static void autoPositionCircles(CirclesAndLines cal) {
  int n = l(cal.circles);
  if (n == 0) ret;
  new L<DPt> l;
  if (n == 1) l.add(new DPt(0.5, 0.5));
  else if (n == 2) addAll(l, new DPt(0.3, 0.3), new DPt(0.7, 0.7));
  else for i to n: l.add(new DPt((i+0.5)/n, 0.5));
  
  for i to n: {
    Circle c = cal.circles.get(i);
    DPt p = l.get(i);
    c.x = p.x;
    c.y = p.y;
  }
}