Unnatural Selection is a puzzle-based life simulation game that features slimy creatures to experiment with, where your assigned objective is to figure what type of stimuli will mutate them into species that you have not discovered yet. You start off with a handful of worms, and if you drag them to a new environment they will start to evolve into a new creature. Some will die and rot away when they cannot adapt, but you'll always get new maggots to play around with when the number of creatures on screen start to dwindle.

There are sixteen evolution branches to find in total, with some requiring the player to feed or starve a creature until it achieves a new form. A walkthrough for the game can be found here.