/// <summary>
 /// Calls the RevealDigit method on the game or passes to the next Successor.
 /// </summary>
 /// <param name="command">The command.</param>
 /// <param name="game">The game on which the RevealDigit method is called.</param>
 public override void ProcessCommand(string command, BullsAndCowsGame game)
 {
     if (command == HelpCommand)
     {
         game.RevealDigit();
         game.CheatAttemptCounter++;
     }
     else if (this.Successor != null)
     {
         this.Successor.ProcessCommand(command, game);
     }
     else
     {
         throw new ArgumentNullException(NullExceptionText);
     }
 }