.page-about {
  --ab-node: 14px;
  --ab-line-col: rgba(22, 224, 200, 0.3);
  --ab-stage-pad: clamp(30px, 4.5vw, 56px);
  background: var(--yb-navy);
}

.page-about a:focus-visible,
.page-about button:focus-visible {
  outline: 3px solid var(--yb-cyan);
  outline-offset: 3px;
}

/* ---------- 首屏封面 ---------- */

.page-about .ab-cover {
  position: relative;
  overflow: hidden;
  padding-top: calc(var(--yb-header-h) + clamp(36px, 6vw, 72px));
  padding-bottom: clamp(52px, 8vw, 104px);
  background:
    radial-gradient(120% 85% at 84% 6%, rgba(22, 224, 200, 0.17), transparent 58%),
    radial-gradient(85% 70% at 2% 98%, rgba(255, 90, 43, 0.13), transparent 60%),
    var(--yb-navy);
}

.page-about .ab-cover::after {
  content: "";
  position: absolute;
  right: -14%;
  top: -20%;
  width: 60%;
  height: 150%;
  background-image: repeating-linear-gradient(
    -68deg,
    rgba(22, 224, 200, 0.09) 0 2px,
    transparent 2px 28px
  );
  pointer-events: none;
}

.page-about .ab-cover__crumb {
  position: relative;
  z-index: 1;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  color: var(--yb-muted);
  margin-bottom: clamp(28px, 5vw, 52px);
}

.page-about .ab-cover__crumb a {
  color: var(--yb-muted);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color 200ms var(--yb-ease), border-color 200ms var(--yb-ease);
}

.page-about .ab-cover__crumb a:hover {
  color: var(--yb-cyan);
  border-color: var(--yb-cyan);
}

.page-about .ab-cover__crumb [aria-current="page"] {
  color: var(--yb-paper);
}

.page-about .ab-cover__sep {
  color: rgba(244, 246, 248, 0.35);
}

.page-about .ab-cover__grid {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(32px, 5vw, 64px);
  align-items: end;
}

.page-about .ab-cover__kicker {
  margin: 0 0 18px;
}

.page-about .ab-cover__title {
  margin: 0;
  font-size: clamp(38px, 7vw, 86px);
  line-height: 1.02;
  letter-spacing: -0.02em;
  color: var(--yb-paper);
  max-width: 15ch;
}

.page-about .ab-cover__lede {
  margin: clamp(20px, 3vw, 30px) 0 0;
  max-width: 40ch;
  font-size: clamp(16px, 1.4vw, 19px);
  line-height: 1.75;
  color: rgba(244, 246, 248, 0.82);
}

.page-about .ab-cover__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: clamp(26px, 4vw, 40px);
}

.page-about .ab-cover__panel {
  border: 1px solid rgba(244, 246, 248, 0.18);
  border-top: 3px solid var(--yb-orange);
  background: rgba(20, 41, 74, 0.72);
  padding: clamp(20px, 3vw, 30px);
}

.page-about .ab-cover__panelTitle {
  margin: 0 0 18px;
  font-size: 13px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--yb-cyan);
}

.page-about .ab-cover__stats {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 18px;
}

.page-about .ab-cover__stat {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding-bottom: 16px;
  border-bottom: 1px solid rgba(244, 246, 248, 0.12);
}

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

.page-about .ab-cover__statNum {
  font-size: clamp(30px, 4vw, 42px);
  font-weight: 700;
  line-height: 1;
  letter-spacing: -0.02em;
  color: var(--yb-yellow);
}

.page-about .ab-cover__statLabel {
  font-size: 14px;
  color: var(--yb-muted);
}

/* ---------- 时间轴骨架 ---------- */

.page-about .ab-stages {
  position: relative;
  padding-top: clamp(48px, 7vw, 88px);
  padding-bottom: clamp(48px, 7vw, 88px);
  background: var(--yb-navy);
}

