.page-about {
  --about-rail: 200px;
  --about-gap: clamp(18px, 3vw, 48px);
  background: var(--ink-950);
  color: var(--white-100);
  overflow-x: clip;
}

.page-about a:focus-visible,
.page-about summary:focus-visible {
  outline: 2px solid var(--lemon-300);
  outline-offset: 3px;
  border-radius: 4px;
}

/* ---------- Hero ---------- */
.page-about .about-hero {
  position: relative;
  padding: clamp(34px, 6vw, 84px) 0 clamp(30px, 5vw, 64px);
  background:
    radial-gradient(110% 82% at 88% -18%, rgba(46, 230, 214, 0.16), transparent 62%),
    radial-gradient(82% 70% at -6% 116%, rgba(255, 122, 26, 0.12), transparent 60%),
    var(--ink-900);
  border-bottom: 1px solid var(--line-700);
}

.page-about .about-hero::after {
  content: "";
  position: absolute;
  right: -6%;
  bottom: -1px;
  width: min(46%, 520px);
  height: 4px;
  background: linear-gradient(90deg, transparent, var(--cyan-400) 42%, var(--orange-500));
  transform: skewX(-32deg);
  transform-origin: right bottom;
  opacity: 0.9;
}

.page-about .breadcrumb ol {
  display: flex;
  flex-wrap: wrap;
  gap: 6px 10px;
  margin: 0 0 clamp(18px, 3vw, 30px);
  padding: 0;
  list-style: none;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--grey-300);
}

.page-about .breadcrumb li + li::before {
  content: "/";
  margin-right: 10px;
  color: var(--line-700);
}

.page-about .breadcrumb a {
  color: var(--grey-300);
  text-decoration: none;
  transition: color 0.2s var(--ease);
}

.page-about .breadcrumb a:hover {
  color: var(--cyan-400);
}

.page-about .breadcrumb [aria-current="page"] {
  color: var(--white-100);
}

.page-about .about-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  margin: 0;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--cyan-400);
}

.page-about .about-eyebrow::before {
  content: "";
  width: 26px;
  height: 2px;
  background: var(--orange-500);
}

.page-about .about-hero h1 {
  margin: clamp(14px, 2vw, 24px) 0 0;
  max-width: 17ch;
  font-family: var(--font-head);
  font-weight: 700;
  font-size: clamp(34px, 7.2vw, 86px);
  line-height: 1.04;
  letter-spacing: -0.02em;
  color: var(--white-100);
  text-wrap: balance;
}

.page-about .about-hero h1 em {
  font-style: normal;
  color: var(--cyan-400);
}

.page-about .about-lede {
  margin: clamp(18px, 2.4vw, 28px) 0 0;
  max-width: 62ch;
  font-size: clamp(15px, 1.6vw, 18px);
  line-height: 1.85;
  color: var(--grey-300);
}

/* ---------- 三步入口 ---------- */
.page-about .about-quickstart {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  align-items: center;
  gap: 16px;
  margin-top: clamp(26px, 4vw, 44px);
  padding: clamp(18px, 2.6vw, 26px);
  background: var(--ink-800);
  border: 1px solid var(--line-700);
  border-radius: var(--radius-organic);
}

.page-about .qs-title {
  margin: 0 0 12px;
  font-family: var(--font-head);
  font-size: 15px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--lemon-300);
}

.page-about .qs-steps {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 22px;
  margin: 0;
  padding: 0;
  list-style: none;
  font-size: 14px;
  color: var(--grey-300);
}

.page-about .qs-steps li {
  display: inline-flex;
  align-items: center;
  gap: 8px;
}

.page-about .qs-idx {
  display: inline-grid;
  place-items: center;
  width: 22px;
  height: 22px;
  border: 1px solid var(--cyan-400);
  border-radius: 50%;
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--cyan-400);
  flex: none;
}

/* ---------- 数据带 ---------- */
.page-about .about-figures {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin-top: clamp(30px, 4.5vw, 52px);
  background: var(--line-700);
  border: 1px solid var(--line-700);
  border-radius: var(--radius-organic);
  overflow: hidden;
}

.page-about .fig-item {
  padding: clamp(16px, 2vw, 24px);
  background: var(--ink-950);
}

