.page-about {
  background: var(--c-cream);
  color: var(--c-text);
  font-family: var(--font-body);
}

/* ========== 分屏首屏 ========== */
.page-about__hero {
  padding: var(--sp-5) var(--sp-4) var(--sp-7);
}
.page-about__hero-grid {
  max-width: var(--container);
  margin: 0 auto;
  display: grid;
  gap: var(--sp-6);
  align-items: center;
}
.page-about__hero-copy {
  min-width: 0;
}
.page-about__eyebrow {
  font-size: var(--fs-small);
  color: var(--c-accent);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  margin: 0 0 var(--sp-3);
}
.page-about__eyebrow::before {
  content: "";
  display: inline-block;
  width: 8px;
  height: 8px;
  margin-right: 8px;
  background: var(--c-accent);
  transform: rotate(45deg);
}
.page-about__hero-copy h1 {
  font-family: var(--font-head);
  font-size: var(--fs-h1);
  line-height: 1.12;
  margin: 0 0 var(--sp-4);
  color: var(--c-primary);
  max-width: 14em;
}
.page-about__lead {
  font-size: 1.0625rem;
  line-height: 1.7;
  margin: 0 0 var(--sp-4);
  color: var(--c-text);
}
.page-about__hero-copy > p:last-child {
  color: var(--c-muted);
  margin: 0;
  max-width: 46ch;
}
.page-about__hero-media {
  position: relative;
}
.page-about__hero-media::before {
  content: "";
  position: absolute;
  top: 10px;
  left: 10px;
  width: 42%;
  height: 58%;
  border: 1px solid rgba(255, 107, 53, 0.45);
  z-index: 2;
  pointer-events: none;
}
.page-about__hero-media::after {
  content: "";
  position: absolute;
  top: 22px;
  left: 22px;
  width: 42%;
  height: 58%;
  background: linear-gradient(135deg, rgba(10, 31, 68, 0.08), transparent);
  z-index: 1;
  pointer-events: none;
}
.page-about__hero-img {
  position: relative;
  z-index: 0;
  display: block;
  width: 100%;
  aspect-ratio: 4 / 5;
  object-fit: cover;
  background: var(--c-gray);
}

/* ========== 通用章节 ========== */
.page-about__section {
  position: relative;
  padding: var(--sp-7) var(--sp-4);
  border-top: 1px solid var(--c-border);
  overflow: hidden;
  background: var(--c-cream);
}
.page-about__section-inner {
  position: relative;
  z-index: 1;
  max-width: var(--container);
  margin: 0 auto;
}
.page-about__section-head {
  margin-bottom: var(--sp-6);
}
.page-about__section-head h2,
.page-about__section-copy h2 {
  font-family: var(--font-head);
  font-size: var(--fs-h2);
  line-height: 1.2;
  color: var(--c-primary);
  margin: 0 0 var(--sp-4);
  max-width: 12em;
}
.page-about__section-head > p:last-child {
  color: var(--c-muted);
  line-height: 1.6;
  margin: 0;
  max-width: 55ch;
}
.page-about__section-copy {
  min-width: 0;
}
.page-about__section-copy p {
  line-height: 1.7;
  margin: 0 0 var(--sp-4);
  color: var(--c-text);
}
.page-about__section-copy p:last-child {
  margin-bottom: 0;
}
.page-about__section-copy ul {
  margin: 0 0 var(--sp-4);
  padding: 0;
  list-style: none;
}
.page-about__section-copy li {
  position: relative;
  padding-left: var(--sp-5);
  margin-bottom: var(--sp-3);
  line-height: 1.65;
  color: var(--c-text);
}
.page-about__section-copy li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.55em;
  width: 10px;
  height: 10px;
  background: var(--c-accent);
  transform: rotate(45deg);
}

/* ========== 旋转章节注释 ========== */
.page-about__rot-note {
  margin: 0 0 var(--sp-4);
  font-size: var(--fs-micro);
  color: var(--c-muted);
  letter-spacing: 0.24em;
  text-transform: uppercase;
  transition: color 0.5s ease;
}
.page-about__section[data-active] .page-about__rot-note {
  color: var(--c-accent);
}

/* ========== 背景大数字 ========== */
.page-about__bg-number {
  position: absolute;
  top: 0.75rem;
  right: var(--sp-4);
  font-family: var(--font-head);
  font-weight: 700;
  font-size: 7rem;
  line-height: 1;
  color: rgba(10, 31, 68, 0.045);
  pointer-events: none;
  user-select: none;
  z-index: 0;
  letter-spacing: -0.02em;
}

/* ========== 使命章节 ========== */
.page-about__section-main {
  display: grid;
  gap: var(--sp-6);
}
.page-about__mission-pull {
  border-left: 2px solid var(--c-accent);
  padding-left: var(--sp-5);
  font-family: var(--font-head);
  font-size: 1.25rem;
  font-weight: 700;
  line-height: 1.55;
  color: var(--c-primary);
  align-self: start;
}
.page-about__mission-pull p {
  margin: 0 0 var(--sp-2);
}
.page-about__mission-pull p:last-child {
  margin-bottom: 0;
  color: var(--c-accent);
}

