.page-about {
  --about-border: 3px solid var(--black);
  --about-shadow: 5px 5px 0 var(--black);
  --about-grid-line: rgba(124, 139, 149, 0.13);
  position: relative;
  background-color: var(--ink-deep);
  background-image:
    repeating-linear-gradient(to right, var(--about-grid-line) 0 1px, transparent 1px 56px),
    repeating-linear-gradient(to bottom, var(--about-grid-line) 0 1px, transparent 1px 56px);
  color: var(--cream);
}

.page-about .section {
  padding: 2.75rem 0;
}

@media (min-width: 768px) {
  .page-about .section {
    padding: 4rem 0;
  }
}

/* ---------- 首屏 ---------- */

.about-hero {
  padding: 1.75rem 0 2.5rem;
  border-bottom: 3px solid var(--black);
}

@media (min-width: 768px) {
  .about-hero {
    padding: 2.5rem 0 4rem;
  }
}

.page-about .about-hero__title {
  margin: 0.9rem 0 1.1rem;
  font-size: clamp(2rem, 8vw, 4.4rem);
  line-height: 1.04;
  letter-spacing: -0.02em;
  color: var(--cream);
  text-wrap: balance;
}

.about-hero__mark {
  color: var(--cyan);
  box-shadow: inset 0 -0.24em 0 rgba(25, 227, 200, 0.22);
}

.page-about .about-hero__lede {
  max-width: 34em;
  margin: 0 0 0.9rem;
  font-size: 1rem;
  line-height: 1.75;
  color: var(--cream);
}

@media (min-width: 768px) {
  .page-about .about-hero__lede {
    font-size: 1.06rem;
  }
}

.about-hero__note {
  max-width: 34em;
  margin: 0;
  font-size: 0.9rem;
  line-height: 1.7;
  color: var(--rock);
  border-left: 2px solid var(--clay);
  padding-left: 0.75rem;
}

.about-stats {
  list-style: none;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: 2rem 0 0;
  padding: 0;
  background-color: var(--line-strong);
  border: var(--about-border);
  box-shadow: var(--about-shadow);
}

@media (min-width: 860px) {
  .about-stats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

.about-stat {
  background-color: var(--panel);
  padding: 1rem 1.05rem;
  transition: background-color 120ms linear;
}

.about-stat:hover {
  background-color: #0f3450;
}

.about-stat__num {
  display: block;
  font-family: var(--font-num);
  font-variant-numeric: tabular-nums;
  font-size: 1.55rem;
  font-weight: 700;
  line-height: 1.1;
  color: var(--cyan);
}

@media (min-width: 768px) {
  .about-stat__num {
    font-size: 1.9rem;
  }
}

.about-stat__label {
  display: block;
  margin-top: 0.35rem;
  font-size: 0.78rem;
  letter-spacing: 0.06em;
  color: var(--rock);
}

/* ---------- 章节索引 ---------- */

.about-index {
  padding: 2rem 0 1rem;
  border-bottom: 1px solid var(--line);
}

.page-about .about-index__list {
  list-style: none;
  display: grid;
  grid-template-columns: 1fr;
  gap: 1px;
  margin: 1rem 0 0;
  padding: 0;
  background-color: var(--line);
  border-top: 1px solid var(--line-strong);
}

@media (min-width: 700px) {
  .page-about .about-index__list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (min-width: 1080px) {
  .page-about .about-index__list {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

.about-index__item {
  background-color: var(--ink-deep);
}

.about-index__link {
  display: flex;
  align-items: baseline;
  gap: 0.7rem;
  min-height: 44px;
  padding: 0.85rem 0.6rem;
  color: var(--cream);
  text-decoration: none;
  font-size: 0.95rem;
  border-bottom: 1px solid var(--line);
  transition: color 120ms linear, background-color 120ms linear;
}

.about-index__link:hover,
.about-index__link:focus-visible {
  color: var(--cyan);
  background-color: var(--panel);
  outline: none;
}

.about-index__num {
  font-family: var(--font-num);
  font-variant-numeric: tabular-nums;
  font-size: 0.8rem;
  color: var(--clay);
  letter-spacing: 0.04em;
}

