Jon Martello's relentless libido has a comic math to it.
At the club, Jon (Joseph Gordon-Levitt) and his pals rate girls on a scale of one to "a dime." He keeps a weekly tally of both his conquests and his far more numerous — and to him more rewarding — porn-aided masturbations. And being a good Catholic boy, every Sunday, he counts up his sins and receives back from the priest his neat sum of Our Fathers and Hail Marys. (He recites them while working out.)
His life is a circle of replenishing lust, a ritual of superficial pleasure that adds up to robotic emptiness. Some like it hot; Jon ("Don," as in Don Juan, to his friends) needs it hot. Even his most attractive catches leave him unsatisfied, and he sneaks out of bed to his laptop. Real sex doesn't measure up to the fantasy of online pornography that lets him "lose himself."
But "Don Jon," the writing-directing debut of Gordon-Levitt, equals something quite substantial: a speedy little comedy about not just sex addiction but modern lives wasted on shallow gratification. There are other contemporary cravings, too: A big-screen TV dominates family meals at his parents' house (Tony Danza and Glenne Headly shouting back-and-forth like a sitcom couple), where Jon's younger sister (Brie Larson) pecks away at her smartphone.
Jon's compulsive routine (echoing the "gym-tan-laundry" of "the Situation" from "The Jersey Shore," a clear inspiration) is broken when he meets Barbara Sugarman (Scarlett Johansson, in full sex bomb). She requires the "long game" of dating and family-meeting before sleeping with Jon, but he judges her worth it. Their first date is a sparring match of Jersey accents, a dueling "Saturday Night Live" sketch.
When their relationship hits a road block (it involves both his porn addiction and, miraculously, Swiffer sweepers), Jon finds himself drawn to an older, less glamorous woman from his night class (Julianne Moore), who epitomizes everything Barbara isn't: unaffectedness over thick makeup; humor over self-seriousness; love over lust.
Until Moore fully enters the film, "Don Jon" is little more than a cartoon, albeit an entertaining one, constantly flashing the pornographic images that roil Jon's mind. Though the point is that Jon is a living cliche, it means the journey here is merely the awakening of a mannequin. (No offense intended to 1987's "Mannequin.")
But as an argument for life, itself, and all its pains and passions, you could hardly do better than Moore. For an actress of great naturalism, it's one of her most suited roles.
There's a growing output of movies to take up sex addiction and its digital stimulation, including Steve McQueen's grim but remarkable "Shame" and the recent, uneven "Thanks for Sharing." ''Don Jon" is a lark, but an enjoyable one with a full-hearted finale, and it further reveals the considerable talents of Gordon-Levitt.
With Jerry Lewis eyebrows and boundless energy, he has already showed his varied skills in "50/50," ''Looper" and, not least of all, as a manic host on the aforementioned "SNL." That he can also, in his first time out, make a modern parable about a New Jersey lothario with a little Catholic satire thrown in, suggests his range is greater still.
"Don Jon," a Relativity Media release, is rated R by the Motion Picture Association of America for "strong graphic sexual material and dialogue throughout, nudity, language and some drug use." Running time: 90 minutes. Three stars out of four.
MPAA rating definition for R: Restricted. Under 17 requires accompanying parent or adult guardian.