.page-about {
  --about-index-width: 80px;
  --about-transition: 0.3s ease;
  font-family: var(--font-body);
  color: var(--color-darkgray);
}

/* ===== Breadcrumb ===== */
.about-breadcrumb {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--color-midgray);
  margin-bottom: 1.5rem;
}
.about-breadcrumb__link {
  color: var(--color-green);
  text-decoration: none;
  transition: opacity var(--about-transition);
}
.about-breadcrumb__link:hover {
  opacity: 0.7;
}
.about-breadcrumb__sep {
  color: var(--color-lightgray);
}
.about-breadcrumb__current {
  color: var(--color-darkgray);
  font-weight: 500;
}

/* ===== Index (mobile hidden) ===== */
.about-index {
  display: none;
}

/* ===== Intro ===== */
.about-intro {
  padding: 3rem 1.5rem 2.5rem;
  background: var(--color-white);
  position: relative;
  z-index: 1;
}
.about-intro__title {
  font-family: var(--font-heading);
  font-weight: 800;
  font-size: 2.4rem;
  line-height: 1.15;
  color: var(--color-black);
  text-transform: uppercase;
  letter-spacing: -0.02em;
  margin: 0 0 1.25rem;
}
.about-intro__lead {
  font-size: 1.05rem;
  line-height: 1.7;
  color: var(--color-darkgray);
  max-width: 640px;
  margin: 0 0 1.5rem;
}
.about-intro__badge {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--color-green);
  border: 1px solid var(--color-green);
  padding: 0.35rem 1rem;
  letter-spacing: 0.04em;
}

/* ===== Chapter common ===== */
.about-chapter {
  position: relative;
  overflow: hidden;
  padding: 3rem 1.5rem;
}
.about-chapter__inner {
  position: relative;
  z-index: 2;
}
.about-chapter__number {
  font-family: var(--font-mono);
  font-size: 3.8rem;
  font-weight: 500;
  line-height: 1;
  margin-bottom: 0.5rem;
  opacity: 0.25;
  user-select: none;
}
.about-chapter__title {
  font-family: var(--font-heading);
  font-weight: 800;
  font-size: 1.6rem;
  text-transform: uppercase;
  letter-spacing: -0.01em;
  margin: 0 0 1.25rem;
  padding-bottom: 0.5rem;
  border-bottom: 3px solid var(--color-green);
  display: inline-block;
}
.about-chapter__text p {
  margin: 0 0 1rem;
  line-height: 1.7;
  font-size: 0.95rem;
}
.about-chapter__text p:last-of-type {
  margin-bottom: 1.25rem;
}
.about-chapter__grid {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}
.about-chapter__media {
  flex-shrink: 0;
}
.about-chapter__img {
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
  border-radius: 4px;
  display: block;
  box-shadow: 0 4px 16px rgba(0,0,0,0.08);
  transition: transform var(--about-transition), box-shadow var(--about-transition);
}
.about-chapter__img:hover {
  transform: scale(1.02);
  box-shadow: 0 8px 28px rgba(0,0,0,0.14);
}

/* ===== Dark chapter ===== */
.about-chapter--dark {
  background: var(--color-black);
  color: var(--color-white);
}
.about-chapter--dark .about-chapter__number {
  color: var(--color-green);
  opacity: 0.3;
}
.about-chapter--dark .about-chapter__title {
  color: var(--color-white);
  border-bottom-color: var(--color-green);
}
.about-chapter--dark .about-chapter__text p {
  color: rgba(255,255,255,0.88);
}
.about-chapter--dark .about-chapter__img {
  box-shadow: 0 4px 20px rgba(0,0,0,0.4);
}

/* ===== Light chapter ===== */
.about-chapter--light {
  background: var(--color-white);
  color: var(--color-darkgray);
}
.about-chapter--light .about-chapter__number {
  color: var(--color-green);
  opacity: 0.2;
}
.about-chapter--light .about-chapter__title {
  color: var(--color-black);
  border-bottom-color: var(--color-green);
}

