As a big fan of retro games, the SFX caught my attention. I also like how u integrated the tuto into the level environment.
But greeting the player with tons of text is not a good idea. and in terms of balancing, u might need to increase the magazine count or add a shot cooldown bcs it runs out super fast.
ALso, i dont see how this has anything to do with the theme. Maybe if u add some art for the farm it would be better. Imagine the walls being hay stacks, and the zombies being infected farm animals, and the player being the farmer. that would be reaally good !!
Other than that good job for the effort mate !