Written, directed by Cate Shortland
Starring: Abbie Cornish, Sam Worthington
At: Harvard Square
Running time: 102 minutes
Unrated (nudity, underage sexuality, drug use, violence, language, messy apartments)
At the center of ''Somersault," a feverish, slightly precious drama from Australian filmmaker Cate Shortland, is Heidi (Abbie Cornish), who is 16 and bursting like an overripe plum. She has reached that stage of adolescence where hormones have assumed full command of the helm, and this is dangerous because Heidi is gorgeous: blond, lean, and moving with coltish ease. Every encounter with a male is charged with sensual possibility, and the girl seems propelled forward on alternating waves of desire and terror. She's like a loaded pistol pointing everywhere at once.
Within the first 15 minutes of ''Somersault," Heidi has awkwardly seduced her mother's biker boyfriend (Damian de Montemas), and Shortland films the scene for maximum bad-idea heat, playing the fantasy in the girl's head as she's willing it to life. Then Mama (Olivia Pigeot) comes home, there's a blowup, and Heidi is off on a bus. She comes to ground in Jindabyne, a tourist destination and party town by a mountain lake in New South Wales; it's off-season, but crowded enough with men and boys. In the bathrooms of bars, Heidi practices her smile.
Shortland shoots these early sequences with blue filters and the jingly-jangly strums of Sydney's Decoder Ring on the soundtrack. Her camera hovers too close to things; the images lack the reassuring perspective that distance brings. This is a filmmaker's conceit, and a little of it goes a long way, but it puts us in Heidi's head with studied immediacy.
The girl cons her way into an apartment owned by a mother-hen innkeeper (Lynette Curran), gets a job at a gas station with a wary peer (Hollie Andrew), and picks up a stray boy or two. Then she meets Joe (Sam Worthington), a local lad and laborer who's as confused as Heidi is about the intersection of love and sex. At one point, Joe comes on to an older gay man (Erik Thomson), who's momentarily nonplused. ''You won't like it," he warns the boy. ''I don't want to like it," Joe answers.
''Somersault," in other words, is about that time in young people's lives when they understand that no one can define them but themselves, a prospect that can scare them into noisy compensatory behavior. Heidi has (or thinks she has) one asset, but her needy lust keeps blowing up in her face. Why does being available turn people against her? How can sex promise such closeness only to deny it?
Not many films tackle the libidos of teenage girls -- ''Thirteen," for one, treats the subject with the alarmism of a monster movie -- and Shortland deserves praise for even bringing it up. ''Somersault" was a hit in its home country, racking up 13 Australian Film Institute awards in 2004. It implies rather than tells, and this allusiveness is a nice change from the stridency of most movie storytelling. Shortland balances showing Heidi as a heartbreaking mess -- doing a jailbait dance here, impulsively swallowing a mouthful of chili peppers there -- and judging her for it.
Yet the movie has more style than depth and it's sometimes in danger of confusing the two. The director's background in short films shows; over the long haul, the images turn merely pretty and the drama evaporates. Cornish -- 22 when the film was shot -- fights like crazy to burn a hole through the artiness, and Heidi is as gauche and carnal and vibrant and shallow as an actress can make her.
Shortland's cool aesthetic threatens to douse her flame, though. In one scene, Joe, having spent the night with Heidi, thaws his car on a frosty morning by pouring hot water on the windshield. That image is a lasting one, but in ''Somersault" the ice never fully melts.
Ty Burr can be reached at email@example.com.