.page-about {
  --about-gap: 20px;
  background: var(--ink-800);
  color: var(--paper);
}

/* 面包屑 */
.page-about .about-crumb {
  max-width: var(--container);
  margin: 0 auto;
  padding: 16px 16px 8px;
}
.page-about .about-crumb__list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  margin: 0;
  padding: 0;
  list-style: none;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.08em;
}
.page-about .about-crumb__link {
  color: var(--mist);
  text-decoration: none;
  transition: color 0.24s var(--ease);
}
.page-about .about-crumb__link:hover {
  color: var(--cinnabar-lt);
}
.page-about .about-crumb__sep {
  color: var(--ink-600);
}
.page-about .about-crumb__current {
  color: var(--gold);
}

/* 首屏框景 */
.page-about .about-hero {
  padding: 0 16px 8px;
}
.page-about .about-hero__frame {
  position: relative;
  max-width: var(--container);
  margin: 0 auto;
  padding: 56px 20px 24px;
  border: 1px solid var(--ink-600);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  gap: 32px;
  justify-content: flex-end;
  min-height: 460px;
}
.page-about .about-hero__frame::before,
.page-about .about-hero__frame::after {
  content: "";
  position: absolute;
  width: 22px;
  height: 22px;
  z-index: 3;
  pointer-events: none;
}
.page-about .about-hero__frame::before {
  top: 10px;
  left: 10px;
  border-top: 2px solid var(--gold);
  border-left: 2px solid var(--gold);
}
.page-about .about-hero__frame::after {
  bottom: 10px;
  right: 10px;
  border-bottom: 2px solid var(--gold);
  border-right: 2px solid var(--gold);
}
.page-about .about-hero__media {
  position: absolute;
  inset: 0;
  z-index: 0;
}
.page-about .about-hero__media img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  opacity: 0.32;
  filter: grayscale(1) contrast(1.15);
}
.page-about .about-hero__frame > .about-hero__inner,
.page-about .about-hero__facts {
  position: relative;
  z-index: 2;
}
.page-about .about-hero__media::after {
  content: "";
  position: absolute;
  inset: 0;
  background:
    linear-gradient(180deg, rgba(6, 14, 24, 0.45) 0%, rgba(11, 26, 43, 0.94) 78%),
    repeating-linear-gradient(90deg, rgba(169, 182, 194, 0.08) 0 1px, transparent 1px 88px);
}
.page-about .about-hero__kicker {
  margin: 0 0 14px;
  font-size: 12px;
  letter-spacing: 0.16em;
  color: var(--mist);
}
.page-about .about-hero__kicker .sg-mono {
  color: var(--cinnabar-lt);
}
.page-about .about-hero__title {
  margin: 0 0 18px;
  font-size: clamp(2rem, 6vw, 3.6rem);
  font-weight: 900;
  line-height: 1.02;
  letter-spacing: -0.03em;
  color: var(--paper);
  max-width: 20ch;
}
.page-about .about-hero__lead {
  margin: 0 0 24px;
  max-width: 56ch;
  font-size: 16px;
  line-height: 1.8;
  color: var(--paper-dim);
}
.page-about .about-hero__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}
.page-about .about-hero__facts {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: 0;
  padding: 0;
  list-style: none;
  background: var(--ink-600);
  border: 1px solid var(--ink-600);
}
.page-about .about-hero__fact {
  padding: 14px 16px;
  background: rgba(11, 26, 43, 0.86);
  font-size: 13px;
  color: var(--mist);
  display: flex;
  flex-direction: column;
  gap: 4px;
}
.page-about .about-hero__fact .sg-mono {
  font-size: 20px;
  font-weight: 700;
  color: var(--gold);
  letter-spacing: 0.04em;
}

