Cheerful films are generally superficial. Deep ones tend to be glum. “Boyhood” fills you with openhearted happiness and awe at its scope and daring. It’s a low-key masterpiece, a wistful comedy that never forgets to keep genuine emotions foremost.

Richard Linklater’s domestic epic looks at the common things in life in an uncommon way. It traces the youth of a good suburban Texas child over the course of 12 years. Link­later shot the movie in chunks from 2002 to 2013. We watch Mason Jr. (Ellar Coltrane) evolve from a dreamy tadpole first-grader to a lanky college freshman.

Within this cozy focus, Linklater contends with the ways we come to terms with our lives practically, culturally, economically, theologically and emotionally. It’s a bold undertaking, yet “Boyhood” wears its novelty lightly.

It never feels contrived or, though it tells a universal tale, predictable. Our hero’s pest of an older sister, Samantha (Linklater’s daughter Lorelei, a real firecracker), grows into an independent, confident young woman. Their divorced parents, Mason and Olivia (Ethan Hawke and Patricia Arquette), add wrinkles and imperfect new partners and pounds.

Looking backward, one can usually discern a trail, find a design in what at the time seemed to be spontaneous decisions. Seen in reverse, a glib storyteller can force a certain unity on life’s random moments. Linklater delights in the improvisatory raggedness of daily existence. The usual mile markers of a coming-of-age tale — the first kiss, the big touchdown, the funeral — are notably absent. The events that punctuate “Boyhood” are small-scale and sweet, love songs to moments and sensations.

Scenes flow casually. The film is astutely observant of compelling little moments. Early on, young Mason Jr. and Olivia repaint his bedroom before moving to a new apartment. When he brushes over the door frame where pencil marks charted his height, you feel the twinge of something irreplaceable being lost. Linklater has not only a director’s eye for detail but a generous soul that makes him share all his characters’ inexpressible feelings.

Coltrane is an actor of exceptional promise. In his early scenes he’s sort of a background player in his own life, dutifully following the dictates of adults who seem to have things all figured out.

He’s beyond touching in a sequence when he’s trying to figure out whether Harry Potter’s magical kids exist in the real world. His dad gently lets him down, but tells him that there are miraculous creatures like whales. Just to be certain, and maybe hoping to hear of a supernatural being his father ignored, the boy follows up, “But right this minute, are there elves?”

Few questions yield such certain answers. Over time he realizes grown-ups are bluffing most of the time. They have no idea what’s coming next. One day they’re cheering Roger Clemens on the Astros pitching mound, then they’re indicting him in a steroid scandal. No wonder he grows up to be an inquisitive young man whimsically vexed by the lack of logic in the universe.

The adults grow alongside the children. Hawke is disarming as a man who became a father before he was done being a child himself. Arquette’s character, strong and careworn and prone to falling for the wrong kind of man, anchors her every scene in honesty. Her reaction to Mason becoming the kind of man she needed, but 20 years late, is all too uncomfortably real. As is her frustration that her kids’ childhood, with all its tribulations, was over so damned fast.

Linklater knows when we’re expecting drama and playfully uses our instincts against us. At one point in Mason Jr.’s adolescence, he hangs out at a construction site with older boys. These louts drink beer, boast about probably fictional sexual adventures, and throw circular saw blades into Sheetrock like ninja throwing stars. Images of severed fingers and slit arteries dance in our imagination.

Linklater teases our anxieties, disarms our fear, then turns our sigh of relief into a joke. The final shot of Mason meshing with his new surrogate family of college friends feels like the most perfectly natural place to leave it on, a reward that the lead character has genuinely earned. “Boyhood” moves you to laugh, to think, and best of all to feel.