.page-about {
  --about-rail: 218px;
  --about-soft: #E3E9EE;
  --about-soft-2: #EDF1F5;
  background: var(--surface);
  color: var(--text);
}

.page-about [hidden] {
  display: none !important;
}

/* ---------- 框景首屏 ---------- */
.page-about .about-hero {
  max-width: var(--wrap);
  margin: 0 auto;
  padding: 26px var(--gutter) 0;
}

.page-about .about-hero__scale {
  display: inline-block;
  margin: 0 0 -1px 16px;
  padding: 4px 10px;
  position: relative;
  z-index: 1;
  background: var(--paper);
  border: 1px solid var(--line);
  border-bottom: 0;
  border-radius: var(--r) var(--r) 0 0;
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.4;
  letter-spacing: 0.06em;
  color: var(--muted);
}

.page-about .about-hero__frame {
  position: relative;
  padding: 22px 20px 28px;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 0 var(--r) var(--r) var(--r);
  overflow: hidden;
}

.page-about .about-hero__frame::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  height: 5px;
  border-top: 1px solid var(--line);
  background-image: repeating-linear-gradient(90deg, var(--line) 0 1px, transparent 1px 14px);
  opacity: 0.8;
  pointer-events: none;
}

.page-about .about-hero__title {
  margin: 16px 0 0;
  font-family: var(--font-display);
  font-size: clamp(27px, 6.2vw, 40px);
  line-height: 1.16;
  font-weight: 800;
  letter-spacing: -0.01em;
  color: var(--text);
}

.page-about .about-hero__lede {
  max-width: 62ch;
  margin: 14px 0 0;
  font-size: 16px;
  line-height: 1.7;
  color: var(--text);
}

.page-about .about-hero__meter {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: 24px 0 0;
  border: 1px solid var(--line);
  border-radius: var(--r);
  background: var(--line);
  overflow: hidden;
}

.page-about .about-hero__meter > div {
  padding: 12px 14px;
  background: var(--surface);
}

.page-about .about-hero__meter dt {
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.4;
  letter-spacing: 0.06em;
  color: var(--muted);
}

.page-about .about-hero__meter dd {
  margin: 6px 0 0;
  font-family: var(--font-mono);
  font-size: 17px;
  line-height: 1.3;
  font-weight: 700;
  color: var(--text);
}

/* ---------- 索引栏 + 叙事主栏 ---------- */
.page-about .about-shell {
  max-width: var(--wrap);
  margin: 0 auto;
  padding: 32px var(--gutter) 72px;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 28px;
}

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

.page-about .about-rail__title {
  margin: 0 0 10px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--muted);
  text-transform: uppercase;
}

.page-about .rail-nav {
  list-style: none;
  margin: 0;
  padding: 0;
}

.page-about .rail-link {
  display: grid;
  grid-template-columns: 34px minmax(0, 1fr);
  align-items: baseline;
  gap: 8px;
  padding: 9px 2px 9px 13px;
  border-left: 2px solid var(--line);
  color: var(--text);
  text-decoration: none;
  font-size: 15px;
  line-height: 1.4;
  transition: border-color var(--dur) var(--ease), color var(--dur) var(--ease);
}

.page-about .rail-link:hover,
.page-about .rail-link:focus-visible {
  border-left-color: var(--cyan);
  color: var(--cyan-ink);
}

.page-about .rail-link__num {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--muted);
}

.page-about .about-flow {
  min-width: 0;
  display: grid;
  gap: 24px;
}

/* ---------- 区块外壳 ---------- */
.page-about .about-sec {
  padding: 24px 20px;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: var(--r);
  scroll-margin-top: calc(var(--header-h) + 16px);
}

.page-about .about-sec__head {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 12px;
  align-items: baseline;
  padding-bottom: 14px;
  margin-bottom: 20px;
  border-bottom: 1px solid var(--line);
}

.page-about .about-sec__num {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--cyan-ink);
}

.page-about .about-sec__title {
  margin: 0;
  font-family: var(--font-display);
  font-size: 20px;
  line-height: 1.3;
  font-weight: 800;
  color: var(--text);
}

.page-about .about-sec__note {
  margin: 18px 0 0;
  font-size: 14px;
  line-height: 1.65;
  color: var(--muted);
}

.page-about .about-sec__note a {
  color: var(--blue);
  text-decoration: underline;
  text-underline-offset: 3px;
}

/* ---------- 01 主张 ---------- */
.page-about .claim-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 24px;
}

.page-about .claim-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 20px;
}

.page-about .claim-item {
  position: relative;
  padding-left: 22px;
}

.page-about .claim-item::before {
  content: "";
  position: absolute;
  left: 0;
  top: 9px;
  width: 12px;
  height: 3px;
  background: var(--orange);
}

.page-about .claim-item__key {
  display: block;
  font-family: var(--font-mono);
  font-size: 13px;
  line-height: 1.5;
  letter-spacing: 0.06em;
  font-weight: 700;
  color: var(--text);
}