/* 左右双栏外壳 */
.page-about .about-shell {
  max-width: var(--container);
  margin: 0 auto;
  padding: 32px 16px 80px;
}
.page-about .about-rail {
  margin-bottom: 32px;
  padding-top: 14px;
  border-top: 2px solid var(--cinnabar);
}
.page-about .about-rail__title {
  margin: 0 0 14px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.2em;
  color: var(--mist);
}
.page-about .about-rail__list {
  margin: 0;
  padding: 0;
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 2px;
}
.page-about .about-rail__link {
  display: flex;
  align-items: baseline;
  gap: 10px;
  padding: 8px 10px;
  border-left: 2px solid transparent;
  color: var(--paper-dim);
  font-size: 14px;
  text-decoration: none;
  transition: color 0.24s var(--ease), border-color 0.24s var(--ease), background-color 0.24s var(--ease);
}
.page-about .about-rail__link .sg-mono {
  font-size: 11px;
  color: var(--ink-600);
  transition: color 0.24s var(--ease);
}
.page-about .about-rail__link:hover {
  color: var(--paper);
  border-left-color: var(--cinnabar-lt);
}
.page-about .about-rail__link:hover .sg-mono {
  color: var(--cinnabar-lt);
}
.page-about .about-rail__link[aria-current="true"] {
  color: var(--cinnabar-lt);
  border-left-color: var(--cinnabar);
  background: rgba(200, 50, 42, 0.08);
}
.page-about .about-rail__link[aria-current="true"] .sg-mono {
  color: var(--cinnabar-lt);
}
.page-about .about-rail__foot {
  margin-top: 20px;
  padding: 14px;
  border: 1px solid var(--ink-600);
  background: rgba(27, 49, 73, 0.4);
}
.page-about .about-rail__code {
  margin: 0 0 6px;
  font-size: 12px;
  color: var(--gold);
}
.page-about .about-rail__hint {
  margin: 0 0 12px;
  font-size: 12px;
  line-height: 1.7;
  color: var(--mist);
}
.page-about .about-rail__copy {
  width: 100%;
  font-size: 12px;
}

/* 章节 */
.page-about .about-section {
  padding: 36px 0;
  border-bottom: 1px solid rgba(46, 74, 103, 0.5);
}
.page-about .about-section:last-child {
  border-bottom: 0;
}
.page-about .about-section__ref {
  margin: 0;
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--cinnabar-lt);
}
.page-about .about-section__define {
  margin: 10px 0 20px;
  font-size: clamp(1.5rem, 4.4vw, 2.4rem);
  font-weight: 900;
  line-height: 1.08;
  letter-spacing: -0.025em;
  color: var(--paper);
  max-width: 18ch;
}
.page-about .about-section__lead {
  margin: 0 0 24px;
  max-width: 60ch;
  font-size: 15px;
  line-height: 1.8;
  color: var(--paper-dim);
}
.page-about .about-section__grid {
  display: grid;
  gap: 20px;
}
.page-about .about-section__prose p {
  margin: 0 0 14px;
  font-size: 15px;
  line-height: 1.85;
  color: var(--paper-dim);
}
.page-about .about-section__prose p:last-child {
  margin-bottom: 0;
}
.page-about .about-section__points {
  margin: 0;
  padding: 0;
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 1px;
  background: var(--ink-600);
  border: 1px solid var(--ink-600);
}
.page-about .about-section__points li {
  display: flex;
  gap: 12px;
  padding: 14px 16px;
  background: var(--ink-700);
  font-size: 14px;
  line-height: 1.75;
  color: var(--paper-dim);
}
.page-about .about-section__points .sg-mono {
  flex: none;
  color: var(--gold);
  font-size: 12px;
  padding-top: 2px;
}

/* 方法章节 */
.page-about .about-section--method {
  background:
    repeating-linear-gradient(90deg, rgba(169, 182, 194, 0.06) 0 1px, transparent 1px 64px);
}
.page-about .about-figure {
  margin: 0 0 24px;
  border: 1px solid var(--ink-600);
  background: var(--ink-900);
}
.page-about .about-figure img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
  border-bottom: 1px solid var(--ink-600);
}
.page-about .about-figure__caption {
  padding: 10px 14px;
  font-size: 12px;
  line-height: 1.7;
  color: var(--mist);
}
.page-about .about-steps {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
}
.page-about .about-step {
  padding: 18px 16px;
  background: var(--ink-700);
  border: 1px solid var(--ink-600);
  border-left: 3px solid var(--cinnabar);
  transition: border-color 0.24s var(--ease), transform 0.24s var(--ease);
}
.page-about .about-step:hover {
  border-color: var(--cinnabar-lt);
  transform: translateY(-3px);
}
.page-about .about-step__num {
  display: block;
  margin-bottom: 8px;
  font-size: 11px;
  letter-spacing: 0.14em;
  color: var(--gold);
}
.page-about .about-step p {
  margin: 8px 0 0;
  font-size: 14px;
  line-height: 1.75;
  color: var(--paper-dim);
}

