The concept:
In this game you play as a hungry squirrel trying to find his nuts. Nuts will fall from the trees above and its your job to collect them before they fall to the ground. If you fail to collect enough nuts in time or if you collect poisonous berries by mistake its game over for you!
Format:
Side on/platform game
Game progression:
As you advance through the game you could encounter different scenes. Perhaps different kinds of forests, a park etc.
You could also introduce different kinds of falling objects - perhaps exploding berries!