.page-about {
  background: var(--by-ink);
  color: var(--by-text);
  font-family: var(--by-font-body);
  font-size: 15px;
  line-height: 1.7;
  overflow-x: hidden;
}

/* ---------- 首屏 ---------- */
.page-about .ab-hero {
  position: relative;
  padding: clamp(1.6rem, 4vw, 2.6rem) 0 clamp(2.2rem, 5vw, 3.4rem);
  background:
    radial-gradient(120% 90% at 6% 0%, rgba(61, 245, 198, 0.15), transparent 58%),
    radial-gradient(90% 80% at 102% 8%, rgba(74, 158, 255, 0.12), transparent 62%),
    linear-gradient(180deg, var(--by-ink) 0%, var(--by-ink-deep) 100%);
  overflow: hidden;
}

.page-about .ab-hero::after {
  content: "";
  position: absolute;
  right: -14rem;
  top: -16rem;
  width: 34rem;
  height: 34rem;
  border-radius: 44% 56% 62% 38% / 50% 42% 58% 50%;
  background: radial-gradient(circle at 34% 36%, rgba(61, 245, 198, 0.16), transparent 70%);
  pointer-events: none;
}

.page-about .ab-hero > .by-container {
  position: relative;
  z-index: 1;
}

.page-about .ab-hero__kicker {
  margin: 1.4rem 0 0.7rem;
  font-family: var(--by-font-mono);
  font-size: 0.78rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--by-neon);
}

.page-about .ab-hero h1 {
  margin: 0;
  font-family: var(--by-font-display);
  font-weight: 700;
  font-size: clamp(2.1rem, 6.4vw, 3.6rem);
  line-height: 1.12;
  letter-spacing: 0.01em;
  color: var(--by-text);
  max-width: 20em;
}

.page-about .ab-hero__lede {
  margin: 1.1rem 0 0;
  max-width: 46em;
  color: rgba(232, 242, 238, 0.84);
}

.page-about .ab-hero__stats {
  list-style: none;
  margin: clamp(1.8rem, 4vw, 2.6rem) 0 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  background: var(--by-edge);
  border: 1px solid var(--by-edge);
  border-radius: var(--by-radius);
  overflow: hidden;
}

.page-about .ab-hero__stat {
  background: linear-gradient(180deg, rgba(22, 58, 49, 0.94), rgba(15, 43, 36, 0.94));
  padding: 0.95rem 1rem 1.1rem;
}

.page-about .ab-hero__statnum {
  display: block;
  font-family: var(--by-font-mono);
  font-weight: 700;
  font-size: clamp(1.45rem, 4.4vw, 2.05rem);
  line-height: 1.15;
  color: var(--by-neon);
  text-shadow: 0 0 18px rgba(61, 245, 198, 0.34);
}

.page-about .ab-hero__statlabel {
  display: block;
  margin-top: 0.35rem;
  font-size: 0.78rem;
  letter-spacing: 0.05em;
  color: var(--by-muted);
}

/* ---------- 主体：左侧年表 + 右侧长卷 ---------- */
.page-about .ab-body {
  padding: clamp(2rem, 5vw, 3.4rem) 0 clamp(3rem, 7vw, 5rem);
  background:
    linear-gradient(180deg, var(--by-ink-deep) 0%, var(--by-ink) 26%, var(--by-ink) 100%);
}

.page-about .ab-body__grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(1.8rem, 4vw, 2.8rem);
}

.page-about .ab-rail {
  border-left: 1px solid var(--by-edge);
  padding-left: 1rem;
}

.page-about .ab-rail__title {
  margin: 0;
  font-family: var(--by-font-mono);
  font-size: 0.78rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--by-muted);
}

.page-about .ab-rail__list {
  list-style: none;
  margin: 0.9rem 0 0;
  padding: 0;
}