/* ---------- 章节通用头部 ---------- */

.about-head {
  max-width: 40em;
  margin-bottom: 1.5rem;
}

.page-about .about-head__title {
  margin: 0.45rem 0 0.85rem;
  font-size: clamp(1.55rem, 5.4vw, 2.6rem);
  line-height: 1.1;
  letter-spacing: -0.01em;
  color: var(--cream);
}

.page-about .about-head__lede {
  margin: 0;
  font-size: 0.98rem;
  line-height: 1.75;
  color: var(--rock);
}

.page-about .about-head__lede--dark {
  color: #3c4a55;
}

.about-head__eyebrow--dark {
  color: var(--clay);
}

/* ---------- 01 起点 ---------- */

.about-chapter {
  border-bottom: 1px solid var(--line);
}

.about-chapter__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.75rem;
}

@media (min-width: 900px) {
  .about-chapter__grid {
    grid-template-columns: 104px minmax(0, 1fr);
    gap: 2.5rem;
  }
}

.about-chapter__num {
  margin: 0;
  font-family: var(--font-num);
  font-variant-numeric: tabular-nums;
  font-size: 1.6rem;
  font-weight: 700;
  line-height: 1;
  color: var(--clay);
  letter-spacing: 0.04em;
}

@media (min-width: 900px) {
  .about-chapter__num {
    font-size: 2.6rem;
    padding-top: 0.35rem;
  }
}

.page-about .about-chapter__title {
  margin: 0 0 1rem;
  font-size: clamp(1.6rem, 5.6vw, 2.7rem);
  line-height: 1.08;
  color: var(--cream);
}

.page-about .about-chapter__prose {
  max-width: 36em;
}

.page-about .about-chapter__prose p {
  margin: 0 0 1rem;
  font-size: 1rem;
  line-height: 1.8;
  color: var(--cream);
}

.about-quote {
  margin: 1.5rem 0 0;
  padding: 0.9rem 1.1rem;
  font-size: 1.02rem;
  line-height: 1.6;
  color: var(--cream);
  background-color: var(--panel);
  border-left: 4px solid var(--cyan);
}

/* ---------- 02 时间线 ---------- */

.about-timeline {
  border-bottom: 1px solid var(--line);
}

.tl {
  list-style: none;
  margin: 0;
  padding: 0 0 0 1.9rem;
  border-left: 2px solid var(--line-strong);
}

.tl__item {
  position: relative;
  padding: 0 0 1.75rem;
  transition: transform 120ms ease;
}

.tl__item::before {
  content: "";
  position: absolute;
  left: -8px;
  top: 0.4rem;
  width: 12px;
  height: 12px;
  box-sizing: border-box;
  border-radius: 50%;
  background-color: var(--ink-deep);
  border: 3px solid var(--cyan);
  transition: background-color 120ms linear, border-color 120ms linear;
}

.tl__item:hover::before,
.tl__item:focus-visible::before,
.tl__item:focus-within::before {
  background-color: var(--coral);
  border-color: var(--coral);
}

.tl__item:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: 4px;
}

.tl__year {
  margin: 0;
  font-family: var(--font-num);
  font-variant-numeric: tabular-nums;
  font-size: 0.82rem;
  letter-spacing: 0.08em;
  color: var(--clay);
}

.tl__title {
  margin: 0.3rem 0 0.4rem;
  font-size: 1.1rem;
  font-weight: 700;
  line-height: 1.35;
  color: var(--cream);
}

.tl__text {
  margin: 0;
  font-size: 0.94rem;
  line-height: 1.7;
  color: var(--rock);
}

.tl__note {
  margin: 0.5rem 0 0;
  font-size: 0.85rem;
  line-height: 1.65;
  color: var(--cream);
  border-left: 2px solid var(--moss);
  padding-left: 0.6rem;
  max-height: 6rem;
  opacity: 1;
  overflow: hidden;
  transition: max-height 200ms ease, opacity 200ms ease;
}

@media (hover: hover) and (min-width: 900px) {
  .tl__note {
    max-height: 0;
    opacity: 0;
  }

