Throw something at the white-armored troopers, and they might toss a grenade back. Or they might just put their hands up. Or they could do something completely new, each time the game gets played.
Video games used to come preprogrammed with canned movements that expert players eventually could anticipate and figure out, but recent advancements in video game design -- and new game consoles with dazzling computing power -- have endowed computer-controlled characters with a sense of self-preservation and unpredictability not seen even a year ago.
The Star Wars game, from publisher LucasArts is just one of the games offering this advanced degree of realism. Game designers say this increasing sophistication is helping to put their medium on par with movies as a form of mainstream entertainment.
"I think you connect to these characters much more," said Torsten Reil, co-founder and chief executive of Britain's NaturalMotion Ltd., the company that developed technology used to breathe life into characters in the Star Wars game.
Called "euphoria," the technology generates animation on the fly, so each moment in a game is unique. The first game to feature it was Take-Two Interactive Software Inc.'s Grand Theft Auto IV , whose April debut rivaled -- and in dollar terms bested -- blockbuster movie openings.
NaturalMotion grew out of research Mr. Reil and colleague Colm Massey did at Oxford University on the way animals and humans move. The resulting technology creates 3-D character animation in real time, simulating the way the body moves so it looks authentic.
Other games deepen their measure of surprise by going in a different direction -- abandoning realism.
For example, Spore , from Sims creator Will Wright, immerses players in a world where not only the main character, but the game universe itself, is the product of its own imagination.
Players design a creature that evolves over several levels -- which are games unto themselves -- into beings capable of intergalactic travel. Because no two characters are the same, each will evolve in a different way.
A few years ago, games began showing off "ragdoll physics," which among other things made computer-controlled enemies look more believable when they died or got shot. But ragdoll technology is for dead bodies. Now Stormtroopers, or the cops in Grand Theft Auto IV , want to stay alive.
Only the latest generation of gaming consoles, Microsoft Corp.'s Xbox 360, Sony Corp.'s PlayStation 3 and Nintendo Co.'s Wii, are powerful enough to handle such complex animation systems.