.page-about {
  --about-meta-w: 150px;
  --about-cut: 18px;
}

.page-about .about-crumb {
  background: var(--c-cream);
  padding-top: clamp(14px, 2.5vw, 22px);
}

/* ---------- 首屏 ---------- */

.page-about .about-hero {
  position: relative;
  background: var(--c-cream);
  padding: clamp(18px, 4vw, 40px) 0 clamp(26px, 5vw, 52px);
  overflow: hidden;
}

.page-about .about-hero::after {
  content: "";
  position: absolute;
  right: -110px;
  top: -90px;
  width: 360px;
  height: 360px;
  border-radius: 50%;
  background: radial-gradient(circle at 50% 50%, rgba(242, 140, 40, 0.20), rgba(242, 140, 40, 0));
  pointer-events: none;
}

.page-about .about-hero__inner {
  position: relative;
  z-index: 1;
  display: grid;
  gap: 26px;
}

@media (min-width: 940px) {
  .page-about .about-hero__inner {
    grid-template-columns: 1.15fr 0.85fr;
    gap: 52px;
    align-items: start;
  }
}

.page-about .about-hero h1 {
  font-family: var(--font-head);
  font-size: clamp(29px, 5.2vw, var(--fs-2xl));
  font-weight: 700;
  line-height: 1.24;
  letter-spacing: -0.01em;
  color: var(--c-ink);
  margin: 10px 0 16px;
}

.page-about .about-hero__lead {
  margin: 0;
  max-width: 34em;
  font-size: var(--fs-base);
  line-height: 1.8;
  color: var(--c-ink);
}

.page-about .about-hero__links {
  list-style: none;
  margin: 22px 0 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 10px 18px;
}

.page-about .about-hero__links a {
  display: inline-block;
  font-family: var(--font-head);
  font-size: var(--fs-base);
  color: var(--c-orange-deep);
  text-decoration: none;
  padding-bottom: 2px;
  border-bottom: 2px solid var(--c-orange-tint);
  transition: border-color var(--t) var(--ease), color var(--t) var(--ease);
}

.page-about .about-hero__links a:hover {
  border-bottom-color: var(--c-orange);
  color: var(--c-ink);
}

.page-about .about-hero__aside {
  background: var(--c-surface);
  border-left: 4px solid var(--c-orange);
  padding: 20px 22px 24px;
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - var(--about-cut)), calc(100% - var(--about-cut)) 100%, 0 100%);
}

.page-about .about-hero__aside-title {
  margin: 0 0 14px;
  font-family: var(--font-head);
  font-size: var(--fs-base);
  font-weight: 600;
  color: var(--c-green);
}

.page-about .about-hero__facts {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 12px;
}

.page-about .about-hero__facts li {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 8px;
  font-size: var(--fs-base);
  line-height: 1.6;
  color: var(--c-ink);
  padding-bottom: 12px;
  border-bottom: 1px dashed var(--c-border);
}

.page-about .about-hero__facts li:last-child {
  padding-bottom: 0;
  border-bottom: 0;
}

.page-about .about-hero__facts .num {
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: var(--fs-md);
  color: var(--c-orange-deep);
  letter-spacing: 0.02em;
}

/* ---------- 章节头 ---------- */

.page-about .section-head {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 10px 14px;
  margin-bottom: 22px;
}

.page-about .section-head h2 {
  flex: 1 1 auto;
  margin: 0;
  font-family: var(--font-head);
  font-size: clamp(24px, 3.4vw, var(--fs-xl));
  font-weight: 700;
  line-height: 1.3;
  letter-spacing: -0.01em;
  color: var(--c-ink);
}

.page-about .section-head__note {
  flex: 1 1 100%;
  margin: 0;
  max-width: 40em;
  font-size: var(--fs-base);
  line-height: 1.75;
  color: var(--c-muted);
}

.page-about .anchor-btn {
  flex: none;
  font-family: var(--font-head);
  font-size: var(--fs-xs);
  color: var(--c-muted);
  background: transparent;
  border: 1px solid var(--c-border);
  border-radius: 999px;
  padding: 4px 12px;
  cursor: pointer;
  white-space: nowrap;
  transition: color var(--t) var(--ease), border-color var(--t) var(--ease);
}

.page-about .anchor-btn:hover {
  color: var(--c-orange-deep);
  border-color: var(--c-orange);
}

