I suck, after a dozen tries I wasn't able to pass the third level :( But the concept is really cool, I did manage to try what the negative values do, and it's a very good idea. Good job, it was fun!
The game is hard, as mentioned I didn't realise how punishing my hitboxes/hurtboxes were... Don't worry if you struggle passing a level, its not you, its me lol. I figured a good build is going negative on the shield, given you can manage passing level 0 (second level) hitless