I loved the intro cutscene at the beginning, it was a great way to set the mood.
I love the mouse and its animations, it's very squishy and cute. On the other hand, I'm not a fan of the shading on the terrain. The fog banding was disorienting at times and there were quite a few occurrences where I couldn't tell the ground from the cliff, or what the incline was. I missed a few stairs that felt completely invisible until I was right against them. The lighting change between the regions was super abrupt and could have benefited from some interpolation, but it also seems like you see the distant regions with the same theme as the one you're in? I also thought the world was way too big, though I appreciate how the ziplines let you essentially fast travel.
I had a bug(?) when I interacted with a ghost and it sent me back to the last zip line I used? Or is it a feature I didn't understand? I was puzzled by quite a few things. Like, you start in front of a locked gate with three symbols, so I set out to gather all 3 and the door opened. Except it opened on nothing, just a bit of terrain I had already visited (almost got stuck there) and the platforms I had fell from and couldn't reach again. So I'm not sure what was the point? But then again, I didn't really understand the wall run. It felt more like an uncontrollable wall jump to me and I fear I've been sequence-breaking quite a bit by using it...
I also never lost any of my powerups. I have no idea if I was supposed to or if it comes later into the game? But I like the "reverse-metroidvania" idea and from what I saw, I can imagine how you could compensate for some missing abilities, so that's pretty cool.
In the end I was too lost and I had to do my taxes, but there's a cool concept here that could shine with more polish. Good job you all! ;)