/* ---------- 时间线 ---------- */

.page-about .about-timeline {
  background: var(--c-surface);
}

.page-about .about-timeline__figure {
  margin: 0 0 clamp(26px, 4vw, 44px);
}

.page-about .tl {
  list-style: none;
  margin: 0;
  padding: 0;
}

.page-about .tl__item {
  position: relative;
  padding-left: 36px;
  padding-bottom: 30px;
}

.page-about .tl__item:last-child {
  padding-bottom: 0;
}

.page-about .tl__item::before {
  content: "";
  position: absolute;
  left: 9px;
  top: 20px;
  bottom: -2px;
  width: 2px;
  background: linear-gradient(to bottom, rgba(46, 107, 79, 0.45), rgba(46, 107, 79, 0.1));
}

.page-about .tl__item:last-child::before {
  display: none;
}

.page-about .tl__dot {
  position: absolute;
  left: 2px;
  top: 6px;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--c-surface);
  border: 2px solid var(--c-green);
  box-shadow: 0 0 0 4px var(--c-surface);
}

.page-about .tl__item--now .tl__dot {
  background: var(--c-orange);
  border-color: var(--c-orange);
  box-shadow: 0 0 0 4px var(--c-orange-tint);
}

.page-about .tl__meta {
  margin-bottom: 8px;
}

.page-about .tl__year {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--fs-md);
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--c-orange-deep);
}

.page-about .tl__phase {
  display: inline-block;
  margin-top: 6px;
  padding: 3px 10px;
  font-family: var(--font-head);
  font-size: var(--fs-xs);
  color: var(--c-green);
  background: var(--c-green-tint);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 8px), calc(100% - 8px) 100%, 0 100%);
}

.page-about .tl__body h3 {
  margin: 0 0 8px;
  font-family: var(--font-head);
  font-size: var(--fs-md);
  font-weight: 600;
  line-height: 1.4;
  color: var(--c-ink);
}

.page-about .tl__body p {
  margin: 0;
  max-width: 34em;
  font-size: var(--fs-base);
  line-height: 1.8;
  color: var(--c-ink);
}

@media (min-width: 800px) {
  .page-about .tl__item {
    padding-left: calc(var(--about-meta-w) + 50px);
    padding-bottom: 40px;
  }

  .page-about .tl__item::before {
    left: calc(var(--about-meta-w) + 22px);
    top: 22px;
  }

  .page-about .tl__dot {
    left: calc(var(--about-meta-w) + 15px);
    top: 8px;
  }

  .page-about .tl__meta {
    position: absolute;
    left: 0;
    top: 0;
    width: var(--about-meta-w);
    margin-bottom: 0;
    text-align: right;
  }
}

/* ---------- 专题研究板 ---------- */

.page-about .board {
  background: var(--c-surface);
  border-top: 3px solid var(--c-orange);
  padding: 20px 22px 24px;
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - var(--about-cut)), calc(100% - var(--about-cut)) 100%, 0 100%);
}

.page-about .board__head {
  display: flex;
  align-items: center;
  gap: 12px;
  list-style: none;
  cursor: pointer;
  padding: 2px 0;
}

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

.page-about .board__head::after {
  content: "＋";
  margin-left: auto;
  font-family: var(--font-head);
  font-size: var(--fs-md);
  line-height: 1;
  color: var(--c-orange-deep);
}

.page-about .board[open] .board__head::after {
  content: "－";
}

.page-about .board__num {
  flex: none;
  display: grid;
  place-items: center;
  width: 34px;
  height: 34px;
  border-radius: 50%;
  background: var(--c-orange);
  color: var(--c-ink);
  font-family: var(--font-mono);
  font-size: var(--fs-base);
  font-weight: 700;
}

.page-about .board__title {
  margin: 0;
  font-family: var(--font-head);
  font-size: var(--fs-md);
  font-weight: 600;
  line-height: 1.4;
  color: var(--c-ink);
}

.page-about .board__body {
  margin-top: 18px;
}

.page-about .board__abstract {
  margin: 0 0 18px;
  padding: 14px 16px;
  background: var(--c-orange-tint);
  color: var(--c-ink);
  font-family: var(--font-head);
  font-size: var(--fs-md);
  font-weight: 600;
  line-height: 1.55;
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 14px), calc(100% - 14px) 100%, 0 100%);
}

