Hey! Thank you for trying out the game and writing a comment!
Yup, I wanted to implement an i-frame, unfortunately, though, I overslept today and had 2 hours to fix like 3 major bugs, but oh well.. my first game on godot and first game in like 2 years, so I am happy! :D
I didn't name the upgrades based on Isaac, but I think subconsciously I must have, because now that I think about it, 100% isaac upgrades :D