/* ========== 里程碑时间线 ========== */
.page-about__timeline-wrap {
  display: grid;
  gap: var(--sp-6);
  margin-top: var(--sp-6);
}
.page-about__timeline {
  list-style: none;
  margin: 0;
  padding: 0;
  position: relative;
  max-width: 44rem;
}
.page-about__timeline::before {
  content: "";
  position: absolute;
  left: 9px;
  top: 6px;
  bottom: 6px;
  width: 2px;
  background: var(--c-border);
}
.page-about__timeline-item {
  position: relative;
  padding-left: var(--sp-7);
  padding-bottom: var(--sp-6);
}
.page-about__timeline-item:last-child {
  padding-bottom: 0;
}
.page-about__timeline-dot {
  position: absolute;
  left: 0;
  top: 2px;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--c-cream);
  border: 3px solid var(--c-border);
  transition: background 0.4s ease, border-color 0.4s ease;
  box-sizing: border-box;
}
.page-about__timeline-item[data-active] .page-about__timeline-dot {
  background: var(--c-accent);
  border-color: var(--c-accent);
}
.page-about__timeline-card h3 {
  font-family: var(--font-head);
  font-size: var(--fs-h3);
  color: var(--c-primary);
  margin: 0 0 var(--sp-2);
}
.page-about__timeline-card p {
  margin: 0;
  color: var(--c-muted);
  line-height: 1.65;
  max-width: 52ch;
}
.page-about__timeline-img {
  width: 100%;
  aspect-ratio: 1 / 1;
  object-fit: cover;
  background: var(--c-gray);
  border: 1px solid var(--c-border);
}

/* ========== 信息整理章节 ========== */
.page-about__systems-grid {
  display: grid;
  gap: var(--sp-6);
}
.page-about__systems-facts {
  background: var(--c-gray);
  border: 1px solid var(--c-border);
  padding: var(--sp-5);
  display: grid;
  gap: var(--sp-5);
}
.page-about__fact {
  border-top: 1px solid var(--c-border);
  padding-top: var(--sp-4);
}
.page-about__fact:first-child {
  border-top: 0;
  padding-top: 0;
}
.page-about__fact-label {
  font-family: var(--font-head);
  font-size: var(--fs-small);
  font-weight: 700;
  letter-spacing: 0.08em;
  color: var(--c-primary);
}
.page-about__fact-value {
  display: block;
  font-family: var(--font-head);
  font-size: 1.375rem;
  font-weight: 700;
  color: var(--c-accent);
  margin: var(--sp-2) 0;
}
.page-about__fact p {
  margin: 0;
  color: var(--c-muted);
  font-size: var(--fs-small);
  line-height: 1.6;
}
.page-about__systems-img {
  display: block;
  width: 100%;
  aspect-ratio: 7 / 4;
  object-fit: cover;
  background: var(--c-gray);
  border: 1px solid var(--c-border);
  margin-top: var(--sp-6);
}

/* ========== 未来计划 ========== */
.page-about__future-note {
  margin-top: var(--sp-6);
  border-top: 2px solid var(--c-primary);
  padding-top: var(--sp-5);
  max-width: 24rem;
}
.page-about__future-note p {
  font-family: var(--font-head);
  font-size: 1.375rem;
  font-weight: 700;
  line-height: 1.5;
  color: var(--c-primary);
  margin: 0;
}

/* ========== 内联链接 ========== */
.page-about__inline-link {
  color: var(--c-accent);
  font-weight: 500;
  text-decoration: underline;
  text-underline-offset: 3px;
  text-decoration-color: rgba(255, 107, 53, 0.35);
  transition: color 0.2s ease, text-decoration-color 0.2s ease;
}
.page-about__inline-link:hover {
  color: var(--c-primary);
  text-decoration-color: var(--c-primary);
}

/* ========== 桌面端布局 ========== */
@media (min-width: 900px) {
  .page-about__hero {
    padding: var(--sp-8) var(--sp-5);
  }
  .page-about__hero-grid {
    grid-template-columns: 1.05fr 0.95fr;
    gap: var(--sp-7);
  }
  .page-about__section {
    padding: var(--sp-8) var(--sp-5);
  }
  .page-about__section-head {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--sp-7);
    align-items: end;
    margin-bottom: var(--sp-7);
  }
  .page-about__section-head h2 {
    margin-bottom: 0;
  }
  .page-about__section-head > p:last-child {
    justify-self: start;
  }
  .page-about__section-main {
    grid-template-columns: 1.2fr 0.8fr;
    gap: var(--sp-7);
  }
  .page-about__timeline-wrap {
    grid-template-columns: minmax(0, 0.9fr) minmax(0, 1.1fr);
    gap: var(--sp-7);
    align-items: start;
  }
  .page-about__timeline-img {
    order: -1;
    min-height: 360px;
  }
  .page-about__systems-grid {
    grid-template-columns: 1fr 1fr;
    gap: var(--sp-7);
    align-items: start;
  }
  .page-about__systems-img {
    max-width: 56rem;
    margin: var(--sp-7) 0 0 auto;
  }
  .page-about__future .page-about__section-inner {
    display: grid;
    grid-template-columns: 1.2fr 0.8fr;
    gap: var(--sp-7);
    align-items: end;
  }
  .page-about__future-note {
    margin-top: 0;
    align-self: end;
  }
  .page-about__bg-number {
    font-size: 12rem;
    right: var(--sp-8);
    top: 1rem;
  }
}

@media (min-width: 1280px) {
  .page-about__rot-note {
    position: absolute;
    left: -36px;
    top: 0;
    writing-mode: vertical-rl;
    letter-spacing: 0.2em;
  }
}