.page-about {
  --ab-red-soft: rgba(184, 56, 74, 0.55);
  --ab-red-faint: rgba(184, 56, 74, 0.14);
  --ab-card-bg: rgba(12, 16, 32, 0.66);
}

/* ---------- 首屏 ---------- */
.page-about .ab-hero {
  position: relative;
  overflow: hidden;
  padding: clamp(36px, 7vw, 88px) 0 clamp(40px, 6vw, 76px);
  background:
    radial-gradient(120% 90% at 88% 0%, rgba(162, 91, 255, 0.20), transparent 62%),
    radial-gradient(90% 70% at 2% 100%, rgba(184, 56, 74, 0.24), transparent 60%),
    linear-gradient(180deg, var(--ink) 0%, var(--nebula) 100%);
}

.page-about .ab-hero__stars {
  position: absolute;
  inset: 0;
  pointer-events: none;
  background-image:
    radial-gradient(1.6px 1.6px at 16% 22%, rgba(242, 245, 247, 0.55), transparent 100%),
    radial-gradient(1.4px 1.4px at 71% 14%, rgba(53, 224, 214, 0.55), transparent 100%),
    radial-gradient(1.2px 1.2px at 44% 58%, rgba(242, 245, 247, 0.34), transparent 100%),
    radial-gradient(1.6px 1.6px at 86% 48%, rgba(162, 91, 255, 0.5), transparent 100%),
    radial-gradient(1.2px 1.2px at 30% 84%, rgba(232, 184, 75, 0.45), transparent 100%);
  opacity: 0.9;
}

.page-about .ab-hero__inner {
  position: relative;
  z-index: 1;
}

.page-about .ab-hero__index {
  margin: 22px 0 14px;
  font-size: 12px;
  letter-spacing: 0.18em;
  color: var(--flag-yellow);
}

.page-about .ab-hero__title {
  margin: 0;
  font-weight: 900;
  font-size: clamp(40px, 10.5vw, 94px);
  line-height: 1.04;
  letter-spacing: -0.02em;
  color: var(--paper);
}

.page-about .ab-hero__line {
  display: block;
}

.page-about .ab-hero__line--em {
  background: linear-gradient(100deg, var(--flag-red) 0%, var(--violet) 52%, var(--cyan) 100%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.page-about .ab-hero__lede {
  margin: clamp(20px, 3vw, 30px) 0 0;
  max-width: 34em;
  font-size: clamp(15px, 1.9vw, 18px);
  line-height: 1.85;
  color: rgba(242, 245, 247, 0.78);
}

.page-about .ab-hero__tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 26px 0 0;
  padding: 0;
  list-style: none;
}

/* ---------- 主体分栏 ---------- */
.page-about .ab-stage {
  padding-top: clamp(28px, 5vw, 64px);
  padding-bottom: clamp(56px, 8vw, 112px);
}

/* 移动端：横向滚动章节索引 */
.page-about .ab-rail {
  position: sticky;
  top: var(--header-h);
  z-index: 4;
  margin: 0 0 22px;
  padding: 12px 0;
  background: linear-gradient(180deg, rgba(7, 10, 20, 0.96) 72%, rgba(7, 10, 20, 0));
}

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

.page-about .ab-rail__list {
  display: flex;
  gap: 8px;
  margin: 0;
  padding: 0 0 4px;
  list-style: none;
  overflow-x: auto;
  scrollbar-width: none;
  -webkit-overflow-scrolling: touch;
}

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

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

.page-about .ab-rail__link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  white-space: nowrap;
  padding: 7px 14px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: rgba(242, 245, 247, 0.03);
  color: var(--mist);
  font-size: 13px;
  line-height: 1.4;
  text-decoration: none;
  transition: color 0.24s var(--ease), border-color 0.24s var(--ease), background 0.24s var(--ease);
}

.page-about .ab-rail__link:hover,
.page-about .ab-rail__link:focus-visible {
  color: var(--paper);
  border-color: var(--line-strong);
  background: rgba(53, 224, 214, 0.09);
  outline: none;
}