.page-about .ab-rail__item + .ab-rail__item {
  margin-top: 0.2rem;
}

.page-about .ab-rail__link {
  display: flex;
  align-items: baseline;
  gap: 0.7rem;
  padding: 0.35rem 0.2rem;
  text-decoration: none;
  color: var(--by-muted);
  border-radius: 6px;
  transition: color 0.2s ease, background 0.2s ease;
}

.page-about .ab-rail__num {
  font-family: var(--by-font-mono);
  font-size: 0.82rem;
  font-weight: 700;
  color: rgba(61, 245, 198, 0.6);
}

.page-about .ab-rail__label {
  font-size: 0.9rem;
}

.page-about .ab-rail__link:hover,
.page-about .ab-rail__link:focus-visible {
  color: var(--by-neon);
  background: var(--by-neon-soft);
}

.page-about .ab-rail__foot {
  margin: 1.2rem 0 0;
  font-family: var(--by-font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.08em;
  color: rgba(155, 179, 170, 0.75);
  display: flex;
  align-items: center;
  gap: 0.45rem;
}

.page-about .ab-rail__foot::before {
  content: "";
  width: 0.42rem;
  height: 0.42rem;
  border-radius: 50%;
  background: var(--by-live);
  box-shadow: 0 0 10px rgba(255, 92, 92, 0.75);
  flex: none;
}

.page-about .ab-stream {
  min-width: 0;
}

/* ---------- 章节 ---------- */
.page-about .ab-chapter {
  padding: clamp(1.9rem, 4.5vw, 2.9rem) 0;
  border-top: 1px solid var(--by-edge);
}

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

.page-about .ab-chapter__head {
  display: flex;
  align-items: flex-start;
  gap: clamp(0.85rem, 2.4vw, 1.5rem);
  margin-bottom: 1rem;
}

.page-about .ab-chapter__num {
  flex: none;
  font-family: var(--by-font-mono);
  font-weight: 700;
  font-size: clamp(1.9rem, 6vw, 3rem);
  line-height: 0.92;
  color: rgba(61, 245, 198, 0.28);
  -webkit-text-stroke: 1px rgba(61, 245, 198, 0.85);
  text-shadow: 0 0 22px rgba(61, 245, 198, 0.2);
  padding-top: 0.15rem;
}

.page-about .ab-chapter__heading {
  min-width: 0;
}

.page-about .ab-chapter__kicker {
  margin: 0 0 0.35rem;
  font-family: var(--by-font-mono);
  font-size: 0.76rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--by-neon);
}

.page-about .ab-chapter__title {
  margin: 0;
  font-family: var(--by-font-display);
  font-weight: 700;
  font-size: clamp(1.45rem, 4.2vw, 2.1rem);
  line-height: 1.25;
  color: var(--by-text);
}

.page-about .ab-chapter__body {
  max-width: 44em;
}

.page-about .ab-chapter__body p {
  margin: 0 0 0.9rem;
  color: rgba(232, 242, 238, 0.86);
}

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

.page-about .ab-chapter__body--after {
  margin-top: 1.3rem;
  padding-top: 1.1rem;
  border-top: 1px dashed var(--by-edge);
}

/* ---------- 图片 ---------- */
.page-about .ab-figure {
  margin: 1.5rem 0 0;
  max-width: 44em;
  border: 1px solid var(--by-edge);
  border-radius: var(--by-radius);
  background: var(--by-panel);
  overflow: hidden;
  box-shadow: var(--by-shadow);
}

.page-about .ab-figure img {
  display: block;
  width: 100%;
  height: auto;
  max-width: 100%;
  object-fit: cover;
  filter: saturate(0.92) contrast(1.04);
  transition: transform 0.4s ease;
}

.page-about .ab-figure:hover img {
  transform: scale(1.015);
}

.page-about .ab-figure figcaption {
  padding: 0.65rem 0.9rem;
  font-family: var(--by-font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.05em;
  color: var(--by-muted);
  border-top: 1px solid var(--by-edge);
}

