I love the gun knockback mechanic and the slide animation, but man the grappling hook is challenging for me to use! I might come back later and try again.
Also your game only works correctly in full screen because you have the stretch mode set to "disabled" in your project settings, I don't know why that is the default in Godot, but it is an easy fix to change the stretch mode to "Viewport" and aspect to "keep". Also the vent particles are working for me in level 1?