.page-about {
  --about-idx-w: 44px;
  --about-gap: 14px;
  --about-line: #17222F;
  padding-bottom: 72px;
}

/* ---------- 首屏 ---------- */
.page-about .about-hero {
  position: relative;
  overflow: hidden;
  padding: 32px 0 28px;
  border-bottom: 1px solid var(--grid);
}

.page-about .about-hero::after {
  content: "";
  position: absolute;
  right: -30%;
  top: -50%;
  width: 80%;
  height: 200%;
  pointer-events: none;
  background:
    radial-gradient(circle at 32% 34%, rgba(0, 229, 208, 0.15), transparent 62%),
    radial-gradient(circle at 72% 68%, rgba(255, 122, 26, 0.10), transparent 60%);
}

.page-about .about-hero > * {
  position: relative;
  z-index: 1;
}

.page-about .about-hero__title {
  margin: 14px 0 0;
  font-size: clamp(32px, 8.2vw, 84px);
  line-height: 1.06;
  font-weight: 900;
  letter-spacing: -0.01em;
  max-width: 15em;
}

.page-about .about-hero__mark {
  color: var(--accent);
}

.page-about .about-hero__lead {
  margin: 20px 0 0;
  max-width: 60ch;
  font-size: 16px;
  line-height: 1.72;
  color: var(--text-2);
}

/* ---------- 数字带 ---------- */
.page-about .about-numbers {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin-top: 28px;
  background: var(--grid);
  border-top: 1px solid var(--grid);
  border-bottom: 1px solid var(--grid);
}

.page-about .about-stat {
  background: var(--bg);
  padding: 16px 12px;
  display: flex;
  flex-direction: column;
  gap: 6px;
  min-width: 0;
}

.page-about .about-stat__num {
  font-family: var(--mono);
  font-size: 26px;
  line-height: 1;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  color: var(--accent);
  animation: aboutLit 520ms var(--snap) both;
}

.page-about .about-stat__label {
  font-size: 12px;
  line-height: 1.5;
  color: var(--text-2);
}

.page-about .about-stat:nth-child(2) .about-stat__num { animation-delay: 70ms; }
.page-about .about-stat:nth-child(3) .about-stat__num { animation-delay: 140ms; }
.page-about .about-stat:nth-child(4) .about-stat__num { animation-delay: 210ms; }
.page-about .about-stat:nth-child(5) .about-stat__num { animation-delay: 280ms; }
.page-about .about-stat:nth-child(6) .about-stat__num { animation-delay: 350ms; }
.page-about .about-stat:nth-child(7) .about-stat__num { animation-delay: 420ms; }
.page-about .about-stat:nth-child(8) .about-stat__num { animation-delay: 490ms; }

@keyframes aboutLit {
  from {
    color: var(--index);
    transform: translateY(6px);
  }
  to {
    color: var(--accent);
    transform: none;
  }
}

/* ---------- 章节索引 ---------- */
.page-about .about-toc {
  display: flex;
  gap: 8px;
  overflow-x: auto;
  margin-top: 24px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--grid);
  scrollbar-width: none;
  -webkit-overflow-scrolling: touch;
}

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

.page-about .about-toc__link {
  flex: 0 0 auto;
  padding: 7px 11px;
  border: 1px solid var(--grid);
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--text-2);
  text-decoration: none;
  white-space: nowrap;
  transition: color var(--fast) var(--snap), border-color var(--fast) var(--snap), background-color var(--fast) var(--snap);
}

.page-about .about-toc__link:hover,
.page-about .about-toc__link:focus-visible {
  color: var(--accent);
  border-color: var(--accent);
  background: rgba(0, 229, 208, 0.06);
  outline: none;
}

/* ---------- 纵向轨道 ---------- */
.page-about .about-track {
  position: relative;
  padding-top: 4px;
}

