.lessons-lead { font-size: var(--fs-lg); color: var(--muted); line-height: 1.6;
    margin-bottom: 22px; }

  /* Age groups — one native <details> per group, same disclosure pattern the
     nav already uses. Native gives keyboard support and the expanded/collapsed
     announcement for free, and keeps the whole page working without JS. The
     groups are independent: opening one never closes another, so a parent whose
     child sits near a boundary can compare two of them side by side. */
  .agroup { background: var(--surface); border: 1px solid var(--line);
    border-radius: var(--r-card); margin-bottom: 10px; }
  .agroup[open] { border-color: var(--brand-tint-strong); }

  /* Two rows rather than one: at 320px an age, a level label and a duration do
     not survive on a single line next to the chevron. */
  .agroup__head { display: grid; grid-template-columns: 1fr auto;
    grid-template-areas: "age chev" "sub chev"; align-items: center;
    column-gap: 12px; row-gap: 2px; padding: 14px 16px; cursor: pointer;
    list-style: none; user-select: none; }
  .agroup__head::-webkit-details-marker { display: none; }
  .agroup__layout { min-width: 0; }
  .agroup__example { margin: 0 0 24px; min-width: 0; }
  /* The poster in its own proportions (spec 031); the link shrinks to it. */
  .agroup__example .photo-open { display: inline-block; max-width: 100%; vertical-align: top; }
  .agroup__poster { display: block; width: auto; max-width: 100%; height: auto; max-height: 420px;
    border-radius: var(--r-card); }
  /* Stacked above the text on a narrow screen, a poster stays a modest picture
     rather than a full-width block, whatever its shape. */
  @media (max-width: 767.98px) {
    .agroup__poster { max-width: min(100%, 220px); max-height: 300px; }
  }
  .agroup__copy { min-width: 0; }
  @media (min-width: 768px) {
    .agroup__layout--illustrated { display: grid; grid-template-columns: minmax(0, 300px) minmax(0, 1fr); gap: 32px; align-items: start; }
    .agroup__example { margin-bottom: 0; }
  }
  .agroup__age { grid-area: age; font-size: var(--fs-lg); font-weight: 700;
    letter-spacing: -.01em; color: var(--ink); }
  .agroup__sub { grid-area: sub; display: flex; flex-wrap: wrap; gap: 2px 8px;
    font-size: var(--fs-sm); }
  .agroup__tag { font-weight: 600; color: var(--muted); }
  .agroup__meta { color: var(--muted-2); }
  .agroup__chev { grid-area: chev; width: 20px; height: 20px; flex-shrink: 0;
    color: var(--brand); transition: transform .15s ease; }
  .agroup[open] .agroup__chev { transform: rotate(180deg); }

  .agroup__body { padding: 2px 16px 16px; font-size: var(--fs-base);
    line-height: 1.65; color: var(--ink); }
  .agroup__subtitle { font-size: var(--fs-xs); text-transform: uppercase;
    letter-spacing: .07em; font-weight: 700; color: var(--brand);
    margin: 16px 0 7px; }
  .agroup__list { list-style: none; display: flex; flex-direction: column; gap: 7px; }
  .agroup__list li { display: flex; gap: 10px; }
  .agroup__list li::before { content: "✦"; color: var(--brand); flex-shrink: 0; }
  .agroup__more { display: inline-block; margin-top: 14px; font-size: var(--fs-sm);
    font-weight: 600; color: var(--brand); text-decoration: none; }
  .agroup__more:hover { text-decoration: underline; }

  /* A collapsed <details> prints as its summary alone, which would silently drop
     two thirds of the page from a saved PDF. ::details-content reaches inside the
     UA slot that hides it; display/visibility on the children cannot. Progressive
     enhancement — a browser without the pseudo-element just prints as before. */
  @media print {
    .agroup::details-content { content-visibility: visible; block-size: auto; }
    .agroup__chev { display: none; }
  }