.page-about {
  --about-rail-w: 220px;
  --about-rule: rgba(168, 201, 184, .28);
  display: block;
  background: var(--paper);
  color: var(--text-on-light);
}

/* ---------- 首屏 ---------- */
.page-about .about-hero {
  position: relative;
  overflow: hidden;
  background: var(--ink);
  color: var(--text-on-dark);
  border-bottom: var(--line-strong) solid var(--black);
  padding-block: clamp(28px, 5vw, 56px) clamp(44px, 7vw, 96px);
}

.page-about .about-hero::after {
  content: "";
  position: absolute;
  inset: 0;
  pointer-events: none;
  background-image: repeating-linear-gradient(90deg, rgba(217, 164, 65, .07) 0 1px, transparent 1px 84px);
}

.page-about .about-hero__inner {
  position: relative;
  z-index: 1;
}

.page-about .about-hero .breadcrumbs {
  color: var(--text-mute-dark);
  font-size: var(--fs-14);
  margin-bottom: 22px;
}

.page-about .about-hero .breadcrumbs a {
  color: var(--text-mute-dark);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color var(--dur-1) var(--ease), border-color var(--dur-1) var(--ease);
}

.page-about .about-hero .breadcrumbs a:hover {
  color: var(--gold-2);
  border-bottom-color: var(--gold-2);
}

.page-about .about-hero__eyebrow {
  color: var(--gold);
  letter-spacing: .12em;
  font-size: var(--fs-12);
  margin: 0 0 14px;
}

.page-about .about-hero__title {
  margin: 0 0 22px;
  font-family: var(--serif);
  font-weight: 900;
  font-size: clamp(2.25rem, 6.6vw, var(--fs-64));
  line-height: 1.1;
  letter-spacing: -0.02em;
  color: var(--near-white);
  max-width: 15ch;
}

.page-about .about-hero__lede {
  margin: 0 0 30px;
  max-width: 60ch;
  font-size: var(--fs-17);
  line-height: 1.78;
  color: var(--text-on-dark);
}

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

/* ---------- 主布局：左轨 + 内容流 ---------- */
.page-about .about-layout {
  display: grid;
  gap: clamp(26px, 4vw, 52px);
  padding-block: clamp(36px, 5vw, 72px) clamp(56px, 8vw, 112px);
}

@media (min-width: 1024px) {
  .page-about .about-layout {
    grid-template-columns: var(--about-rail-w) minmax(0, 1fr);
    gap: clamp(40px, 5vw, 76px);
  }
}

/* ---------- 左轨 ---------- */
.page-about .about-rail__title {
  margin: 0 0 14px;
  font-size: var(--fs-12);
  letter-spacing: .18em;
  color: var(--moss);
}

.page-about .about-rail__list {
  list-style: none;
  margin: 0;
  padding: 0;
  position: relative;
}

.page-about .about-rail__list::before {
  content: "";
  position: absolute;
  left: 9px;
  top: 10px;
  bottom: 10px;
  width: var(--line-thin);
  background: var(--jade);
}

.page-about .about-rail__item {
  position: relative;
}

.page-about .about-rail__item::before {
  content: "";
  position: absolute;
  left: 4px;
  top: 50%;
  transform: translateY(-50%);
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--moss);
  box-shadow: 0 0 0 3px var(--paper);
  transition: background var(--dur-2) var(--ease), transform var(--dur-2) var(--ease);
  z-index: 1;
}

.page-about .about-rail__item:hover::before {
  background: var(--gold);
  transform: translateY(-50%) scale(1.25);
}

.page-about .about-rail__link {
  display: flex;
  align-items: baseline;
  gap: 10px;
  padding: 10px 12px 10px 30px;
  color: var(--text-mute-light);
  text-decoration: none;
  font-size: var(--fs-14);
  line-height: 1.5;
  border-radius: var(--radius-pill);
  transition: color var(--dur-2) var(--ease), background var(--dur-2) var(--ease);
}

