Addictive & educational
The idea is simple- guide your ladybug around the map trying to eat as many aphids as you can. Aphids that survive reproduce and pass their traits onto their offspring. And, in accelerated time, you can see how the population traits of the aphids change. Pay particular attention to the speed counter- you'll be amazed at what happens.
Now, if only someone could produce a simple flash game that explains why bananas aren't the atheist's worst nightmare, we'd be all set!