.page-about .fig-num {
  display: block;
  font-family: var(--font-mono);
  font-size: clamp(24px, 3.4vw, 38px);
  line-height: 1;
  letter-spacing: -0.02em;
  color: var(--cyan-400);
}

.page-about .fig-item:nth-child(2) .fig-num {
  color: var(--orange-500);
}

.page-about .fig-item:nth-child(4) .fig-num {
  color: var(--sage-500);
}

.page-about .fig-label {
  display: block;
  margin-top: 8px;
  font-size: 13px;
  line-height: 1.55;
  color: var(--grey-300);
}

/* ---------- 章节骨架 ---------- */
.page-about .about-section {
  padding: clamp(42px, 7vw, 96px) 0;
  border-bottom: 1px solid var(--line-700);
}

.page-about .about-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(16px, 2vw, 28px);
}

.page-about .about-rail {
  display: flex;
  flex-direction: row;
  align-items: baseline;
  gap: 14px;
}

.page-about .about-num {
  font-family: var(--font-mono);
  font-size: clamp(38px, 6vw, 84px);
  line-height: 0.9;
  letter-spacing: -0.05em;
  color: rgba(46, 230, 214, 0.22);
}

.page-about .about-section--accent .about-num {
  color: rgba(255, 122, 26, 0.26);
}

.page-about .about-rail-label {
  margin: 0;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--grey-300);
}

.page-about .about-body h2 {
  margin: 0 0 18px;
  max-width: 20ch;
  font-family: var(--font-head);
  font-weight: 700;
  font-size: clamp(25px, 4vw, 46px);
  line-height: 1.12;
  letter-spacing: -0.02em;
  color: var(--white-100);
}

.page-about .about-body > p {
  margin: 0 0 18px;
  max-width: 68ch;
  font-size: clamp(15px, 1.5vw, 17px);
  line-height: 1.85;
  color: var(--grey-300);
}

.page-about .about-highlight {
  margin: 26px 0;
  padding-left: 18px;
  border-left: 3px solid var(--cyan-400);
  font-family: var(--font-head);
  font-size: clamp(17px, 2.3vw, 24px);
  line-height: 1.5;
  letter-spacing: -0.01em;
  color: var(--white-100);
}

.page-about .about-section--accent .about-highlight {
  border-left-color: var(--orange-500);
}

/* ---------- 双栏说明 ---------- */
.page-about .about-duo {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 16px;
  margin: 26px 0;
}

.page-about .about-duo > div {
  padding: 20px;
  background: var(--ink-900);
  border: 1px solid var(--line-700);
  border-left: 3px solid var(--cyan-400);
  border-radius: var(--radius-organic);
}

.page-about .about-section--accent .about-duo > div {
  border-left-color: var(--orange-500);
}

.page-about .about-duo h3 {
  margin: 0 0 8px;
  font-family: var(--font-head);
  font-size: 17px;
  letter-spacing: 0.01em;
  color: var(--white-100);
}

.page-about .about-duo p {
  margin: 0;
  font-size: 14px;
  line-height: 1.75;
  color: var(--grey-300);
}

/* ---------- 折叠旁注 ---------- */
.page-about .about-fold {
  margin-top: 24px;
  background: var(--ink-900);
  border: 1px solid var(--line-700);
  border-radius: var(--radius-organic);
  overflow: hidden;
}

.page-about .about-fold summary {
  position: relative;
  padding: 15px 48px 15px 20px;
  list-style: none;
  cursor: pointer;
  font-family: var(--font-head);
  font-size: 15px;
  letter-spacing: 0.04em;
  color: var(--lemon-300);
}

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

.page-about .about-fold summary::after {
  content: "+";
  position: absolute;
  right: 20px;
  top: 50%;
  transform: translateY(-50%);
  font-family: var(--font-mono);
  font-size: 16px;
  color: var(--cyan-400);
}

.page-about .about-fold[open] summary::after {
  content: "–";
}

.page-about .about-fold p {
  margin: 0;
  padding: 0 20px 20px;
  max-width: 64ch;
  font-size: 14px;
  line-height: 1.85;
  color: var(--grey-300);
}

/* ---------- 版本时间线 ---------- */
.page-about .about-timeline {
  margin: 30px 0 28px;
}

.page-about .tl-track {
  display: none;
}

.page-about .tl-nodes {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 22px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.page-about .tl-node {
  padding-left: 18px;
  border-left: 2px solid var(--line-700);
}

