Like a masterpiece, there is already everything what needed. Not more, nor less.
Of course if to speak about a game for wide audience, there might be some more features. Though I would consider keeping current mechanic as a separate game mode. Say freemode or something.
As for additional features, there might be some levels with puzzles. For example, there is some amount of spheres which are already set on screen. Player has only one or two spheres to set up in right place. Another example, more elements like black holes or maybe white spheres which can be eaten by any other.
To tell the truth I don't know if the game can be economically profitable for you, because you know nowadays players like more shooters or runners than relaxing puzzles. So it's only up to you which way to choose for the game.
The only thing that I can say for sure is that I've never written so damn long comments for gamejams lol.
Cheers!