.page-about .ab-rail__dot,
.page-about .ab-rail__idx {
  display: none;
}

/* ---------- 章节通用 ---------- */
.page-about .ab-sec {
  position: relative;
  padding-bottom: clamp(48px, 7vw, 96px);
  scroll-margin-top: calc(var(--header-h) + 56px);
}

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

.page-about .ab-sec__head {
  display: flex;
  align-items: baseline;
  gap: 12px;
  margin-bottom: clamp(16px, 3vw, 26px);
  padding-bottom: 12px;
  border-bottom: 1px solid var(--line);
}

.page-about .ab-sec__idx {
  flex: none;
  margin: 0;
  font-size: 12px;
  letter-spacing: 0.16em;
  color: var(--flag-red);
}

.page-about .ab-sec__title {
  margin: 0;
  font-size: clamp(23px, 4.4vw, 34px);
  font-weight: 800;
  line-height: 1.24;
  letter-spacing: -0.01em;
  color: var(--paper);
}

.page-about .ab-sec__body {
  font-size: 16px;
  line-height: 1.88;
  color: rgba(242, 245, 247, 0.8);
}

.page-about .ab-sec__body p {
  margin: 0 0 1.15em;
  max-width: 34em;
}

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

.page-about .ab-lead {
  font-size: clamp(17px, 2.2vw, 20px);
  line-height: 1.8;
  color: var(--paper);
}

.page-about .ab-aside {
  margin-top: 1.4em;
  padding: 16px 18px;
  border-left: 2px solid var(--flag-red);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  background: rgba(184, 56, 74, 0.07);
  font-size: 14px;
  line-height: 1.8;
  color: var(--mist);
}

.page-about .ab-aside a {
  color: var(--cyan);
  text-decoration: none;
  border-bottom: 1px solid rgba(53, 224, 214, 0.4);
  transition: color 0.2s var(--ease), border-color 0.2s var(--ease);
}

.page-about .ab-aside a:hover,
.page-about .ab-aside a:focus-visible {
  color: var(--paper);
  border-bottom-color: var(--paper);
  outline: none;
}

/* ---------- 服务对象 ---------- */
.page-about .ab-who {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
  margin-top: 28px;
}

.page-about .ab-who__item {
  padding: 18px 20px;
  border: 1px solid var(--line);
  border-radius: var(--radius-md);
  background: var(--ab-card-bg);
  transition: border-color 0.26s var(--ease), transform 0.26s var(--ease);
}

.page-about .ab-who__item:hover {
  border-color: rgba(53, 224, 214, 0.4);
  transform: translateY(-4px);
}

.page-about .ab-who__t {
  margin: 0 0 6px;
  font-size: 15px;
  font-weight: 700;
  color: var(--paper);
}

.page-about .ab-who__d {
  margin: 0;
  font-size: 14px;
  line-height: 1.75;
  color: var(--mist);
}

/* ---------- 分类折叠 ---------- */
.page-about .ab-clusters {
  margin: 26px 0 0;
  border-top: 1px solid var(--line);
}

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

.page-about .ab-cluster__sum {
  display: flex;
  align-items: baseline;
  gap: 12px;
  padding: 16px 30px 16px 0;
  cursor: pointer;
  list-style: none;
  position: relative;
  transition: color 0.22s var(--ease);
}

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

.page-about .ab-cluster__sum::after {
  content: "+";
  position: absolute;
  right: 4px;
  top: 50%;
  transform: translateY(-50%);
  font-family: var(--font-mono);
  font-size: 18px;
  line-height: 1;
  color: var(--cyan);
}

.page-about .ab-cluster[open] .ab-cluster__sum::after {
  content: "−";
}

.page-about .ab-cluster__sum:hover {
  color: var(--paper);
}

.page-about .ab-cluster__sum:focus-visible {
  outline: 1px solid var(--line-strong);
  outline-offset: 4px;
  border-radius: var(--radius-sm);
}

.page-about .ab-cluster__letter {
  flex: none;
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--flag-red);
}

.page-about .ab-cluster__name {
  font-size: 16px;
  font-weight: 700;
  color: var(--paper);
}