  .tl__item:hover .tl__note,
  .tl__item:focus-within .tl__note {
    max-height: 6rem;
    opacity: 1;
  }
}

/* ---------- 03 数据来源 ---------- */

.about-sources {
  border-bottom: 1px solid var(--line);
}

.about-sources__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
}

@media (min-width: 900px) {
  .about-sources__grid {
    grid-template-columns: minmax(0, 7fr) minmax(0, 4fr);
    gap: 3rem;
    align-items: start;
  }
}

@media (min-width: 1080px) {
  .about-sources__grid {
    grid-template-columns: minmax(0, 7fr) minmax(0, 3fr);
  }
}

.about-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin: 1.25rem 0 0;
}

/* ---------- 图片容器 ---------- */

.about-figure {
  margin: 0;
  border: var(--about-border);
  box-shadow: var(--about-shadow);
  background-color: var(--panel);
  overflow: hidden;
}

.about-figure img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
  filter: saturate(1.05) contrast(1.05);
}

.about-figure--flat {
  box-shadow: none;
}

.about-figure__cap {
  display: block;
  padding: 0.6rem 0.75rem;
  font-size: 0.78rem;
  line-height: 1.5;
  letter-spacing: 0.02em;
  color: var(--rock);
  border-top: 1px solid var(--line);
  background-color: var(--ink-deep);
}

.about-sources__aside .about-figure {
  margin-top: 0;
}

/* ---------- 04 团队（反白） ---------- */

.page-about .about-team {
  background-color: var(--cream);
  color: var(--ink-deep);
  background-image: none;
  border-top: 3px solid var(--black);
  border-bottom: 3px solid var(--black);
}

.page-about .about-team .about-head__title {
  color: var(--ink-deep);
}

.about-team__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.75rem;
}

@media (min-width: 900px) {
  .about-team__grid {
    grid-template-columns: minmax(0, 7fr) minmax(0, 4fr);
    gap: 3rem;
    align-items: start;
  }
}

.about-team__body p {
  margin: 0 0 1rem;
  font-size: 1rem;
  line-height: 1.8;
  color: #23323d;
}

.about-team__stats {
  list-style: none;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.75rem;
  margin: 0;
  padding: 0;
}

.about-team__stat {
  border: 2px solid var(--ink-deep);
  box-shadow: 4px 4px 0 var(--ink-deep);
  padding: 0.75rem 0.7rem;
  background-color: #fbf7ef;
}

.about-team__stat-num {
  display: block;
  font-family: var(--font-num);
  font-variant-numeric: tabular-nums;
  font-size: 1.15rem;
  font-weight: 700;
  line-height: 1.2;
  color: var(--clay);
}

.about-team__stat-label {
  display: block;
  margin-top: 0.3rem;
  font-size: 0.76rem;
  letter-spacing: 0.06em;
  color: #4a5863;
}

.page-about .about-team .about-figure {
  margin-top: 2rem;
  box-shadow: 5px 5px 0 var(--ink-deep);
  border-color: var(--ink-deep);
  background-color: var(--ink-deep);
}

.page-about .about-team .about-figure__cap {
  color: var(--rock);
}

/* ---------- 05 覆盖 ---------- */

.about-coverage {
  border-bottom: 1px solid var(--line);
}

.about-coverage .about-figure {
  margin-bottom: 1.75rem;
}

.about-coverage__stats {
  list-style: none;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: 0 0 1.5rem;
  padding: 0;
  background-color: var(--line-strong);
  border: var(--about-border);
}

@media (min-width: 860px) {
  .about-coverage__stats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

.about-coverage__stat {
  background-color: var(--panel);
  padding: 0.95rem 1rem;
}

.about-coverage__num {
  display: block;
  font-family: var(--font-num);
  font-variant-numeric: tabular-nums;
  font-size: 1.2rem;
  font-weight: 700;
  line-height: 1.25;
  color: var(--cyan);
}

.about-coverage__label {
  display: block;
  margin-top: 0.35rem;
  font-size: 0.76rem;
  letter-spacing: 0.06em;
  color: var(--rock);
}