.page-about .about-rail__num {
  font-size: var(--fs-12);
  color: var(--moss);
  letter-spacing: .08em;
  flex: none;
}

.page-about .about-rail__link:hover,
.page-about .about-rail__link:focus-visible {
  color: var(--ink);
  background: rgba(217, 164, 65, .16);
}

.page-about .about-rail__link:focus-visible {
  outline: var(--line-strong) solid var(--gold);
  outline-offset: 2px;
}

@media (max-width: 1023px) {
  .page-about .about-rail {
    overflow-x: auto;
    padding-bottom: 6px;
    scrollbar-width: thin;
  }

  .page-about .about-rail__list {
    display: flex;
    gap: 8px;
  }

  .page-about .about-rail__list::before,
  .page-about .about-rail__item::before {
    display: none;
  }

  .page-about .about-rail__link {
    padding: 9px 16px;
    border: var(--line-thin) solid var(--moss);
    white-space: nowrap;
    background: var(--near-white);
  }
}

/* ---------- 章节 ---------- */
.page-about .about-stream {
  min-width: 0;
}

.page-about .chapter {
  padding-block: clamp(34px, 5vw, 64px);
}

.page-about .chapter:first-child {
  padding-top: 0;
}

.page-about .chapter__head {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 14px;
  padding-bottom: 16px;
  border-bottom: var(--line-thin) solid var(--gold);
  margin-bottom: 22px;
}

.page-about .chapter__index {
  margin: 0;
  font-size: var(--fs-14);
  letter-spacing: .12em;
  color: var(--gold);
  flex: none;
}

.page-about .chapter__title {
  margin: 0;
  font-family: var(--serif);
  font-weight: 800;
  font-size: clamp(1.4rem, 3.4vw, var(--fs-40));
  line-height: 1.2;
  letter-spacing: -0.015em;
  color: var(--ink);
}

.page-about .chapter__lede {
  margin: 0 0 24px;
  max-width: 62ch;
  font-size: var(--fs-17);
  line-height: 1.75;
  color: var(--text-on-light);
}

.page-about .chapter__body {
  display: grid;
  gap: 14px;
  max-width: 68ch;
  font-size: var(--fs-17);
  line-height: 1.78;
  color: var(--text-on-light);
}

.page-about .chapter__body p {
  margin: 0;
}

.page-about .about-note {
  margin: 22px 0 0;
  max-width: 62ch;
  font-size: var(--fs-14);
  line-height: 1.75;
  color: var(--text-mute-light);
  padding-left: 16px;
  border-left: var(--line-thin) solid var(--jade);
}

.page-about .about-note a {
  color: var(--moss);
  text-decoration: none;
  border-bottom: 1px solid var(--gold);
}

.page-about .about-note a:hover {
  color: var(--gold);
}

.page-about .about-subtitle {
  margin: 0 0 14px;
  font-family: var(--serif);
  font-weight: 700;
  font-size: var(--fs-21);
  color: var(--ink);
}

.page-about .about-figure {
  margin: 0;
}

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

.page-about .about-figure .img-frame__caption {
  font-size: var(--fs-12);
  color: var(--text-mute-light);
  line-height: 1.6;
}

/* ---------- 数据板 ---------- */
.page-about .data-board {
  margin-top: 24px;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  background: var(--ink-2);
  border: var(--line-strong) solid var(--black);
  border-radius: var(--radius-card);
  box-shadow: var(--shadow-hard);
  overflow: hidden;
}

@media (min-width: 560px) {
  .page-about .data-board {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (min-width: 1024px) {
  .page-about .data-board {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

.page-about .data-row {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
  padding: 14px 18px;
  border-bottom: var(--line-thin) solid var(--about-rule);
}

.page-about .data-key {
  font-size: var(--fs-14);
  color: var(--text-mute-dark);
}

.page-about .data-value {
  font-size: var(--fs-21);
  font-weight: 700;
  color: var(--gold-2);
  letter-spacing: .04em;
  white-space: nowrap;
}

