.page-about {
  --about-measure: 640px;
  --about-gap: clamp(24px, 3.2vw, 52px);
  background: var(--bo-paper);
  color: #1B241F;
}

/* ---------- 封面 ---------- */
.page-about .about-cover {
  position: relative;
  overflow: hidden;
  background: var(--bo-coal);
  color: var(--bo-white);
  padding: clamp(22px, 3vw, 36px) 0 clamp(48px, 7vw, 96px);
}

.page-about .about-cover::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background-image:
    repeating-linear-gradient(90deg, transparent 0 67px, rgba(154, 170, 162, 0.13) 67px 68px),
    radial-gradient(120% 90% at 8% 0%, rgba(18, 53, 43, 0.9), transparent 62%);
  -webkit-mask-image: linear-gradient(180deg, rgba(0, 0, 0, 0.95), transparent 82%);
  mask-image: linear-gradient(180deg, rgba(0, 0, 0, 0.95), transparent 82%);
}

.page-about .about-cover > .bo-container {
  position: relative;
  z-index: 1;
}

.page-about .about-cover__crumb {
  font-family: var(--bo-font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.1em;
  color: var(--bo-muted);
  margin-bottom: clamp(28px, 5vw, 58px);
}

.page-about .about-cover__crumb a {
  color: var(--bo-white);
  text-decoration: none;
  border-bottom: 1px solid rgba(242, 245, 243, 0.35);
}

.page-about .about-cover__crumb a:hover,
.page-about .about-cover__crumb a:focus-visible {
  color: var(--bo-orange);
  border-bottom-color: var(--bo-orange);
}

.page-about .about-cover__sep {
  margin: 0 0.5em;
  color: var(--bo-muted);
}

.page-about .about-cover__kicker {
  margin: 0;
  font-family: var(--bo-font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.24em;
  color: var(--bo-orange);
}

.page-about .about-cover__title {
  margin: 16px 0 0;
  max-width: 15ch;
  font-family: var(--bo-font-display);
  font-size: clamp(2.3rem, 8.4vw, 5rem);
  font-weight: 900;
  line-height: 0.98;
  letter-spacing: -0.035em;
}

.page-about .about-cover__lede {
  max-width: 46ch;
  margin: clamp(20px, 3vw, 30px) 0 0;
  font-size: clamp(1rem, 2.1vw, 1.1rem);
  line-height: 1.82;
  color: rgba(242, 245, 243, 0.82);
}

.page-about .about-cover__stats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 22px 20px;
  max-width: 780px;
  margin: clamp(32px, 5vw, 54px) 0 0;
  padding-top: clamp(20px, 3vw, 28px);
  border-top: 1px solid rgba(242, 245, 243, 0.18);
}

.page-about .about-cover__stat dt {
  margin-bottom: 6px;
  font-family: var(--bo-font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.16em;
  color: var(--bo-muted);
}

.page-about .about-cover__stat dd {
  margin: 0;
  font-size: 0.92rem;
  color: rgba(242, 245, 243, 0.88);
}

.page-about .about-cover__num {
  margin-right: 4px;
  font-family: var(--bo-font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 1.6rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--bo-lime);
}

/* ---------- 章节基底 ---------- */
.page-about .about-chapter {
  padding: clamp(48px, 7.5vw, 104px) 0;
}

.page-about .about-chapter--paper {
  background: var(--bo-paper);
  color: #1B241F;
}

.page-about .about-chapter--ink {
  background: var(--bo-ink);
  color: var(--bo-white);
}

.page-about .about-chapter--coal {
  background: var(--bo-coal);
  color: var(--bo-white);
}

.page-about .about-chapter__inner {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  row-gap: clamp(26px, 4vw, 38px);
}

.page-about .about-chapter__num {
  margin: 0;
  font-family: var(--bo-font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 0.8rem;
  letter-spacing: 0.24em;
  color: var(--bo-orange);
}

