/* ── Lesson page layout ── */
.lesson-main {
  max-width: 900px;
  margin: 0 auto;
  padding: calc(var(--nav-h) + 48px) 24px 80px;
}

.lesson-breadcrumb {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.8125rem;
  color: var(--text-3);
  margin-bottom: 32px;
  flex-wrap: wrap;
}
.lesson-breadcrumb a { color: var(--text-3); transition: color var(--t); }
.lesson-breadcrumb a:hover { color: var(--violet-2); }
.lesson-breadcrumb span { color: var(--text-3); }

.lesson-header { margin-bottom: 32px; }
.lesson-chapter-label {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--violet-2);
  margin-bottom: 12px;
}
.lesson-header h1 {
  font-size: clamp(1.5rem, 3.5vw, 2.25rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.15;
  margin-bottom: 16px;
}
.lesson-header-meta {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
}

/* YouTube embed */
.lesson-video-wrap {
  position: relative;
  width: 100%;
  padding-top: 56.25%; /* 16:9 */
  border-radius: var(--radius-lg);
  overflow: hidden;
  background: #000;
  margin-bottom: 40px;
  box-shadow: 0 20px 60px rgba(0,0,0,0.5);
}
.lesson-video-wrap iframe {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  border: none;
}

/* Content body */
.lesson-content {
  background: var(--bg-2);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 36px 40px;
  margin-bottom: 32px;
}
.lesson-content h2 {
  font-size: 1rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-3);
  margin-bottom: 20px;
}
.lesson-body { color: var(--text-2); line-height: 1.8; font-size: 0.9375rem; }
.lesson-body p { margin-bottom: 14px; }
.lesson-body p:last-child { margin-bottom: 0; }
.lesson-body strong { color: var(--text); font-weight: 600; }
.lesson-body a { color: var(--violet-2); }
.lesson-body a:hover { color: var(--violet); }
.lesson-body ul { margin: 12px 0 14px 20px; }
.lesson-body ul li { margin-bottom: 6px; }
.lesson-body .code-block { margin: 16px 0; font-size: 0.8125rem; }

/* Nav between lessons */
.lesson-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-top: 40px;
}
.lesson-nav-btn {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 18px 20px;
  background: var(--bg-2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  text-decoration: none;
  transition: all var(--t) var(--ease);
}
.lesson-nav-btn:hover {
  border-color: var(--border-2);
  background: var(--bg-3);
}
.lesson-nav-btn.next { text-align: right; }
.lesson-nav-label {
  font-size: 0.75rem;
  color: var(--text-3);
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}
.lesson-nav-title {
  font-size: 0.9375rem;
  font-weight: 600;
  color: var(--text);
  line-height: 1.3;
}

@media (max-width: 600px) {
  .lesson-content { padding: 24px 20px; }
  .lesson-nav { grid-template-columns: 1fr; }
  .lesson-nav-btn.next { text-align: left; }
}