Ender playing a new ‘Game’ in exciting movie

How much of “Ender’s Game” can you alter for a movie and still be true to Orson Scott Card’s novel?

Can you change the hero from a freakishly brilliant 6-year-old, who spends years preparing for a battle against a distant enemy, into a young teenager who needs only a few months to master warfare?

Can you soften the title character from someone with uncontrollable rage, who murders two bullies by smashing them to pulp, into a boy who kills no one and goes to the bedside of one victim to see if he’ll recover? (Ender isn’t even responsible in that case: He shoves his assailant, and the boy slips and hits a concrete step with his head.)

Can you strip away a long subplot, reducing Ender’s brother to a mean sibling with a few lines and Ender’s sister to an empathic nonentity?

Can you give Ender (Asa Butterfield) a female confidant (Hailee Steinfeld) to whom he confides humanitarian feelings on the eve of destruction, so we’ll like him better?

The movie does all these things and caps them with a sudden ending – too sudden to make much sense – that turns this story into a more conventional “teen comes of age and saves the planet” narrative.

But writer-director Gavin Hood tells the story he has chosen efficiently, exploring the crucial idea that a foe we don’t understand may not be a foe at all. And a superb performance by Butterfield keeps us attached emotionally to Ender at all times. He’s not the mercurial kid from the book, but that may be a good thing for viewers who don’t demand fidelity.

The filmmakers, mindful of Card’s recent proclamations against homosexuality and gay marriage, have changed a couple of things to avoid controversy. Enemy soldiers, invariably referred to as “buggers” in the book, now get called by their formal name of Formics. Bonzo, Ender’s nemesis in battle school, has been changed from a handsome boy on whom Ender has a brief kid-crush to a homely little creep.

The book gave Ender a surrogate dad in gruff Col. Graff (Harrison Ford), who readies him for the combat that could preserve humankind. Now he also gets a surrogate mom, an empathic female psychologist (Viola Davis) who watches over him.

Yet most moviegoers will remember the battle sequences, first inside a gravity-free room at school and then in outer space, because they rock the theater as they need to do. And when that sudden ending comes, Butterfield carries off the complex emotions and improbable plot twist well. (The book’s main narrative flaw, which would involve a spoiler here, hasn’t been solved in the film. In fact, plot compression makes it more obvious.)

Hood has chosen his supporting cast of young people wisely, although Ender’s crew comes across like one of those improbably balanced platoons in a World War II movie: a white guy, a white girl, a black guy, a kid who seems to be a Latino and a Muslim who tells Ender “Peace be with you” in Arabic. (In the future, the human brotherhood hates creatures that look like giant ants, not each other.)

The happiest surprise is Ben Kingsley, who can act up a storm with unblinking ebony eyes, as iconic fighter pilot Mazer Rackham. In this retelling, he’s half-Maori and has elaborate face decorations that connect him with warriors in his bloodline. “Why?” you may wonder. In a movie that takes this many liberties, why not?