Holy shit that opening sequence!
Really cool concept with having puzzles around ejecting your heart to go through barriers and being able to walk around for a short amount of time heartless. The visual effect of that was tremendous as well and worked well.
I was a little confused at first about the heart ejecting mechanic, I think partially because of being unable to move after the preceding instruction (and before heart ejection), so I thought I probably still couldn't move at first and then wasn't sure what I ejected or that I could/should collect it. I went through that scene several times, thinking maybe I just had to go through the door and reach some milestone to proceed.
I could maybe say some minor things about some weird clipping with the models around doors, but man what a feat to do all this 3D modelling in the first place for a jam.
Oh, and fantastic job with the level design, too. I'm the type of person who very easily gets lost, like, just in general, but I never felt lost playing this game. The key card dynamic was introduced and made sense, and there were so many little touches with the map, the signs, just super cool.
Voice acting was also amazing, and loved having the text + the audio. Definitely felt reminiscent to something like Portal.