Thanks for the feedback! We probably could have made this more clear, but you can use the walnuts when you get the slingshot during level 2.
Pretty much. In lvl 1 it's a dodging game until you obtain the pesticide spray bottle, which is your melee attack. You start collecting walnuts so you have ammo when you get the slingshot in lvl 2. We played back and forth with the idea of making walnuts available before the slingshot and I think it came down too we didn't have enough time to test both styles so we ended up with what we already had in engine.
Since the slingshot seems to be a common pain point with players this is great feedback for us to implement when revisiting these level designs if we return to this project, so again, thank you so much for letting us know about this!!