Is there a generation of 12-year-old girls out there yearning for a 12-year-old action-hunk to obsess about? If so, their prayers have been answered. In "The Karate Kid," Jaden Smith, in only his third film, emerges as a charismatic star with what would seem, to this non-12-year-old girl, to be a precocious romantic appeal.

The movie is a sort-of remake of the 1984 "Karate Kid," which turned 23-year-old Ralph Macchio into a generational touchstone back in the day. Here, the bones of the original story remain, but they've been freely reassembled. In the first film, Macchio's fish-out-of-water character had been forced to relocate from New Jersey to California — a puny challenge in this global age. Now, Smith's character, Dre Parker, has to relocate all the way to China with his widowed mother (Taraji P. Henson), who's been transferred there by the company for which she works. (A vague plot element, but really, who cares?)

So Dre arrives in Beijing, friendless and alienated, and enrolls in some sort of international school. He hates his life. But then he meets a cute girl, a violin prodigy named Meiying (angel-faced Wenwen Han), whose disapproving father will soon complicate their budding relationship. Then, unfortunately, he meets a less-charming group of local hooligans led by an older kid named Cheng (Zhenwei Wang), who immediately start pushing him around. Dre tries to retaliate with some meager karate moves he learned off television back in the States, but the hooligans just sneer. Karate is a trifling Japanese discipline; the native Chinese martial art is kung fu (or, more precisely, I suppose, wushu). As we see, the movie's title is entirely vestigial.

One day, during a beatdown by Cheng and his friends, Dre is rescued by the maintenance man in the apartment building he now calls home. This is Mr. Han, and he's played, in a bit of perfect casting, by the great Jackie Chan. Chan is such a warm and appealing presence that his entry into the story gives it a new emotional glow. Unbeknown to anyone, Mr. Han is actually a kung-fu master who has withdrawn from the world following a personal tragedy about which we only later learn. Informed that Cheng and company are members of a kung-fu team called the Fighting Dragons, he takes Dre to their training school to try to smooth things over. There, however, they also encounter the Dragons' instructor, the snarling Master Li (Rongguang Yu), whose exhortations to his students ("No Mercy! Our enemies deserve pain!") suggest that he hasn't entirely internalized the spiritual component of his chosen art.

At the point where Mr. Han volunteers Dre for an upcoming kung-fu tournament in which he'll face off against the various Dragons, we begin a long wait for that showdown to actually happen. The movie runs nearly two-and-a-half hours, and you can tick off whole sequences that might have been cut, mainly welcome-to-Beijing travelogue footage of the city's streets and parks and exotic markets (fried scorpions!). There are some lovely scenes at a sort of kung-fu temple high up in the mountains, and a visually arresting (if implausible) training session with Mr. Han and Dre high atop the Great Wall. This material takes up a lot of time, though. Presumably, having gone to considerable trouble to stage these and other interludes (including a rarely allowed visit to Beijing's Forbidden City), director Harald Zwart was reluctant to compress them.

Still, the movie flows. And the classical simplicity of the story leads us along smoothly to the high-flying tournament confrontation that concludes the picture. (Although the famous "crane kick" of the 1984 film, which belatedly crops up at this juncture, comes out of nowhere and for no particular reason.) Chan himself, who's now 56 years old, doesn't whip out any of the astonishing acrobatics for which he's become famous over the last 40-odd years; but any slack in that department is skillfully taken up by Jaden Smith, who underwent what must have been intense training to develop whiplash martial skills of his own. As an actor, with his thoughtful composure and subtle humor, he strongly resembles his father, Will Smith, who co-produced the movie with his son's mom, Jada Pinkett Smith. Happily, what they have wrought is not an exercise in rich-and-famous nepotism — it's a showcase for a worthy heir. The kung-fu kid delivers.

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