.page-about .about-league-data {
  grid-template-columns: minmax(0, 1fr);
}

@media (min-width: 560px) {
  .page-about .about-league-data {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

/* ---------- 流程 / 数字 双栏 ---------- */
.page-about .about-split {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(22px, 3vw, 34px);
  margin-top: 8px;
}

@media (min-width: 820px) {
  .page-about .about-split {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    align-items: start;
  }
}

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

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

.page-about .step-list__item {
  display: grid;
  grid-template-columns: 42px minmax(0, 1fr);
  gap: 12px;
  align-items: start;
  padding: 14px 16px;
  background: var(--near-white);
  border: var(--line-thin) solid var(--black);
  border-radius: 12px;
  box-shadow: 4px 4px 0 rgba(10, 24, 20, .14);
  transition: transform var(--dur-2) var(--ease), box-shadow var(--dur-2) var(--ease);
}

.page-about .step-list__item:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-hard);
}

.page-about .step-list__num {
  font-size: var(--fs-14);
  color: var(--moss);
  letter-spacing: .08em;
}

.page-about .step-list__item strong {
  display: block;
  margin-bottom: 3px;
  font-size: var(--fs-17);
  color: var(--ink);
}

.page-about .step-list__item p {
  margin: 0;
  font-size: var(--fs-14);
  line-height: 1.7;
  color: var(--text-mute-light);
}

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

/* ---------- 九级段位 ---------- */
.page-about .about-split--rank {
  margin-top: 26px;
}

@media (min-width: 820px) {
  .page-about .about-split--rank {
    grid-template-columns: minmax(0, 1fr) 240px;
    align-items: end;
  }
}

.page-about .rank-ladder {
  list-style: none;
  margin: 0;
  padding: 20px 14px 14px;
  display: flex;
  align-items: flex-end;
  gap: clamp(3px, 1vw, 10px);
  background: var(--ink);
  border: var(--line-strong) solid var(--black);
  border-radius: var(--radius-card);
  box-shadow: var(--shadow-hard);
}

.page-about .rank-step {
  flex: 1 1 0;
  min-width: 0;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  align-items: center;
  gap: 6px;
}

.page-about .rank-step__num {
  font-size: var(--fs-12);
  color: var(--gold-2);
  letter-spacing: .06em;
}

.page-about .rank-step__bar {
  display: block;
  width: 100%;
  height: var(--bar-h, 40px);
  background: linear-gradient(180deg, var(--moss), #1E4C3C);
  border: var(--line-thin) solid var(--black);
  border-bottom: 0;
  border-radius: 6px 6px 2px 2px;
  transition: background var(--dur-2) var(--ease), transform var(--dur-2) var(--ease);
}

.page-about .rank-step:hover .rank-step__bar {
  background: linear-gradient(180deg, var(--gold), var(--gold-2));
  transform: translateY(-3px);
}

.page-about .rank-step__name {
  font-size: var(--fs-12);
  color: var(--text-mute-dark);
  white-space: nowrap;
}

.page-about .rank-step:nth-child(1) .rank-step__bar { --bar-h: 28px; }
.page-about .rank-step:nth-child(2) .rank-step__bar { --bar-h: 44px; }
.page-about .rank-step:nth-child(3) .rank-step__bar { --bar-h: 60px; }
.page-about .rank-step:nth-child(4) .rank-step__bar { --bar-h: 76px; }
.page-about .rank-step:nth-child(5) .rank-step__bar { --bar-h: 92px; }
.page-about .rank-step:nth-child(6) .rank-step__bar { --bar-h: 108px; }
.page-about .rank-step:nth-child(7) .rank-step__bar { --bar-h: 124px; }
.page-about .rank-step:nth-child(8) .rank-step__bar { --bar-h: 140px; }
.page-about .rank-step:nth-child(9) .rank-step__bar { --bar-h: 156px; background: linear-gradient(180deg, var(--gold), var(--gold-2)); }

.page-about .rank-cards {
  list-style: none;
  margin: 26px 0 0;
  padding: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 12px;
}

