/* ========================================
   LearnAI — chapter deck navigator + waypoint rail
   Replaces the accordion table of contents. Chapter content
   (timeline map, lessons, buttons, images) is untouched.
   ======================================== */

/* Accent palette shared by cards, waypoints, and chapter heads.
   Mirrors the transit-map era colors. */
[data-accent="history"] {
  --card-accent: #ecc179;
  --card-accent-strong: #b98a2e;
  --card-accent-soft: rgba(224, 189, 114, 0.2);
}

[data-accent="works"] {
  --card-accent: #6cb5ff;
  --card-accent-strong: #0071e3;
  --card-accent-soft: rgba(85, 170, 255, 0.2);
}

[data-accent="agents"] {
  --card-accent: #4fdcaa;
  --card-accent-strong: #178f68;
  --card-accent-soft: rgba(71, 217, 165, 0.2);
}

/* ---------- Cover ---------- */
.learn-cover-sub {
  max-width: 560px;
  margin: 16px 0 0;
  color: var(--color-text-muted);
  font-size: 17px;
  line-height: 1.5;
}

/* ---------- Chapter deck ---------- */
.learn-deck {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 18px;
  margin-top: 38px;
}

.learn-card {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 10px;
  padding: 22px 22px 18px;
  overflow: hidden;
  border: 1px solid rgba(255, 255, 255, 0.09);
  border-radius: 20px;
  background:
    linear-gradient(rgba(255, 255, 255, 0.032) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255, 255, 255, 0.032) 1px, transparent 1px),
    radial-gradient(circle at 88% -12%, var(--card-accent-soft), transparent 52%),
    linear-gradient(160deg, #10263c, #081525 64%);
  background-size: 26px 26px, 26px 26px, auto, auto;
  color: #eef4fa;
  text-decoration: none;
  box-shadow: 0 18px 44px rgba(10, 24, 40, 0.16);
  transition: transform 0.28s cubic-bezier(0.2, 0.7, 0.3, 1), box-shadow 0.28s ease, border-color 0.28s ease;
}

.learn-card::after {
  content: "";
  position: absolute;
  inset: auto 0 0 0;
  height: 3px;
  background: linear-gradient(90deg, var(--card-accent), transparent 88%);
  opacity: 0.55;
  transform: scaleX(0.22);
  transform-origin: left;
  transition: transform 0.32s ease, opacity 0.32s ease;
}

.learn-card:hover,
.learn-card:focus-visible {
  transform: translateY(-5px);
  border-color: color-mix(in srgb, var(--card-accent) 55%, transparent);
  box-shadow:
    0 26px 58px rgba(10, 24, 40, 0.26),
    0 0 0 1px color-mix(in srgb, var(--card-accent) 30%, transparent);
}

.learn-card:hover::after,
.learn-card:focus-visible::after {
  opacity: 1;
  transform: scaleX(1);
}

.learn-card:focus-visible {
  outline: 3px solid color-mix(in srgb, var(--card-accent) 50%, transparent);
  outline-offset: 3px;
}

.learn-card-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.learn-card-num {
  color: var(--card-accent);
  font-size: 13px;
  font-weight: 850;
  letter-spacing: 0.16em;
}

.learn-card-tag {
  padding: 4px 10px;
  border: 1px solid rgba(255, 255, 255, 0.14);
  border-radius: 999px;
  color: rgba(238, 244, 250, 0.66);
  font-size: 10px;
  font-weight: 750;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  white-space: nowrap;
}

.learn-card-art {
  width: 100%;
  height: 84px;
  margin: 6px 0 2px;
}

.learn-card h3 {
  margin: 0;
  color: #f5f9fd;
  font-size: 23px;
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.05;
}

.learn-card > p {
  margin: 0;
  color: rgba(214, 226, 238, 0.78);
  font-size: 13.5px;
  line-height: 1.5;
}

.learn-card-foot {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-top: auto;
  padding-top: 14px;
}

