We will create the function that makes a background in a separate file. We will ensure the background will be available (in scope) to the main function by using a vertex array reference.

As we will be writing other functions that share data with the main function, we will write them all in their own .cpp files. We will provide prototypes for these functions in a new header file that we will include (with an include directive) in ZombieArena.cpp.

To achieve this, let's first make the new header file. Right-click Header Files in the Solution Explorer and select Add | New Item.... In the Add New Item window, highlight (by left-clicking) Header File (.h), and then in the Name field type ZombieArena.h. Finally click the Add button. We are now ready to code the header file for our new function.

In this new ZombieArena.h header file, add the following highlighted code including the function prototype:

#pragma once 
using namespace sf;
int...