.page-about {
  --about-rail: 7.5rem;
  --about-gap: clamp(3rem, 8vw, 6.5rem);
  position: relative;
  color: var(--text);
  background:
    radial-gradient(1100px 640px at 86% -6%, rgba(107, 63, 212, .20), transparent 62%),
    radial-gradient(820px 560px at 4% 8%, rgba(51, 214, 198, .11), transparent 60%),
    var(--felt);
  padding-bottom: clamp(3.5rem, 9vw, 7rem);
}

.page-about .breadcrumb {
  padding-top: clamp(1.1rem, 3vw, 1.75rem);
  font-size: .8125rem;
}

/* ---------- 首屏 ---------- */

.page-about .about-hero {
  padding: clamp(1.25rem, 3.5vw, 2.25rem) 0 clamp(2rem, 5vw, 3.25rem);
}

.page-about .about-hero__frame {
  display: grid;
  gap: clamp(1.75rem, 4vw, 3rem);
  padding: clamp(1.6rem, 4.2vw, 3.4rem);
  background: linear-gradient(155deg, rgba(20, 65, 58, .85) 0%, rgba(11, 43, 38, .94) 58%, rgba(43, 51, 48, .88) 100%);
}

.page-about .about-hero__eyebrow {
  color: var(--neon);
  letter-spacing: .22em;
}

.page-about .about-hero h1 {
  margin: .85rem 0 0;
  font-size: clamp(1.85rem, 5.4vw, 3.4rem);
  line-height: 1.14;
  font-weight: 900;
  letter-spacing: -.01em;
  color: var(--cream);
  text-shadow: 0 0 26px rgba(217, 166, 58, .22);
}

.page-about .about-hero__lede {
  margin: 1.1rem 0 0;
  max-width: 48ch;
  font-size: clamp(.95rem, 1.5vw, 1.0625rem);
  line-height: 1.85;
  color: var(--text);
}

.page-about .about-facts {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: 0;
  padding: 0;
  list-style: none;
  border: 1px solid var(--line-soft);
  border-radius: var(--radius-md);
  background: var(--line-soft);
  overflow: hidden;
}

.page-about .about-facts__item {
  display: flex;
  flex-direction: column;
  gap: .4rem;
  padding: 1rem 1.1rem 1.1rem;
  background: rgba(11, 43, 38, .78);
}

.page-about .about-facts__num {
  font-family: var(--font-mono);
  font-size: clamp(1.3rem, 2.6vw, 1.75rem);
  font-weight: 700;
  line-height: 1;
  letter-spacing: -.02em;
  color: var(--gold-bright);
}

.page-about .about-facts__label {
  font-size: .8125rem;
  line-height: 1.5;
  color: var(--moss);
}

/* ---------- 主体两栏 ---------- */

.page-about .about-body {
  display: grid;
  gap: clamp(1.75rem, 4vw, 2.5rem);
}

.page-about .about-rail {
  position: sticky;
  top: 3.5rem;
  z-index: 5;
  padding: .5rem 0 .6rem;
  background: linear-gradient(to bottom, rgba(11, 43, 38, .97) 76%, rgba(11, 43, 38, 0));
}

.page-about .about-rail__list {
  display: flex;
  gap: .5rem;
  margin: 0;
  padding: 0 0 .25rem;
  list-style: none;
  overflow-x: auto;
  scrollbar-width: none;
}

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

.page-about .about-rail__node {
  display: inline-flex;
  align-items: center;
  gap: .5rem;
  padding: .4rem .8rem;
  border: 1px solid var(--line-soft);
  border-radius: 999px;
  font-family: var(--font-mono);
  font-size: .75rem;
  font-weight: 600;
  letter-spacing: .04em;
  color: var(--moss);
  text-decoration: none;
  white-space: nowrap;
  transition: color .22s ease, border-color .22s ease, background-color .22s ease;
}

.page-about .about-rail__node:hover,
.page-about .about-rail__node:focus-visible {
  color: var(--gold-bright);
  border-color: var(--line-gold);
  background: rgba(217, 166, 58, .10);
}

.page-about .about-rail__dot {
  width: 7px;
  height: 7px;
  flex: none;
  border-radius: 50%;
  border: 1px solid var(--gold);
  background: transparent;
}

.page-about .about-chapters {
  display: flex;
  flex-direction: column;
  gap: var(--about-gap);
}

/* ---------- 章节 ---------- */

.page-about .about-chapter {
  scroll-margin-top: 7rem;
}

.page-about .about-chapter::before {
  content: "";
  display: block;
  height: 9px;
  margin-bottom: clamp(1.4rem, 3.4vw, 2.1rem);
  border-bottom: 1px solid var(--line-gold);
  background-image: repeating-linear-gradient(to right, rgba(217, 166, 58, .6) 0 1px, transparent 1px 18px);
  background-size: 100% 7px;
  background-position: bottom left;
  background-repeat: no-repeat;
}