.page-about .ab-stages::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: repeating-linear-gradient(
    38deg,
    rgba(22, 224, 200, 0.045) 0 1px,
    transparent 1px 34px
  );
  pointer-events: none;
}

.page-about .ab-stages__head {
  position: relative;
  margin-bottom: clamp(30px, 5vw, 56px);
  padding-left: var(--ab-stage-pad);
}

.page-about .ab-stages__title {
  margin: 12px 0 0;
  max-width: 18ch;
  color: var(--yb-paper);
}

.page-about .ab-layout {
  position: relative;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(34px, 5vw, 60px);
}

.page-about .ab-layout__main {
  position: relative;
  min-width: 0;
}

/* 斜向主线：每阶段左侧 2px 竖线沿内容延伸 */
.page-about .ab-layout__main::before {
  content: "";
  position: absolute;
  left: 7px;
  top: 12px;
  bottom: 12px;
  width: 2px;
  background: linear-gradient(
    180deg,
    rgba(22, 224, 200, 0.6) 0%,
    rgba(22, 224, 200, 0.28) 42%,
    rgba(255, 201, 60, 0.4) 74%,
    rgba(255, 90, 43, 0.55) 100%
  );
  transform: skewX(-3deg);
  transform-origin: top center;
}

.page-about .ab-stage {
  position: relative;
  padding-left: var(--ab-stage-pad);
  padding-bottom: clamp(40px, 6vw, 76px);
}

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

.page-about .ab-stage::before {
  content: "";
  position: absolute;
  left: 7px;
  top: 0;
  bottom: 0;
  width: 2px;
  background: var(--ab-line-col);
}

.page-about .ab-stage:last-child::before {
  bottom: auto;
  height: clamp(60px, 8vw, 96px);
}

.page-about .ab-stage::after {
  content: "";
  position: absolute;
  left: 1px;
  top: clamp(14px, 2.4vw, 26px);
  width: var(--ab-node);
  height: var(--ab-node);
  border-radius: 50%;
  background: var(--yb-cyan);
  box-shadow: 0 0 0 5px rgba(22, 224, 200, 0.14);
}

.page-about .ab-stage--hot::after {
  background: var(--yb-orange);
  box-shadow: 0 0 0 6px rgba(255, 90, 43, 0.18);
}

.page-about .ab-stage__meta {
  display: flex;
  align-items: baseline;
  gap: 14px;
  flex-wrap: wrap;
  margin-bottom: clamp(14px, 2vw, 22px);
}

.page-about .ab-stage__num {
  margin: 0;
  font-size: clamp(56px, 11vw, 96px);
  font-weight: 700;
  line-height: 0.86;
  letter-spacing: -0.045em;
  color: var(--yb-cyan);
}

.page-about .ab-stage--warm .ab-stage__num {
  color: var(--yb-yellow);
}

.page-about .ab-stage--hot .ab-stage__num {
  color: var(--yb-orange);
}

.page-about .ab-stage__phase {
  margin: 0;
  font-size: 12px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--yb-muted);
  padding: 4px 10px;
  border: 1px solid rgba(244, 246, 248, 0.2);
}

.page-about .ab-stage__body {
  max-width: 62ch;
}

.page-about .ab-stage__title {
  margin: 0 0 18px;
  color: var(--yb-paper);
  font-size: clamp(22px, 2.6vw, 30px);
  line-height: 1.28;
}

.page-about .ab-stage__body .yb-body {
  margin: 0 0 16px;
  color: rgba(244, 246, 248, 0.78);
}

.page-about .ab-stage__body .yb-body:last-child {
  margin-bottom: 0;
}

/* ---------- 旁注 ---------- */

.page-about .yb-aside.ab-aside {
  margin: clamp(20px, 3vw, 28px) 0 0;
  padding: 16px 18px;
  background: rgba(255, 201, 60, 0.09);
  border-left: 3px solid var(--yb-yellow);
  color: rgba(244, 246, 248, 0.86);
  font-size: 14px;
  line-height: 1.75;
}

