Highdea: evolutionarily-accurate Spore
I'm no gamer, but I was under the impression that Spore followed the laws of evolution on Earth as we know it instead of being as sandboxy as it is. We were watching a playthrough and the guy put a single arm on his creature and I about lost my mind. The Rule, as indicated extensively by the fossil record, is that chordates exclusively have paired limbs that are capped at four.
What if we had just the first two stages of Spore, and you can sandbox but only within the set evolutionary rules - and you get points when you make an animal that actually exists or existed? That's how you level up.
Worst? case scenario: this turns into a race to create Homo sapiens, and I guess you win once you do?
Best case scenario: you can sorta predict how, say, frogs are going to evolve next by having a record of their successful changes and a way to trial-and-error what they might try next. Although I'd be really surprised if that doesn't already exist to some degree in the zoology space
Either way I think I'd play the hell out of it