Ok, so I'm a programmer and have no art skills at all. But I have some pre-existing art from a game I made a few years ago. The rules say you can use pre-made art, just not a premade game or prototype. So the game will be different from the game I made before but the art will be the same. This is the game I made before: Fuzzballs
The fuzzballs look enough like furry Tribble that they could pass for a Tribble. I'm thinking to make the game play kind of like a "Breakdown" type game where blocks rise from the bottom and you click groups of similar color blocks of 3 or more to remove them. The goal is to keep them from piling up to the top of the screen. Maybe change the mechanic of them rising from the bottom, to a mechanic where they "breed" and multiply on there own.