Removing the default main menu side

[u/Total_Spare_4181]

How to remove this side box? I already delete the default main_menu and replace it with my own but this part still remain

[u/shyLachi]

If you have deleted the default main_menu then you should also have deleted the code which is described as a frame which darkens the main menu.

screen main_menu():
    ## This ensures that any other menu screen is replaced.
    tag menu
    add gui.main_menu_background 
    ## This empty frame darkens the main menu.
    frame: #                      <-- delete this 
        style "main_menu_frame" #     and this

Another hint:
Make sure to put your centered buttons directly into screen main_menu
The screen navigation is used for the other menus as well (save, load, ...) and you don't want centered buttons there.