Ok it's good for a first game jam, there are a lot of things to say, between the spawn of the zombies next to the player, some upgrades that don't work (the regeneration didn't seem to work) and as someone already said the background has no variation so it's hard to see when you move.
To go a little deeper, the camera is not very nice, it should ideally go a little further forward than the player when he moves, since you're on Unity, you can use the Cinemachine plugin which allows you to have a complete and simplified control of the camera, the zombies, in the theory that it does not spawn on the player's screen, are going to be too easy to dodge and besides that's a bit of a problem, either you give a reward for killing a zombie, or you create a special zombie that is threatening, for example a zombie that runs very fast or jumps, the player is going to be surprised for sure and for the wood / stone are not very useful.
And finally, let's finish on the good points because if this comment is long, it's because I really enjoyed your game, you did a good job to make the progression of the resources more and more difficult, the zombies are becoming more resistant, the concept of mixing a clicker / survival is a good idea and even if the game is sometimes incomplete, it's still fun!
Keep going, you'll get better for sure.