@media (min-width: 760px) {
  .page-about .board__abstract {
    font-size: var(--fs-lg);
  }
}

.page-about .board__text p {
  margin: 0 0 13px;
  max-width: 36em;
  font-size: var(--fs-base);
  line-height: 1.82;
  color: var(--c-ink);
}

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

.page-about .board__figure {
  margin: 20px 0 0;
}

.page-about .board__more {
  margin: 18px 0 0;
  font-family: var(--font-head);
  font-size: var(--fs-base);
}

.page-about .board__more a {
  color: var(--c-orange-deep);
  text-decoration: none;
  border-bottom: 1px solid var(--c-orange-tint);
}

.page-about .board__more a:hover {
  border-bottom-color: var(--c-orange-deep);
}

/* ---------- 合作生态 ---------- */

.page-about .echo {
  display: grid;
  gap: 30px;
}

@media (min-width: 880px) {
  .page-about .echo {
    grid-template-columns: 0.9fr 1.1fr;
    align-items: center;
    gap: 48px;
  }
}

.page-about .echo__grid {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 13px;
  padding: 34px 20px;
  background: var(--c-cream);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 22px), calc(100% - 22px) 100%, 0 100%);
}

.page-about .echo__row {
  display: flex;
  gap: 13px;
}

.page-about .echo__row:nth-child(2),
.page-about .echo__row:nth-child(3) {
  transform: translateX(12px);
}

.page-about .echo__dot {
  width: 15px;
  height: 15px;
  border-radius: 50%;
  background: var(--c-green);
  transition: transform var(--t) var(--ease), background-color var(--t) var(--ease);
}

.page-about .echo__row--cloud .echo__dot {
  background: var(--c-orange);
}

.page-about .echo__dot:hover {
  transform: scale(1.45);
  background: var(--c-orange-deep);
}

.page-about .echo__side p {
  margin: 0 0 20px;
  max-width: 34em;
  font-size: var(--fs-base);
  line-height: 1.8;
  color: var(--c-ink);
}

.page-about .echo__legend {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 12px;
}

.page-about .echo__legend li {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  font-size: var(--fs-base);
  line-height: 1.7;
  color: var(--c-ink);
}

.page-about .echo__legend strong {
  font-family: var(--font-head);
  font-weight: 600;
  color: var(--c-green);
}

.page-about .echo__key {
  flex: none;
  margin-top: 8px;
  width: 12px;
  height: 12px;
  border-radius: 50%;
}

.page-about .echo__key--brand {
  background: var(--c-green);
}

.page-about .echo__key--cloud {
  background: var(--c-orange);
}

/* ---------- 用户反馈 ---------- */

.page-about .about-voice {
  background: var(--c-surface);
}

.page-about .voice p {
  margin: 0 0 14px;
  max-width: 38em;
  font-size: var(--fs-base);
  line-height: 1.8;
  color: var(--c-ink);
}

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

.page-about .about-voice__figure {
  margin: clamp(26px, 4vw, 40px) 0 0;
}

/* ---------- 收尾 ---------- */

.page-about .about-next {
  background: var(--c-orange);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 26px), calc(100% - 26px) 100%, 0 100%);
}

.page-about .about-next__inner {
  display: grid;
  gap: 22px;
}

@media (min-width: 820px) {
  .page-about .about-next__inner {
    grid-template-columns: 1.3fr 0.7fr;
    align-items: center;
    gap: 40px;
  }
}

.page-about .about-next h2 {
  margin: 0 0 10px;
  font-family: var(--font-head);
  font-size: clamp(23px, 3.2vw, var(--fs-lg));
  font-weight: 700;
  line-height: 1.35;
  color: var(--c-ink);
}

.page-about .about-next p {
  margin: 0;
  max-width: 34em;
  font-size: var(--fs-base);
  line-height: 1.75;
  color: var(--c-ink);
}

.page-about .about-next__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

/* ---------- 焦点与动效 ---------- */

.page-about a:focus-visible,
.page-about button:focus-visible,
.page-about summary:focus-visible {
  outline: 2px solid var(--c-vermilion);
  outline-offset: 2px;
}

@media (prefers-reduced-motion: reduce) {
  .page-about *,
  .page-about *::before,
  .page-about *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
  }

  .page-about .echo__dot:hover,
  .page-about .echo__row:nth-child(2),
  .page-about .echo__row:nth-child(3) {
    transform: none;
  }
}