I'm not sure how to improve this game in that regard because some people find it really easy and some people find it incredibly difficult. But I plan to use a third-party audio positioning library in my next game, which will hopefully improve things.
I will admit that the zombies were a bit of an afterthought and this whole game is a tech demo of sorts, and if I hadn't had the time limit of this also being a college project it could have ended up more polished. Originally, there was a backstory, but it sort of got pushed aside when I realised how much time I really had when I also factored in coursework, etc... I think that the next game I make will be a massive improvement on this, probably with a proper story, etc. Hopefully whenever that comes out, you'll be able to play it and let me know if it's actually better!
Anyway, thanks for the review. I appreciate people letting me know what they think, so that I can improve. It can be hard to read sometimes when it's very negative, but failing is the first step towards succeeding, right?