.page-about .about-chapter__title {
  margin: 0 0 20px;
  font-family: var(--bo-font-display);
  font-size: clamp(1.55rem, 4.4vw, 2.35rem);
  font-weight: 800;
  line-height: 1.1;
  letter-spacing: -0.025em;
}

.page-about .about-chapter__body p {
  margin: 0 0 1.15em;
  font-family: var(--bo-font-text);
  font-size: 1.0313rem;
  line-height: 1.85;
}

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

.page-about .about-chapter__body a,
.page-about .about-chapter__tail a {
  color: var(--bo-orange);
  text-decoration: none;
  border-bottom: 1px solid currentColor;
}

.page-about .about-chapter__body a:hover,
.page-about .about-chapter__tail a:hover {
  color: var(--bo-amber);
}

.page-about .about-chapter__tail {
  margin: clamp(24px, 3.5vw, 38px) 0 0;
  max-width: 62ch;
  font-size: 0.95rem;
  line-height: 1.8;
  color: #4A5A52;
}

/* ---------- 边注 ---------- */
.page-about .about-aside {
  padding-left: clamp(16px, 2vw, 22px);
  border-left: 1px solid rgba(58, 74, 68, 0.35);
  transition: border-color 0.25s ease;
}

.page-about .about-aside:hover {
  border-left-color: var(--bo-orange);
}

.page-about .about-aside__quote {
  margin: 0 0 12px;
  font-family: var(--bo-font-display);
  font-size: clamp(1.3rem, 3.4vw, 1.72rem);
  font-weight: 800;
  line-height: 1.26;
  letter-spacing: -0.02em;
}

.page-about .about-aside__note {
  margin: 0;
  font-size: 0.84rem;
  line-height: 1.72;
  color: #5E6F67;
}

.page-about .about-chapter--ink .about-aside,
.page-about .about-chapter--coal .about-aside {
  border-left-color: rgba(242, 245, 243, 0.22);
}

.page-about .about-chapter--ink .about-aside:hover,
.page-about .about-chapter--coal .about-aside:hover {
  border-left-color: var(--bo-lime);
}

.page-about .about-chapter--ink .about-aside__note,
.page-about .about-chapter--coal .about-aside__note {
  color: var(--bo-muted);
}

/* ---------- 图片 ---------- */
.page-about .about-chapter__lead {
  margin: 0 0 clamp(28px, 5vw, 56px);
}

.page-about .bo-figure__img {
  display: block;
  width: 100%;
  height: auto;
  object-fit: cover;
}

.page-about .about-chapter--paper .bo-figure__cap,
.page-about .about-signoff .bo-figure__cap {
  color: #5E6F67;
}

.page-about .about-pipeline__figure {
  margin: clamp(30px, 4.5vw, 48px) 0 0;
}

/* ---------- 时间轴 ---------- */
.page-about .about-timeline {
  list-style: none;
  margin: clamp(36px, 5vw, 62px) 0 0;
  padding: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  row-gap: 26px;
}

.page-about .about-timeline__item {
  position: relative;
  padding-left: 20px;
  border-left: 1px solid rgba(216, 242, 74, 0.45);
}

.page-about .about-timeline__label {
  display: block;
  margin-bottom: 8px;
  font-family: var(--bo-font-mono);
  font-size: 0.76rem;
  letter-spacing: 0.12em;
  color: var(--bo-lime);
}

.page-about .about-timeline__text {
  display: block;
  font-size: 0.88rem;
  line-height: 1.72;
  color: rgba(242, 245, 243, 0.75);
}

/* ---------- 两步说明 ---------- */
.page-about .about-steps {
  list-style: none;
  margin: clamp(28px, 4vw, 44px) 0 0;
  padding: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 18px;
}

.page-about .about-steps__item {
  padding: 20px 20px 22px;
  border: 1px solid rgba(58, 74, 68, 0.32);
  border-top: 3px solid var(--bo-orange);
  background: rgba(255, 255, 255, 0.42);
}

.page-about .about-steps__num {
  margin: 0 0 10px;
  font-family: var(--bo-font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.22em;
  color: var(--bo-orange);
}

