Maybe the Peanuts gang hasn’t been on the big screen in decades because they’ve had so much success on the small one, with specials like “The Great Pumpkin” and “A Charlie Brown Christmas” that have been annual TV traditions since the 1960s.

Thankfully, “The Peanuts Movie” isn’t just a small-screen special writ large. The filmmakers take advantage of their cinematic scope with a bigger story, more sophisticated animation and effective use of 3-D that gives new depth to the Peanuts world. But the characters loved by generations of fans — Lucy, Linus, Snoopy, Woodstock and beloved blockhead Charlie Brown — are as charming and timeless as ever.

It’s been nearly 40 years since the last Peanuts film, 1977’s “Race for Your Life, Charlie Brown.” The gang’s other theatrical outings were “A Boy Named Charlie Brown” in 1969 and “Snoopy, Come Home” in 1972.

“The Peanuts Movie,” written by the son and grandson of Peanuts creator Charles M. Schulz, doesn’t cover new thematic territory, but it doesn’t really need to. Relying on 50 years of character development, the Peanuts gang stays true to their original selves — there’s no new edge or post-modern snark in the mix. The central concepts (be honest, be yourself, do your best) are as gentle as the curves of Charlie Brown’s silhouette.

There are two simultaneous stories at play in the film: one set in the “real world” of Charlie Brown and his friends, and a more fantastical tale of Snoopy as his alter-ego, the Flying Ace.

“The Peanuts Movie” opens during wintertime, and a snowy introductory scene with Woodstock sets viewers up for the 3-D experience. Charlie Brown and the gang are excited about a new kid moving into their neighbourhood. She turns out to be the Little Red-Haired Girl, and Charlie is instantly smitten.

School starts up again, bringing a series of challenges. First of all, the Little Red-Haired Girl is in Charlie’s class.

“I just came down with a serious case of inadequacy,” he says.

Then there is the talent show, school-wide tests, book reports and other kid-sized hurdles to overcome. The story follows the gang through the school year, focusing on Charlie’s foibles. Sally Brown plays a supporting role. Everything looks as colorful and round as the comic strip.

Meanwhile, Snoopy types himself into a high-flying adventure atop his doghouse as he battles his nemesis, the Red Baron. These sequences are distinguished by more realistic background animation — snowy mountains and grassy landscapes that look more like the world outside the movie theatre. Snoopy’s Flying Ace, aided by a team of Woodstock mechanics, flies off in pursuit of his love, Fifi, just as Charlie Brown tries to work up the nerve to introduce himself to the Little Red-Haired Girl.

Director Steve Martino cast child actors to voice the Peanuts gang, and used vintage recordings of late actor-producer Bill Melendez to realize Snoopy and Woodstock’s inimitable expressions. A catchy new song contributed by pop star Meghan Trainor is a bouncy bonus.

While “The Peanuts Movie” may lack the wink-wink wisdom aimed at adults often found in Pixar releases, it retains the wholesome appeal of those stalwart TV specials. The 3-D makes it look modern, but the Peanuts’ sweetness is satisfyingly old-fashioned.

“The Peanuts Movie,” a Twentieth Century Fox release, is rated G by the Motion Picture Association of America. Running time: 92 minutes. Three stars out of four.

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MPAA definition of G: General audiences. All ages admitted.

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Follow AP Entertainment Writer Sandy Cohen at www.twitter.com/APSandy .