Nice little zombies survival game, If u want make a goal for the player, I see u have tons of variety in ur shop which is nice, but there's no goal in the game, add a goal for the player maybe if u kill a zombie he drop ammo (instead of having infinite ammo), or maybe after a certain amount of kills a boss spawns, also add more variety in the zombies, make some of them faster maybe, some crawl, some are tanky.
What uve made so far is a lot of work for a game jam and I admire ur work brother good stuff! and if u want to add more features to the game consider the stuff I said above if ud like :D