The solution was to create a header file called "define.h", and move all of the #defines and typedefs to there. Then I just include the define.h file at the top of handmade.h.
This was what I ended up having to do.
I thought stdint.h
was some win32 specific header, but it seems it is a header file in the C standard library
A little frustrating to follow this stuff 8 years later, using new windows APIs, VSCode and MSVC and having to figure out why Casey's code doesn't compile. But I guess that's the learning