.circle {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  border: 2px solid #ffffff; /* white outline when not done */
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  transition: all 0.4s ease;
  background: transparent;
}

.circle.done {
  background: linear-gradient(135deg,#4f46e5,#3b82f6); /* gradient fill */
  border-color: transparent;
  transform: scale(1.2);
}

.subtopic:hover .circle {
  transform: scale(1.1);
}

.subtopic-name mark {
  background-color: #facc15; /* yellow highlight for search */
  color: #1f2937;
  border-radius: 2px;
  padding: 0 2px;
}