.page-about .claim-item__text {
  margin: 6px 0 0;
  font-size: 16px;
  line-height: 1.7;
  color: var(--text);
}

.page-about .claim-item__how {
  margin: 8px 0 0;
  padding-left: 10px;
  border-left: 3px solid var(--cyan);
  font-size: 14px;
  line-height: 1.65;
  color: var(--muted);
}

.page-about .about-fig {
  margin: 0;
}

/* ---------- 02 团队 ---------- */
.page-about .team-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 14px;
}

.page-about .team-card {
  padding: 18px 16px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-left: 3px solid var(--line);
  border-radius: var(--r);
  transition: border-left-color var(--dur) var(--ease);
}

.page-about .team-card:hover {
  border-left-color: var(--cyan);
}

.page-about .team-card--lead {
  background: var(--paper);
  border-left-color: var(--orange);
}

.page-about .team-card__head {
  display: flex;
  align-items: baseline;
  gap: 4px;
}

.page-about .team-card__num {
  font-family: var(--font-mono);
  font-size: 34px;
  line-height: 1;
  font-weight: 700;
  color: var(--text);
}

.page-about .team-card__unit {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--muted);
}

.page-about .team-card__title {
  margin: 10px 0 0;
  font-family: var(--font-display);
  font-size: 17px;
  line-height: 1.4;
  font-weight: 700;
  color: var(--text);
}

.page-about .team-card__text {
  margin: 8px 0 0;
  font-size: 15px;
  line-height: 1.7;
  color: var(--muted);
}

.page-about .team-note {
  margin: 18px 0 0;
  padding-top: 14px;
  border-top: 1px dashed var(--line);
  font-size: 14px;
  line-height: 1.7;
  color: var(--muted);
}

/* ---------- 03 版本档案 ---------- */
.page-about .ver-figure {
  margin-bottom: 28px;
}

.page-about .ver-list {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 22px;
}

.page-about .ver-card {
  position: relative;
  padding: 24px 18px 18px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--r);
  box-shadow: 0 5px 0 -1px var(--about-soft), 0 10px 0 -3px var(--about-soft-2);
}

.page-about .ver-card--now {
  border-color: var(--cyan-ink);
}

.page-about .ver-card--now .ver-card__badge {
  border-color: var(--cyan-ink);
  color: var(--cyan-ink);
}

.page-about .ver-card__badge {
  position: absolute;
  top: 0;
  left: 16px;
  transform: translateY(-50%);
  padding: 3px 9px;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: var(--r);
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.4;
  letter-spacing: 0.06em;
  font-weight: 700;
  color: var(--muted);
}

.page-about .ver-card__phase {
  display: block;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--muted);
}

.page-about .ver-card__title {
  margin: 8px 0 0;
  font-family: var(--font-display);
  font-size: 17px;
  line-height: 1.45;
  font-weight: 700;
  color: var(--text);
}

.page-about .ver-card__text {
  margin: 8px 0 0;
  font-size: 15px;
  line-height: 1.7;
  color: var(--text);
}

.page-about .fold {
  margin-top: 14px;
  padding-top: 12px;
  border-top: 1px solid var(--line);
}

.page-about .fold__btn {
  display: flex;
  align-items: center;
  gap: 10px;
  width: 100%;
  padding: 0;
  background: transparent;
  border: 0;
  cursor: pointer;
  font-family: var(--font-body);
  font-size: 14px;
  line-height: 1.5;
  color: var(--muted);
  text-align: left;
  transition: color var(--dur) var(--ease);
}

.page-about .fold__btn:hover,
.page-about .fold__btn:focus-visible {
  color: var(--cyan-ink);
}

.page-about .fold__idx {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--cyan-ink);
  padding-left: 12px;
  border-left: 2px solid var(--cyan);
}

.page-about .ver-copy {
  margin-top: 12px;
  padding: 6px 12px;
  background: transparent;
  border: 1px solid var(--line);
  border-radius: var(--r);
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.4;
  letter-spacing: 0.06em;
  color: var(--muted);
  cursor: pointer;
  transition: border-color var(--dur) var(--ease), color var(--dur) var(--ease);
}

.page-about .ver-copy:hover,
.page-about .ver-copy:focus-visible {
  border-color: var(--cyan);
  color: var(--cyan-ink);
}

/* ---------- 04 维护机制（深色区） ---------- */
.page-about .about-sec--dark {
  background: var(--ink);
  border-color: #223041;
}

.page-about .about-sec--dark .about-sec__head {
  border-bottom-color: rgba(195, 205, 214, 0.22);
}

.page-about .about-sec--dark .about-sec__num {
  color: var(--cyan);
}

.page-about .about-sec--dark .about-sec__title {
  color: var(--on-dark);
}

.page-about .mech-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 16px;
}

.page-about .mech-item {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 6px;
  padding-bottom: 16px;
  border-bottom: 1px solid rgba(195, 205, 214, 0.18);
}

