Maybe the "Peanuts" gang didn’t come to the big screen before 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 visual 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.

"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 postmodern 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.

"THE PEANUTS MOVIE" Rated: G Opens today

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 neighborhood. 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, schoolwide 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 theater. 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 "Peanuts’" sweetness is satisfyingly old-fashioned.