body.how {
  background: var(--paper);
}

.how-progress {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  z-index: 40;
  background: transparent;
  pointer-events: none;
}
.how-progress i {
  display: block;
  height: 100%;
  width: 100%;
  background: var(--accent);
  transform: scaleX(0);
  transform-origin: left center;
  will-change: transform;
}

.how .nav { z-index: 20; }

.how-chapters {
  position: sticky;
  top: 57px;
  z-index: 15;
  display: flex;
  gap: 0.35rem;
  padding: 0.55rem 6vw;
  overflow-x: auto;
  background: var(--paper);
  border-bottom: 1px solid var(--line);
  -webkit-overflow-scrolling: touch;
}
.how-chapters a {
  flex: 0 0 auto;
  color: var(--muted);
  text-decoration: none;
  font-weight: 600;
  font-size: 0.82rem;
  padding: 0.35rem 0.7rem;
  border-radius: 999px;
  white-space: nowrap;
}
.how-chapters a.is-active {
  background: var(--navy);
  color: var(--white);
}

.how-hero {
  display: grid;
  gap: 2rem;
  align-items: center;
  min-height: calc(100vh - 110px);
  padding: 3rem 6vw 4rem;
  max-width: 1120px;
  margin: 0 auto;
}
@media (min-width: 900px) {
  .how-hero { grid-template-columns: 1fr 1fr; }
}
.how-hero h1 {
  font-size: clamp(2.4rem, 6vw, 4rem);
  line-height: 1.05;
  letter-spacing: -0.04em;
  color: var(--navy);
  margin: 0 0 1rem;
}
.how-hero .lede { font-size: 1.15rem; max-width: 34rem; }
.how-hero-art {
  margin: 0;
  border-radius: 16px;
  overflow: hidden;
  aspect-ratio: 4 / 3;
  box-shadow: 0 24px 50px rgba(11, 31, 51, 0.16);
}
.how-hero-art img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.scroll-hint {
  margin-top: 2.5rem;
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--accent);
}

.scene {
  min-height: calc(var(--frames, 4) * 78vh);
  position: relative;
}
.scene.is-dark {
  background: var(--navy);
  color: #e8eef4;
}
.scene.is-dark .scene-copy > p,
.scene.is-dark .beat { color: #b7c6d3; }
.scene.is-dark h2 { color: #fff; }

.scene-sticky {
  position: sticky;
  top: 110px;
  height: calc(100vh - 110px);
  display: grid;
  gap: 1.5rem;
  align-items: center;
  padding: 1.25rem 6vw;
  max-width: 1120px;
  margin: 0 auto;
}
@media (min-width: 900px) {
  .scene-sticky { grid-template-columns: 0.92fr 1.08fr; }
}

.kicker {
  color: var(--accent);
  font-weight: 700;
  font-size: 0.78rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin: 0 0 0.55rem;
}
.scene-copy h2 {
  font-size: clamp(1.55rem, 3.2vw, 2.4rem);
  letter-spacing: -0.03em;
  line-height: 1.12;
  margin: 0 0 0.75rem;
  color: var(--navy);
}
.scene-copy > p {
  color: var(--muted);
  font-size: 1.02rem;
  max-width: 34rem;
}
.beat {
  margin: 0.7rem 0 0;
  font-weight: 600;
  color: var(--navy);
  opacity: 0.22;
}

.scene-visual {
  position: relative;
  width: 100%;
  aspect-ratio: 4 / 3;
  border-radius: 16px;
  overflow: hidden;
  background: #101820;
  transform: translateZ(0);
}
.frame {
  position: absolute;
  inset: 0;
  margin: 0;
  opacity: 0;
  will-change: opacity;
  pointer-events: none;
}
.frame.is-on { opacity: 1; }
.frame img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.frame figcaption {
  position: absolute;
  left: 1rem;
  right: 1rem;
  bottom: 1rem;
}
.chip, .ask, .card, .hero-num, .alert, .big, .wa {
  background: rgba(11, 31, 51, 0.88);
  color: #fff;
  border-radius: 10px;
  padding: 0.7rem 0.9rem;
  font-weight: 700;
  backdrop-filter: none;
}
.chip.dark, .ask.dark, .hero-num.dark {
  background: rgba(246, 244, 239, 0.94);
  color: var(--navy);
}
.stack {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}
.stack span {
  background: rgba(11, 31, 51, 0.9);
  color: #fff;
  border-radius: 8px;
  padding: 0.45rem 0.7rem;
  font-size: 0.88rem;
  font-weight: 600;
}
.pills {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}
.pills span {
  background: rgba(11, 31, 51, 0.9);
  color: #fff;
  border-radius: 999px;
  padding: 0.4rem 0.7rem;
  font-size: 0.8rem;
  font-weight: 700;
}
.pills.light span {
  background: rgba(246, 244, 239, 0.94);
  color: var(--navy);
}
.mono {
  font-family: ui-monospace, Consolas, monospace;
  font-size: 0.82rem;
  line-height: 1.5;
  background: rgba(11, 31, 51, 0.9);
  color: #ffb089;
  border-radius: 10px;
  padding: 0.75rem 0.9rem;
}
.card small { display: block; font-weight: 500; opacity: 0.8; margin-top: 0.2rem; }
.hero-num { font-size: 2.4rem; letter-spacing: -0.04em; text-align: center; }
.alert {
  background: #c44b1b;
  text-align: center;
  letter-spacing: 0.04em;
  font-size: 1.15rem;
}
.big { font-size: 1.15rem; text-align: center; }
.big b { font-size: 1.35rem; }
.wa { max-width: 85%; }
.wa.out { margin-left: auto; background: #005c4b; }
.wa.in { background: #1f2c34; }
.wa.chart { display: flex; flex-direction: column; gap: 0.25rem; font-size: 0.8rem; }

.how-end {
  padding: 5rem 6vw 4rem;
  text-align: center;
  max-width: 40rem;
  margin: 0 auto;
}
.how-end h2 {
  color: var(--navy);
  font-size: clamp(1.7rem, 3vw, 2.3rem);
  letter-spacing: -0.03em;
}
.how-end p { color: var(--muted); margin: 0 auto 1.4rem; }

@media (prefers-reduced-motion: reduce) {
  .scene { min-height: auto; }
  .scene-sticky { position: relative; top: 0; height: auto; padding-bottom: 2rem; }
  .scene-visual { position: relative; aspect-ratio: auto; height: auto; }
  .frame {
    position: relative;
    opacity: 1 !important;
    margin-bottom: 0.75rem;
    aspect-ratio: 4 / 3;
  }
  .beat { opacity: 1 !important; }
}