.page-about .yb-aside.ab-aside--cyan {
  background: rgba(22, 224, 200, 0.08);
  border-left-color: var(--yb-cyan);
}

.page-about .ab-aside p {
  margin: 0;
}

.page-about .ab-aside__label {
  margin-bottom: 6px !important;
  font-size: 12px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--yb-yellow);
}

.page-about .ab-aside--cyan .ab-aside__label {
  color: var(--yb-cyan);
}

/* ---------- 三条内容线 ---------- */

.page-about .ab-lines {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 14px;
  margin: clamp(20px, 3vw, 28px) 0;
}

.page-about .ab-line {
  position: relative;
  padding: 20px 20px 22px;
  background: rgba(20, 41, 74, 0.68);
  border: 1px solid rgba(244, 246, 248, 0.12);
  border-top: 3px solid var(--yb-cyan);
  transition: transform 200ms var(--yb-ease), border-color 200ms var(--yb-ease);
}

.page-about .ab-line:hover {
  transform: translateY(-4px);
  border-color: rgba(22, 224, 200, 0.5);
}

.page-about .ab-line__no {
  margin: 0 0 10px;
  font-size: 13px;
  letter-spacing: 0.12em;
  color: var(--yb-yellow);
}

.page-about .ab-line__title {
  margin: 0 0 10px;
  font-size: 18px;
  color: var(--yb-paper);
}

.page-about .ab-line__text {
  margin: 0;
  font-size: 15px;
  line-height: 1.72;
  color: rgba(244, 246, 248, 0.74);
}

/* ---------- 版本卡 ---------- */

.page-about .ab-versions {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 16px;
  margin: clamp(20px, 3vw, 28px) 0 0;
}

.page-about .ab-version {
  padding: 22px 22px 24px;
  border: 1px solid rgba(244, 246, 248, 0.14);
  background: rgba(20, 41, 74, 0.6);
  transition: transform 220ms var(--yb-ease), box-shadow 220ms var(--yb-ease);
}

.page-about .ab-version:hover {
  transform: translateY(-4px);
}

.page-about .ab-version--lead {
  border-left: 4px solid var(--yb-orange);
}

.page-about .ab-version--lead:hover {
  box-shadow: 8px 8px 0 0 rgba(255, 90, 43, 0.55);
}

.page-about .ab-version--sub {
  border-left: 4px solid var(--yb-yellow);
  background: rgba(11, 27, 51, 0.72);
}

.page-about .ab-version__tag {
  margin: 0 0 12px;
  font-size: clamp(28px, 4vw, 40px);
  font-weight: 700;
  line-height: 1;
  letter-spacing: -0.02em;
  color: var(--yb-orange);
}

.page-about .ab-version--sub .ab-version__tag {
  color: var(--yb-yellow);
}

.page-about .ab-version__title {
  margin: 0 0 12px;
  font-size: 17px;
  color: var(--yb-paper);
}

.page-about .ab-version__list {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 10px;
}

.page-about .ab-version__list li {
  position: relative;
  padding-left: 18px;
  font-size: 15px;
  line-height: 1.7;
  color: rgba(244, 246, 248, 0.76);
}

.page-about .ab-version__list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 10px;
  width: 8px;
  height: 2px;
  background: var(--yb-orange);
}

.page-about .ab-version__text {
  margin: 0;
  font-size: 15px;
  line-height: 1.72;
  color: rgba(244, 246, 248, 0.76);
}

/* ---------- 团队比例图 ---------- */

.page-about .ab-bars {
  display: grid;
  gap: 14px;
  margin: clamp(22px, 3vw, 30px) 0 clamp(26px, 4vw, 36px);
}

.page-about .ab-bar {
  display: grid;
  grid-template-columns: 72px minmax(0, 1fr) 34px;
  align-items: center;
  gap: 12px;
}

.page-about .ab-bar__label {
  font-size: 13px;
  color: var(--yb-muted);
}

.page-about .ab-bar__track {
  position: relative;
  display: block;
  height: 10px;
  background: rgba(244, 246, 248, 0.1);
  overflow: hidden;
}

