@Override
    public void displayMenu() {       
        String command;
        do {
            this.display();
            // get command entered
            command = this.getCommand();
            switch (command) {
                case "B":
                    control.displayBoardHelp();
                    break;
                case "G":
                    control.displayGameHelp();
                    break;                  
                case "M":
                    control.displayMarkerHelp();
                    break;
                 case "P":
                    control.displayPlayerHelp();
                    break; 
            }
            
        } while(!"Q".equals(command)); 
    }