.page-about .about-track::before {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  left: calc(var(--about-idx-w) / 2);
  width: 1px;
  background: linear-gradient(180deg, transparent, var(--grid) 5%, var(--grid) 92%, transparent);
  pointer-events: none;
}

.page-about .about-sec {
  position: relative;
  display: grid;
  grid-template-columns: var(--about-idx-w) minmax(0, 1fr);
  gap: var(--about-gap);
  padding: 30px 0;
  border-top: 1px solid var(--grid);
}

.page-about .about-sec__idx {
  position: relative;
  z-index: 1;
  text-align: center;
  padding: 4px 0;
  background: var(--bg);
  font-family: var(--mono);
  font-size: 24px;
  line-height: 1;
  font-weight: 700;
  letter-spacing: -0.02em;
  font-variant-numeric: tabular-nums;
  color: var(--index);
}

.page-about .about-sec__body {
  min-width: 0;
}

.page-about .about-sec__title {
  margin: 8px 0 0;
  font-size: clamp(21px, 5vw, 34px);
  line-height: 1.16;
  font-weight: 800;
  letter-spacing: -0.01em;
}

.page-about .about-lead {
  margin: 14px 0 0;
  max-width: 56ch;
  font-size: 15.5px;
  line-height: 1.72;
  color: var(--text-2);
}

.page-about .about-p {
  margin: 0 0 12px;
  font-size: 15px;
  line-height: 1.72;
  color: var(--text-2);
}

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

.page-about .about-p--wide {
  margin-top: 18px;
  padding-left: 14px;
  border-left: 2px solid var(--accent-2);
  color: var(--text);
}

/* ---------- 两栏与阶段表 ---------- */
.page-about .about-cols {
  display: grid;
  gap: 20px;
  margin-top: 18px;
}

.page-about .about-stages {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 1px;
  background: var(--grid);
  border: 1px solid var(--grid);
}

.page-about .about-stages li {
  background: var(--panel);
  padding: 12px 14px;
  display: grid;
  gap: 6px;
}

.page-about .about-stages__k {
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.1em;
  color: var(--accent-2);
}

.page-about .about-stages__v {
  font-size: 14px;
  line-height: 1.6;
  color: var(--text-2);
}

/* ---------- 卡片 ---------- */
.page-about .about-cards {
  display: grid;
  gap: 12px;
  margin-top: 20px;
}

.page-about .about-card {
  background: var(--panel);
  border: 1px solid var(--grid);
  padding: 18px 16px;
  transition: border-color var(--fast) var(--snap), background-color var(--fast) var(--snap);
}

.page-about .about-card:hover {
  border-color: var(--accent);
  background: #101B28;
}

.page-about .about-card__code {
  margin: 0;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  color: var(--accent);
}

.page-about .about-card__title {
  margin: 10px 0 0;
  font-size: 18px;
  line-height: 1.3;
  font-weight: 800;
}

.page-about .about-card__text {
  margin: 10px 0 0;
  font-size: 14px;
  line-height: 1.68;
  color: var(--text-2);
}

/* ---------- 要点列表 ---------- */
.page-about .about-points {
  list-style: none;
  margin: 18px 0 0;
  padding: 0;
  display: grid;
  gap: 11px;
}

.page-about .about-points li {
  position: relative;
  padding-left: 18px;
  font-size: 14.5px;
  line-height: 1.68;
  color: var(--text-2);
}

.page-about .about-points li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.68em;
  width: 8px;
  height: 1px;
  background: var(--accent);
}

/* ---------- 折叠面板 ---------- */
.page-about .about-details {
  margin-top: 20px;
  border: 1px solid var(--grid);
  background: var(--panel);
}

.page-about .about-details > summary {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 14px 16px;
  cursor: pointer;
  list-style: none;
  font-size: 15px;
  font-weight: 600;
  color: var(--text);
  transition: color var(--fast) var(--snap);
}

.page-about .about-details > summary::-webkit-details-marker {
  display: none;
}