.page-about .about-steps__title {
  margin: 0 0 8px;
  font-family: var(--bo-font-display);
  font-size: 1.08rem;
  font-weight: 800;
  letter-spacing: -0.01em;
}

.page-about .about-steps__text {
  margin: 0;
  font-size: 0.9rem;
  line-height: 1.76;
  color: #4A5A52;
}

/* ---------- 四道关 ---------- */
.page-about .about-gate {
  list-style: none;
  margin: clamp(28px, 4vw, 46px) 0 0;
  padding: 0;
}

.page-about .about-gate__item {
  display: grid;
  grid-template-columns: 44px minmax(0, 1fr);
  column-gap: 16px;
  padding: 20px 0;
  border-top: 1px solid rgba(242, 245, 243, 0.18);
}

.page-about .about-gate__item:last-child {
  border-bottom: 1px solid rgba(242, 245, 243, 0.18);
}

.page-about .about-gate__idx {
  padding-top: 3px;
  font-family: var(--bo-font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 0.95rem;
  letter-spacing: 0.06em;
  color: var(--bo-lime);
}

.page-about .about-gate__title {
  margin: 0 0 6px;
  font-family: var(--bo-font-display);
  font-size: 1.05rem;
  font-weight: 800;
  letter-spacing: 0.01em;
}

.page-about .about-gate__text {
  margin: 0;
  font-size: 0.92rem;
  line-height: 1.78;
  color: rgba(242, 245, 243, 0.78);
}

/* ---------- 收束 ---------- */
.page-about .about-signoff {
  background: var(--bo-paper);
  padding: clamp(32px, 5vw, 60px) 0 clamp(44px, 6vw, 78px);
}

.page-about .about-signoff__inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  padding-top: clamp(20px, 3vw, 30px);
  border-top: 1px solid rgba(58, 74, 68, 0.3);
}

.page-about .about-signoff__text {
  margin: 0;
  font-family: var(--bo-font-display);
  font-size: clamp(1.05rem, 2.6vw, 1.4rem);
  font-weight: 800;
  letter-spacing: -0.015em;
  color: #1B241F;
}

.page-about .about-subst {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
  color: #1B241F;
}

.page-about .about-subst__board {
  width: 34px;
  height: 34px;
  border: 2px solid var(--bo-orange);
  background: linear-gradient(135deg, var(--bo-orange) 0 50%, transparent 50% 100%);
  transition: transform 0.25s ease;
}

.page-about .about-subst:hover .about-subst__board,
.page-about .about-subst:focus-visible .about-subst__board {
  transform: translateY(-3px);
}

.page-about .about-subst__label {
  font-family: var(--bo-font-mono);
  font-size: 0.78rem;
  letter-spacing: 0.16em;
  border-bottom: 1px solid rgba(58, 74, 68, 0.5);
}

/* ---------- 响应式 ---------- */
@media (min-width: 720px) {
  .page-about .about-cover__stats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .page-about .about-steps {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 22px;
  }
}

@media (min-width: 860px) {
  .page-about .about-timeline {
    grid-template-columns: repeat(5, minmax(0, 1fr));
    row-gap: 0;
  }

  .page-about .about-timeline__item {
    padding: 34px 20px 0 0;
    border-left: 0;
    border-top: 1px solid rgba(242, 245, 243, 0.2);
  }

  .page-about .about-timeline__item::before {
    content: "";
    position: absolute;
    top: -1px;
    left: 0;
    width: 1px;
    height: 20px;
    background: var(--bo-lime);
  }
}

@media (min-width: 1024px) {
  .page-about .about-chapter__inner {
    grid-template-columns: 56px minmax(0, 1.35fr) minmax(0, 1fr);
    column-gap: var(--about-gap);
    align-items: start;
  }

  .page-about .about-chapter__num {
    padding-top: 10px;
  }

  .page-about .about-pipeline__figure {
    margin-left: 56px;
    max-width: 900px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .about-subst__board,
  .page-about .about-aside {
    transition: none;
  }
}