Like many girls of my generation, I first played The Sims at a sleepover. It was at my friend Hannah's house; three 11-year-olds huddled in front of her dad's bulky old computer monitor at midnight, gazing into a miniature house populated by tiny people going about their inexplicably compelling daily business. We took turns sending them to work, changing the wallpaper, and ordering them to put dirty dishes in the dishwasher instead of leaving them to gather flies. We bought them a little telly, a nice couch, a blender, paging covetously through the game's furniture catalogue. With a thrill, we discovered we could make Sims "smooch" (though we were disappointed to learn that they couldn't actually bone down – that wouldn't happen until The Sims 2).

Peek behind the graphics of two new games and you ll find the same artificial intelligence that s at work in Pentagon-sponsored war simulations. In the Sims 2 (due out spring 2004, $50), a player manages the life of a simulated human being who interacts with other computer-generated people and things. The Sims 2 is an evolution of the original (the best-selling computer game ever): Characters display more acute awareness of their surroundings-turning their heads if someone enters a room, or losing their train of thought when distracted. You can roughly predict where each ball is going to spin, but from second to second it depends on how it reflects off a bumper.†Each time a Sims character acts, the game s program engine calculates how his mood is affected. If he s hungry when he cooks a meal, his overall happiness will rise more than if he s not.