/* ── SIDEBAR STYLES ─────────────────────────────────────────── */

/* Sidebar Loading State */
.sidebar-loading {
  padding: 2rem;
  text-align: center;
  color: var(--text-muted);
  font-size: 0.9rem;
}

/* Section Details Element */
.section {
  border: none;
  border-bottom: 1px solid var(--border-light);
}

.section:last-child {
  border-bottom: none;
}

.section > summary {
  padding: 1.25rem 1.5rem;
  cursor: pointer;
  list-style: none;
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--text);
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: var(--transition);
  user-select: none;
}

.section > summary:hover {
  background: var(--brand-lighter);
  color: var(--brand-dark);
}

.section[open] > summary {
  background: var(--brand-lighter);
  color: var(--brand-dark);
  border-bottom: 1px solid var(--border-light);
}

.section summary::-webkit-details-marker {
  display: none;
}

.section-icon {
  width: 16px;
  height: 16px;
  transform: rotate(-90deg);
  transition: var(--transition);
  color: var(--text-light);
  flex-shrink: 0;
}

.section[open] .section-icon {
  transform: rotate(0deg);
  color: var(--brand);
}

/* Lessons Container */
.lessons {
  background: var(--panel);
}

/* Individual Lesson Item */
.lesson {
  padding: 1rem 1.5rem 1rem 2.5rem;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-muted);
  cursor: pointer;
  transition: var(--transition);
  border-left: 3px solid transparent;
  position: relative;
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.lesson::before {
  content: '';
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--text-light);
  flex-shrink: 0;
  transition: var(--transition);
}

.lesson:hover {
  background: var(--brand-lighter);
  color: var(--brand-dark);
  border-left-color: var(--brand);
}

.lesson:hover::before {
  background: var(--brand);
  transform: scale(1.2);
}

.lesson.active {
  background: var(--brand-light);
  color: var(--brand-dark);
  border-left-color: var(--brand);
  font-weight: 600;
}

.lesson.active::before {
  background: var(--brand);
  transform: scale(1.2);
}

/* Lesson Number Label */
.lesson-number {
  font-size: 0.8rem;
  color: var(--text-light);
  font-weight: 500;
  min-width: 24px;
}

.lesson.active .lesson-number {
  color: var(--brand);
}

/* Completed Lesson State */
.lesson.completed {
  background: var(--success-light);
  color: var(--success);
  border-left-color: var(--success);
}

.lesson.completed::before {
  background: var(--success);
}

.completion-check {
  margin-left: auto;
  color: var(--success);
  font-weight: bold;
  font-size: 0.9rem;
}

/* ── RESPONSIVE ADJUSTMENTS ─────────────────────────────────────── */

@media (max-width: 768px) {
  .section > summary {
    padding: 1rem 1.25rem;
    font-size: 0.9rem;
  }

  .lesson {
    padding: 0.875rem 1.25rem 0.875rem 2rem;
    font-size: 0.85rem;
  }
}