/* learn.css — layout for the public /learn knowledge base. Loaded AFTER
   tokens.css and tools.css, which supply the shared chrome (body, atmosphere,
   brand, breadcrumb, headings, prose, formula, cta, footer). This file adds
   only the two-column sidebar + content layout and the nav. */

/* Brand sits above the two-column shell, aligned to its left edge. */
.learn-top {
  position: relative;
  z-index: 2;
  max-width: 80rem;
  margin: 0 auto 1.75rem;
}

.learn-shell {
  position: relative;
  z-index: 2;
  max-width: 80rem;
  margin: 0 auto;
  display: flex;
  gap: 1.5rem;
  align-items: flex-start;
}

/* Left sidebar. Sticky on desktop, offset below the 4rem sticky top-nav. */
.learn-sidebar {
  flex: 0 0 18rem;
  position: sticky;
  top: 5.5rem;
  align-self: flex-start;
  max-height: calc(100vh - 7rem);
  overflow-y: auto;
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 0.5rem;
}

/* Content column. Overrides the tools.css `main` width so it flexes. */
.learn-main {
  flex: 1 1 auto;
  min-width: 0;
  width: auto;
  max-width: 46rem;
  margin: 0;
}

/* ── Lesson content figures (inline images + captions) ─────────────────── */
.lesson-figure {
  margin: 1.5rem 0;
  max-width: 46rem;
}
.lesson-figure img {
  display: block;
  width: 100%;
  height: auto;
  border: 1px solid var(--border);
  border-radius: var(--r);
}
.lesson-figure figcaption {
  margin-top: 0.5rem;
  font-size: 0.8rem;
  line-height: 1.6;
  color: var(--text-secondary);
}

/* ── Sidebar nav (course curriculum panel) ─────────────────────────────── */
.learn-nav-toggle { display: none; }

/* Panel header. */
.learn-nav-head {
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
  padding: 0.5rem 0.55rem 0.65rem;
  margin-bottom: 0.35rem;
  border-bottom: 1px solid var(--border);
}
.learn-nav-eyebrow {
  font-family: var(--font-sans);
  font-size: 0.6875rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--text-secondary);
}
.learn-nav-meta { font-size: 0.75rem; color: var(--text-muted); }

/* Module block = one category. Hairline between modules. */
.learn-nav .learn-cat { border-bottom: 1px solid var(--border-sub); }
.learn-nav .learn-cat:last-child { border-bottom: none; }

.learn-nav summary {
  list-style: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.55rem;
  border-radius: var(--rm);
}
.learn-nav summary::-webkit-details-marker { display: none; }
.learn-cat-head { display: flex; flex-direction: column; gap: 0.1rem; flex: 1 1 auto; min-width: 0; }
.learn-cat-eyebrow {
  font-size: 0.625rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--text-muted);
}
.learn-cat-title {
  font-family: var(--font-sans);
  font-size: 1rem;
  font-weight: 600;
  letter-spacing: 0.01em;
  line-height: 1.25;
  color: var(--text-primary);
}
.learn-cat-count {
  flex: none;
  font-size: 0.6875rem;
  color: var(--text-muted);
  white-space: nowrap;
}
/* Chevron sits at the right edge and rotates open. */
.learn-nav summary::after {
  content: '';
  flex: none;
  width: 0; height: 0;
  border-left: 5px solid var(--text-muted);
  border-top: 4px solid transparent;
  border-bottom: 4px solid transparent;
  transition: transform 0.15s ease;
}
.learn-nav details[open] > summary::after { transform: rotate(90deg); }
.learn-nav summary:hover { background: var(--bg-elevated); }

