  position: absolute;
  left: calc(-1.35rem - 4px);
  top: 0.45rem;
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--flag-blue);
  box-shadow: 0 0 0 3px var(--ink-900);
}

.page-about .about-timeline__item:nth-child(2)::before {
  background: var(--flag-green);
}

.page-about .about-timeline__item:nth-child(3)::before {
  background: var(--flag-yellow);
}

.page-about .about-timeline__item:nth-child(4)::before {
  background: var(--flag-red);
}

.page-about .about-timeline__meta {
  margin: 0 0 0.3rem;
  font-family: var(--font-data);
  font-size: 0.8125rem;
  letter-spacing: 0.08em;
  color: var(--text-2);
}

.page-about .about-timeline__year {
  color: var(--flag-blue);
}

.page-about .about-timeline__item h3 {
  margin: 0 0 0.35rem;
  font-family: var(--font-heading);
  font-size: 1.15rem;
  letter-spacing: 0.01em;
}

.page-about .about-timeline__item p {
  margin: 0;
  max-width: 36em;
  color: var(--text-2);
  line-height: 1.8;
}

.page-about .about-timeline__item a {
  color: var(--flag-blue);
  text-decoration: none;
  border-bottom: 1px solid rgba(58, 143, 224, 0.45);
}

/* ---------- 团队卡片 ---------- */
.page-about .about-teams {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--gap);
  margin-top: 0.5rem;
}

.page-about .about-team {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  padding: 1.35rem 1.1rem 1.25rem;
  background: var(--ink-700);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  transition: transform 180ms var(--ease), background-color 180ms var(--ease), border-color 180ms var(--ease);
}

.page-about .about-team::before {
  content: "";
  position: absolute;
  inset: 0 0 auto 0;
  height: 2px;
  background: var(--flag-blue);
}

.page-about .about-team:nth-child(2)::before {
  background: var(--flag-green);
}

.page-about .about-team:nth-child(3)::before {
  background: var(--flag-yellow);
}

.page-about .about-team:nth-child(4)::before {
  background: var(--flag-white);
}

.page-about .about-team:hover,
.page-about .about-team:focus-within,
.page-about .about-team:focus {
  transform: translateY(-2px);
  background: var(--ink-600);
  border-color: var(--line-strong);
}

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

.page-about .about-team__num {
  margin: 0;
  font-size: 0.8125rem;
  letter-spacing: 0.08em;
  color: var(--flag-blue);
}

.page-about .about-team h3 {
  margin: 0;
  font-size: 1.0625rem;
}

.page-about .about-team__role {
  margin: 0;
  font-size: 0.8125rem;
  letter-spacing: 0.04em;
  color: var(--stone);
}

.page-about .about-team__more {
  margin: 0;
  max-height: 0;
  overflow: hidden;
  opacity: 0;
  font-size: 0.9rem;
  line-height: 1.75;
  color: var(--text-2);
  transition: max-height 200ms var(--ease), opacity 200ms var(--ease), margin-top 200ms var(--ease);
}

.page-about .about-team:hover .about-team__more,
.page-about .about-team:focus .about-team__more,
.page-about .about-team:focus-within .about-team__more {
  max-height: 14rem;
  opacity: 1;
  margin-top: 0.5rem;
}

@media (hover: none) {
  .page-about .about-team__more {
    max-height: none;
    opacity: 1;
    margin-top: 0.5rem;
  }
}

/* ---------- 三道手 ---------- */
.page-about .about-steps {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: 1fr;
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}

.page-about .about-steps__item {
  background: var(--ink-800);
  padding: 1.25rem 1.25rem 1.5rem;
}

.page-about .about-steps__index {
  display: block;
  font-size: 1.5rem;
  letter-spacing: 0.04em;
  color: var(--flag-blue);
}

.page-about .about-steps__item:nth-child(2) .about-steps__index {
  color: var(--flag-yellow);
}

