/* TechForge — unified lesson / guide pages (Phase 3) */

body.lesson-page {
  padding-top: calc(var(--topbar-h) + var(--safe-top));
}

.lesson-layout {
  display: grid;
  grid-template-columns: 220px minmax(0, 1fr);
  gap: 32px;
  max-width: 1100px;
  margin: 0 auto;
  padding: 32px max(20px, var(--safe-left)) 80px max(20px, var(--safe-right));
}

/* ── Table of contents ── */
.lesson-toc {
  position: sticky;
  top: calc(var(--topbar-h) + var(--safe-top) + 16px);
  align-self: start;
  max-height: calc(100dvh - var(--topbar-h) - var(--safe-top) - 32px);
  overflow-y: auto;
  padding-right: 4px;
}
.lesson-toc-label {
  font-family: var(--mono);
  font-size: 9px;
  letter-spacing: 2px;
  text-transform: uppercase;
  color: var(--text3);
  margin-bottom: 10px;
  font-weight: 700;
}
.lesson-toc a {
  display: block;
  font-size: 12px;
  color: var(--text3);
  text-decoration: none;
  padding: 6px 10px;
  border-radius: var(--r-sm);
  border-left: 2px solid transparent;
  transition: color .15s, background .15s, border-color .15s;
}
.lesson-toc a:hover,
.lesson-toc a.active {
  color: var(--text);
  background: var(--surface);
  border-left-color: var(--accent);
}

/* ── Header (aligned with .pg-head) ── */
.lesson-main { min-width: 0; }

.lesson-breadcrumb {
  font-family: var(--mono);
  font-size: 11px;
  color: var(--text3);
  margin-bottom: 14px;
}
.lesson-breadcrumb a {
  color: var(--text3);
  text-decoration: none;
  transition: color .15s;
}
.lesson-breadcrumb a:hover { color: var(--accent); }

.lesson-header {
  margin-bottom: 40px;
  padding-bottom: 32px;
  border-bottom: 1px solid var(--border);
}
.lesson-crumb {
  font-family: var(--mono);
  font-size: 11px;
  font-weight: 600;
  color: var(--accent);
  letter-spacing: .1em;
  text-transform: uppercase;
  margin-bottom: 12px;
  display: flex;
  align-items: center;
  gap: 8px;
}
.lesson-crumb::before {
  content: '';
  display: inline-block;
  width: 18px;
  height: 2px;
  background: var(--accent);
  border-radius: 1px;
}

.lesson-title {
  font-family: var(--display);
  font-size: clamp(28px, 4.5vw, 40px);
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.1;
  color: var(--text);
  margin: 0 0 12px;
}
.lesson-sub {
  font-size: 15px;
  color: var(--text2);
  line-height: 1.75;
  max-width: 640px;
  margin: 0 0 18px;
}

.lesson-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
}
.lesson-meta-tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 12px;
  border-radius: var(--r-full);
  font-family: var(--mono);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: .03em;
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--text3);
}
.lesson-actions {
  display: flex;
  gap: 8px;
  margin-left: auto;
  flex-wrap: wrap;
}

.lesson-btn {
  font-family: var(--mono);
  font-size: 10px;
  font-weight: 700;
  padding: 7px 14px;
  border-radius: var(--r-md);
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text2);
  cursor: pointer;
  transition: all .15s;
  -webkit-tap-highlight-color: transparent;
}
.lesson-btn:hover {
  border-color: var(--border2);
  color: var(--text);
  transform: translateY(-1px);
}
.lesson-btn.active {
  border-color: var(--accent);
  color: var(--accent);
  background: color-mix(in srgb, var(--accent) 6%, transparent);
}

/* ── Sections (aligned with .sec-title) ── */
.lesson-section {
  margin-bottom: 44px;
  scroll-margin-top: calc(var(--topbar-h) + var(--safe-top) + 20px);
}
.lesson-section h2 {
  font-family: var(--display);
  font-size: 22px;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -0.01em;
  margin: 0 0 16px;
  display: flex;
  align-items: center;
  gap: 10px;
}
.lesson-section h2 .sec-icon {
  font-size: 20px;
  line-height: 1;
}

