I think there's too much vignette and post processing effects if you're going for a jolly arcade feel but if you're going for the creepy zombie shooter vibe, I don't think this music is the best choice for that

I think the HP Bar covers too much of the screen too, also idle animation. You can actually get away with zero walk cycles as long as you have some sort of idle animation 

Good job on the diegetic links though, can't believe you pulled that off in 24 hours. 

Overall great game 

Wall placing feels good, shooting feels good, but a goal/end to the game would make it way better and fun to play. Maybe reach level #, collect # coins,etc. But overall, great job!