anchor.diff:  %all() -> [player_wield].
   %all() -> [attack_with_modifiers].
   %all() -> [one_sided_fight].
  -all() -> [counterattack_behaviour].
  +%all() -> [counterattack_behaviour].
  +%all() -> [player_wield_body_part_is_full].
  +all() -> [player_remove].
   %all() ->
       %[player_move,
        %player_move_fail,
  
positive.code:     ?WAIT100,
      undefined = val(item, player),
      Helmet = val(item, head1),
      Head = val(body_part, Helmet),
      Head = val(body_part, DexBuff),
      attempt(Config, Player, {move, <<"helmet">>, from, current_body_part, to, Player}),
      ?WAIT100,
      Helmet = val(item, player),
      undefined = val(body_part, Helmet),
      undefined = val(body_part, DexBuff),
      undefined = val(item, head1).
  
negative.code:     ?WAIT100,
      undefined = val(item, Player),
      Helmet = val(item, head1),
      {Head, head} = val(body_part, Helmet).
  
  player_wield_missing_body_part(Config) ->
      start(?WORLD_4),
  