"Patti Cake$" is rated R.Running time: 108 minutes. Three stars out of four. The Sundance sensation "Patti Cake$" may flow with formulaic beats but it's got spirit for miles (eight of them, at least) and features one of the best mother-daughter relationships of the year. Patricia Dombrowski (the terrific newcomer Danielle Macdonald) is an overweight, white New Jersey 23-year-old living a hardscrabble life in the shadow of New York City. She's cruelly called "Dumbo" by many in town, but she's got a nickname of her own. "Killa P," she calls herself, because, as she states matter-of-factly, "I murder the beat." And she does. Our first glimpse of her is in a grimy, dirty-dish-strewn kitchen freestyling while munching on a Pop Tart. Later, her best friend and optimistic music partner Hareesh (Siddharth Dhananjay) will, from behind his pharmacy counter, announce her arrival on the store PA system, as she strolls down the toothpaste aisle, with the kind of grandiose pomp traditionally reserved for James Brown. The distance between dream and reality has long been measured - and usually shrunk - by the movies, though the gap has rarely been so extreme as in "Patti Cake$." When Patti arrives at her bartending job - the only employment keeping her and her hard-drinking mom (Bridget Everett) just out of their creditors' reach - her boss tells her, "Toilet's still clogged and the karaoke isn't going to set itself up." When she walks down the street rapping along with her headphones, she magically rises in the air with the music only to be brought down to earth by the blare of a horn. Patti wants to be a rapper, a notion she's a little reticent to even admit because of its apparent absurdity. But in Hareesh she has a faithful supporter. He nudges her into a battle at a local gas station where she's derided as "white Precious" but holds her own in rhyme and attitude. Patti's hip-hop won't be confused for anything that would, in our reality, be characterized as especially good. But trained on limericks by her chain-smoking grandmother (Cathy Moriarty), she's verbally inventive and can unleash verses in torrents. She gathers together an unlikely group, with Hareesh on beat and back-up, and a painfully shy heavy-metal anarchist who goes by the name Basterd the Antichrist (Mamoudou Athie) on guitar. They begin recording, saving up money and believing. By piling on the eccentricity (the anarchist lives in a shack in the woods near a cemetery) and, later, the predictably manipulative moments (someone will die at just the right juncture), writer-director Geremy Jasper - a music-video veteran making his directorial debut - shows himself a good study of a well-trod genre: the Sundance-style indie underdog tale. The film was, after all, developed at the Sundance screenwriting lab where it surely was injected with the requisite quirks. It's easy to dismiss "Patti Cake$" as an indie "8 Mile," and wonder why it's seemingly so much easier to make movies about white rappers than black ones. Jasper at least acknowledges this in one painful scene where Patti's idol derides her as a "culture vulture." But "Patti Cake$" is hard to resist because of Macdonald's pluck. Patti has much more working against her than the color of her skin. Macdonald's performance, a breakthrough for the previously unknown Australian actress, is too humble and winning. What really resonates is the dynamic between her and Everett, the foul-mouthed cabaret comedian. Everett's Barb is a wreck of dashed dreams, failed romance and way too much alcohol. Patti's aspirations dredge up Barb's lost future. She was a once-promising frontwoman for a hair band in the '80s (her lone LP is titled "Barbed Wire") who blames her failed music career on an unwanted pregnancy. When Everett and Macdonald are on screen together, something more soulful comes of "Patti Cake$." In the end, the kind of music Patti makes hardly matters. It's that she has the gumption to go for it.