.page-about {
  background: var(--ink);
  color: var(--paper);
  overflow-x: hidden;
  --about-rail-w: 220px;
}

.page-about .about-top {
  padding-top: clamp(1rem, 3.5vw, 2rem);
}

/* ---------- 首屏 ---------- */
.page-about .about-hero {
  padding: clamp(1.4rem, 4vw, 2.5rem) 0 clamp(3rem, 8vw, 5.5rem);
}

.page-about .about-hero__grid {
  display: grid;
  gap: clamp(1.8rem, 5vw, 3.5rem);
  align-items: end;
}

.page-about .about-hero__tick {
  display: block;
  width: 3.25rem;
  height: 4px;
  background: var(--accent);
  margin-bottom: clamp(1rem, 3vw, 1.6rem);
}

.page-about .about-hero__eyebrow {
  margin: 0 0 1rem;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.16em;
  color: var(--accent);
}

.page-about .about-hero__title {
  margin: 0 0 1.3rem;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(2.3rem, 8.4vw, 4.4rem);
  line-height: 1.04;
  letter-spacing: -0.01em;
}

.page-about .about-hero__title span {
  display: block;
  color: var(--accent);
}

.page-about .about-hero__lede {
  margin: 0 0 0.9rem;
  max-width: 38ch;
  font-size: 1rem;
  line-height: 1.85;
  color: var(--muted);
}

.page-about .about-hero__lede--strong {
  color: var(--paper);
}

.page-about .about-hero__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.7rem;
  margin-top: 1.7rem;
}

.page-about .about-hero__media {
  position: relative;
  margin: 0;
  clip-path: polygon(0 0, 100% 0, 100% 90%, 0 100%);
}

.page-about .about-hero__media .media-frame__img {
  display: block;
  width: 100%;
  height: auto;
  object-fit: cover;
}

/* ---------- 通用章节 ---------- */
.page-about .section {
  padding-block: clamp(2.8rem, 7vw, 5.5rem);
}

.page-about .about-head {
  display: grid;
  gap: 0.55rem;
  max-width: 62ch;
}

.page-about .about-head__index {
  margin: 0;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.18em;
  color: var(--accent);
}

.page-about .about-head h2 {
  margin: 0;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(1.6rem, 4.6vw, 2.5rem);
  line-height: 1.14;
}

.page-about .about-head__note {
  margin: 0;
  color: var(--muted);
  line-height: 1.85;
  max-width: 52ch;
}

/* ---------- 01 起点 ---------- */
.page-about .about-origin__grid {
  display: grid;
  gap: 1.2rem;
}

.page-about .about-origin .chapter-mark {
  margin: 0;
  font-family: var(--font-mono);
  font-size: clamp(2.6rem, 11vw, 5.5rem);
  line-height: 0.9;
  letter-spacing: -0.02em;
  color: var(--line);
}

.page-about .about-origin__title {
  margin: 0 0 1.1rem;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(1.5rem, 4.4vw, 2.3rem);
  line-height: 1.16;
}

.page-about .about-origin__body p {
  margin: 0 0 1rem;
  line-height: 1.9;
  color: var(--muted);
  max-width: 64ch;
}

.page-about .about-origin__body p:last-child {
  margin-bottom: 0;
  color: var(--paper);
}

/* ---------- 02 时间轴 ---------- */
.page-about .about-line__grid {
  display: grid;
  gap: clamp(1.6rem, 4vw, 3rem);
  margin-top: clamp(1.8rem, 5vw, 3rem);
}

.page-about .about-rail__list {
  display: flex;
  gap: 0.5rem;
  margin: 0;
  padding: 0 0 0.4rem;
  list-style: none;
  overflow-x: auto;
}

.page-about .about-rail__link {
  display: inline-flex;
  align-items: baseline;
  gap: 0.45rem;
  padding: 0.45rem 0.7rem;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  white-space: nowrap;
  text-decoration: none;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--muted);
  transition: color 0.18s var(--ease), border-color 0.18s var(--ease);
}

.page-about .about-rail__link:hover,
.page-about .about-rail__link:focus-visible {
  color: var(--accent);
  border-color: var(--accent);
  outline: none;
}

.page-about .about-rail__year {
  color: var(--paper);
  font-weight: 700;
}

.page-about .about-node {
  padding-bottom: clamp(2.2rem, 6vw, 3.6rem);
  scroll-margin-top: 110px;
}

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

.page-about .about-node__mark {
  margin: 0 0 0.55rem;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.16em;
  color: var(--card-yellow);
  transition: color 0.18s var(--ease);
}

.page-about .about-node:target .about-node__mark {
  color: var(--accent);
}

.page-about .about-node__title {
  margin: 0 0 0.7rem;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: clamp(1.25rem, 3.4vw, 1.75rem);
  line-height: 1.22;
}

