.page-about {
  --about-pad: clamp(34px, 6vw, 76px);
  --about-stick: calc(var(--header-h) + 96px);
  background: var(--deep);
  color: var(--paper);
  overflow-x: clip;
}

/* ---------- 首屏 ---------- */
.page-about .about-hero {
  position: relative;
  padding: clamp(20px, 4vw, 38px) 0 clamp(30px, 5vw, 60px);
  border-bottom: 1px solid var(--line-dark);
  background:
    radial-gradient(880px 420px at 6% -12%, rgba(57, 230, 208, 0.16), transparent 62%),
    radial-gradient(760px 400px at 102% -4%, rgba(255, 106, 42, 0.2), transparent 60%),
    var(--deep);
}

.page-about .about-hero::after {
  content: "";
  position: absolute;
  inset: 0;
  pointer-events: none;
  background-image:
    linear-gradient(to right, rgba(207, 199, 183, 0.07) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(207, 199, 183, 0.07) 1px, transparent 1px);
  background-size: 64px 64px;
  -webkit-mask-image: linear-gradient(to bottom, rgba(0, 0, 0, 0.8), transparent 86%);
  mask-image: linear-gradient(to bottom, rgba(0, 0, 0, 0.8), transparent 86%);
}

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

.page-about .crumbs {
  margin-bottom: clamp(18px, 3vw, 30px);
}

.page-about .about-hero__grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(20px, 3.6vw, 40px);
  align-items: start;
}

.page-about .about-hero__figure {
  margin: 0;
  border: 2px solid var(--line-strong);
  box-shadow: var(--shadow-hard);
  background: var(--panel);
  border-radius: var(--radius);
  overflow: hidden;
}

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

.page-about .about-hero__figure .media__caption {
  padding: 10px 14px;
  border-top: 1px solid var(--line-dark);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.08em;
  color: var(--paper-dim);
  background: var(--night);
}

.page-about .about-hero__lead h1 {
  margin: 0.24em 0 0.5em;
  font-family: var(--font-display);
  font-weight: 800;
  letter-spacing: -0.02em;
  font-size: clamp(31px, 5.4vw, 62px);
  line-height: 1.06;
  color: var(--paper);
}

.page-about .about-hero__lead .eyebrow {
  color: var(--cyan);
}

.page-about .about-hero__lead .lead {
  max-width: 56ch;
  color: var(--paper-dim);
  font-size: clamp(15px, 1.7vw, 18px);
  line-height: 1.85;
  margin: 0 0 22px;
}

.page-about .about-hero__facts {
  list-style: none;
  margin: 0;
  padding: 16px 0 0;
  border-top: 1px solid var(--line-dark);
  display: flex;
  flex-wrap: wrap;
  gap: 10px 26px;
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--paper-dim);
}

.page-about .about-hero__facts li {
  display: flex;
  align-items: baseline;
  gap: 7px;
}

.page-about .about-hero__facts .num {
  font-family: var(--font-mono);
  font-size: 14px;
  font-weight: 700;
  color: var(--signal);
  letter-spacing: 0.02em;
}

/* ---------- 章节索引条 ---------- */
.page-about .about-toc {
  position: sticky;
  top: var(--header-h);
  z-index: 6;
  background: var(--night);
  border-bottom: 1px solid var(--line-dark);
}

.page-about .about-toc__inner {
  display: flex;
  gap: 8px;
  overflow-x: auto;
  padding: 10px 0;
  scrollbar-width: thin;
  -webkit-overflow-scrolling: touch;
}

.page-about .about-toc__inner a {
  flex: 0 0 auto;
  padding: 7px 13px;
  border: 1px solid var(--line-strong);
  border-radius: var(--radius);
  color: var(--paper);
  font-size: 12.5px;
  letter-spacing: 0.04em;
  text-decoration: none;
  transition: color 0.18s var(--ease), border-color 0.18s var(--ease), background 0.18s var(--ease);
}

.page-about .about-toc__inner a:hover,
.page-about .about-toc__inner a:focus-visible {
  border-color: var(--signal);
  color: var(--signal);
  background: rgba(255, 106, 42, 0.08);
  outline: none;
}

/* ---------- 常规章节 ---------- */
.page-about .about-sec {
  padding: var(--about-pad) 0;
}

.page-about .about-sec__grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 16px;
  align-items: start;
}

.page-about .about-sec__side {
  display: flex;
  align-items: baseline;
  gap: 12px;
}

.page-about .about-sec__num {
  font-family: var(--font-serif);
  font-size: clamp(30px, 3.4vw, 46px);
  line-height: 1;
  color: var(--signal);
}

.page-about .about-sec__label {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--cyan);
  border-top: 1px solid var(--line-dark);
  padding-top: 6px;
}

.page-about .about-sec__body {
  padding: clamp(20px, 3.4vw, 42px);
  border-radius: var(--radius);
  min-width: 0;
}

