Move bar in ponggame with arrowkeys

For a schoolproject I am programming a pong ball game. I want to move the bar using the arrowkeys on my keyboard, but can only find a global function that works. But I actually want to avoid using global functions. Does someone have an alternative for me?

clear, clc, clf, clear all;
% ----------------------------- Lay out ----------------------------------%
Background = figure('color', [.2 .3 .8], 'KeyPressFcn', @keyboardFunction);
xaxis = [0 100];
yaxis = [-5 100];
GameField  = axes('color', 'black', 'xlim', [xaxis(1) xaxis(2)],...
    'ylim', [yaxis(1) yaxis(2)], 'xticklabels', [], ...
    'yticklabels', []) %How to put axis off?

PosBall    =[20 40]                                     %Initial position ball
VelBall    =[1 1]                                       %Initial direction ball
Ball       = line(PosBall(1),PosBall(2),'Marker', 'o', 'MarkerSize',...
              10, 'MarkerFaceColor', 'white','MarkerEdgeColor','white') %Actual ball
         
global CenterBar  = 45;
Bar        = line([CenterBar - 5, CenterBar + 5], [0 0], 'LineWidth', 4, 'Color', 'b')

% -------------------------Control ball-----------------------------------%

tic;          
while toc <20
    if PosBall(1) < xaxis(1) || PosBall(1) > xaxis(2)
        VelBall(1) = - VelBall(1);
    end
    if  PosBall(2) > yaxis(2)
        VelBall(2) = -VelBall(2);
    end
    if PosBall(2) < yaxis(1)
        if abs(PosBall(1) - CenterBar) < 5
            VelBall(2) = -VelBall(2);
        else
            disp("You lost the game!")
            close all;return;
        end
      
    end
    
    PosBall = PosBall + VelBall;
    set(Ball, 'Xdata', PosBall(1), 'Ydata', PosBall(2));
    
    
    set(Bar, 'Xdata', [CenterBar - 5, CenterBar + 5])
    pause(.02);
end
            
function keyboardFunction(figure, event)
global CenterBar
switch event.Key
    case 'leftarrow'
        CenterBar = CenterBar - 2;
    case 'rightarrow'
        CenterBar = CenterBar + 2;
end
end

Answer 1

[Manas Meena]

You might find the following file exchange links useful as references

• https://www.mathworks.com/matlabcentral/fileexchange/63044-pong-game?s_tid=srchtitle
• https://www.mathworks.com/matlabcentral/fileexchange/45619-pingpong-game?s_tid=srchtitle