.about-coverage__foot {
  max-width: 36em;
  margin: 0;
  font-size: 0.96rem;
  line-height: 1.8;
  color: var(--cream);
  border-top: 1px solid var(--line);
  padding-top: 1.25rem;
}

/* ---------- 06 坚持 ---------- */

.about-principles-section {
  border-bottom: 1px solid var(--line);
}

.about-principles {
  list-style: none;
  display: grid;
  grid-template-columns: 1fr;
  gap: 1px;
  margin: 0;
  padding: 0;
  background-color: var(--line-strong);
  border: var(--about-border);
  box-shadow: var(--about-shadow);
}

@media (min-width: 700px) {
  .about-principles {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

.principle {
  background-color: var(--panel);
  padding: 1.25rem 1.1rem 1.4rem;
  transition: background-color 120ms linear;
}

.principle:hover {
  background-color: #0f3450;
}

.principle__k {
  margin: 0 0 0.6rem;
  font-family: var(--font-num);
  font-variant-numeric: tabular-nums;
  font-size: 0.76rem;
  letter-spacing: 0.1em;
  color: var(--moss);
}

.principle__t {
  margin: 0 0 0.5rem;
  font-size: 1.08rem;
  line-height: 1.4;
  color: var(--cream);
}

.principle__d {
  margin: 0;
  font-size: 0.92rem;
  line-height: 1.75;
  color: var(--rock);
}

/* ---------- 07 注册 ---------- */

.about-signup {
  border-bottom: 1px solid var(--line);
}

.steps {
  list-style: none;
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
  margin: 0;
  padding: 0;
}

@media (min-width: 800px) {
  .steps {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

.step {
  position: relative;
  border: var(--about-border);
  box-shadow: var(--hard-shadow);
  background-color: var(--panel);
  padding: 1.1rem 1.05rem 1.25rem;
}

.step__num {
  margin: 0 0 0.7rem;
  font-family: var(--font-num);
  font-variant-numeric: tabular-nums;
  font-size: 1.4rem;
  font-weight: 700;
  line-height: 1;
  color: var(--coral);
}

.step__title {
  margin: 0 0 0.5rem;
  font-size: 1.02rem;
  line-height: 1.4;
  color: var(--cream);
}

.step__text {
  margin: 0;
  font-size: 0.92rem;
  line-height: 1.75;
  color: var(--rock);
}

.about-signup__note {
  max-width: 36em;
  margin: 1.5rem 0 0;
  padding: 0.9rem 1rem;
  font-size: 0.94rem;
  line-height: 1.8;
  color: var(--cream);
  background-color: rgba(108, 143, 98, 0.14);
  border-left: 4px solid var(--moss);
}

/* ---------- 收尾 ---------- */

.about-outro {
  padding: 2.5rem 0 3rem;
  background-color: var(--black);
  border-top: 3px solid var(--cyan);
}

.about-outro__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
}

@media (min-width: 900px) {
  .about-outro__grid {
    grid-template-columns: minmax(0, 7fr) minmax(0, 3fr);
    gap: 3rem;
    align-items: center;
  }
}

.page-about .about-outro__title {
  margin: 0 0 0.85rem;
  font-size: clamp(1.5rem, 5vw, 2.3rem);
  line-height: 1.12;
  color: var(--cream);
}

.about-outro__text {
  max-width: 34em;
  margin: 0 0 1.25rem;
  font-size: 0.96rem;
  line-height: 1.8;
  color: var(--rock);
}

.about-outro__links {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.75rem;
  margin: 0;
}

.about-contact {
  border: var(--about-border);
  box-shadow: var(--about-shadow);
  background-color: var(--panel);
  padding: 1.15rem 1.1rem 1.25rem;
}

.about-contact__label {
  margin: 0 0 0.5rem;
  color: var(--rock);
}

.about-contact__value {
  margin: 0 0 0.9rem;
  font-family: var(--font-num);
  font-size: 0.92rem;
  line-height: 1.5;
  word-break: break-all;
  color: var(--cyan);
}

.about-contact__btn {
  width: 100%;
}

@media (min-width: 480px) {
  .about-contact__btn {
    width: auto;
  }
}