/* =========================================================
   Lesson page styles — unified content-page chrome
   ========================================================= */

.lesson-shell {
  padding-top: 72px;
  min-height: 100vh;
  position: relative;
}

.lesson-hero {
  position: relative;
  padding: 64px 0 40px;
  border-bottom: 1px solid var(--line);
  overflow: hidden;
}
.lesson-hero::before {
  content: '';
  position: absolute; inset: 0;
  background:
    radial-gradient(circle at 12% 30%, color-mix(in oklab, var(--indigo) 20%, transparent), transparent 50%),
    radial-gradient(circle at 88% 60%, color-mix(in oklab, var(--teal) 16%, transparent), transparent 55%);
  z-index: -1;
}
html.dark .lesson-hero::before {
  background:
    radial-gradient(circle at 12% 30%, rgba(79, 70, 229, 0.32), transparent 55%),
    radial-gradient(circle at 88% 60%, rgba(13, 148, 136, 0.22), transparent 55%);
}

.lesson-eyebrow {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 6px 12px;
  background: var(--bg-elev);
  border: 1px solid var(--line);
  border-radius: 999px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--ink-3);
  margin-bottom: 18px;
}

.lesson-hero h1 {
  font-family: var(--font-display);
  font-size: clamp(36px, 5.4vw, 60px);
  font-weight: 500;
  letter-spacing: -0.03em;
  line-height: 1.05;
  max-width: 18ch;
}
.lesson-hero h1 em {
  font-style: normal;
  background: linear-gradient(120deg, var(--indigo), var(--violet) 50%, var(--teal));
  -webkit-background-clip: text; background-clip: text;
  -webkit-text-fill-color: transparent;
}
.lesson-hero p.intro {
  color: var(--ink-3);
  font-size: clamp(16px, 1.5vw, 18px);
  margin-top: 18px;
  max-width: 64ch;
  line-height: 1.6;
}
.lesson-meta {
  display: flex; flex-wrap: wrap;
  gap: 18px;
  margin-top: 28px;
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--ink-3);
  letter-spacing: 0.06em;
}
.lesson-meta span { display: inline-flex; align-items: center; gap: 6px; }
.lesson-meta span .dt { width: 6px; height: 6px; border-radius: 50%; background: var(--teal-2); }

/* Layout: side TOC + article */
.lesson-body {
  display: grid;
  grid-template-columns: 220px minmax(0, 1fr);
  gap: 56px;
  padding: 56px 0 96px;
  align-items: start;
}

.toc {
  position: sticky;
  top: 96px;
  font-size: 14px;
}
.toc h5 {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-4);
  margin-bottom: 14px;
  font-weight: 500;
}
.toc ol {
  list-style: none;
  border-left: 1px solid var(--line);
  padding-left: 0;
}
.toc ol li { padding: 0; }
.toc ol li a {
  display: block;
  padding: 8px 14px;
  margin-left: -1px;
  border-left: 1px solid transparent;
  color: var(--ink-3);
  font-size: 13.5px;
  line-height: 1.4;
  transition: color 0.2s, border-color 0.2s;
}
.toc ol li a:hover { color: var(--ink); }
.toc ol li a.active {
  color: var(--indigo);
  border-left-color: var(--indigo);
  font-weight: 500;
}

.article {
  max-width: 720px;
}
.article > section {
  padding: 32px 0 16px;
  scroll-margin-top: 96px;
  border-top: 1px solid var(--line);
}
.article > section:first-child { border-top: 0; padding-top: 0; }

.article h2 {
  font-size: clamp(26px, 3.4vw, 36px);
  letter-spacing: -0.025em;
  margin-bottom: 16px;
  color: var(--ink);
  font-weight: 600;
  position: relative;
}
.article h2 .num {
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 400;
  color: var(--ink-4);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  display: block;
  margin-bottom: 6px;
}
.article h3 {
  font-size: 20px;
  margin: 28px 0 10px;
  color: var(--ink-2);
  letter-spacing: -0.015em;
}
.article p,
.article li {
  font-size: 16.5px;
  line-height: 1.75;
  color: var(--ink-2);
  margin-bottom: 14px;
}
.article ul, .article ol { padding-left: 22px; margin-bottom: 16px; }
.article li::marker { color: var(--ink-4); }
.article strong { color: var(--ink); font-weight: 600; }
.article em { color: var(--ink-2); font-style: italic; }
.article code {
  font-family: var(--font-mono);
  font-size: 14px;
  background: var(--bg-soft);
  padding: 2px 6px;
  border-radius: 5px;
  border: 1px solid var(--line);
  color: var(--ink);
}
.article a { color: var(--indigo); border-bottom: 1px solid color-mix(in oklab, var(--indigo) 30%, transparent); }
.article a:hover { border-bottom-color: var(--indigo); }