/* ===== Background image for first chapter ===== */
.about-chapter__bg-wrap {
  position: absolute;
  inset: 0;
  z-index: 0;
  overflow: hidden;
}
.about-chapter__bg-img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center;
  display: block;
}
.about-chapter__overlay {
  position: absolute;
  inset: 0;
  z-index: 1;
  background: linear-gradient(135deg, rgba(0,0,0,0.82) 0%, rgba(0,0,0,0.55) 60%, rgba(0,0,0,0.3) 100%);
}

/* ===== Link ===== */
.about-link {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  font-weight: 500;
  text-decoration: none;
  padding: 0.5rem 1.2rem;
  border: 1px solid;
  transition: all var(--about-transition);
  letter-spacing: 0.02em;
}
.about-link--green {
  color: var(--color-green);
  border-color: var(--color-green);
}
.about-link--green:hover {
  background: var(--color-green);
  color: var(--color-white);
}
.about-link--blue {
  color: var(--color-blue);
  border-color: var(--color-blue);
}
.about-link--blue:hover {
  background: var(--color-blue);
  color: var(--color-white);
}

/* ===== Tablet / Desktop (≥768px) ===== */
@media (min-width: 768px) {
  .about-intro {
    padding: 4rem 2rem 3rem;
  }
  .about-intro__title {
    font-size: 3.2rem;
  }
  .about-intro__lead {
    font-size: 1.15rem;
  }
  .about-chapter {
    padding: 4rem 2rem;
  }
  .about-chapter__number {
    font-size: 5rem;
  }
  .about-chapter__title {
    font-size: 2rem;
  }
  .about-chapter__grid {
    flex-direction: row;
    align-items: center;
    gap: 2.5rem;
  }
  .about-chapter__text {
    flex: 1;
  }
  .about-chapter__media {
    flex: 0 0 45%;
    max-width: 480px;
  }
  .about-chapter--dark .about-chapter__grid .about-chapter__media {
    order: 2;
  }
  .about-chapter--dark .about-chapter__grid .about-chapter__text {
    order: 1;
  }
}

/* ===== Desktop (≥1024px) with fixed index ===== */
@media (min-width: 1024px) {
  .page-about {
    display: flex;
    min-height: 80vh;
  }
  .about-index {
    display: flex;
    flex-direction: column;
    position: fixed;
    top: var(--header-height);
    left: 0;
    width: var(--about-index-width);
    height: calc(100vh - var(--header-height));
    z-index: 10;
    background: var(--color-black);
    padding: 2rem 0;
    align-items: center;
    justify-content: flex-start;
    gap: 1.8rem;
    border-right: 1px solid rgba(255,255,255,0.08);
  }
  .about-index__link {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.2rem;
    text-decoration: none;
    color: var(--color-lightgray);
    transition: color var(--about-transition);
    padding: 0.4rem 0.2rem;
    writing-mode: vertical-rl;
    text-orientation: mixed;
  }
  .about-index__link:hover {
    color: var(--color-green);
  }
  .about-index__num {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    font-weight: 500;
    letter-spacing: 0.06em;
    writing-mode: horizontal-tb;
  }
  .about-index__label {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    font-weight: 400;
    writing-mode: horizontal-tb;
    margin-top: 0.15rem;
  }
  .about-content {
    margin-left: var(--about-index-width);
    flex: 1;
    max-width: 100%;
  }
  .about-intro {
    padding: 5rem 3rem 3.5rem;
  }
  .about-intro__title {
    font-size: 4rem;
  }
  .about-chapter {
    padding: 5rem 3rem;
  }
  .about-chapter__number {
    font-size: 6.5rem;
  }
  .about-chapter__title {
    font-size: 2.4rem;
  }
  .about-chapter__grid {
    gap: 3.5rem;
  }
  .about-chapter__text p {
    font-size: 1rem;
  }
}

/* ===== Large desktop (≥1280px) ===== */
@media (min-width: 1280px) {
  .about-intro {
    padding: 6rem 4rem 4rem;
  }
  .about-chapter {
    padding: 6rem 4rem;
  }
  .about-chapter__number {
    font-size: 8rem;
  }
  .about-chapter__title {
    font-size: 2.8rem;
  }
}