.main-about-history {
  --ah-sticky-top: calc(var(--header-h) + 5rem);
  position: relative;
  min-height: 10vh;
  background-color: var(--color-white);
}

/* Lenis 下 background-attachment:fixed 无效，用固定层保证背景不随滚动移动 */
.main-about-history::before {
  content: "";
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background-color: var(--color-white);
  background-image: url("../images/about-history.jpg");
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
}

.main-about-history > * {
  position: relative;
  z-index: 1;
}

.ah-page {
  padding-top: var(--ah-sticky-top);
  padding-bottom: 7.5rem;
  padding-left: 18.75rem;
  padding-right: 18.75rem;
}

.ah-layout {
  display: grid;
  grid-template-columns: max-content 2px minmax(0, 1fr);
  gap: 5rem; /* 80px：年份 / 轨道 / 内容 */
  align-items: start;
}

.ah-nav__years {
  position: sticky;
  width: 12.5rem;
  top: var(--ah-sticky-top);
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 1rem;
}

.ah-nav__item {
  position: relative;
  display: block;
  color: var(--color-text-link);
  font-family: "D-DIN-PRO";
  font-size: var(--font-24);
  font-weight: 400;
  line-height: var(--font-24);
  text-decoration: none;
  transform: scale(1);
  transform-origin: right center;
  transition: color 0.25s ease, transform 0.25s ease, font-weight 0.25s ease;
}

.ah-nav__item:hover {
  color: var(--color-text-muted);
}

.ah-nav__item.is-active {
  z-index: 1;
  color: var(--color-text);
  font-weight: 500;
  /* 约等于原 font-64 / font-24，不占布局，避免进度条回弹 */
  transform: scale(calc(64 / 24));
  margin: 1rem 0;
}

.ah-nav__rail {
  position: sticky;
  top: var(--ah-sticky-top);
  align-self: start;
  width: 2px;
  background: rgba(46, 53, 58, 0.1);
  border-radius: 1px;
}

/* 轨道原点：始终固定在顶部 */
.ah-nav__rail::before {
  content: "";
  position: absolute;
  left: 50%;
  transform: translateX(-50%);
  top: 0;
  z-index: 2;
  width: .75rem;
  height: .75rem;
  border-radius: 50%;
  background: var(--color-primary);
}

/* 红线：铺满轨道高度，用 scaleY 表示进度（合成层，不触发布局） */
.ah-nav__indicator {
  position: absolute;
  top: 0;
  left: 0;
  width: 2px;
  height: 100%;
  background: var(--color-primary);
  border-radius: 1px;
  transform: scaleY(0.04);
  transform-origin: top center;
  will-change: transform;
}

.ah-content {
  min-width: 0;
}

.ah-block + .ah-block {
  margin-top: 3em;
  padding-top: 3rem;
  border-top: 1px solid #ebebeb;
}

.ah-block {
  scroll-margin-top: calc(var(--ah-sticky-top) + 1rem);
}

.ah-richtext {
  color: #666;
  font-family: "MiSans VF", "PingFang SC", sans-serif;
  font-size: var(--font-18);
  font-weight: 400;
  line-height: var(--font-32);
}
.ah-richtext p{
  width: 100%!important;
}
.ah-richtext > *:first-child {
  margin-top: 0;
}

.ah-richtext > *:last-child {
  margin-bottom: 0;
}

.ah-richtext h1,
.ah-richtext h2,
.ah-richtext h3,
.ah-richtext h4,
.ah-richtext strong {
  color: var(--color-text);
  font-weight: 600;
}

.ah-richtext h1,
.ah-richtext h2,
.ah-richtext h3,
.ah-richtext h4 {
  margin: 2rem 0 1rem;
  font-size: var(--font-20);
  line-height: var(--font-32);
}

.ah-richtext h1:first-child,
.ah-richtext h2:first-child,
.ah-richtext h3:first-child,
.ah-richtext h4:first-child {
  margin-top: 0;
}

.ah-richtext p {
  margin: 0 0 0.75rem;
}

.ah-richtext ul,
.ah-richtext ol {
  margin: 0 0 1.5rem;
  padding-left: 1.25rem;
}
.ah-richtext ul {
  list-style-type: disc;
}
.ah-richtext ol {
  list-style-type: decimal;
}
.ah-richtext li {
  list-style: inherit;
}
.ah-richtext li + li {
  margin-top: 0.75rem;
}

.ah-richtext li::marker {
  color: #999;
}

.ah-richtext a {
  color: var(--color-primary);
  text-decoration: underline;
}

.ah-richtext img {
  max-width: 100%!important;
  height: auto!important;
  vertical-align: middle!important;
}

@media (max-width: 992px) {
  .main-about-history {
    --ah-years-h: 3.75rem; /* 移动端年份导航固定高度 */
  }

  .ah-page {
    padding-top: calc(var(--header-h, 5.5rem) + 2rem);
    padding-bottom: 4rem;
    padding-left: var(--p-x);
    padding-right: var(--p-x);
  }

  .ah-layout {
    grid-template-columns: 1fr;
    gap: 2rem;
  }

  .ah-nav__years {
    position: sticky;
    top: var(--header-h, 5.5rem);
    z-index: 5;
    box-sizing: border-box;
    width: 100%;
    height: var(--ah-years-h);
    min-height: var(--ah-years-h);
    max-height: var(--ah-years-h);
    flex-direction: row;
    align-items: center;
    gap: 1.25rem;
    overflow-x: auto;
    overflow-y: hidden;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
    padding: 0 var(--p-x);
    background: rgba(255, 255, 255, 0.96);
    backdrop-filter: blur(8px);
  }

  .ah-nav__years::-webkit-scrollbar {
    display: none;
  }

  .ah-nav__item {
    flex: 0 0 auto;
    font-size: var(--font-18);
    line-height: 1;
    transform: scale(1);
    transform-origin: center center;
    transition: color 0.25s ease, transform 0.25s ease;
  }

  .ah-nav__item.is-active {
    color: var(--color-text);
    font-weight: 500;
    transform: scale(1.45);
    transform-origin: center;
  }

  .ah-nav__rail {
    display: none;
  }

  /* 移动端：头部 + 固定年份导航，单独偏移 */
  .ah-block {
    scroll-margin-top: calc(var(--header-h, 5.5rem) + var(--ah-years-h) + 0.75rem);
  }

  .ah-block + .ah-block {
    margin-top: 2rem;
    padding-top: 2rem;
  }
}