.lesson-prose {
  color: var(--text2);
  font-size: 14.5px;
  line-height: 1.8;
  margin: 0 0 16px;
}
.lesson-prose strong { color: var(--text); font-weight: 600; }

/* Diagram — matches premium code-block shadow */
.lesson-diagram {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px 22px;
  margin: 16px 0;
  overflow-x: auto;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.35);
}
.lesson-diagram pre {
  font-family: var(--mono);
  font-size: 12px;
  line-height: 1.55;
  color: var(--text2);
  margin: 0;
  white-space: pre;
}

/* Code — use .code-block pattern when generated; legacy .lesson-code alias */
.lesson-code,
.lesson-section .code-block {
  margin: 16px 0;
}

.lesson-list {
  margin: 0 0 16px;
  padding-left: 22px;
  color: var(--text2);
  font-size: 14px;
  line-height: 1.75;
}
.lesson-list li { margin-bottom: 8px; }
.lesson-list li::marker { color: var(--accent); }

/* Interview cards */
.lesson-iq {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 16px 18px;
  margin-bottom: 12px;
  transition: border-color .18s, transform .18s;
}
.lesson-iq:hover {
  border-color: var(--border2);
  transform: translateY(-1px);
}
.lesson-iq q {
  display: block;
  font-size: 13.5px;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 8px;
  font-style: normal;
}
.lesson-iq p {
  font-size: 13px;
  color: var(--text3);
  margin: 0;
  line-height: 1.65;
}

/* Cheat sheet grid */
.lesson-cheat {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 12px;
}
.lesson-cheat-item {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--r-md);
  padding: 14px;
  transition: border-color .15s;
}
.lesson-cheat-item:hover { border-color: var(--border2); }
.lesson-cheat-item strong {
  display: block;
  font-family: var(--mono);
  font-size: 11px;
  color: var(--accent);
  margin-bottom: 6px;
  letter-spacing: .04em;
}
.lesson-cheat-item span {
  font-size: 12.5px;
  color: var(--text3);
  line-height: 1.55;
}

/* Exercises */
.lesson-exercise {
  border-left: 3px solid var(--accent);
  padding: 14px 18px;
  background: color-mix(in srgb, var(--accent) 4%, transparent);
  border-radius: 0 var(--r-md) var(--r-md) 0;
  margin-bottom: 12px;
}
.lesson-exercise strong {
  display: block;
  font-size: 13px;
  color: var(--text);
  margin-bottom: 6px;
}
.lesson-exercise p {
  font-size: 13px;
  color: var(--text3);
  margin: 0;
  line-height: 1.65;
}

/* Related topics */
.lesson-related {
  margin-top: 48px;
  padding-top: 28px;
  border-top: 1px solid var(--border);
}
.lesson-related h3 {
  font-family: var(--display);
  font-size: 16px;
  font-weight: 700;
  margin: 0 0 14px;
  color: var(--text);
}
.lesson-related-links {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}
.lesson-related-links a {
  font-size: 12px;
  font-weight: 600;
  padding: 7px 14px;
  border-radius: var(--r-full);
  border: 1px solid var(--border);
  color: var(--text2);
  text-decoration: none;
  transition: all .15s;
}
.lesson-related-links a:hover {
  border-color: var(--accent);
  color: var(--accent);
  background: color-mix(in srgb, var(--accent) 5%, transparent);
}

@media (max-width: 900px) {
  .lesson-layout {
    grid-template-columns: 1fr;
    gap: 0;
    padding-top: 20px;
  }
  .lesson-toc {
    position: static;
    max-height: none;
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
    padding-bottom: 20px;
    margin-bottom: 8px;
    border-bottom: 1px solid var(--border);
  }
  .lesson-toc-label { width: 100%; }
  .lesson-toc a {
    border: 1px solid var(--border);
    border-left: 1px solid var(--border);
    font-size: 11px;
    padding: 5px 10px;
  }
  .lesson-actions {
    margin-left: 0;
    width: 100%;
    margin-top: 10px;
  }
  .lesson-section h2 { font-size: 19px; }
}