Very cute aesthetic, the enemies didn't have as much effort put into them as the rest of the models clearly did which was a bit of a missed opportunity, but that's alright. The visual style of the game is excellent, I would only suggest some indication of which heart piece you're controlling and maybe some more attention to the enemies than the setting, since players pay a lot of attention to the entities they're supposed to avoid/interact with.
The jumping mechanic feels like it needed some work, it was hard to see how high in the air the hearts were which made some levels harder than they needed to be.
There's also the side-effect of the constantly rotating camera of never developing the muscle memory/training to complete levels you struggle with. Because the timing is never exactly the same, the controls never line up in the same direction you had the last time you encountered a challenge, so while the camera movement adds some visual variety it detracts massively from the experience, unless the player completes every level on their first try and never needs to get better at the challenges they're facing.
I think there could have been a little more thought put into the 'controlling two pieces' mechanic. Every level I played had some challenge to it, but not once was it necessary to switch control to the other piece. Even when the third enemy type showed up I found I could manouvre around them if I tried hard enough and switching control to divert attention couldn't really be used - especially since my other half starts in a 'cage' of bombs in that level. While switching control was possible, it didn't contribute anything to the game aside from bumping up the theme's relevance - which, after reading "a full heart is stronger than 2 halves" I was excited to see played with, but once both hearts make their whole the level ends.
In its current form, the game is more about getting to the goal (the other half) than working together. That being said, it's a very cute concept and the setting is made well, so I think it could go far and be a really good game in the future.