/* 服务对象 */
.page-about .about-audience {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
}
.page-about .about-audience__item {
  padding: 20px 18px;
  border: 1px solid var(--ink-600);
  background: rgba(27, 49, 73, 0.5);
  transition: border-color 0.24s var(--ease), transform 0.24s var(--ease);
}
.page-about .about-audience__item:hover {
  border-color: var(--cinnabar-lt);
  transform: translateY(-3px);
}
.page-about .about-audience__code {
  margin: 0 0 8px;
  font-size: 11px;
  letter-spacing: 0.14em;
  color: var(--cinnabar-lt);
}
.page-about .about-audience__item p:last-of-type {
  margin: 8px 0 0;
  font-size: 14px;
  line-height: 1.78;
  color: var(--paper-dim);
}
.page-about .about-audience__tail {
  margin: 20px 0 0;
  font-size: 14px;
  line-height: 1.8;
  color: var(--mist);
}
.page-about .about-audience__tail a,
.page-about .about-team__flow a,
.page-about .about-trust__cta a {
  color: var(--cinnabar-lt);
  text-decoration: underline;
  text-underline-offset: 3px;
}
.page-about .about-audience__tail a:hover,
.page-about .about-team__flow a:hover {
  color: var(--paper);
}

/* 版本演进 */
.page-about .about-timeline {
  display: grid;
  gap: 28px;
}
.page-about .about-timeline__list {
  position: relative;
  margin: 0;
  padding: 0;
  list-style: none;
}
.page-about .about-timeline__list::before {
  content: "";
  position: absolute;
  left: 10px;
  top: 10px;
  bottom: 10px;
  width: 2px;
  background: linear-gradient(180deg, var(--cinnabar) 0%, var(--ink-600) 100%);
}
.page-about .about-timeline__item {
  position: relative;
  padding: 0 0 26px 40px;
}
.page-about .about-timeline__item:last-child {
  padding-bottom: 0;
}
.page-about .about-timeline__node {
  position: absolute;
  left: 0;
  top: 2px;
  display: block;
  width: 22px;
  height: 22px;
  text-decoration: none;
}
.page-about .about-timeline__dot {
  display: block;
  width: 100%;
  height: 100%;
  border-radius: 50%;
  border: 2px solid var(--cinnabar);
  background: var(--ink-800);
  transition: background-color 0.24s var(--ease), box-shadow 0.24s var(--ease);
}
.page-about .about-timeline__node:hover .about-timeline__dot {
  background: var(--cinnabar-lt);
}
.page-about .about-timeline__body {
  padding: 12px 14px;
  border: 1px solid transparent;
  transition: background-color 0.24s var(--ease), border-color 0.24s var(--ease);
}
.page-about .about-timeline__ver {
  margin: 0 0 6px;
  font-size: 13px;
  letter-spacing: 0.1em;
  color: var(--gold);
}
.page-about .about-timeline__body p {
  margin: 6px 0 0;
  font-size: 14px;
  line-height: 1.76;
  color: var(--paper-dim);
}
.page-about .about-timeline__item:target .about-timeline__body {
  background: rgba(27, 49, 73, 0.72);
  border-color: var(--ink-600);
}
.page-about .about-timeline__item:target .about-timeline__dot {
  background: var(--cinnabar);
  box-shadow: 0 0 0 6px rgba(200, 50, 42, 0.2);
}
.page-about .about-timeline__figure {
  margin: 0;
  border: 1px solid var(--ink-600);
  background: var(--ink-900);
  align-self: start;
}
.page-about .about-timeline__figure img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
}

