I was hoping for another theme, and when I read that the theme of this compo would be evolution, I first had no idea what a game based on this theme could be like. But after some time, I came up with the following idea:

A platform game in which you start in a lake as a fish, where you have an item that transforms you into an amphibian which can both swim and walk on land. On land, you have to find an item that will transform you into some sort of animal that cannot swim, but jump higher than an amphibian. By means of your jumping skills you can enter the area where another item is hidden, which will transform you into a bird. Now you can fly and find the exit from the current level. In the next level, you will start as a fish again.

I think this is too ambitious to be implemented in two days, and my graphic skills are too weak, so I will not pursue this project now, but maybe I have given inspiration to somebody else. I think it would be quite a cool game if properly executed.