.page-about .about-steps__item:nth-child(3) .about-steps__index {
  color: var(--flag-green);
}

.page-about .about-steps__item h3 {
  margin: 0.5rem 0 0.4rem;
  font-size: 1.0625rem;
}

.page-about .about-steps__item p {
  margin: 0;
  font-size: 0.9375rem;
  line-height: 1.8;
  color: var(--text-2);
}

.page-about .about-conflict {
  margin-top: var(--gap);
  padding: 1rem 1.2rem;
  background: var(--glass);
  border-left: 2px solid var(--flag-yellow);
  border-radius: 0 var(--radius) var(--radius) 0;
}

.page-about .about-conflict__key {
  margin: 0 0 0.4rem;
  color: var(--flag-yellow);
}

.page-about .about-conflict p:last-child {
  margin: 0;
  max-width: 36em;
  font-size: 0.9375rem;
  line-height: 1.8;
  color: var(--text-2);
}

/* ---------- 四类并置 ---------- */
.page-about .about-desk {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  margin-bottom: 1.4rem;
}

.page-about .about-desk__item {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 0.65rem;
  background: var(--ink-800);
  padding: 1.1rem 1.1rem 1.25rem;
}

.page-about .about-desk__item p {
  margin: 0;
  font-size: 0.9375rem;
  line-height: 1.8;
  color: var(--text-2);
}

/* ---------- 使用者 ---------- */
.page-about .about-audience {
  list-style: none;
  margin: 0 0 1.5rem;
  padding: 0;
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--gap);
}

.page-about .about-audience__item {
  padding-top: 1rem;
  border-top: 2px solid var(--line-strong);
}

.page-about .about-audience__item:nth-child(1) {
  border-top-color: var(--flag-blue);
}

.page-about .about-audience__item:nth-child(2) {
  border-top-color: var(--flag-green);
}

.page-about .about-audience__item:nth-child(3) {
  border-top-color: var(--flag-yellow);
}

.page-about .about-audience__num {
  margin: 0 0 0.5rem;
  font-size: 0.8125rem;
  letter-spacing: 0.08em;
  color: var(--text-2);
}

.page-about .about-audience__item h3 {
  margin: 0 0 0.45rem;
  font-family: var(--font-heading);
  font-size: 1.15rem;
}

.page-about .about-audience__item p {
  margin: 0;
  font-size: 0.9375rem;
  line-height: 1.8;
  color: var(--text-2);
}

.page-about .about-next {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.75rem;
  margin-top: clamp(1.5rem, 4vw, 2.25rem);
}

.page-about .about-next a:focus-visible {
  outline: 2px solid var(--flag-blue);
  outline-offset: 2px;
}

/* ---------- 桌面增强 ---------- */
@media (min-width: 720px) {
  .page-about .about-teams {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .page-about .about-desk {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

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

  .page-about .about-hero__stats {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (min-width: 860px) {
  .page-about .about-steps {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

@media (min-width: 960px) {
  .page-about .about-hero__grid {
    grid-template-columns: minmax(0, 1.65fr) minmax(0, 1fr);
    gap: var(--about-gap);
  }

  .page-about .about-hero__stats {
    grid-template-columns: 1fr;
  }

  .page-about .about-body {
    grid-template-columns: var(--about-rail-w) minmax(0, 1fr);
  }

  .page-about .about-rail {
    position: sticky;
    top: calc(var(--header-h) + 1.5rem);
    align-self: start;
    max-height: calc(100vh - var(--header-h) - 3rem);
    overflow: auto;
    border-bottom: 0;
    padding-bottom: 0;
  }

  .page-about .about-rail__list {
    flex-direction: column;
    gap: 0;
    overflow: visible;
    padding-bottom: 0;
  }

  .page-about .about-rail__item {
    flex: none;
  }

  .page-about .about-rail__link {
    padding: 0.6rem 0.75rem;
  }

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

@media (min-width: 1200px) {
  .page-about .about-teams {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

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

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