.page-about .mech-item:last-child {
  padding-bottom: 0;
  border-bottom: 0;
}

.page-about .mech-item__key {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--cyan);
}

.page-about .mech-item__text {
  margin: 0;
  font-size: 15px;
  line-height: 1.72;
  color: var(--on-dark);
}

.page-about .mech-links {
  margin: 20px 0 0;
  display: flex;
  flex-wrap: wrap;
  gap: 10px 22px;
}

.page-about .mech-links a {
  color: var(--cyan);
  font-size: 14px;
  text-decoration: underline;
  text-decoration-color: rgba(0, 229, 200, 0.45);
  text-underline-offset: 4px;
}

.page-about .mech-links a:hover,
.page-about .mech-links a:focus-visible {
  text-decoration-color: var(--cyan);
}

/* ---------- 05 边界说明 ---------- */
.page-about .edge-figure {
  margin: 0 0 22px;
}

.page-about .filter-bar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  margin-bottom: 14px;
}

.page-about .filter-bar__label {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--muted);
  margin-right: 2px;
}

.page-about .filter-btn {
  padding: 6px 14px;
  background: transparent;
  border: 1px solid var(--line);
  border-radius: 999px;
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.4;
  letter-spacing: 0.06em;
  color: var(--muted);
  cursor: pointer;
  transition: background var(--dur) var(--ease), border-color var(--dur) var(--ease), color var(--dur) var(--ease);
}

.page-about .filter-btn:hover,
.page-about .filter-btn:focus-visible {
  border-color: var(--orange);
  color: var(--orange-ink);
}

.page-about .filter-btn[aria-pressed="true"] {
  background: var(--orange);
  border-color: var(--orange);
  color: var(--ink);
}

.page-about .edge-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 1px;
  border: 1px solid var(--line);
  border-radius: var(--r);
  background: var(--line);
  overflow: hidden;
}

.page-about .edge-item {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 4px;
  padding: 14px 16px;
  background: var(--paper);
}

.page-about .edge-item__tag {
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.4;
  letter-spacing: 0.06em;
  color: var(--cyan-ink);
}

.page-about .edge-item__text {
  margin: 0;
  font-size: 15px;
  line-height: 1.72;
  color: var(--text);
}

/* ---------- 06 接着看 ---------- */
.page-about .next-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 1px;
  border: 1px solid var(--line);
  border-radius: var(--r);
  background: var(--line);
  overflow: hidden;
}

.page-about .next-link {
  display: grid;
  grid-template-columns: 34px minmax(0, 1fr);
  align-items: baseline;
  gap: 10px;
  padding: 15px 16px;
  background: var(--paper);
  text-decoration: none;
  color: var(--text);
  transition: background var(--dur) var(--ease);
}

.page-about .next-link:hover,
.page-about .next-link:focus-visible {
  background: var(--surface);
}

.page-about .next-link__num {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--cyan-ink);
}

.page-about .next-link__text {
  font-size: 15px;
  line-height: 1.6;
}

/* ---------- 响应式 ---------- */
@media (max-width: 979px) {
  .page-about .about-rail {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
  }

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

  .page-about .about-rail__title {
    display: none;
  }

  .page-about .rail-nav {
    display: flex;
    gap: 8px;
    width: max-content;
  }

  .page-about .rail-link {
    grid-template-columns: auto auto;
    gap: 6px;
    padding: 7px 14px;
    border: 1px solid var(--line);
    border-radius: 999px;
    white-space: nowrap;
    font-size: 14px;
  }

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

@media (min-width: 620px) {
  .page-about .about-hero__meter {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

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

  .page-about .team-card--lead {
    grid-column: span 2;
  }

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

  .page-about .mech-item {
    grid-template-columns: 76px minmax(0, 1fr);
    gap: 14px;
    align-items: start;
  }
}

@media (min-width: 720px) {
  .page-about .about-sec {
    padding: 30px 30px 28px;
  }

  .page-about .about-sec__title {
    font-size: 22px;
    line-height: 1.28;
  }

  .page-about .edge-item {
    grid-template-columns: 76px minmax(0, 1fr);
    gap: 14px;
    align-items: start;
  }

  .page-about .claim-item__text {
    font-size: 17px;
  }
}

@media (min-width: 900px) {
  .page-about .about-hero__frame {
    padding: 28px 30px 32px;
  }

  .page-about .claim-layout {
    grid-template-columns: minmax(0, 1.05fr) minmax(0, 0.85fr);
    gap: 30px;
    align-items: start;
  }

  .page-about .ver-list {
    gap: 28px;
  }
}

@media (min-width: 980px) {
  .page-about .about-shell {
    grid-template-columns: var(--about-rail) minmax(0, 1fr);
    gap: 46px;
    align-items: start;
  }

  .page-about .about-rail__inner {
    position: sticky;
    top: calc(var(--header-h) + 20px);
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .rail-link,
  .page-about .team-card,
  .page-about .filter-btn,
  .page-about .next-link,
  .page-about .ver-copy,
  .page-about .fold__btn {
    transition: none;
  }
}