I'm in the process of modifying the current ant game to be like polyworld. However, it's not going well. But, I should have more time in the summer holiday coming up in two weeks.
If you haven't seen it there is a good google talk http://www.youtube.com/watch?v=_m97_kL4ox0
If you looked at the link you will see that polyworld is a game where you have a population of triangles. Each triangle has certain genetic structure that produces action and each triangle has a metabolism so they need to eat or they will die. The triangles can reproduce(which, cost energy or you get a bug where they all have a massive orgy and just eat the kids) and they have their life capped.
So what I propose is a game similar to that, but instead you have about 500 triangles each on a 2D level, but with multiple people playing against each other. The winner is the person with the most triangles at the end.
So where is the AI in this?
I think if we allow the person to only control how they breed and what genetics they can choose from breeding(you could say choose only move forward for the genetics of the offspring or even choose not to mate if the partner has crap genes). So the AI would be choosing what genes get passed on to offspring. This is different from other games as you aren't controlling the character, but instead you are controlling what they produce and hence controlling the evolution of the triangles. Saying that I suppose you should force the AI to choose 50/50 from both partners.
So there would be like 20 generic genetic codes like move forward, ability to move backwards. Then useful abilities like being able to tell if someone wants to mate or they will try to eat you. Then overpowered abilities like being able to stop opponent triangles or forcing someone to mate with you or even teleporting a short distance. I suppose I should add that the player can't choose the genes of the triangle at the start and we just make it random at the beginning, so for example if you get no information to move the triangle would sit there.
The genetic information will cost metabolism and the more overpowered the more metabolism it would use. I suppose you could also allow the ability to mate with other opponents and have the person with the most metabolism have the child so it counts as there.
P.S. Sorry if that was vague. However, if you think about it you have big potential for tactics. More importantly it's something different. Also, I think it won't be that hard to program with, for example you could just make the AI just choose the gene move forward and nothing else. But, yeah the AI could choose how much of a certain gene it wants in a population. If it loosing really badly you might make the AI, then choose genes that are good for surviving but aren't that powerful.
P.P.S. So in short can we have a breeding game? A game that you are only controlling what genes get passed down to offspring.