How to write GUI pushbutton callback function when you have the code(with no GUI)

I have the code for a game that runs well, but I want to add a graphical user interface(GUI) to that. To start with, I created a pushbutton(New Game) and pasted the entire code under the "function pushbutton1_Callback(hObject, eventdata, handles)". I thought I could run the game code by clicking the New Game button, but it didn't work. The error is "Undefined function or variable 'pushbutton1_Callback'." and "Error while evaluating UIControl Callback". So I'm wondering if there are certain special rules in writing callback function. How do you do it when you already have a code? Thank you!!

Answer 1

[Walter Roberson]

It does not take much.

function MyGame
   pushbutton1 = uicontrol('Style', 'push', 'String', 'New game', 'Callback', @pushbutton1_Callback);

function pushbutton1_Callback(hObject, eventdata)
  ... now put some code for starting the game here

Those two can go into MyGame.m or you can put the function pushbutton1_Callback into pushbutton1_Callback.m as long as it is the first function of that separate .m file.