@media (min-width: 560px) {
  .page-about .rank-cards {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (min-width: 1024px) {
  .page-about .rank-cards {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

.page-about .rank-card {
  padding: 16px 18px;
  background: var(--near-white);
  border: var(--line-thin) solid var(--black);
  border-radius: 12px;
  transition: transform var(--dur-2) var(--ease), box-shadow var(--dur-2) var(--ease), border-color var(--dur-2) var(--ease);
}

.page-about .rank-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-hard);
  border-color: var(--gold);
}

.page-about .rank-card__lv {
  margin: 0 0 4px;
  font-size: var(--fs-12);
  letter-spacing: .12em;
  color: var(--moss);
}

.page-about .rank-card__name {
  margin: 0 0 8px;
  font-family: var(--serif);
  font-weight: 700;
  font-size: var(--fs-21);
  color: var(--ink);
}

.page-about .rank-card__desc {
  margin: 0;
  font-size: var(--fs-14);
  line-height: 1.72;
  color: var(--text-mute-light);
}

/* ---------- 分段切换 ---------- */
.page-about .segmented {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: 26px;
  padding: 6px;
  background: var(--ink-2);
  border: var(--line-thin) solid var(--black);
  border-radius: var(--radius-pill);
}

.page-about .segmented__btn {
  flex: 1 1 auto;
  min-width: 0;
  padding: 10px 16px;
  border: 0;
  background: transparent;
  color: var(--text-mute-dark);
  font-family: var(--sans);
  font-size: var(--fs-14);
  border-radius: var(--radius-pill);
  cursor: pointer;
  transition: background var(--dur-2) var(--ease), color var(--dur-2) var(--ease);
}

.page-about .segmented__btn:hover {
  color: var(--gold-2);
}

.page-about .segmented__btn[aria-selected="true"] {
  background: var(--gold);
  color: var(--ink);
  font-weight: 500;
}

.page-about .segmented__btn[aria-selected="true"]:hover {
  color: var(--ink);
}

.page-about .segmented__btn:focus-visible {
  outline: var(--line-strong) solid var(--gold);
  outline-offset: 2px;
}

.page-about .segmented-panel {
  margin-top: 22px;
}

.page-about .segmented-panel + .segmented-panel {
  margin-top: 22px;
}

/* ---------- 研究板卡片 ---------- */
.page-about .board-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 16px;
}

@media (min-width: 720px) {
  .page-about .board-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

.page-about .board-card {
  position: relative;
  overflow: hidden;
  padding: 20px 20px 20px 26px;
  background: var(--near-white);
  border: var(--line-strong) solid var(--black);
  border-radius: 12px;
  box-shadow: var(--shadow-hard-inv);
  transition: transform var(--dur-2) var(--ease), box-shadow var(--dur-2) var(--ease);
}

.page-about .board-card::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: 6px;
  background: var(--moss);
}

.page-about .board-grid .board-card:nth-child(1)::before { background: var(--gold); }
.page-about .board-grid .board-card:nth-child(2)::before { background: var(--moss); }
.page-about .board-grid .board-card:nth-child(3)::before { background: var(--jade); }
.page-about .board-grid .board-card:nth-child(4)::before { background: var(--cinnabar); }

.page-about .board-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-hard-lg);
}

.page-about .board-card__label {
  margin: 0 0 10px;
  font-family: var(--mono);
  font-size: var(--fs-12);
  letter-spacing: .18em;
  color: var(--moss);
}

.page-about .board-card p:not(.board-card__label) {
  margin: 0;
  font-size: var(--fs-14);
  line-height: 1.78;
  color: var(--text-mute-light);
}

/* ---------- 赛事分组 ---------- */
.page-about .league-groups {
  list-style: none;
  margin: 26px 0 0;
  padding: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 14px;
}

@media (min-width: 720px) {
  .page-about .league-groups {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

.page-about .league-group {
  padding: 20px;
  background: var(--ink-2);
  border: var(--line-thin) solid var(--black);
  border-radius: 12px;
  box-shadow: var(--shadow-hard-inv);
  transition: transform var(--dur-2) var(--ease);
}