.learn-nav ul { list-style: none; margin: 0.1rem 0 0.5rem; padding: 0; }
.learn-nav li { margin: 0; }
.learn-nav a {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-size: 0.875rem;
  line-height: 1.35;
  color: var(--text-muted);
  text-decoration: none;
  padding: 0.45rem 0.55rem;
  border-radius: var(--rm);
  transition: background 0.15s ease, color 0.15s ease;
}
.learn-idx {
  flex: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 1.4rem;
  font-size: 0.6875rem;
  font-weight: 600;
  font-variant-numeric: tabular-nums;
  color: var(--text-muted);
  opacity: 0.75;
}
.learn-idx-dot::before { content: '•'; font-size: 0.9rem; line-height: 1; opacity: 0.9; }
.learn-lesson-title { min-width: 0; }
.learn-nav a:hover { background: var(--bg-elevated); color: var(--text-primary); }
.learn-nav a:hover .learn-idx { color: var(--text-primary); }
.learn-nav a[aria-current="page"] {
  background: var(--bg-elevated);
  color: var(--text-primary);
  font-weight: 600;
}
.learn-nav a[aria-current="page"] .learn-idx { color: var(--text-primary); opacity: 1; }

/* ── Hub / pillar article lists (static, crawlable) ────────────────────── */
.learn-cat-block { margin: 2.25rem 0; }
.learn-cat-block > h2 { margin-bottom: 0.4rem; }
.learn-cat-block > p { color: var(--text-muted); font-size: 0.875rem; line-height: 1.7; margin-bottom: 1rem; max-width: 46rem; }
.learn-article-list { list-style: none; padding: 0; margin: 0; display: grid; gap: 0.75rem; }
.learn-article-list a {
  display: block;
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 1rem 1.25rem;
  text-decoration: none;
  transition: border-color 0.15s ease, transform 0.1s ease;
}
.learn-article-list a:hover { border-color: var(--green); transform: translateY(-2px); }
.learn-article-list .t { color: var(--text-primary); font-weight: 500; font-size: 0.9375rem; }
.learn-article-list .d { color: var(--text-muted); font-size: 0.8125rem; line-height: 1.6; margin-top: 0.25rem; }

/* ── Article building blocks ───────────────────────────────────────────── */
/* Answer-first callout. Leads each article with the direct answer. */
.answer {
  background: var(--green-tint);
  border-left: 2px solid var(--green);
  border-radius: var(--rm);
  padding: 1rem 1.25rem;
  margin: 1.25rem 0 1.75rem;
  color: var(--text-primary);
  font-size: 0.95rem;
  line-height: 1.65;
}
.answer strong { font-weight: 600; }

.article-meta { font-size: 0.6875rem; letter-spacing: 0.08em; text-transform: uppercase; color: var(--whisper); margin-bottom: 1.25rem; }

.takeaways {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 1.25rem 1.5rem;
  margin: 2.25rem 0;
}
.takeaways h2 { margin-top: 0; margin-bottom: 0.75rem; font-size: 1.05rem; }

.related { margin-top: 2.25rem; }
.related h2 { font-size: 1.05rem; margin-bottom: 0.75rem; }
.related ul { list-style: none; padding: 0; margin: 0; display: grid; gap: 0.5rem; }
.related a { color: var(--text-muted); text-decoration: none; border-bottom: 1px solid var(--border); padding-bottom: 1px; font-size: 0.875rem; transition: color 0.15s ease, border-color 0.15s ease; }
.related a:hover { color: var(--green); border-color: var(--green); }

/* ── Mobile ────────────────────────────────────────────────────────────── */
@media (max-width: 768px) {
  .learn-shell { flex-direction: column; gap: 1.25rem; }
  .learn-sidebar {
    position: static;
    flex: 1 1 auto;
    width: 100%;
    max-height: none;
    overflow: visible;
    background: transparent;
    border: none;
    border-radius: 0;
    padding: 0;
  }
  .learn-nav-toggle {
    display: block;
    width: 100%;
    text-align: left;
    background: var(--bg-surface);
    border: 1px solid var(--border);
    border-radius: var(--rm);
    color: var(--text-primary);
    font-family: var(--font-sans);
    font-size: 0.8125rem;
    font-weight: 600;
    padding: 0.7rem 0.9rem;
    cursor: pointer;
  }
  .learn-nav { display: none; margin-top: 0.5rem; }
  .learn-nav.open {
    display: block;
    background: var(--bg-surface);
    border: 1px solid var(--border);
    border-radius: var(--r);
    padding: 0.4rem;
  }
  .learn-main { max-width: 100%; }
}