.page-about {
  --about-node: 46px;
  --about-indent: 84px;
  background: linear-gradient(180deg, var(--ink-900) 0%, var(--ink-800) 44%, var(--ink-900) 100%);
  color: var(--snow);
  font-family: var(--font-sans);
}

.page-about .grid {
  align-items: start;
}

/* ---------- 首屏 ---------- */

.page-about .about-hero {
  padding: clamp(22px, 4vw, 44px) 0 clamp(28px, 4.5vw, 56px);
}

.page-about .about-hero__main {
  max-width: 46rem;
}

.page-about .about-hero__title {
  margin: 14px 0 20px;
  font-size: clamp(2.1rem, 6.2vw, 4.1rem);
  font-weight: 900;
  line-height: 1.02;
  letter-spacing: -0.04em;
  color: var(--snow);
}

.page-about .about-hero__lead {
  margin: 0;
  max-width: 40rem;
  font-size: clamp(1rem, 1.5vw, 1.1rem);
  line-height: 1.78;
  color: var(--gray);
}

.page-about .about-hero__side {
  margin-top: clamp(24px, 3vw, 8px);
}

.page-about .about-facts {
  margin: 0;
  padding: 0;
  list-style: none;
  border-top: 2px solid var(--ink-700);
}

.page-about .about-facts__item {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 15px 0;
  border-bottom: 2px solid var(--ink-700);
}

.page-about .about-facts__num {
  font-family: var(--font-mono);
  font-size: 1.85rem;
  font-weight: 500;
  line-height: 1;
  color: var(--cyan);
  font-variant-numeric: tabular-nums;
}

.page-about .about-facts__label {
  font-size: 0.86rem;
  line-height: 1.6;
  color: var(--gray);
}

/* ---------- 开篇全景图 ---------- */

.page-about .about-pano {
  margin: 0 0 clamp(48px, 7vw, 104px);
}

.page-about .media-frame {
  border: 2px solid var(--ink-700);
  box-shadow: var(--shadow-hard);
  background: var(--ink-800);
  overflow: hidden;
}

.page-about .media-frame img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: 100%;
  object-fit: cover;
}

.page-about .media-frame__caption {
  display: block;
  margin: 14px 0 0;
  font-size: 0.82rem;
  line-height: 1.6;
  color: var(--gray);
}

/* ---------- 纵向时间轴骨架 ---------- */

.page-about .about-track {
  padding: 0 0 clamp(48px, 7vw, 100px);
}

.page-about .about-steps {
  position: relative;
}

.page-about .about-step {
  position: relative;
  padding: 0 0 clamp(56px, 7vw, 96px) var(--about-indent);
}

.page-about .about-step::before {
  content: "";
  position: absolute;
  left: calc(var(--about-node) / 2 - 1px);
  top: 0;
  bottom: 0;
  width: 2px;
  background: var(--ink-700);
}

.page-about .about-step:last-child {
  padding-bottom: clamp(24px, 3vw, 40px);
}

.page-about .about-step:last-child::before {
  bottom: auto;
  height: 56px;
}

.page-about .about-step__marker {
  position: absolute;
  left: 0;
  top: 0;
  width: var(--about-node);
  height: var(--about-node);
  display: grid;
  place-items: center;
  background: var(--ink-900);
  border: 2px solid var(--ink-700);
  color: var(--gray);
  font-size: 0.84rem;
  transition: border-color 0.3s ease, color 0.3s ease, box-shadow 0.3s ease;
}

.page-about .about-step.is-visible .about-step__marker {
  border-color: var(--cyan);
  color: var(--cyan);
  box-shadow: 0 0 0 6px rgba(61, 240, 208, 0.08);
}

.page-about .about-step__body {
  max-width: 46rem;
}

.page-about .about-step__title {
  margin: 10px 0 18px;
  font-size: clamp(1.5rem, 3.2vw, 2.5rem);
  font-weight: 800;
  line-height: 1.12;
  letter-spacing: -0.03em;
  color: var(--snow);
}

.page-about .about-step__text {
  margin: 0 0 18px;
  max-width: 40rem;
  font-size: 1rem;
  line-height: 1.8;
  color: var(--gray);
}

.page-about .about-step__text--after {
  margin-top: 24px;
}

.page-about .about-step__figure {
  margin: 28px 0 0;
}

.page-about .about-step__figure--square {
  max-width: 32rem;
}

/* ---------- 双线示意 SVG ---------- */

.page-about .route-figure {
  margin: 28px 0 0;
  padding: 20px clamp(14px, 2vw, 26px);
  background: var(--ink-800);
  border: 2px solid var(--ink-700);
}

.page-about .route-svg {
  display: block;
  width: 100%;
  max-width: 640px;
  height: auto;
}

.page-about .route-svg .route-a {
  fill: none;
  stroke: var(--cyan);
  stroke-width: 2.5;
  stroke-linejoin: round;
}

.page-about .route-svg .route-b {
  fill: none;
  stroke: var(--gray);
  stroke-width: 2.5;
  stroke-dasharray: 9 7;
  stroke-linejoin: round;
}

.page-about .route-svg .route-guide {
  stroke: var(--ink-700);
  stroke-width: 1.5;
  stroke-dasharray: 4 6;
}

.page-about .route-svg .route-dot {
  fill: var(--orange);
}

.page-about .route-svg .route-label {
  font-family: var(--font-mono);
  font-size: 13px;
  fill: var(--gray);
}

.page-about .route-svg .route-label--mid {
  fill: var(--orange);
  font-size: 12px;
}

.page-about .route-figure__caption {
  margin: 14px 0 0;
  font-size: 0.82rem;
  line-height: 1.6;
  color: var(--gray);
}