/* Callouts (mapped from original .example-box / .analogy-box / .key-points) */
.article .example-box,
.article .analogy-box,
.article .key-points,
.article .callout {
  background: var(--bg-elev);
  border: 1px solid var(--line);
  border-left: 3px solid var(--indigo);
  border-radius: 14px;
  padding: 22px 26px;
  margin: 28px 0;
  position: relative;
  overflow: hidden;
}
.article .analogy-box { border-left-color: var(--teal); }
.article .key-points { border-left-color: var(--violet); }
.article .example-box::before,
.article .analogy-box::before,
.article .key-points::before {
  content: 'Example';
  position: absolute; top: 12px; right: 16px;
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-4);
}
.article .analogy-box::before { content: 'Analogy'; }
.article .key-points::before { content: 'Key points'; }

.article .example-box p:last-child,
.article .analogy-box p:last-child,
.article .key-points p:last-child,
.article .example-box ul:last-child,
.article .analogy-box ul:last-child,
.article .key-points ul:last-child { margin-bottom: 0; }

/* Tables */
.article table {
  width: 100%;
  border-collapse: collapse;
  margin: 24px 0;
  font-size: 14.5px;
}
.article th, .article td {
  text-align: left;
  padding: 12px 14px;
  border-bottom: 1px solid var(--line);
  vertical-align: top;
}
.article th {
  background: var(--bg-soft);
  font-weight: 600;
  font-size: 12px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--ink-3);
}

/* Comparison/grid items in original — generic catch */
.article .comparison-grid,
.article .pillars-grid,
.article .topics-grid,
.article .grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 14px;
  margin: 22px 0;
}
.article .comparison-item,
.article .pillar-card,
.article .topic-card,
.article .grid > * {
  background: var(--bg-elev);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 18px;
  font-size: 14.5px;
  line-height: 1.55;
}
.article .comparison-item h3,
.article .pillar-card h3,
.article .topic-card h3 { font-size: 16px; margin: 0 0 8px; color: var(--ink); }

/* Lesson nav (prev/next) */
.lesson-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
  margin-top: 56px;
  padding-top: 32px;
  border-top: 1px solid var(--line);
}
.lesson-nav a {
  display: flex;
  flex-direction: column;
  padding: 18px 22px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: var(--bg-elev);
  transition: border-color 0.2s, transform 0.2s var(--ease-out);
  font-size: 14px;
  color: var(--ink);
}
.lesson-nav a:hover {
  border-color: var(--indigo);
  transform: translateY(-2px);
}
.lesson-nav .lbl {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-4);
  margin-bottom: 4px;
}
.lesson-nav .next { text-align: right; align-items: flex-end; }
.lesson-nav .ti { font-weight: 500; font-size: 16px; letter-spacing: -0.015em; }

/* Reading progress bar */
.read-progress {
  position: fixed;
  top: 70px; left: 0;
  height: 2px;
  width: 0%;
  background: linear-gradient(90deg, var(--indigo), var(--teal));
  z-index: 99;
  transition: width 0.1s linear;
}

/* Hide all the original deck chrome inside .article */
.article .progress-container,
.article .navigation,
.article .slide-number,
.article .progress-bar { display: none !important; }
.article .slide,
.article .presentation-container {
  display: block !important;
  background: transparent !important;
  box-shadow: none !important;
  padding: 0 !important;
  border-radius: 0 !important;
  min-height: 0 !important;
  width: 100% !important;
  max-width: 100% !important;
  animation: none !important;
}

@media (max-width: 880px) {
  .lesson-body { grid-template-columns: 1fr; gap: 32px; }
  .toc { position: static; }
  .toc ol { display: flex; gap: 6px; flex-wrap: wrap; border-left: 0; padding-left: 0; }
  .toc ol li a { padding: 6px 12px; border: 1px solid var(--line); border-radius: 999px; font-size: 12.5px; }
  .toc ol li a.active { border-color: var(--indigo); background: color-mix(in oklab, var(--indigo) 8%, transparent); }
  .lesson-nav { grid-template-columns: 1fr; }
  .lesson-nav .next { text-align: left; align-items: flex-start; }
  .article > section { scroll-margin-top: 80px; }
}