Eh, something with enough sliders to tweak the sim into other types of sandboxes seems most obvious

Then players can shape entity generation, gravity, to their vibe

Not quite Blender level turn teapot into a unintelligible smear of geometry range of tuning

The baseline being Earth world model then tweak entities individually, and such changes spread through the entity population over subsequent ticks of the world loop

Even include ability to speed up and slow the diffusion of the new parameters