/* ---------- 版本列表 ---------- */

.page-about .vlist {
  margin: 26px 0 26px;
  padding: 0;
  list-style: none;
  border-top: 2px solid var(--ink-700);
}

.page-about .vlist__item {
  display: grid;
  grid-template-columns: 76px 1fr;
  gap: 6px 20px;
  padding: 16px 0;
  border-bottom: 1px solid var(--ink-700);
}

.page-about .vlist__ver {
  grid-row: span 2;
  align-self: start;
  font-size: 1.05rem;
  font-weight: 500;
  color: var(--cyan);
  font-variant-numeric: tabular-nums;
}

.page-about .vlist__name {
  font-size: 1rem;
  font-weight: 700;
  color: var(--snow);
}

.page-about .vlist__desc {
  font-size: 0.92rem;
  line-height: 1.72;
  color: var(--gray);
}

/* ---------- 合作生态分段切换 ---------- */

.page-about .eco {
  margin: 26px 0 0;
}

.page-about .eco__tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  padding-bottom: 16px;
  border-bottom: 2px solid var(--ink-700);
}

.page-about .eco__tab {
  appearance: none;
  min-height: 44px;
  padding: 10px 18px;
  font: inherit;
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--gray);
  background: transparent;
  border: 2px solid var(--ink-700);
  cursor: pointer;
  transition: background-color 0.18s ease, color 0.18s ease, border-color 0.18s ease;
}

.page-about .eco__tab:hover {
  border-color: var(--gray);
  color: var(--snow);
}

.page-about .eco__tab.is-active {
  background: var(--cyan);
  border-color: var(--cyan);
  color: var(--ink-900);
}

.page-about .eco__tab:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: 2px;
}

.page-about .eco__panels {
  padding-top: 22px;
}

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

.page-about .eco__panel:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: 4px;
}

.page-about .eco__list {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 14px;
}

.page-about .eco__list li {
  position: relative;
  padding-left: 22px;
  font-size: 0.96rem;
  line-height: 1.75;
  color: var(--gray);
}

.page-about .eco__list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.62em;
  width: 9px;
  height: 9px;
  background: var(--orange);
}

/* ---------- 收尾入口 ---------- */

.page-about .about-next {
  padding: clamp(42px, 6vw, 84px) 0 clamp(56px, 8vw, 112px);
  border-top: 2px solid var(--ink-700);
}

.page-about .about-next__title {
  margin: 12px 0 28px;
  font-size: clamp(1.5rem, 3vw, 2.2rem);
  font-weight: 800;
  line-height: 1.14;
  letter-spacing: -0.03em;
  color: var(--snow);
}

.page-about .about-next__list {
  margin: 0;
  padding: 0;
  list-style: none;
  border-top: 2px solid var(--ink-700);
}

.page-about .about-next__list > li {
  border-bottom: 1px solid var(--ink-700);
}

.page-about .about-next__link {
  display: grid;
  grid-template-columns: 42px 1fr 28px;
  gap: 14px;
  align-items: center;
  min-height: 44px;
  padding: 20px 6px;
  color: var(--snow);
  text-decoration: none;
  transition: color 0.2s ease, background-color 0.2s ease;
}

.page-about .about-next__link:hover,
.page-about .about-next__link:focus-visible {
  color: var(--cyan);
  background: rgba(61, 240, 208, 0.05);
}

.page-about .about-next__link:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: 2px;
}

.page-about .about-next__idx {
  font-size: 0.86rem;
  color: var(--gray);
  font-variant-numeric: tabular-nums;
}

.page-about .about-next__text {
  font-size: 1rem;
  line-height: 1.6;
}

.page-about .about-next__arrow {
  font-family: var(--font-mono);
  font-size: 1.1rem;
  text-align: right;
  transition: transform 0.24s ease;
}

.page-about .about-next__link:hover .about-next__arrow,
.page-about .about-next__link:focus-visible .about-next__arrow {
  transform: translateX(6px);
}

/* ---------- 进入视口显现 ---------- */

.page-about [data-reveal-init] {
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 0.24s ease, transform 0.24s ease;
}

.page-about [data-reveal-init].is-visible {
  opacity: 1;
  transform: none;
}

@media (prefers-reduced-motion: reduce) {
  .page-about [data-reveal-init] {
    opacity: 1;
    transform: none;
    transition: none;
  }

  .page-about .about-next__arrow,
  .page-about .about-step__marker {
    transition: none;
  }
}

/* ---------- 窄屏 ---------- */

@media (max-width: 899px) {
  .page-about .about-step {
    padding-left: 58px;
    padding-bottom: 56px;
  }

  .page-about .about-step::before {
    left: 17px;
  }

  .page-about .about-step__marker {
    width: 36px;
    height: 36px;
    font-size: 0.72rem;
  }

  .page-about .about-hero__side {
    margin-top: 32px;
  }

  .page-about .about-next__link {
    grid-template-columns: 34px 1fr 24px;
    gap: 12px;
    padding: 18px 0;
  }
}

@media (max-width: 599px) {
  .page-about .about-hero__title {
    letter-spacing: -0.02em;
  }

  .page-about .about-facts__num {
    font-size: 1.5rem;
  }

  .page-about .vlist__item {
    grid-template-columns: 1fr;
    gap: 6px;
  }

  .page-about .vlist__ver {
    grid-row: auto;
  }

  .page-about .eco__tab {
    flex: 1 1 100%;
    text-align: left;
  }

  .page-about .about-next__text {
    font-size: 0.94rem;
  }
}

@media (min-width: 1200px) {
  .page-about .about-step__body {
    max-width: 52rem;
  }
}