sub whereami {
  my $self = shift;
  $self->{parent}->locate($self);
}

# in Parent

sub locate {
  my $self = shift;
  my $child = shift;

  foreach my $x (0 .. $xmax) {
      foreach my $y (0 .. $ymax) {
          return ($x, $y) if $self->{children}[$x][$y] eq $child;
      }
   }
}