.page-about .ab-bar__fill {
  display: block;
  height: 100%;
  background: linear-gradient(90deg, var(--yb-cyan), var(--yb-yellow));
}

.page-about .ab-bar--39 .ab-bar__fill { width: 39%; }
.page-about .ab-bar--25 .ab-bar__fill { width: 25%; }
.page-about .ab-bar--21 .ab-bar__fill { width: 21%; }
.page-about .ab-bar--14 .ab-bar__fill { width: 14%; background: linear-gradient(90deg, var(--yb-yellow), var(--yb-orange)); }

.page-about .ab-bar__val {
  font-size: 16px;
  font-weight: 700;
  text-align: right;
  color: var(--yb-paper);
}

/* ---------- 图片 ---------- */

.page-about .ab-figure {
  margin: clamp(22px, 3vw, 32px) 0;
  border: 1px solid rgba(244, 246, 248, 0.16);
}

.page-about .ab-figure--wide {
  max-width: 100%;
}

.page-about .ab-figure--portrait {
  max-width: 460px;
}

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

.page-about .ab-figure .yb-figure__caption {
  padding: 12px 16px;
  font-size: 13px;
  line-height: 1.7;
  color: var(--yb-muted);
  border-top: 1px solid rgba(244, 246, 248, 0.12);
  background: rgba(20, 41, 74, 0.5);
}

/* ---------- 延伸入口 ---------- */

.page-about .ab-next__links {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 12px;
  margin-top: clamp(24px, 4vw, 34px);
}

.page-about .ab-nextlink {
  display: block;
  padding: 18px 20px;
  text-decoration: none;
  border: 1px solid rgba(244, 246, 248, 0.18);
  border-left: 3px solid var(--yb-cyan);
  background: rgba(20, 41, 74, 0.5);
  transition: background-color 200ms var(--yb-ease), transform 200ms var(--yb-ease), border-color 200ms var(--yb-ease);
}

.page-about .ab-nextlink:hover,
.page-about .ab-nextlink:focus-visible {
  background: var(--yb-cyan);
  border-color: var(--yb-cyan);
  transform: translateY(-4px);
}

.page-about .ab-nextlink__label {
  display: block;
  font-size: 12px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--yb-cyan);
  margin-bottom: 8px;
}

.page-about .ab-nextlink__title {
  display: block;
  font-size: 15px;
  line-height: 1.65;
  color: var(--yb-paper);
}

.page-about .ab-nextlink:hover .ab-nextlink__label,
.page-about .ab-nextlink:focus-visible .ab-nextlink__label,
.page-about .ab-nextlink:hover .ab-nextlink__title,
.page-about .ab-nextlink:focus-visible .ab-nextlink__title {
  color: var(--yb-navy);
}

/* ---------- 右栏索引 ---------- */

.page-about .ab-rail {
  border: 1px solid rgba(244, 246, 248, 0.16);
  border-top: 3px solid var(--yb-cyan);
  background: rgba(20, 41, 74, 0.62);
  padding: 20px 18px 22px;
}

.page-about .ab-rail__title {
  margin: 0 0 14px;
  font-size: 12px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--yb-cyan);
}

.page-about .ab-rail__list {
  list-style: none;
  margin: 0;
  padding: 0;
  counter-reset: none;
}

.page-about .ab-rail__link {
  display: flex;
  align-items: baseline;
  gap: 10px;
  padding: 9px 0;
  font-size: 14px;
  text-decoration: none;
  color: var(--yb-muted);
  border-bottom: 1px solid rgba(244, 246, 248, 0.1);
  transition: color 200ms var(--yb-ease), padding-left 200ms var(--yb-ease);
}

.page-about .ab-rail__link:hover,
.page-about .ab-rail__link:focus-visible {
  color: var(--yb-cyan);
  padding-left: 5px;
}

.page-about .ab-rail__no {
  font-size: 12px;
  color: var(--yb-yellow);
}

.page-about .ab-rail__note {
  margin: 16px 0 0;
  font-size: 13px;
  line-height: 1.75;
  color: var(--yb-muted);
}