.page-about .ab-cluster__hint {
  font-size: 13px;
  color: var(--mist);
}

.page-about .ab-cluster__box {
  padding: 0 0 20px 0;
}

.page-about .ab-cluster__box p {
  margin: 0;
  max-width: 34em;
  font-size: 15px;
  line-height: 1.85;
  color: rgba(242, 245, 247, 0.76);
}

/* ---------- 图片 ---------- */
.page-about .ab-figure {
  margin: clamp(26px, 4vw, 40px) 0 0;
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  overflow: hidden;
  background: linear-gradient(140deg, rgba(36, 26, 70, 0.9), rgba(7, 10, 20, 0.92));
  box-shadow: var(--shadow-soft);
}

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

.page-about .ab-figure figcaption {
  padding: 13px 20px 16px;
  border-top: 1px solid var(--line);
  font-size: 12px;
  letter-spacing: 0.08em;
  line-height: 1.7;
  color: var(--mist);
}

/* ---------- 回归三步 ---------- */
.page-about .ab-steps {
  margin: 28px 0 0;
  padding: 0;
  list-style: none;
  counter-reset: none;
}

.page-about .ab-step {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 14px;
  padding: 20px 0;
  border-top: 1px solid var(--line);
}

.page-about .ab-step:last-child {
  border-bottom: 1px solid var(--line);
}

.page-about .ab-step__n {
  flex: none;
  font-size: 18px;
  line-height: 1.5;
  color: var(--flag-yellow);
}

.page-about .ab-step__t {
  margin: 0 0 8px;
  font-size: 16px;
  font-weight: 700;
  color: var(--paper);
}

.page-about .ab-step__main p {
  margin: 0;
  max-width: 34em;
  font-size: 15px;
  line-height: 1.85;
  color: rgba(242, 245, 247, 0.76);
}

/* ---------- 双端对照 ---------- */
.page-about .ab-dual {
  display: grid;
  grid-template-columns: 1fr;
  gap: 14px;
  margin: 28px 0 0;
}

.page-about .ab-dual__col {
  padding: 22px 20px 24px;
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  background: var(--ab-card-bg);
}

.page-about .ab-dual__col--pc {
  box-shadow: inset 0 1px 0 rgba(53, 224, 214, 0.22);
}

.page-about .ab-dual__col--mb {
  box-shadow: inset 0 1px 0 rgba(184, 56, 74, 0.26);
}

.page-about .ab-dual__head {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--line);
}

.page-about .ab-dual__badge {
  flex: none;
  padding: 3px 9px;
  border-radius: var(--radius-sm);
  font-size: 11px;
  letter-spacing: 0.14em;
}

.page-about .ab-dual__col--pc .ab-dual__badge {
  color: var(--cyan);
  border: 1px solid rgba(53, 224, 214, 0.4);
  background: rgba(53, 224, 214, 0.08);
}

.page-about .ab-dual__col--mb .ab-dual__badge {
  color: var(--flag-red);
  border: 1px solid rgba(184, 56, 74, 0.5);
  background: rgba(184, 56, 74, 0.1);
}

.page-about .ab-dual__t {
  margin: 0;
  font-size: 18px;
  font-weight: 700;
  color: var(--paper);
}

.page-about .ab-dual__list {
  margin: 0;
  padding: 0;
  list-style: none;
}

.page-about .ab-dual__list li {
  position: relative;
  padding: 0 0 0 18px;
  margin-bottom: 12px;
  font-size: 14.5px;
  line-height: 1.8;
  color: rgba(242, 245, 247, 0.78);
}

.page-about .ab-dual__list li:last-child {
  margin-bottom: 0;
}

.page-about .ab-dual__list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.75em;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--mist);
}

.page-about .ab-dual__col--pc .ab-dual__list li::before {
  background: var(--cyan);
}

.page-about .ab-dual__col--mb .ab-dual__list li::before {
  background: var(--flag-red);
}

/* ---------- 规模数据 ---------- */
.page-about .ab-stats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  margin: 28px 0 30px;
  padding: 0;
}

.page-about .ab-stat {
  padding: 18px 16px;
  border: 1px solid var(--line);
  border-radius: var(--radius-md);
  background: linear-gradient(160deg, rgba(36, 26, 70, 0.7), rgba(7, 10, 20, 0.6));
}