.page-about .about-node p {
  margin: 0 0 0.9rem;
  line-height: 1.9;
  color: var(--muted);
  max-width: 58ch;
}

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

.page-about .about-node__figure {
  position: relative;
  margin: 1.4rem 0 0;
  clip-path: polygon(0 0, 100% 0, 100% 100%, var(--cut) 100%, 0 calc(100% - var(--cut)));
}

.page-about .about-node__figure .media-frame__img {
  display: block;
  width: 100%;
  height: auto;
  object-fit: cover;
}

/* ---------- 03 标签分组 ---------- */
.page-about .about-tags__grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 0.75rem;
  margin: clamp(1.6rem, 4vw, 2.4rem) 0 0;
  padding: 0;
  list-style: none;
}

.page-about .about-tag-card {
  position: relative;
  padding: 1.1rem 1.1rem 1rem;
  background: var(--surface);
  border: 1px solid var(--line);
  clip-path: polygon(0 0, calc(100% - var(--cut)) 0, 100% var(--cut), 100% 100%, 0 100%);
  transition: background 0.18s var(--ease), border-color 0.18s var(--ease);
}

.page-about .about-tag-card:hover,
.page-about .about-tag-card:focus-within,
.page-about .about-tag-card:focus-visible {
  background: var(--ink-deep);
  border-color: var(--accent);
  outline: none;
}

.page-about .about-tag-card__code {
  margin: 0 0 0.5rem;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.16em;
  color: var(--accent);
}

.page-about .about-tag-card__title {
  margin: 0 0 0.45rem;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1.15rem;
  color: var(--paper);
}

.page-about .about-tag-card__desc {
  margin: 0;
  font-size: 0.9rem;
  line-height: 1.75;
  color: var(--muted);
}

.page-about .about-tag-card__sample {
  margin: 0.7rem 0 0;
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.7;
  letter-spacing: 0.04em;
  color: var(--accent);
  opacity: 0.85;
}

/* ---------- 04 团队 ---------- */
.page-about .about-team__grid {
  display: grid;
  gap: clamp(1.6rem, 4vw, 3rem);
  align-items: center;
}

.page-about .about-team__media {
  position: relative;
  margin: 0;
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - var(--cut)), calc(100% - var(--cut)) 100%, 0 100%);
}

.page-about .about-team__media .media-frame__img {
  display: block;
  width: 100%;
  height: auto;
  object-fit: cover;
}

.page-about .about-team__title {
  margin: 0.5rem 0 1.1rem;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(1.5rem, 4.2vw, 2.2rem);
  line-height: 1.16;
}

.page-about .about-team__text {
  margin: 0 0 1rem;
  line-height: 1.9;
  color: var(--muted);
  max-width: 58ch;
}

.page-about .about-team__roles {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1.1rem;
  margin: 1.7rem 0 0;
  padding: 1.3rem 0 0;
  list-style: none;
  border-top: 1px solid var(--line);
}

.page-about .about-team__role {
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.7;
  color: var(--muted);
}

.page-about .about-team__num {
  display: block;
  margin-bottom: 0.3rem;
  font-family: var(--font-mono);
  font-size: 1.7rem;
  font-weight: 700;
  line-height: 1;
  color: var(--accent);
}

/* ---------- 05 原则 ---------- */
.page-about .about-rules__inner {
  position: relative;
  padding-block: clamp(0.5rem, 2vw, 1rem);
}

.page-about .about-rules__inner::before {
  content: "";
  position: absolute;
  inset: -1rem -50vw auto;
  height: 180px;
  background: repeating-linear-gradient(135deg, rgba(28, 62, 112, 0.55) 0 1px, transparent 1px 12px);
  opacity: 0.5;
  pointer-events: none;
  z-index: 0;
}

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

.page-about .expander {
  margin-top: clamp(1.5rem, 4vw, 2.4rem);
  border-top: 1px solid var(--line);
}

.page-about .expander__item {
  border-bottom: 1px solid var(--line);
}

.page-about .expander__trigger {
  display: flex;
  align-items: center;
  gap: 0.85rem;
  width: 100%;
  padding: 1.15rem 0;
  background: none;
  border: 0;
  color: var(--paper);
  text-align: left;
  cursor: pointer;
  font-family: var(--font-display);
  font-size: clamp(1.05rem, 2.6vw, 1.35rem);
  font-weight: 700;
  transition: color 0.18s var(--ease);
}

.page-about .expander__trigger:hover {
  color: var(--accent);
}

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

.page-about .about-rule__index {
  flex: none;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--index);
}

