Asa Butterfield has a simmering presence in the title role of “Ender’s Game,” and Harrison Ford is generally gruff as Col. Graff. (AP)

There’s a moral heft to “Ender’s Game” that lends ballast to the science-fiction adventure about futuristic military-academy cadets. Based on the popular and award-winning 1985 novel by Orson Scott Card, the film doesn’t need added suspense, bigger action or a better dramatic twist; it’s got all of those, in more than serviceable amounts. But it benefits greatly, at least for those who care about such things, by actually being about something — the morality of war and its methods — in a way that most movies of this type are not.

“Wait a minute,” my 14-year-old son protested, as we were chatting on the way home from the screening. “ ‘Pacific Rim’ was about something, too.” That’s right, I admitted. It was about robots fighting monsters. (It was also about 20 minutes too long.) Other than that, I pointed out, there was not much “there” there.

As someone who is perfectly content to have his adrenal gland stimulated instead of his brain, my son and his adolescent cohort are a large part of the film’s target demographic. This is somewhat ironic, considering that the film’s hero is a teenage whiz kid being groomed to lead a fighting force of similarly brilliant, highly trained children against a race of buglike aliens. Asa Butterfield plays the 15-year-old Ender Wiggin, a student soldier training to fight the Formics (or Buggers, as they are known), who 50 years before the action of the film attacked Earth, killing millions before being driven back to their home planet.

Why children? Basically, they can multitask. Because of their youth, as the film explains, these military prodigies can assimilate complex battle information and devise effective attack strategies more quickly and easily than adults. This is thanks to the same wiring that makes them so good at video games.

And yes, gaming figures prominently here. Several scenes feature a high-tech version of laser tag played in a weightless arena. It’s actually kind of cool. Others show Ender playing a video game on an iPad-like device that he controls with his mind. These sequences will probably be of less interest to viewers old enough to have mortgages than to those with enough free time to spend 20 hours a week playing “Call of Duty.”

Be that as it may, the gaming scenes — and the way they illuminate Ender’s fiercely competitive streak — are critical to the story, which moves along briskly.

Central to its narrative is this: Ender is not just a brainiac; he also doesn’t like to lose. In fact, his nickname, explained in the book as originating from a childhood mispronunciation of Andrew, is a convenient description of his combat MO. Ender doesn’t just want to win whatever battle he’s currently fighting; he wants to end all future battles that might come his way.

This old — and highly debatable — notion of the war to end all wars, of course, is precisely what the film grapples with, with surprising depth. In addition to the climactic battle, it’s a theme that comes up a couple of times in Ender’s tangles with bullies, where he goes way too far in his attempt to forestall future attacks. It’s precisely that killer instinct, the film tells us, and not merely Ender’s leadership abilities, that make him teacher’s pet.

One note: There are a couple of deaths in the book that have been softened for the film. That seems a little chicken-hearted of writer-director Gavin Hood (“X-Men Origins: Wolverine”). His audience can take it, and it would have made for a better and tougher film.

As Ender’s gruff mentor, Col. Graff, Harrison Ford is a bit one-note, though the role doesn’t call for much more than barking and scowling. Butterfield is pretty great, though. Although scrawny, the actor has a piercing intensity, last seen in “Hugo” and deepening with adolescence, that makes you believe he really could finish you if pushed too far. Moisés Arias, a performer who’s usually known for playing goofballs, also makes a surprising and powerful impression as the bully Bonzo.

But “Ender’s Game” is more than a parable about bullying, or a disquisition on the concept of the “just war.” It’s also a rousing action film, especially in Imax. You may come for the candy coating, but you’ll ruminate on the chewy nougat filling all the way home.

★ ★ ★

PG-13. At area theaters. Contains sci-fi action and violence. 114 minutes.