I like the art, its cute.
It's already difficult to place and fit animals to fill a box, even more cumbersome to solve with only 4 colors. There isn't a way to remove animals from box, so you're kind of stuck with the choices you made. The most you can do is reorganize the animals already in the box.
I think adding a removing feature would easily make this a more enjoyable game. But for a concept like this, managing to get it done within the jam's time frame is impressive.