This game has a lot of juice, with the animations of the arms and the sounds that play, that go a long way to make the action satisfying.
The idea of punching out the heart and pulling it back in is interesting and I could see a lot of cool interactions happening with this if you guys keep working on this after the jam is over, which I think you should because I think there is a lot of potential with this mechanic.
The 3D models are really impressive for 48 hours; most people don't attempt 3D because they can't get this far with it in the allotted time frame.
You guys went for more of level-based or chronological design rather than an infinite gameplay loop like a horde mode which is the way to go, I think. It makes a big difference to me as a player to know that there is going to be a progression of the mechanics and that there is a finite goal or end.
I liked that you had in-game tutorials, because many games don't, however, I had some trouble reading them due to the white text on overlaying the bright gameplay in the background. I think you would be better off with less text and more button prompts anyway - allow the player to see what happens when they press a button rather than tell them. However, specific details like the behavior of the heart is understandable, although ideally that would not be explained in text either.
Other than the tutorials, I really didn't have much feedback. It's a very ambitious and impressive submission for 48 hours.
I would love your rating / comments on my game as well, so I can know what to improve.