.page-about .about-sec__body.panel--paper {
  background: var(--paper);
  color: var(--ink);
  border: 2px solid var(--line-paper);
  box-shadow: 10px 10px 0 rgba(3, 10, 18, 0.48);
}

.page-about .about-sec__body--dark {
  background: var(--panel);
  color: var(--paper);
  border: 2px solid var(--line-strong);
  box-shadow: 10px 10px 0 rgba(3, 10, 18, 0.52);
}

.page-about .about-sec__body h2 {
  margin: 0 0 0.55em;
  font-family: var(--font-display);
  font-weight: 800;
  letter-spacing: -0.012em;
  font-size: clamp(23px, 3vw, 34px);
  line-height: 1.2;
}

.page-about .about-sec__body p {
  margin: 0 0 1.05em;
  font-size: clamp(15px, 1.55vw, 17px);
  line-height: 1.82;
}

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

.page-about .about-sec__body--dark p {
  color: var(--paper-dim);
}

.page-about .about-sec__body--dark h2 {
  color: var(--paper);
}

.page-about .about-link {
  color: inherit;
  text-decoration: underline;
  text-decoration-thickness: 2px;
  text-underline-offset: 3px;
  text-decoration-color: var(--signal);
}

.page-about .about-sec__body--dark .about-link {
  color: var(--cyan);
  text-decoration-color: var(--cyan);
}

.page-about .about-link:hover {
  color: var(--signal);
}

.page-about .about-pull {
  margin: 20px 0;
  padding: 8px 0 8px 18px;
  border-left: 4px solid var(--signal);
  font-family: var(--font-serif);
  font-size: clamp(17px, 2.1vw, 22px);
  line-height: 1.62;
  color: #16293c;
}

/* ---------- 数据展签 ---------- */
.page-about .about-figs {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
  margin: 20px 0 22px;
}

.page-about .about-fig {
  border: 2px solid rgba(7, 16, 24, 0.82);
  background: rgba(255, 255, 255, 0.46);
  padding: 12px 14px;
  border-radius: var(--radius);
}

.page-about .about-fig b {
  display: block;
  font-family: var(--font-display);
  font-weight: 800;
  letter-spacing: -0.02em;
  font-size: clamp(21px, 2.6vw, 30px);
  line-height: 1.12;
  color: #071018;
}

.page-about .about-fig span {
  display: block;
  margin-top: 6px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.08em;
  color: #3b4a58;
}

.page-about .about-sec__body--dark .about-fig {
  border-color: var(--line-strong);
  background: rgba(255, 255, 255, 0.045);
}

.page-about .about-sec__body--dark .about-fig b {
  color: var(--cyan);
}

.page-about .about-sec__body--dark .about-fig span {
  color: var(--paper-dim);
}

/* ---------- 版本里程碑 ---------- */
.page-about .about-timeline {
  padding: var(--about-pad) 0;
  border-top: 1px solid var(--line-dark);
  border-bottom: 1px solid var(--line-dark);
  background:
    linear-gradient(180deg, rgba(16, 42, 68, 0.9), rgba(6, 17, 28, 0.96)),
    var(--night);
}

.page-about .about-timeline__head {
  max-width: 62ch;
  margin-bottom: clamp(20px, 3vw, 34px);
}

.page-about .about-timeline__head h2 {
  margin: 0.3em 0 0.5em;
  font-family: var(--font-display);
  font-weight: 800;
  letter-spacing: -0.018em;
  font-size: clamp(26px, 3.6vw, 42px);
  line-height: 1.14;
  color: var(--paper);
}

.page-about .about-timeline__intro {
  margin: 0;
  font-size: clamp(14.5px, 1.5vw, 17px);
  line-height: 1.8;
  color: var(--paper-dim);
}

.page-about .about-timeline__fig {
  margin: 0 0 clamp(22px, 3.4vw, 36px);
  border: 2px solid var(--line-strong);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow-soft);
  background: var(--deep);
}

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

.page-about .about-timeline__fig .media__caption {
  padding: 10px 14px;
  border-top: 1px solid var(--line-dark);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.08em;
  color: var(--paper-dim);
}

.page-about .about-timeline__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 14px;
}

.page-about .about-timeline__item {
  position: relative;
  border-left: 3px solid var(--line-strong);
  padding-left: 18px;
}

.page-about .about-timeline__item::before {
  content: "";
  position: absolute;
  left: -8px;
  top: 7px;
  width: 13px;
  height: 13px;
  border-radius: 50%;
  background: var(--cyan);
  border: 2px solid var(--night);
}

.page-about .about-timeline__item.is-current::before {
  background: var(--signal);
}

.page-about .about-timeline__item details {
  padding-bottom: 4px;
}

.page-about .about-timeline__item summary {
  cursor: pointer;
  list-style: none;
  display: block;
  outline: none;
}

