/* ==========================================================================
   Lesson Mode
   H2-based card splitting, step-by-step navigation
   ========================================================================== */

/* ── Lesson Header Bar ── */
.lesson-header {
  position: sticky;
  top: 36px; /* below progress bar */
  z-index: 998;
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 8px 16px;
  background: var(--bg-secondary, #282c34);
  border-bottom: 1px solid var(--border-color, rgba(255,255,255,0.08));
  transition: background-color 0.3s ease;
}

.lesson-progress-bar {
  flex: 1;
  height: 8px;
  background: var(--bg-tertiary, #2d3748);
  border-radius: 4px;
  overflow: hidden;
}

.lesson-progress-fill {
  height: 100%;
  border-radius: 4px;
  background: var(--success, #4ecdc4);
  transition: width 0.4s ease;
}

.lesson-section-text {
  font-size: 12px;
  color: var(--text-muted, #718096);
  white-space: nowrap;
  font-variant-numeric: tabular-nums;
}

.lesson-hearts {
  display: flex;
  gap: 2px;
  font-size: 14px;
}

/* ── Section Cards ── */
.lesson-section {
  display: none;
  animation: section-fade-in 0.3s ease;
}

.lesson-section.active {
  display: block;
}

@keyframes section-fade-in {
  0%   { opacity: 0; transform: translateY(10px); }
  100% { opacity: 1; transform: translateY(0); }
}

/* ── Navigation Buttons ── */
.lesson-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 20px 0;
  margin-top: 16px;
  border-top: 1px solid var(--border-color, rgba(255,255,255,0.08));
}

.lesson-nav-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 10px 24px;
  border-radius: 8px;
  border: none;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  transition: background-color 0.2s ease, transform 0.15s ease;
}

.lesson-nav-btn:active { transform: scale(0.97); }

.lesson-nav-btn.next {
  background: var(--accent, #61dafb);
  color: var(--text-inverse, #1a1a2e);
}

.lesson-nav-btn.next:hover { background: var(--accent-hover, #79e3ff); }

.lesson-nav-btn.prev {
  background: var(--bg-tertiary, #2d3748);
  color: var(--text-primary, #e0e0e0);
}

.lesson-nav-btn.prev:hover { background: var(--bg-hover, rgba(255,255,255,0.1)); }

.lesson-nav-btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
  transform: none;
}

/* ── Lesson Complete Screen ── */
.lesson-complete {
  display: none;
  text-align: center;
  padding: 40px 20px;
}

.lesson-complete.active { display: block; }

.lesson-complete h2 {
  font-size: 24px;
  color: var(--text-primary, #e0e0e0);
  margin: 0 0 8px;
}

.lesson-complete .complete-emoji { font-size: 48px; margin-bottom: 12px; }

.lesson-complete .xp-summary {
  font-size: 20px;
  font-weight: 700;
  color: #FFD700;
  margin: 16px 0;
}

.lesson-complete .stats-row {
  display: flex;
  justify-content: center;
  gap: 24px;
  margin: 16px 0;
  font-size: 14px;
  color: var(--text-muted, #718096);
}

.lesson-complete .stat-value {
  font-weight: 700;
  color: var(--text-primary, #e0e0e0);
  font-size: 18px;
  display: block;
}

.lesson-complete .next-lesson-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-top: 24px;
  padding: 14px 32px;
  border-radius: 8px;
  border: none;
  background: var(--accent, #61dafb);
  color: var(--text-inverse, #1a1a2e);
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.15s ease;
}

.lesson-complete .next-lesson-btn:hover { transform: scale(1.03); }

/* ── Lesson Mode Toggle ── */
.lesson-mode-toggle {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-top: 8px;
  padding-top: 8px;
  border-top: 1px solid var(--border-color, rgba(255,255,255,0.08));
  font-size: 12px;
  color: var(--text-muted, #718096);
}

.lesson-mode-switch {
  position: relative;
  width: 36px;
  height: 20px;
  background: var(--bg-tertiary, #2d3748);
  border-radius: 10px;
  cursor: pointer;
  transition: background-color 0.3s ease;
  border: none;
  padding: 0;
}

.lesson-mode-switch::after {
  content: '';
  position: absolute;
  top: 2px;
  left: 2px;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--text-muted, #718096);
  transition: transform 0.3s ease, background-color 0.3s ease;
}

.lesson-mode-switch.active {
  background: var(--accent, #61dafb);
}

.lesson-mode-switch.active::after {
  transform: translateX(16px);
  background: #fff;
}

/* ── Responsive ── */
@media (max-width: 768px) {
  .lesson-header {
    top: 28px;
    padding: 6px 10px;
  }
  .lesson-nav { padding: 16px 0; }
  .lesson-nav-btn { padding: 8px 16px; font-size: 13px; }
  .lesson-complete h2 { font-size: 20px; }
}