.learn-card-meta {
  color: rgba(238, 244, 250, 0.6);
  font-size: 11px;
  font-weight: 750;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.learn-card-cta {
  display: grid;
  place-items: center;
  flex: 0 0 auto;
  width: 36px;
  height: 36px;
  border: 1px solid color-mix(in srgb, var(--card-accent) 55%, transparent);
  border-radius: 50%;
  color: var(--card-accent);
  font-size: 17px;
  line-height: 1;
  transition: background 0.25s ease, color 0.25s ease, transform 0.25s ease;
}

.learn-card:hover .learn-card-cta,
.learn-card:focus-visible .learn-card-cta {
  background: var(--card-accent);
  color: #081525;
  transform: translateY(3px);
}

/* ---------- Chapters: always open ---------- */
.learn-chapters {
  gap: clamp(56px, 7vw, 96px);
  padding-top: clamp(40px, 5vw, 64px);
}

.learn-chapter {
  border-top: 0;
}

.learn-chapter-head {
  align-items: start;
  margin-bottom: 24px;
  padding-top: 22px;
  border-top: 2px solid color-mix(in srgb, var(--card-accent-strong, #111820) 55%, transparent);
  grid-template-columns: 72px minmax(0, 1fr);
}

.learn-chapter .learn-section-kicker {
  color: var(--card-accent-strong, var(--color-accent));
}

.learn-chapter .learn-chapter-number {
  color: color-mix(in srgb, var(--card-accent-strong, #111820) 34%, transparent);
}

/* ---------- Waypoint rail ---------- */
.learn-waypoints {
  position: fixed;
  left: 50%;
  bottom: 18px;
  z-index: 90;
  display: flex;
  gap: 4px;
  padding: 5px;
  border: 1px solid rgba(255, 255, 255, 0.14);
  border-radius: 999px;
  background: rgba(8, 21, 37, 0.9);
  -webkit-backdrop-filter: blur(14px);
  backdrop-filter: blur(14px);
  box-shadow: 0 14px 38px rgba(8, 21, 37, 0.35);
  opacity: 0;
  pointer-events: none;
  transform: translate(-50%, 78px);
  transition: transform 0.35s cubic-bezier(0.2, 0.7, 0.3, 1), opacity 0.3s ease;
}

.learn-waypoints.is-visible {
  opacity: 1;
  pointer-events: auto;
  transform: translate(-50%, 0);
}

.learn-waypoints a {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 9px 15px;
  border-radius: 999px;
  color: rgba(238, 244, 250, 0.68);
  font-size: 12.5px;
  font-weight: 750;
  text-decoration: none;
  white-space: nowrap;
  transition: background 0.25s ease, color 0.25s ease;
}

.learn-waypoints a:hover {
  color: #ffffff;
  background: rgba(255, 255, 255, 0.07);
}

.learn-waypoints a.is-active {
  color: #ffffff;
  background: rgba(255, 255, 255, 0.12);
}

.learn-waypoints .wp-dot {
  flex: 0 0 auto;
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--card-accent);
  opacity: 0.65;
  transition: opacity 0.25s ease, box-shadow 0.25s ease;
}

.learn-waypoints a.is-active .wp-dot {
  opacity: 1;
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--card-accent) 30%, transparent);
}

.learn-waypoints a:focus-visible {
  outline: 3px solid color-mix(in srgb, var(--card-accent) 55%, transparent);
  outline-offset: 2px;
}

/* ---------- Responsive ---------- */
@media (max-width: 980px) {
  .learn-deck {
    grid-template-columns: 1fr;
    gap: 14px;
  }

  .learn-card {
    padding: 20px 20px 16px;
  }

  .learn-card-art {
    height: 72px;
  }
}

@media (max-width: 700px) {
  .learn-chapter-head {
    grid-template-columns: 48px minmax(0, 1fr);
    gap: 10px;
  }

  .learn-waypoints {
    bottom: 12px;
    max-width: calc(100vw - 16px);
  }

  .learn-waypoints a {
    gap: 6px;
    padding: 8px 11px;
    font-size: 11px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .learn-card,
  .learn-card::after,
  .learn-card-cta,
  .learn-waypoints {
    transition-duration: 0.01ms !important;
  }
}