double yDiff = Math.abs(e.getY() - dragStart.getY());
int radius = (int) Math.round(Math.hypot(xDiff, yDiff));
CircleObstacle obstacle = new CircleObstacle(
(int) Math.round(dragStart.getX()),
(int) Math.round(dragStart.getY()), radius);
queue.addPersistent(obstacle.drawObject());
obstacles.add(obstacle);
break;
}
default: {
// add rectangle obstacle