Characters strut their stuff, shake their fists, and dance down the streets of a sweltering New York City in “The Wackness,” a moody, pot-filled celebration of a city in which the frustration of missed connections gives way to the inspiration of casual encounters. From street to street, under the searing summer sun that unites all New Yorkers in a mutual malaise, Jonathan Levine mixes teenage sweat with sexual angst and shows how living in the moment — tomorrow be damned — can turn out to be the perfect mistake.

Set in 1994 to the beats and rhymes of that year’s hip-hop hits, “The Wackness” is a peculiar and beguiling surprise, the cinematic version of one of those endless summer afternoons that line the median between adolescence and adulthood. It’s also a work of expertly calibrated performances. Let’s start where every review of “The Wackness” should begin — with songs of praise for Ben Kingsley, who steals the show as a bong-hitting therapist named Dr. Squires. The good doctor is more dysfunctional than the high-schoolers he treats in exchange for marijuana. As an adult who is sick of adulthood, and a therapist who is sick of fixing every ailment with prescriptions, Mr. Kingsley explodes off the screen as a grumbling, giddy, glorious screw-up.

Holding his own next to the Oscar winner is young Josh Peck, who manages to tap his inner nerd to give us one of the more believable big-screen teenagers in quite a while. The mood of his shy yet suave Luke seems to modulate by the moment as Luke tries to keep a lid on all the uncertainty raging underneath. Early on around the dinner table, it is clear that Luke, like most people his age, doesn’t know what he wants for the future. He hates the way his parents fight and tries to alleviate their persistent money troubles by shelling out marijuana from a cart he pushes through the city.

Luke knows his place: He’s a schoolyard outcast who retreats to his Walkman and his mix tapes to get lost in the beats of Notorious B.I.G. and Nas. So when Dr. Squires’s stepdaughter Stephanie (Olivia Thirlby) — one of the popular kids — says she wants to hang out with him, Luke’s head goes spinning. Later, when the two get lost in Central Park, boom box blasting and hormones raging, Luke’s confusion finally rises to the surface: What’s going on here?

The title says everything yet nothing about the movie. The term is coined by Stephanie when she takes Luke out to her parents’ Fire Island home, criticizing her summer fling for fixating on the negative — ignoring the “dopeness” and focusing only on the “wackness.” In this way, Luke is just like her stepfather: Both of them are ready to climb out of their ruts and into new adventures.

Mr. Levine, who won the Audience Award at this year’s Sundance Film Festival, sees a similar conflict playing out in a gentrifying, Giuliani-era New York City. Long before Stephanie utters the title, Dr. Squires and Luke have a similar conversation in a Times Square still in transition from debauched to Disneyfied. Stumbling out beneath the neon lights, Squires tells Luke that he can’t treat his life the way Mr. Giuliani has treated the city, by pushing the city’s problems under the rug. Life is not about ignoring the wackness, but about embracing it as a core element of humanity.

It’s a refreshing refrain to a familiar tune about one young man’s coming of age. Luke isn’t just a heart-smitten nerd looking for acceptance, nor is he a nihilistic druggie exploiting his friends. Stephanie isn’t just an angel or a manipulator. Squires isn’t just a father figure or a man enduring a midlife crisis. “The Wackness” lives by the same credo as its characters, embracing the good and bad of this trio as it basks in the wonder and the degradations of urban life. It’s a glorious mix tape of a movie (both Luke and Squires make mix tapes of their own), kicking things off with a rock track, slowing it down with a ballad, switching gears with that rare B-side, and rounding it out with a familiar yet fresh classic. Making a mix tape, as any John Cusack character will tell you, is a careful science, and it’s clear from track one that Mr. Levine has good taste.

ssnyder@nysun.com