A scenario whereby the following applies:
- Terrain variation
- Food appears, creatures need to eat food to not die, food is competed over by the group of creatures
- When a creature dies, food appears in it's place
- Different creatures can interact with each other (bones and joints become physical objects, being able to push each other)
- Mutations also occur in the layout of joints, muscles... of a creature
- Fitness measured by how long creature is alive
This would create a more realistic scenario, whereby creatures not only adapt how they use their body, but their body layout as well, to meet the challenges of not dying.