.learning-deep-dive {
  margin-top: 1.2rem;
  padding: clamp(1.1rem, 3vw, 1.7rem);
  background: linear-gradient(135deg, rgba(36, 92, 94, 0.07), rgba(255, 255, 255, 0.68));
  border: 1px solid rgba(47, 118, 109, 0.24);
  border-radius: 1rem;
}

.learning-deep-dive__heading {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 1rem;
}

.learning-deep-dive__heading .eyebrow { color: var(--vermilion-dark); }
.learning-deep-dive__heading :is(h2, h3, h4) { margin: 0.25rem 0 0; font-family: var(--font-display); font-size: clamp(1.25rem, 2.3vw, 1.7rem); }
.learning-deep-dive__heading > span { color: var(--text-muted); font-size: 0.64rem; font-weight: 800; }

.learning-deep-dive__story {
  padding: 1rem;
  color: var(--on-brand);
  background: var(--surface-brand-strong);
  border-radius: 0.7rem;
}

.learning-deep-dive__story > span { color: #9dc6c2; font-size: 0.55rem; font-weight: 900; letter-spacing: 0.08em; }
.learning-deep-dive__story :is(h3, h4, h5) { margin: 0.4rem 0; font-family: var(--font-display); font-size: 1rem; }
.learning-deep-dive__story p { margin: 0; color: rgba(255, 255, 255, 0.72); font-size: 0.72rem; line-height: 1.8; }

.learning-deep-dive__facts {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.55rem;
  margin-top: 0.7rem;
}

.learning-deep-dive__facts div { padding: 0.8rem; background: var(--surface-page); border-radius: 0.65rem; }
.learning-deep-dive__facts dt { color: var(--mineral); font-size: 0.56rem; font-weight: 900; letter-spacing: 0.06em; }
.learning-deep-dive__facts dd { margin: 0.35rem 0 0; color: var(--text-primary); font-size: 0.7rem; font-weight: 700; line-height: 1.65; }

.learning-deep-dive__details { margin-top: 0.7rem; overflow: hidden; background: var(--surface-card); border: 1px solid var(--line); border-radius: 0.7rem; }
.learning-deep-dive__details + .learning-deep-dive__details { margin-top: 0.5rem; }
.learning-deep-dive__details summary { display: flex; align-items: center; justify-content: space-between; gap: 1rem; padding: 0.85rem 1rem; cursor: pointer; color: var(--text-heading); font-family: var(--font-display); font-size: 0.85rem; font-weight: 700; list-style: none; }
.learning-deep-dive__details summary::-webkit-details-marker { display: none; }
.learning-deep-dive__toggle-mark { color: var(--vermilion); font-family: var(--font-body); font-size: 1rem; font-style: normal; }
.learning-deep-dive__toggle-mark i { font-style: normal; }
.learning-deep-dive__toggle-mark i:last-child,
.learning-deep-dive__details[open] > summary .learning-deep-dive__toggle-mark i:first-child { display: none; }
.learning-deep-dive__details[open] > summary .learning-deep-dive__toggle-mark i:last-child { display: inline; }
.learning-deep-dive__details-body { padding: 0 1rem 1rem; }

.learning-deep-dive__timeline { display: grid; gap: 0.5rem; }
.learning-deep-dive__timeline article { display: grid; grid-template-columns: 78px minmax(0, 1fr); gap: 0.7rem; padding-top: 0.55rem; border-top: 1px solid var(--line); }
.learning-deep-dive__timeline time { color: var(--vermilion-dark); font-size: 0.66rem; font-weight: 900; }
.learning-deep-dive__timeline :is(h4, h5, h6) { margin: 0; font-size: 0.75rem; }
.learning-deep-dive__timeline p { margin: 0.25rem 0 0; color: var(--text-muted); font-size: 0.68rem; line-height: 1.7; }

.learning-deep-dive__signals { display: grid; gap: 0.45rem; margin: 0; padding: 0; list-style: none; }
.learning-deep-dive__signals li { padding: 0.7rem 0.8rem; color: var(--text-muted); background: var(--surface-tinted); border-left: 3px solid var(--world-accent, var(--mineral)); border-radius: 0 0.45rem 0.45rem 0; font-size: 0.7rem; line-height: 1.65; }
.learning-deep-dive__signals strong { color: var(--text-heading); }

.learning-deep-dive__trap { padding: 0.9rem; background: rgba(217, 74, 50, 0.07); border-radius: 0.55rem; }
.learning-deep-dive__trap strong { color: var(--vermilion-dark); font-size: 0.7rem; }
.learning-deep-dive__trap p { margin: 0.35rem 0 0; color: var(--text-muted); font-size: 0.7rem; line-height: 1.7; }
.learning-deep-dive__recall { display: grid; gap: 0.45rem; }
.learning-deep-dive__recall details { padding: 0.75rem; background: var(--surface-page); border-radius: 0.5rem; }
.learning-deep-dive__recall summary { cursor: pointer; color: var(--text-primary); font-size: 0.72rem; font-weight: 800; }
.learning-deep-dive__recall p { margin: 0.5rem 0 0; color: var(--mineral); font-size: 0.7rem; line-height: 1.7; }
.learning-deep-dive__zh { margin: 0.7rem 0 0; padding: 0.8rem; color: var(--text-muted); background: rgba(255, 255, 255, 0.72); border-radius: 0.55rem; font-size: 0.7rem; line-height: 1.7; }
.learning-deep-dive__zh strong { color: var(--mineral); }
.learning-deep-dive__source { display: inline-block; margin-top: 0.75rem; color: var(--mineral); font-size: 0.66rem; font-weight: 900; text-underline-offset: 0.2rem; }

@media (max-width: 640px) {
  .learning-deep-dive__heading { align-items: start; flex-direction: column; }
  .learning-deep-dive__facts { grid-template-columns: 1fr; }
  .learning-deep-dive__timeline article { grid-template-columns: 1fr; gap: 0.2rem; }
}