/* ---------- 版本节点 ---------- */
.page-about .ab-versions {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 1px;
  margin-top: 1.4rem;
  background: var(--by-edge);
  border: 1px solid var(--by-edge);
  border-radius: var(--by-radius);
  overflow: hidden;
}

.page-about .ab-version {
  position: relative;
  padding: 1.05rem 1.1rem 1.2rem 1.3rem;
  background: linear-gradient(160deg, rgba(22, 58, 49, 0.96), rgba(10, 31, 26, 0.96));
  transition: background 0.25s ease;
}

.page-about .ab-version::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: 3px;
  background: linear-gradient(180deg, var(--by-neon), rgba(61, 245, 198, 0.05));
  opacity: 0.55;
  transition: opacity 0.25s ease;
}

.page-about .ab-version:hover {
  background: linear-gradient(160deg, rgba(31, 74, 63, 0.98), rgba(15, 43, 36, 0.98));
}

.page-about .ab-version:hover::before {
  opacity: 1;
}

.page-about .ab-version__year {
  display: inline-block;
  font-family: var(--by-font-mono);
  font-weight: 700;
  font-size: 1.15rem;
  letter-spacing: 0.06em;
  color: var(--by-neon);
  text-shadow: 0 0 14px rgba(61, 245, 198, 0.3);
}

.page-about .ab-version__title {
  margin: 0.45rem 0 0.4rem;
  font-size: 1.02rem;
  font-weight: 600;
  line-height: 1.4;
  color: var(--by-text);
}

.page-about .ab-version__desc {
  margin: 0;
  font-size: 0.86rem;
  line-height: 1.65;
  color: rgba(155, 179, 170, 0.95);
}

/* ---------- 结尾入口 ---------- */
.page-about .ab-cta {
  margin-top: clamp(2rem, 5vw, 3rem);
  padding: clamp(1.5rem, 4vw, 2.2rem);
  border: 1px solid var(--by-edge);
  border-radius: var(--by-radius);
  background:
    radial-gradient(120% 120% at 0% 0%, rgba(61, 245, 198, 0.13), transparent 58%),
    linear-gradient(160deg, rgba(22, 58, 49, 0.96), rgba(10, 31, 26, 0.98));
}

.page-about .ab-cta__title {
  margin: 0;
  font-family: var(--by-font-display);
  font-weight: 700;
  font-size: clamp(1.35rem, 3.6vw, 1.85rem);
  line-height: 1.25;
  color: var(--by-text);
}

.page-about .ab-cta__text {
  margin: 0.8rem 0 0;
  max-width: 44em;
  color: rgba(232, 242, 238, 0.84);
}

.page-about .ab-cta__links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.7rem;
  margin-top: 1.3rem;
}

/* ---------- 焦点可见性 ---------- */
.page-about a:focus-visible {
  outline: 2px solid var(--by-neon);
  outline-offset: 2px;
  border-radius: 6px;
}

/* ---------- 窄屏微调 ---------- */
@media (max-width: 519px) {
  .page-about .ab-hero__stats {
    grid-template-columns: minmax(0, 1fr);
  }

  .page-about .ab-cta__links .by-btn {
    width: 100%;
    text-align: center;
  }
}

/* ---------- 桌面栅格 ---------- */
@media (min-width: 700px) {
  .page-about .ab-versions {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (min-width: 980px) {
  .page-about .ab-body__grid {
    grid-template-columns: minmax(0, 3fr) minmax(0, 9fr);
    gap: clamp(2rem, 5vw, 4.6rem);
  }

  .page-about .ab-rail {
    position: sticky;
    top: 6.5rem;
    align-self: start;
  }
}

@media (min-width: 1180px) {
  .page-about .ab-hero h1 {
    max-width: 16em;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .ab-figure img,
  .page-about .ab-version,
  .page-about .ab-rail__link {
    transition: none;
  }

  .page-about .ab-figure:hover img {
    transform: none;
  }
}