.page-about .ab-rail__note a {
  color: var(--yb-cyan);
  text-decoration: none;
  border-bottom: 1px solid rgba(22, 224, 200, 0.5);
}

.page-about .ab-rail__note a:hover {
  border-color: var(--yb-cyan);
}

/* ---------- 收口 ---------- */

.page-about .ab-close {
  padding-top: clamp(40px, 6vw, 72px);
  padding-bottom: clamp(48px, 7vw, 88px);
}

.page-about .ab-close__scale {
  height: 14px;
  margin-bottom: clamp(26px, 4vw, 44px);
  border-top: 2px solid rgba(22, 224, 200, 0.55);
  background-image: repeating-linear-gradient(
    to right,
    rgba(22, 224, 200, 0.55) 0 1px,
    transparent 1px 26px
  );
}

.page-about .ab-close__grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(26px, 4vw, 48px);
  align-items: start;
}

.page-about .ab-close__title {
  margin: 0 0 14px;
  color: var(--yb-paper);
  font-size: clamp(26px, 4vw, 44px);
}

.page-about .ab-close__text {
  margin: 0;
  max-width: 42ch;
  color: rgba(244, 246, 248, 0.75);
}

.page-about .ab-close__links {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 0;
}

.page-about .ab-closelink {
  display: block;
  padding: 15px 4px 15px 22px;
  position: relative;
  font-size: 15px;
  line-height: 1.65;
  text-decoration: none;
  color: rgba(244, 246, 248, 0.82);
  border-bottom: 1px solid rgba(244, 246, 248, 0.14);
  transition: color 200ms var(--yb-ease), padding-left 200ms var(--yb-ease);
}

.page-about .ab-closelink::before {
  content: "";
  position: absolute;
  left: 0;
  top: 50%;
  width: 10px;
  height: 2px;
  background: var(--yb-orange);
  transform: translateY(-50%);
  transition: width 200ms var(--yb-ease), background-color 200ms var(--yb-ease);
}

.page-about .ab-closelink:hover,
.page-about .ab-closelink:focus-visible {
  color: var(--yb-cyan);
  padding-left: 28px;
}

.page-about .ab-closelink:hover::before,
.page-about .ab-closelink:focus-visible::before {
  width: 18px;
  background: var(--yb-cyan);
}

/* ---------- 响应式 ---------- */

@media (min-width: 700px) {
  .page-about .ab-lines {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .page-about .ab-versions {
    grid-template-columns: minmax(0, 1.35fr) minmax(0, 1fr);
  }

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

  .page-about .ab-close__grid {
    grid-template-columns: minmax(0, 4fr) minmax(0, 6fr);
  }
}

@media (min-width: 960px) {
  .page-about .ab-cover__grid {
    grid-template-columns: minmax(0, 7fr) minmax(280px, 4fr);
  }

  .page-about .ab-cover__title {
    max-width: 13ch;
  }
}

@media (min-width: 1080px) {
  .page-about .ab-layout {
    grid-template-columns: minmax(0, 1fr) 236px;
    align-items: start;
  }

  .page-about .ab-layout__rail {
    position: sticky;
    top: calc(var(--yb-header-h) + 32px);
  }
}

@media (max-width: 520px) {
  .page-about .ab-bar {
    grid-template-columns: 64px minmax(0, 1fr) 28px;
    gap: 8px;
  }

  .page-about .ab-stage__meta {
    gap: 10px;
  }

  .page-about .ab-cover__actions .yb-btn {
    flex: 1 1 auto;
    text-align: center;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .ab-line,
  .page-about .ab-version,
  .page-about .ab-nextlink,
  .page-about .ab-closelink,
  .page-about .ab-rail__link {
    transition: none;
  }

  .page-about .ab-line:hover,
  .page-about .ab-version:hover,
  .page-about .ab-nextlink:hover {
    transform: none;
  }
}