static L<Pt> circlePoints(int x, int y, int radius) {
  new L<Pt> points;
  int steps = radius;
  for i to steps: {
    double phi = 2*pi()/steps;
    points.add(new Pt(iround(x+radius*sin(phi)), iround(y+radius*cos(phi)));
  }
  ret points;
}