.rbs-panel {
  background: #ffffff;
  border-radius: 16px;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
  padding: 24px;
  max-width: 720px;
  margin: 0 auto;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}

.rbs-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 1px solid #e5e7eb;
}

.rbs-title {
  font-size: 1.25rem;
  font-weight: 700;
  color: #111827;
}

.rbs-score {
  font-size: 1rem;
  color: #4b5563;
}

.rbs-score b {
  color: #2563eb;
}

.rbs-progress {
  font-size: 0.9rem;
  color: #6b7280;
  margin-bottom: 16px;
}

.rbs-question-text {
  font-size: 1.1rem;
  line-height: 1.6;
  color: #1f2937;
  margin-bottom: 16px;
  padding: 16px;
  background: #f9fafb;
  border-radius: 12px;
}

.rbs-hint {
  font-size: 0.85rem;
  color: #6b7280;
  margin-bottom: 12px;
}

.rbs-options {
  display: grid;
  gap: 12px;
  margin-bottom: 16px;
}

.rbs-option {
  display: block;
  width: 100%;
  text-align: left;
  padding: 14px 18px;
  font-size: 1rem;
  color: #374151;
  background: #ffffff;
  border: 2px solid #e5e7eb;
  border-radius: 12px;
  cursor: pointer;
  transition: all 0.2s ease;
}

.rbs-option:hover:not(:disabled) {
  border-color: #3b82f6;
  background: #eff6ff;
}

.rbs-option:disabled {
  cursor: default;
}

.rbs-option.correct {
  border-color: #22c55e;
  background: #f0fdf4;
  color: #166534;
}

.rbs-option.wrong {
  border-color: #ef4444;
  background: #fef2f2;
  color: #991b1b;
}

.rbs-feedback {
  min-height: 24px;
  margin-bottom: 16px;
}

.rbs-correct {
  color: #16a34a;
  font-weight: 600;
}

.rbs-wrong {
  color: #dc2626;
  font-weight: 600;
}

.rbs-explanation {
  margin-top: 8px;
  padding: 12px;
  background: #f3f4f6;
  border-radius: 8px;
  font-size: 0.9rem;
  color: #4b5563;
}

.rbs-actions {
  text-align: center;
}

.rbs-btn {
  padding: 12px 24px;
  font-size: 1rem;
  color: #ffffff;
  background: #2563eb;
  border: none;
  border-radius: 10px;
  cursor: pointer;
  transition: background 0.2s ease;
}

.rbs-btn:hover {
  background: #1d4ed8;
}

.rbs-end {
  text-align: center;
  padding: 32px 16px;
}

.rbs-end-icon {
  font-size: 3rem;
  margin-bottom: 12px;
}

.rbs-end-title {
  font-size: 1.4rem;
  font-weight: 700;
  color: #111827;
  margin-bottom: 16px;
}

.rbs-end-stat {
  font-size: 1.1rem;
  color: #4b5563;
  margin-bottom: 8px;
}

.rbs-empty {
  text-align: center;
  padding: 40px 16px;
  color: #9ca3af;
}