That struct wouldn't actually have been in the original game. The idiomatic C analogue would be static variables inside functions, or (occasionally) global vari

That struct wouldn't actually have been in the original game. The idiomatic C analogue would be static variables inside functions, or (occasionally) global variables, but that wouldn't make it a memory-accurate reimplementation. I think the game code proper starts around line 670, but still, there's quite a lot of emulator code interspersed with the game logic after that point. (Multiple-line functions for something that would've been a single memory read in the original game.)