Don’t expect this to be Call of Duty standard but then those games typically have a 50GB or higher footprint on disk. Anarch comes with 10 levels, 6 weapons, 7 enemy types and 3 ammo types and runs in 200 KB of disk space and runs in 32KB RAM. It’s 100% C but doesn’t use any FPU, GPU or file I/O. It’s old skool 90s style.
If you’ve played original Doom you’ll have an idea what it’s like.
Interestingly, the creator has put everything, source code, graphics etc into the public domain which is a very philanthropic gesture. So if you want to understand how to write a FPS (first-person-shooter) in C, take a look. You can even play it in a browser.
I’ve added this to the C Code links page (on the top menu).