Really well done, especially considering the time limit. The music in particular added nicely to the whimsical yet eerie atmosphere, I loved it.
Gameplay could get just a little frustrating, but not impossible. I realize you want to get players to slow down and really think through their strategy, but sometimes watching for really tiny movements feels less challenging and more irritating. Again, not saying it's bad! But for the future, maybe consider levels that rely more on figuring out a specific order of actions/pathways over delicate motor control. Just something to consider. Also, is there no replay button? I didn't see one when I finished the game, so I had to reload the page because I wanted to see if I had missed anything the first time. Maybe add a mute button as well.
As for the story, (SPOILER for any players who want to get to it themselves!) I thought it had just the right balance between what the player gets to know and leaving pieces open and mysterious. Personally, up until the end I never questioned that the white rabbits were evil, but I guess years of video games and owning a particularly mean little lapdog have caused me to automatically assume anything small, white, and fluffy is evil. (Ever hear of the rabbit epidemic in Australia? Rabbits could destroy the world if we let them.) What did surprise me, though, was the implication that the shadow bunnies are evil, too. Were they just manipulating the fox as a pawn in their war? What was with the shadow bunny coming out of the white one when you choose to kill the shadow bunny in the end? Is the fox just crazy?
I thought it was interesting that the player seems to be able to make a choice at the end, but unless I missed something you're still forced into one single ending. That seems like a missed opportunity; you could make different endings based on whether you kill only white bunnies, only shadow bunnies, or both.
Anyway, it's a fun, if short game, with good use of atmosphere and a unique mechanic. If you ever consider going further with this concept, maybe in a longer, more complex game, I'd love to see it!