.page-about .ab-stat__k {
  margin: 0 0 8px;
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--mist);
}

.page-about .ab-stat__v {
  margin: 0;
  font-size: clamp(24px, 5vw, 32px);
  font-weight: 700;
  line-height: 1.1;
  color: var(--paper);
}

.page-about .ab-stat__u {
  display: inline-block;
  margin-left: 6px;
  font-family: var(--font-sans);
  font-size: 12px;
  font-weight: 400;
  letter-spacing: 0.06em;
  color: var(--flag-yellow);
}

/* ---------- 平板及以上 ---------- */
@media (min-width: 700px) {
  .page-about .ab-who {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

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

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

  .page-about .ab-step {
    gap: 20px;
  }
}

/* ---------- 桌面：3 / 7 纵向时间轴 ---------- */
@media (min-width: 1000px) {
  .page-about .ab-stage {
    display: grid;
    grid-template-columns: minmax(180px, 3fr) 7fr;
    gap: clamp(36px, 5vw, 76px);
    align-items: start;
  }

  .page-about .ab-rail {
    position: sticky;
    top: calc(var(--header-h) + 32px);
    z-index: 1;
    margin: 0;
    padding: 4px 0 4px 22px;
    background: none;
    background-image: linear-gradient(
      180deg,
      rgba(184, 56, 74, 0.6) 0%,
      rgba(162, 91, 255, 0.42) 54%,
      rgba(53, 224, 214, 0.24) 100%
    );
    background-repeat: no-repeat;
    background-size: 1px 100%;
    background-position: 0 0;
  }

  .page-about .ab-rail__title {
    display: block;
    margin: 0 0 20px;
    font-size: 11px;
    letter-spacing: 0.2em;
    color: var(--mist);
  }

  .page-about .ab-rail__list {
    display: block;
    overflow: visible;
    padding: 0;
  }

  .page-about .ab-rail__item + .ab-rail__item {
    margin-top: 2px;
  }

  .page-about .ab-rail__link {
    position: relative;
    display: block;
    padding: 10px 0;
    border: 0;
    border-radius: 0;
    background: none;
    font-size: 14px;
  }

  .page-about .ab-rail__link:hover,
  .page-about .ab-rail__link:focus-visible {
    background: none;
  }

  .page-about .ab-rail__idx {
    display: block;
    font-size: 10px;
    letter-spacing: 0.16em;
    color: rgba(232, 184, 75, 0.7);
    transition: color 0.24s var(--ease);
  }

  .page-about .ab-rail__label {
    display: block;
    margin-top: 4px;
    transition: color 0.24s var(--ease);
  }

  .page-about .ab-rail__dot {
    display: block;
    position: absolute;
    left: -26px;
    top: 50%;
    transform: translateY(-50%);
    width: 9px;
    height: 9px;
    border-radius: 50%;
    background: var(--ink);
    border: 1px solid var(--ab-red-soft);
    transition: background 0.24s var(--ease), border-color 0.24s var(--ease), box-shadow 0.24s var(--ease);
  }

  .page-about .ab-rail__link:hover .ab-rail__dot,
  .page-about .ab-rail__link:focus-visible .ab-rail__dot {
    background: var(--flag-red);
    border-color: var(--flag-red);
    box-shadow: 0 0 0 5px var(--ab-red-faint);
  }

  .page-about .ab-rail__link:hover .ab-rail__idx,
  .page-about .ab-rail__link:focus-visible .ab-rail__idx {
    color: var(--flag-yellow);
  }

  .page-about .ab-rail__link:hover .ab-rail__label,
  .page-about .ab-rail__link:focus-visible .ab-rail__label {
    color: var(--paper);
  }

  .page-about .ab-sec__head {
    gap: 18px;
  }

  .page-about .ab-sec__idx {
    font-size: 13px;
  }
}

/* ---------- 动效克制 ---------- */
@media (prefers-reduced-motion: reduce) {
  .page-about .ab-who__item,
  .page-about .ab-rail__link,
  .page-about .ab-rail__dot,
  .page-about .ab-aside a {
    transition: none;
  }

  .page-about .ab-who__item:hover {
    transform: none;
  }
}
</main>