.
                                        O
                               x     x y     x
                             y       g e        y
                           g           n           g
                          e            ●             e
                         O          O x            O
                         x          y    g           x
                         y          e    n           y
                          g          O  x            g
                           e          y  g           e
                            n          e            n
                              O        n        O
                                  x     O     x
                                         x