/* 团队 */
.page-about .about-team {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
}
.page-about .about-team__item {
  padding: 20px 18px;
  border: 1px solid var(--ink-600);
  background: var(--ink-700);
}
.page-about .about-team__num {
  margin: 0 0 6px;
  font-size: 26px;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--cinnabar-lt);
}
.page-about .about-team__item p:last-child {
  margin: 8px 0 0;
  font-size: 14px;
  line-height: 1.78;
  color: var(--paper-dim);
}
.page-about .about-team__flow {
  margin-top: 20px;
  padding: 18px;
  border-left: 3px solid var(--gold);
  background: rgba(27, 49, 73, 0.42);
}
.page-about .about-team__flow p {
  margin: 0 0 10px;
  font-size: 14px;
  line-height: 1.8;
  color: var(--paper-dim);
}
.page-about .about-team__flow p:last-child {
  margin-bottom: 0;
}

/* 资质与合作 */
.page-about .about-section--trust {
  background:
    repeating-linear-gradient(90deg, rgba(169, 182, 194, 0.06) 0 1px, transparent 1px 64px);
}
.page-about .about-trust {
  display: grid;
  grid-template-columns: 1fr;
  gap: 16px;
}
.page-about .about-trust__col {
  padding: 20px 18px;
  border: 1px solid var(--ink-600);
  background: rgba(11, 26, 43, 0.66);
}
.page-about .about-trust__list {
  margin: 12px 0 0;
  padding: 0;
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.page-about .about-trust__list li {
  position: relative;
  padding-left: 18px;
  font-size: 14px;
  line-height: 1.78;
  color: var(--paper-dim);
}
.page-about .about-trust__list li::before {
  content: "·";
  position: absolute;
  left: 4px;
  top: -2px;
  color: var(--cinnabar-lt);
  font-weight: 700;
}
.page-about .about-trust__cta {
  margin-top: 20px;
  padding: 22px 18px;
  border: 1px solid var(--ink-600);
  background: var(--ink-700);
  display: flex;
  flex-direction: column;
  gap: 16px;
  align-items: flex-start;
}
.page-about .about-trust__cta p {
  margin: 0;
  font-size: 14px;
  line-height: 1.8;
  color: var(--paper-dim);
}

/* 平板 */
@media (min-width: 640px) {
  .page-about .about-hero__frame {
    padding: 64px 40px 28px;
    min-height: 500px;
  }
  .page-about .about-hero__facts {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
  .page-about .about-shell {
    padding: 40px 24px 96px;
  }
  .page-about .about-steps {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
  .page-about .about-audience {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
  .page-about .about-team {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
  .page-about .about-trust {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
  .page-about .about-section__grid {
    grid-template-columns: minmax(0, 1.2fr) minmax(0, 1fr);
    gap: 28px;
    align-items: start;
  }
}

/* 桌面：左轨 + 主内容 */
@media (min-width: 1024px) {
  .page-about .about-shell {
    display: grid;
    grid-template-columns: var(--rail-w) minmax(0, 1fr);
    gap: 56px;
    align-items: start;
  }
  .page-about .about-rail {
    position: sticky;
    top: calc(var(--sg-header-h) + 20px);
    margin-bottom: 0;
  }
  .page-about .about-section {
    padding: 44px 0;
  }
  .page-about .about-timeline {
    grid-template-columns: minmax(0, 1.35fr) minmax(0, 1fr);
    gap: 40px;
    align-items: start;
  }
  .page-about .about-timeline__figure {
    position: sticky;
    top: calc(var(--sg-header-h) + 20px);
  }
  .page-about .about-hero__frame {
    padding: 88px 56px 32px;
    min-height: 540px;
  }
  .page-about .about-hero__title {
    font-size: clamp(2.8rem, 4.4vw, 4rem);
  }
  .page-about .about-trust__cta {
    flex-direction: row;
    align-items: center;
    justify-content: space-between;
  }
  .page-about .about-trust__cta p {
    max-width: 62ch;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .about-step,
  .page-about .about-audience__item,
  .page-about .about-timeline__dot,
  .page-about .about-rail__link {
    transition: none;
  }
  .page-about .about-step:hover,
  .page-about .about-audience__item:hover {
    transform: none;
  }
}