.page-about .tl-node:nth-child(1) {
  border-left-color: var(--sage-500);
}

.page-about .tl-node:nth-child(2) {
  border-left-color: var(--orange-500);
}

.page-about .tl-node:nth-child(3) {
  border-left-color: var(--cyan-400);
}

.page-about .tl-year {
  display: block;
  font-family: var(--font-mono);
  font-size: 22px;
  letter-spacing: -0.02em;
  color: var(--white-100);
}

.page-about .tl-tag {
  display: inline-block;
  margin-top: 6px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--grey-300);
}

.page-about .tl-title {
  margin: 10px 0 6px;
  font-family: var(--font-head);
  font-size: 18px;
  line-height: 1.3;
  letter-spacing: -0.01em;
  color: var(--white-100);
}

.page-about .tl-desc {
  margin: 0;
  max-width: 36ch;
  font-size: 14px;
  line-height: 1.75;
  color: var(--grey-300);
}

/* ---------- 图片容器 ---------- */
.page-about .media-frame {
  margin: clamp(26px, 4vw, 40px) 0 0;
}

.page-about .media-frame img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
  border: 1px solid var(--line-700);
  border-radius: var(--radius-organic);
}

.page-about .media-frame figcaption {
  margin-top: 10px;
  font-size: 12.5px;
  line-height: 1.6;
  letter-spacing: 0.02em;
  color: var(--sage-500);
}

/* ---------- 下一步 ---------- */
.page-about .about-next {
  padding: clamp(42px, 6vw, 84px) 0 clamp(56px, 8vw, 110px);
  background: linear-gradient(180deg, var(--ink-950), var(--ink-900));
}

.page-about .about-next h2 {
  margin: 0;
  font-family: var(--font-head);
  font-size: clamp(22px, 3.4vw, 36px);
  letter-spacing: -0.02em;
  color: var(--white-100);
}

.page-about .next-links {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 1px;
  margin: 26px 0 0;
  padding: 0;
  list-style: none;
  background: var(--line-700);
  border: 1px solid var(--line-700);
  border-radius: var(--radius-organic);
  overflow: hidden;
}

.page-about .next-links a {
  display: block;
  height: 100%;
  padding: clamp(20px, 2.4vw, 26px);
  background: var(--ink-950);
  text-decoration: none;
  transition: background 0.25s var(--ease);
}

.page-about .next-links a:hover {
  background: var(--ink-800);
}

.page-about .next-links span {
  display: block;
  font-family: var(--font-head);
  font-size: 19px;
  letter-spacing: -0.01em;
  color: var(--white-100);
}

.page-about .next-links em {
  display: block;
  margin-top: 7px;
  font-style: normal;
  font-size: 13.5px;
  line-height: 1.75;
  color: var(--grey-300);
}

/* ---------- 响应式 ---------- */
@media (min-width: 720px) {
  .page-about .about-duo,
  .page-about .next-links {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

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

  .page-about .about-quickstart {
    grid-template-columns: minmax(0, 1fr) auto;
    gap: 24px;
  }
}

@media (min-width: 860px) {
  .page-about .tl-track {
    display: block;
    height: 20px;
    margin-bottom: 18px;
  }

  .page-about .tl-track svg {
    display: block;
    width: 100%;
    height: 20px;
  }

  .page-about .tl-nodes {
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 28px;
  }

  .page-about .tl-node {
    padding-left: 0;
    padding-top: 16px;
    border-left: 0;
    border-top: 2px solid var(--line-700);
  }

  .page-about .tl-node:nth-child(1) {
    border-top-color: var(--sage-500);
  }

  .page-about .tl-node:nth-child(2) {
    border-top-color: var(--orange-500);
  }

  .page-about .tl-node:nth-child(3) {
    border-top-color: var(--cyan-400);
  }
}

@media (min-width: 980px) {
  .page-about .about-grid {
    grid-template-columns: var(--about-rail) minmax(0, 1fr);
    gap: var(--about-gap);
  }

  .page-about .about-rail {
    flex-direction: column;
    align-items: flex-start;
    gap: 10px;
  }

  .page-about .about-hero h1 {
    max-width: 19ch;
  }
}

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

  .page-about .next-links {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .next-links a,
  .page-about .breadcrumb a {
    transition: none;
  }
}