Award-winning actor Joseph Gordon-Levitt's first foray as feature writer-director is an assured comedy of modern mores that is by turns hilarious, smart and touching.

He is aided and abetted by a talented ensemble cast, who relish the script's bounty of razor-sharp dialogue and colourful characters.

Don Jon has faint echoes of Saturday Night Fever, albeit without that film's darker undertones, with its swaggering, bed-hopping hero and attractive New York locales. Only here, the central figure doesn't get his kicks by thrusting his hips to the Bee Gees, but from spending unhealthy amounts of time watching X-rated films on his laptop.

Real sex is good "but it's not as good as porn", asserts New Jersey ladies' man Jon Martello (Joseph Gordon-Levitt), whose unrealistic attitude to sex - fuelled by the fantasy scenarios in his favourite films - makes it impossible for him to forge lasting relationships.

That changes when he encounters gum-chewing sex bomb, Barbara Sugarman (Scarlett Johansson). Romance blossoms and Barbara encourages Jon to better himself by taking night classes. She also charms Jon's parents, Jon Sr (Tony Danza) and Angela (Glenne Headly), but fractures appear in the fledgling relationship when Barbara catches Jon at his laptop.

"I'm not a junkie, it's not heroin!" he protests, promising to give up his adult films and devote himself to Barbara.

However, old habits are hard to break and Jon turns to Esther (Julianne Moore), a mature student in his night class, for advice.

Don Jon spreads the wealth between the cast. Gordon-Levitt is a charismatic hero heading for a fall while Johansson is a hoot with a pitch perfect 'Noo Joizey' accent and Moore injects heart-tugging emotion when she finally reveals the heartbreak of her character's past.

Some of the quieter, seemingly throwaway moments deliver the biggest laughs, like Jon taking umbrage with his local priest (Paul Ben-Victor) over the unjustness of one confessional penance, or the moment Jon's sister (Brie Larson), who has been mute for more than an hour, finally breaks her silence.

Strong language and occasional glimpses of pornography account for the 18 certificate but for the most part, Don Jon shies away from explicit, lurid and gratuitous detail.

Less is definitely more.