.page-about .about-chapter__head {
  display: flex;
  align-items: baseline;
  gap: clamp(.9rem, 3vw, 1.9rem);
  margin-bottom: clamp(1.1rem, 2.8vw, 1.6rem);
}

.page-about .about-chapter__num {
  flex: none;
  font-family: var(--font-mono);
  font-size: clamp(2.6rem, 8vw, 4.8rem);
  font-weight: 800;
  line-height: .82;
  letter-spacing: -.05em;
  color: var(--gold);
}

.page-about .about-chapter__kicker {
  margin: 0;
  font-family: var(--font-mono);
  font-size: .6875rem;
  font-weight: 600;
  letter-spacing: .22em;
  text-transform: uppercase;
  color: var(--neon);
}

.page-about .about-chapter h2 {
  margin: .45rem 0 0;
  max-width: 24ch;
  font-size: clamp(1.3rem, 3vw, 1.95rem);
  font-weight: 800;
  line-height: 1.3;
  color: var(--cream);
}

.page-about .about-chapter__grid {
  display: grid;
  gap: clamp(1.5rem, 4vw, 2.75rem);
}

.page-about .about-chapter__text p {
  max-width: 64ch;
  margin: 0;
  font-size: clamp(.94rem, 1.35vw, 1.0625rem);
  line-height: 1.85;
  color: var(--text);
}

.page-about .about-chapter__text p + p {
  margin-top: .9rem;
}

.page-about .about-chapter__lede {
  max-width: 64ch;
  margin: 0 0 clamp(1.3rem, 3vw, 1.9rem);
  font-size: clamp(1rem, 1.6vw, 1.125rem);
  line-height: 1.8;
  color: var(--cream);
}

.page-about .about-chapter__note {
  max-width: 64ch;
  margin: clamp(1.25rem, 3vw, 1.75rem) 0 0;
  padding-left: .95rem;
  border-left: 2px solid var(--line-neon);
  font-size: .875rem;
  line-height: 1.8;
  color: var(--moss);
}

.page-about .about-chapter__figure {
  margin: 0;
}

.page-about .media {
  border: 1px solid var(--line-gold);
  border-radius: var(--radius-md);
  background: linear-gradient(140deg, var(--felt-deep), rgba(51, 214, 198, .14));
  overflow: hidden;
}

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

.page-about .media--wide {
  aspect-ratio: 3 / 2;
}

.page-about .media--tall {
  aspect-ratio: 3 / 4;
}

/* ---------- 房间分类卡片 ---------- */

.page-about .about-modes {
  display: grid;
  gap: 1px;
  margin: 0;
  padding: 0;
  list-style: none;
  border: 1px solid var(--line-soft);
  border-radius: var(--radius-md);
  background: var(--line-soft);
  overflow: hidden;
}

.page-about .about-mode {
  display: flex;
  flex-direction: column;
  gap: .55rem;
  padding: 1.25rem 1.15rem 1.35rem;
  background: rgba(11, 43, 38, .8);
  transition: background-color .25s ease;
}

.page-about .about-mode:hover {
  background: rgba(20, 65, 58, .9);
}

.page-about .about-mode__id {
  font-family: var(--font-mono);
  font-size: .6875rem;
  font-weight: 700;
  letter-spacing: .18em;
  color: var(--gold-bright);
  opacity: .8;
}

.page-about .about-mode h3 {
  margin: 0;
  font-size: 1.1rem;
  font-weight: 800;
  color: var(--cream);
}

.page-about .about-mode__time {
  display: flex;
  align-items: baseline;
  gap: .3rem;
  margin: 0;
  font-family: var(--font-mono);
  font-size: 1.5rem;
  font-weight: 700;
  line-height: 1;
  letter-spacing: -.02em;
  color: var(--gold);
}

.page-about .about-mode__time small {
  font-family: var(--font-sans);
  font-size: .6875rem;
  font-weight: 400;
  letter-spacing: 0;
  color: var(--moss);
}

.page-about .about-mode p:last-child {
  margin: 0;
  font-size: .875rem;
  line-height: 1.7;
  color: var(--moss);
}

/* ---------- 版本双轨 ---------- */

.page-about .about-tracks {
  display: grid;
  gap: clamp(1rem, 2.5vw, 1.5rem);
  margin: 0 0 1.15rem;
  padding: clamp(1.15rem, 3vw, 1.75rem);
  border: 1px solid var(--line-gold);
  border-radius: var(--radius-md);
  background: linear-gradient(150deg, rgba(20, 65, 58, .72), rgba(11, 43, 38, .92));
}

