anchor.diff:  %% following code.
   -define(KNOWN_COMMANDS, #{<<"look">> => cmd_look,
                             <<"go">> => cmd_go,
  +                          <<"g">> => cmd_go,
                             <<"get">> => cmd_get,
                             <<"take">> => cmd_get,
                             <<"quit">> => cmd_quit,
  -                          <<"exit">> => cmd_exit}).
  +                          <<"exit">> => cmd_exit,
  +                          <<"help">> => cmd_help,
  +                          <<"h">> => cmd_help,
  +                          <<"?">> => cmd_help}).
   
   %% Initial locations of all objects in the game. Items in the
   %% inventory are marked by special location indicated by atom 'body'.
  
positive.code: cmd_get(_Cmd, _Object, State, Reply) ->
      {State, Reply}.
  
  %% @doc Stop the game
  -spec cmd_quit(Cmd :: binary(), Args :: [binary()], State :: state(), Reply :: reply()) -> {state(), reply()}.
  cmd_quit(_Cmd, _Object, State, Reply) ->
  
negative.code: console_play(GamePid) ->
      io:format("~n>>> "),
      receive
          {_Port, {data, {_EolFlag, []}}} ->
              ?MODULE:console_play(GamePid);
          {_Port, {data, {_EolFlag, Line}}} ->
              [Cmd | Args ] = [ list_to_binary(Token) || Token <- string:tokens(Line, " \t\n") ],
              console_play_command(Cmd, Args, GamePid);
  