.page-about .league-group:hover {
  transform: translateY(-4px);
}

.page-about .league-group .tag {
  display: inline-block;
  margin-bottom: 12px;
}

.page-about .league-group p {
  margin: 0;
  font-size: var(--fs-14);
  line-height: 1.75;
  color: var(--text-on-dark);
}

/* ---------- 校对关卡 ---------- */
.page-about .gate-list {
  list-style: none;
  margin: 0 0 4px;
  padding: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 16px;
}

@media (min-width: 720px) {
  .page-about .gate-list {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

.page-about .gate {
  position: relative;
  padding: 22px 20px;
  background: var(--near-white);
  border: var(--line-strong) solid var(--black);
  border-radius: 12px;
  box-shadow: var(--shadow-hard-inv);
  transition: transform var(--dur-2) var(--ease), box-shadow var(--dur-2) var(--ease);
}

.page-about .gate:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-hard-lg);
}

.page-about .gate__num {
  display: inline-block;
  padding: 4px 12px;
  margin-bottom: 14px;
  border-radius: var(--radius-pill);
  background: var(--ink);
  color: var(--gold-2);
  font-size: var(--fs-12);
  letter-spacing: .1em;
}

.page-about .gate__title {
  margin: 0 0 10px;
  font-family: var(--serif);
  font-weight: 700;
  font-size: var(--fs-21);
  color: var(--ink);
}

.page-about .gate p {
  margin: 0;
  font-size: var(--fs-14);
  line-height: 1.75;
  color: var(--text-mute-light);
}

/* ---------- 下一步 ---------- */
.page-about .about-next {
  margin-top: clamp(36px, 5vw, 64px);
  padding: clamp(24px, 4vw, 40px);
  background: var(--ink);
  border: var(--line-strong) solid var(--black);
  border-radius: var(--radius-card);
  box-shadow: var(--shadow-hard);
}

.page-about .about-next__title {
  margin: 0 0 22px;
  font-family: var(--serif);
  font-weight: 800;
  font-size: clamp(1.25rem, 2.8vw, var(--fs-28));
  color: var(--near-white);
}

.page-about .about-next__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 12px;
}

@media (min-width: 780px) {
  .page-about .about-next__list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

.page-about .about-next__link {
  display: block;
  padding: 16px 18px;
  border: var(--line-thin) solid var(--moss);
  border-radius: 12px;
  text-decoration: none;
  transition: border-color var(--dur-2) var(--ease), background var(--dur-2) var(--ease), transform var(--dur-2) var(--ease);
}

.page-about .about-next__link:hover,
.page-about .about-next__link:focus-visible {
  border-color: var(--gold);
  background: rgba(217, 164, 65, .12);
  transform: translateY(-4px);
}

.page-about .about-next__link:focus-visible {
  outline: var(--line-strong) solid var(--gold);
  outline-offset: 2px;
}

.page-about .about-next__label {
  display: block;
  margin-bottom: 6px;
  font-family: var(--serif);
  font-weight: 700;
  font-size: var(--fs-21);
  color: var(--gold-2);
}

.page-about .about-next__hint {
  display: block;
  font-size: var(--fs-14);
  line-height: 1.7;
  color: var(--text-mute-dark);
}

@media (prefers-reduced-motion: reduce) {
  .page-about .step-list__item,
  .page-about .rank-card,
  .page-about .board-card,
  .page-about .gate,
  .page-about .league-group,
  .page-about .about-next__link,
  .page-about .rank-step__bar,
  .page-about .about-rail__item::before {
    transition: none;
  }

  .page-about .step-list__item:hover,
  .page-about .rank-card:hover,
  .page-about .board-card:hover,
  .page-about .gate:hover,
  .page-about .league-group:hover,
  .page-about .about-next__link:hover {
    transform: none;
  }

  .page-about .rank-step:hover .rank-step__bar {
    transform: none;
  }
}