.page-about .about-track {
  display: grid;
  gap: .55rem;
}

.page-about .about-track__cap {
  display: flex;
  align-items: center;
  gap: .5rem;
  margin: 0;
  font-size: .9375rem;
  font-weight: 800;
  color: var(--cream);
}

.page-about .about-track__cap::before {
  content: "";
  width: 10px;
  height: 10px;
  flex: none;
  border-radius: 50%;
}

.page-about .about-track--beta .about-track__cap::before {
  background: var(--violet);
  box-shadow: 0 0 10px rgba(107, 63, 212, .85);
}

.page-about .about-track--stable .about-track__cap::before {
  background: var(--gold);
  box-shadow: 0 0 10px rgba(217, 166, 58, .8);
}

.page-about .about-track__rule {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  height: 22px;
  border-bottom: 1px solid var(--line-soft);
}

.page-about .about-track__rule i {
  display: block;
  flex: 1 1 0;
  border-radius: 1px;
}

.page-about .about-track--beta .about-track__rule {
  gap: 4px;
}

.page-about .about-track--beta .about-track__rule i {
  height: 12px;
  background: var(--violet);
  opacity: .78;
}

.page-about .about-track--stable .about-track__rule {
  gap: 11px;
}

.page-about .about-track--stable .about-track__rule i {
  height: 19px;
  background: var(--gold);
  opacity: .82;
}

.page-about .about-track__note {
  margin: 0;
  font-size: .875rem;
  line-height: 1.75;
  color: var(--moss);
}

/* ---------- 节点规格表 ---------- */

.page-about .about-specs {
  display: grid;
  gap: 0;
  margin: clamp(1.3rem, 3vw, 1.9rem) 0 0;
  border-top: 1px solid var(--line-soft);
}

.page-about .about-specs__row {
  display: grid;
  gap: .3rem;
  padding: .95rem 0;
  border-bottom: 1px solid var(--line-soft);
}

.page-about .about-specs dt {
  font-family: var(--font-mono);
  font-size: .75rem;
  font-weight: 600;
  letter-spacing: .14em;
  color: var(--neon);
}

.page-about .about-specs dd {
  margin: 0;
  font-size: .9375rem;
  line-height: 1.7;
  color: var(--text);
}

/* ---------- 章节收尾 ---------- */

.page-about .about-next {
  display: flex;
  flex-wrap: wrap;
  gap: .75rem;
  margin-top: clamp(1.4rem, 3.2vw, 2rem);
}

/* ---------- 桌面栅格 ---------- */

@media (min-width: 760px) {
  .page-about .about-facts {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

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

  .page-about .about-specs__row {
    grid-template-columns: 12rem minmax(0, 1fr);
    gap: 1.25rem;
    align-items: baseline;
  }
}

@media (min-width: 900px) {
  .page-about .about-chapter__grid {
    grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
    align-items: center;
  }

  .page-about .about-chapter__grid--flip .about-chapter__text {
    order: 2;
  }
}

@media (min-width: 1024px) {
  .page-about .about-hero__frame {
    grid-template-columns: minmax(0, 1.2fr) minmax(0, .8fr);
    align-items: center;
  }

  .page-about .about-body {
    grid-template-columns: var(--about-rail) minmax(0, 1fr);
    gap: clamp(2.5rem, 5vw, 4.5rem);
  }

  .page-about .about-rail {
    top: 5.5rem;
    align-self: start;
    padding: 1.5rem 0;
    background: none;
  }

  .page-about .about-rail__list {
    position: relative;
    flex-direction: column;
    gap: 0;
    overflow: visible;
    padding: 0;
  }

  .page-about .about-rail__list::before {
    content: "";
    position: absolute;
    left: 4px;
    top: .9rem;
    bottom: .9rem;
    width: 1px;
    background: linear-gradient(to bottom, var(--line-gold), var(--line-neon), var(--line-gold));
  }

  .page-about .about-rail__node {
    gap: 1.05rem;
    padding: .85rem 0;
    border: 0;
    border-radius: 0;
    background: none;
    font-size: .8125rem;
  }

  .page-about .about-rail__node:hover,
  .page-about .about-rail__node:focus-visible {
    background: none;
    color: var(--gold-bright);
  }

  .page-about .about-rail__node:hover .about-rail__dot,
  .page-about .about-rail__node:focus-visible .about-rail__dot {
    background: var(--gold);
    box-shadow: 0 0 0 3px rgba(217, 166, 58, .18);
  }

  .page-about .about-mode {
    padding: 1.5rem 1.35rem 1.6rem;
  }
}

@media (min-width: 1180px) {
  .page-about .about-modes {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

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