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

.page-about .about-timeline__item summary:focus-visible {
  outline: 2px solid var(--signal);
  outline-offset: 3px;
}

.page-about .about-timeline__version {
  display: block;
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: 0.12em;
  color: var(--cyan);
}

.page-about .about-timeline__item.is-current .about-timeline__version {
  color: var(--signal);
}

.page-about .about-timeline__title {
  display: block;
  margin: 5px 0 0;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: clamp(16px, 1.8vw, 18px);
  line-height: 1.4;
  color: var(--paper);
}

.page-about .about-timeline__title::after {
  content: " ＋";
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--paper-dim);
}

.page-about .about-timeline__item details[open] .about-timeline__title::after {
  content: " －";
  color: var(--signal);
}

.page-about .about-timeline__item p {
  margin: 10px 0 0;
  font-size: 14px;
  line-height: 1.78;
  color: var(--paper-dim);
}

/* ---------- 企业协作步骤 ---------- */
.page-about .about-tags {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 16px 0 20px;
  padding: 0;
}

.page-about .about-tags li {
  padding: 6px 12px;
  border: 2px solid rgba(7, 16, 24, 0.8);
  border-radius: var(--radius);
  background: rgba(255, 255, 255, 0.5);
  font-size: 13px;
  font-weight: 600;
  color: #0d2033;
}

.page-about .about-steps {
  list-style: none;
  counter-reset: none;
  margin: 8px 0 20px;
  padding: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 10px;
}

.page-about .about-steps li {
  border: 2px solid rgba(7, 16, 24, 0.8);
  background: rgba(255, 255, 255, 0.4);
  padding: 12px 14px;
  border-radius: var(--radius);
}

.page-about .about-steps .num {
  display: block;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.16em;
  color: #b8431a;
}

.page-about .about-steps strong {
  display: block;
  margin: 4px 0 5px;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 16px;
  color: #071018;
}

.page-about .about-steps p {
  margin: 0;
  font-size: 14px;
  line-height: 1.72;
  color: #223242;
}

/* ---------- 收尾 ---------- */
.page-about .about-next {
  padding: clamp(28px, 4.6vw, 60px) 0 clamp(40px, 6vw, 80px);
}

.page-about .about-next__panel {
  border: 2px solid var(--line-strong);
  border-left: 6px solid var(--signal);
  background: var(--panel);
  padding: clamp(20px, 3.4vw, 40px);
  box-shadow: var(--shadow-hard);
  border-radius: var(--radius);
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 20px;
}

.page-about .about-next__text h2 {
  margin: 0.25em 0 0.5em;
  font-family: var(--font-display);
  font-weight: 800;
  letter-spacing: -0.016em;
  font-size: clamp(22px, 3vw, 32px);
  line-height: 1.2;
  color: var(--paper);
}

.page-about .about-next__text p {
  margin: 0;
  max-width: 58ch;
  font-size: clamp(14.5px, 1.5vw, 16.5px);
  line-height: 1.8;
  color: var(--paper-dim);
}

.page-about .about-next__text .eyebrow {
  color: var(--cyan);
}

.page-about .about-next__links {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  align-content: start;
}

/* ---------- 断点 ---------- */
@media (min-width: 620px) {
  .page-about .about-figs {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

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

  .page-about .about-next__panel {
    grid-template-columns: minmax(0, 1.15fr) minmax(0, 0.85fr);
    align-items: center;
  }
}

@media (min-width: 900px) {
  .page-about .about-sec__grid {
    grid-template-columns: 168px minmax(0, 1fr);
    gap: clamp(24px, 4vw, 56px);
  }

  .page-about .about-sec__side {
    flex-direction: column;
    align-items: flex-start;
    gap: 10px;
    position: sticky;
    top: var(--about-stick);
  }

  .page-about .about-sec__label {
    width: 100%;
  }

  .page-about .about-timeline__list {
    grid-template-columns: repeat(5, minmax(0, 1fr));
    gap: 0;
    border-top: 2px solid var(--line-strong);
  }

  .page-about .about-timeline__item {
    border-left: 0;
    border-right: 1px solid var(--line-dark);
    padding: 26px 18px 0 0;
  }

  .page-about .about-timeline__item:last-child {
    border-right: 0;
    padding-right: 0;
  }

  .page-about .about-timeline__item::before {
    left: 0;
    top: -9px;
  }
}

@media (min-width: 980px) {
  .page-about .about-hero__grid {
    grid-template-columns: minmax(0, 5fr) minmax(0, 7fr);
    gap: clamp(28px, 3.6vw, 52px);
  }

  .page-about .about-hero__figure {
    grid-column: 1;
    grid-row: 1;
  }

  .page-about .about-hero__lead {
    grid-column: 2;
    grid-row: 1;
  }
}

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

@media (prefers-reduced-motion: reduce) {
  .page-about .about-toc__inner a {
    transition: none;
  }
}