.page-about .about-details > summary::before {
  content: "+";
  font-family: var(--mono);
  font-size: 15px;
  color: var(--accent);
  line-height: 1;
}

.page-about .about-details[open] > summary::before {
  content: "–";
}

.page-about .about-details > summary:hover,
.page-about .about-details > summary:focus-visible {
  color: var(--accent);
  outline: none;
}

.page-about .about-details__list {
  list-style: none;
  margin: 0;
  padding: 0 16px 16px;
  border-top: 1px solid var(--grid);
  display: grid;
  gap: 10px;
}

.page-about .about-details__list li {
  position: relative;
  padding: 12px 0 0 16px;
  font-size: 14px;
  line-height: 1.65;
  color: var(--text-2);
}

.page-about .about-details__list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 20px;
  width: 6px;
  height: 6px;
  border: 1px solid var(--accent);
}

/* ---------- 内联链接 ---------- */
.page-about .about-links {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 20px;
  margin-top: 18px;
}

.page-about .about-link {
  position: relative;
  font-size: 14px;
  font-weight: 600;
  color: var(--accent);
  text-decoration: none;
  padding-bottom: 3px;
  border-bottom: 1px solid rgba(0, 229, 208, 0.4);
  transition: border-color var(--fast) var(--snap), color var(--fast) var(--snap);
}

.page-about .about-link:hover,
.page-about .about-link:focus-visible {
  color: var(--accent-soft);
  border-bottom-color: var(--accent-soft);
  outline: none;
}

/* ---------- 图片 ---------- */
.page-about .about-figure {
  margin: 22px 0 0;
  border: 1px solid var(--grid);
  background: var(--panel);
}

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

.page-about .about-figure figcaption {
  padding: 10px 12px;
  border-top: 1px solid var(--grid);
  font-size: 12px;
  line-height: 1.6;
  color: var(--text-2);
}

/* ---------- 收尾 ---------- */
.page-about .about-next {
  margin-top: 36px;
  padding: 22px 18px;
  border: 1px solid var(--grid);
  background:
    linear-gradient(120deg, rgba(0, 229, 208, 0.10), transparent 60%),
    var(--panel);
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.page-about .about-next__text {
  margin: 0;
  max-width: 52ch;
  font-size: 15px;
  line-height: 1.7;
  color: var(--text);
}

.page-about .about-next__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

/* ---------- 断点 ---------- */
@media (min-width: 560px) {
  .page-about .about-numbers {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .page-about .about-stat__num {
    font-size: 30px;
  }

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

  .page-about .about-next {
    flex-direction: row;
    align-items: center;
    justify-content: space-between;
  }
}

@media (min-width: 900px) {
  .page-about {
    --about-idx-w: 118px;
    --about-gap: 28px;
  }

  .page-about .about-hero {
    padding: 56px 0 44px;
  }

  .page-about .about-hero__lead {
    font-size: 17px;
  }

  .page-about .about-numbers {
    margin-top: 36px;
  }

  .page-about .about-stat {
    padding: 22px 18px;
  }

  .page-about .about-stat__num {
    font-size: 36px;
  }

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

  .page-about .about-sec {
    padding: 44px 0;
  }

  .page-about .about-sec__idx {
    font-size: 64px;
    padding: 6px 0;
  }

  .page-about .about-lead {
    font-size: 16.5px;
  }

  .page-about .about-p {
    font-size: 15.5px;
  }

  .page-about .about-cols {
    grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
    gap: 32px;
    align-items: start;
  }

  .page-about .about-cards {
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 16px;
  }

  .page-about .about-card {
    padding: 22px 20px;
  }

  .page-about .about-figure {
    margin-top: 28px;
  }

  .page-about .about-sec:last-child {
    padding-bottom: 56px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .about-stat__num {
    animation: none;
    color: var(--accent);
    transform: none;
  }

  .page-about .about-toc__link,
  .page-about .about-card,
  .page-about .about-link,
  .page-about .about-details > summary {
    transition: none;
  }
}