.page-about .expander__icon {
  flex: none;
  width: 9px;
  height: 9px;
  margin-left: auto;
  border-right: 2px solid var(--accent);
  border-bottom: 2px solid var(--accent);
  transform: rotate(45deg) translate(-2px, -2px);
  transition: transform 0.18s var(--ease);
}

.page-about .expander__trigger[aria-expanded="true"] .expander__icon {
  transform: rotate(135deg) translate(-2px, -2px);
}

.page-about .expander__panel {
  padding: 0 0 1.35rem;
}

.page-about .expander__panel p {
  margin: 0;
  max-width: 62ch;
  line-height: 1.9;
  color: var(--muted);
}

/* ---------- 06 一起维护 ---------- */
.page-about .about-join__inner {
  display: grid;
  gap: 0.6rem;
  max-width: 72ch;
}

.page-about .about-join__title {
  margin: 0 0 0.5rem;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(1.6rem, 4.4vw, 2.4rem);
  line-height: 1.14;
}

.page-about .about-join__text {
  margin: 0;
  line-height: 1.9;
  color: var(--muted);
  max-width: 60ch;
}

.page-about .about-join__cards {
  display: grid;
  gap: 0.75rem;
  margin-top: 1.5rem;
}

.page-about .about-join__card {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 1.15rem 1.25rem;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  color: var(--paper);
  text-decoration: none;
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.06em;
  transition: border-color 0.18s var(--ease), color 0.18s var(--ease);
}

.page-about .about-join__card:hover,
.page-about .about-join__card:focus-visible {
  border-color: var(--accent);
  color: var(--accent);
  outline: none;
}

.page-about .about-join__foot {
  margin: 1.2rem 0 0;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--index);
}

.page-about .about-join__foot a {
  color: var(--accent);
  text-decoration: none;
  border-bottom: 1px solid currentColor;
}

/* ---------- 断点 ---------- */
@media (min-width: 640px) {
  .page-about .about-tags__grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

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

@media (min-width: 900px) {
  .page-about .about-hero__grid {
    grid-template-columns: minmax(0, 7fr) minmax(0, 5fr);
  }

  .page-about .about-origin__grid {
    grid-template-columns: minmax(0, 3fr) minmax(0, 7fr);
    gap: 2rem;
  }

  .page-about .about-line__grid {
    grid-template-columns: minmax(0, 3fr) minmax(0, 7fr);
    gap: clamp(2rem, 5vw, 4.5rem);
  }

  .page-about .about-rail {
    align-self: start;
    position: sticky;
    top: 108px;
  }

  .page-about .about-rail__list {
    flex-direction: column;
    gap: 0;
    overflow: visible;
    padding: 0.3rem 0 0.3rem 1.15rem;
    position: relative;
  }

  .page-about .about-rail__list::before {
    content: "";
    position: absolute;
    left: 0;
    top: 0.9rem;
    bottom: 0.9rem;
    width: 1px;
    background: var(--line);
  }

  .page-about .about-rail__link {
    border: 0;
    border-radius: 0;
    padding: 0.5rem 0;
    position: relative;
    background: none;
  }

  .page-about .about-rail__link::before {
    content: "";
    position: absolute;
    left: -1.15rem;
    top: 50%;
    width: 7px;
    height: 7px;
    margin-top: -3px;
    border-radius: 50%;
    background: var(--line);
    transition: background 0.18s var(--ease), box-shadow 0.18s var(--ease);
  }

  .page-about .about-rail__link:hover::before,
  .page-about .about-rail__link:focus-visible::before {
    background: var(--accent);
    box-shadow: 0 0 0 3px rgba(255, 107, 44, 0.22);
  }

  .page-about .about-team__grid {
    grid-template-columns: minmax(0, 5fr) minmax(0, 7fr);
    gap: clamp(2rem, 5vw, 4rem);
  }

  .page-about .about-team__roles {
    grid-template-columns: repeat(5, minmax(0, 1fr));
  }
}

@media (min-width: 1000px) {
  .page-about .about-tags__grid {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .page-about .about-tag-card__sample {
    max-height: 0;
    opacity: 0;
    margin-top: 0;
    overflow: hidden;
    transition: max-height 0.18s var(--ease), opacity 0.18s var(--ease), margin-top 0.18s var(--ease);
  }

  .page-about .about-tag-card:hover .about-tag-card__sample,
  .page-about .about-tag-card:focus-within .about-tag-card__sample,
  .page-about .about-tag-card:focus-visible .about-tag-card__sample {
    max-height: 4.5rem;
    opacity: 1;
    margin-top: 0.7rem;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .about-tag-card__sample,
  .page-about .expander__icon,
  .page-about .about-rail__link,
  .page-about .about-join__card {
    transition: none;
  }
}