This art style is FAB and the level art is great, too.
Your save mechanic was also AWESOME. 10/10.
The vent opening confused me because I thought I was supposed to go into it. I think you're trying to foreshadow the arrival of the scientist character. If the GBC supports screen shake and maybe some falling particle things, I think that would be more effective for what you're going for without confusion.
I think your background doors need better signifiers for which ones can and can't be interacted with. That was throwing me off in the beginning. (3D games signal this by either blocking unusable doors, or removing handles from unusable doors .)
Combat felt broken; my tailwhip seemed to do nothing. I don't know what's actually happening behind the scenes, but that's my perception as a player due to the lack of feedback on hit.
The levels feel too corridor-heavy and thus bland gameplay-wise. I'm walking in a straight line too often and it gets boring. If you ever get the chance, studying AAA level design would be really useful here. One of the things they do is constantly mix up which direction you're moving in (literally breaking up straight lines), the context you're moving in (combat, stealth, town, climbing), and which movement mechanics you're using to progress (walking, running, crouching, jumping, climbing, etc.) This stops the player from tuning out due to repetition.
Loved that you leaned into Die Hard but with cute animals. That's a game I didn't even know I needed in my life. With some additional level, mechanic, and sound effect work, I think this could be really cool.