sub new {
    my $class = shift;
    my $extends = $class->SUPER::new( @_ );
    $extends->setFlyBehaviour( src::bo::behaviour::fly::CannotFly->new() );
    $extends->setQuackBehaviour( src::bo::behaviour::quack::CanSqeek->new() );
    my $self = {
        COLOR => { 'VALUE' => undef, 'ACCESS' => 'protected' },
    };
    my $closure = sub {
        my $field = shift;
        if ( exists $self->{$field} ) {
            $self->{$field}->{'ACCESS'} eq 'private'
                and caller(0) eq __PACKAGE__
                || confess "$field is private";
            $self->{$field}->{'ACCESS'} eq 'protected'
                and caller(0)->isa(__PACKAGE__)
                || confess "$field is protected";
            if ( @_ ) { $self->{$field}->{'VALUE'} = shift; }
            return $self->{$field}->{'VALUE'};
        }
        else {
            return $extends->($field,@_);
        }
    };
    bless ($closure, $class);
    return $closure;
}