Life to the next level
The Game of Life, that is.
A somewhat different take on the "sustainable existence" meme of game is found in the RGB Game. In this one, the beings consist of different color dots which equate to different characteristics (speed, lifespan & sight range) and look for food. They multiply when saturated.
It takes a little time to get the hang of how these things behave and what makes the system more sustainable, but for fans of Conway's original game (or other variations of cellular automata), it's well worth a look.