def step(self):
        """Prompt the environment to change."""
        current_state = max(self.infos(type=State),
                            key=attrgetter('creation_time'))
        current_contents = float(current_state.contents)
        new_contents = 1 - current_contents
        info_out = State(origin=self, contents=new_contents)
        transformations.Mutation(info_in=current_state, info_out=info_out)