Joseph Gordon-Levitt and Zooey Deschanel

Joseph Gordon-Levitt and Zooey Deschanel (Fox Searchlight)

Here's a romantic comedy that remembers that the best romances have a touch of the bittersweet. That's the happy accident happily titled (500) Days of Summer.

How happy? This pairing of Joseph Gordon-Levitt (The Lookout) and the quirky Zooey Deschanel can be like new love itself -- giddy and irrational. The movie they inhabit is a world tinted by infatuation and sprinkled with fairy dust.ƒ|.ƒ|. and lovely animated effects and a big dance number.

How accidental? The director, Marc Webb, has mostly music videos (for Jesse McCartney and Green Day) on his resume. The writers might soon be able to leave Pink Panther 2 off their list of credits.

It's a love story told out of order, with droll narration about how "This is not a love story.ƒ|ƒ|. of boy meets girl." We chart Tom's 500 day relationship with Summer (get it?) by days -- day 4: the co-workers at the greeting card company realize they both love the music of The Smiths; day 288: she's tuned him out.

It's an IKEA courtship, with cute scenes such as pretending to be married in the pretend rooms at the Swedish retailer.

Even the arguments are cute.

"You're happy? We've been like Sid & Nancy for months."

The joke is who is Sid and who is Nancy in this meltdown.

No moon-eyed moment passes without a giggle, no cornball "She's Like the Wind" musical cliche without a snicker of irony. But the troubles ahead are obvious. He's into love, or at least open to the possibility.

"You don't believe in that, do you?" she retorts.

"It's love. It's not Santa Claus."

The trappings will be familiar to anybody who has ever been to a movie romance -- Tom's support group consists of his pals and his much younger but wiser sister (Chloe Moretz). But the dialogue is consistently hilarious, such as when Tom and Summer watch a porn film together.

"That looks pretty doable."

Both leads are winning in every frame, even when they're doing each other wrong. Deschanel finally has a vehicle for her offbeat charms, her funny way with a look or a line or a moment at the karaoke mike. Gordon-Levitt hangs with her and does hang-dog ("winning her back") well.

It isn't Hugh and Andie or Meg and whomever, but (500) Days offers hope that Hollywood can pass that romance baton to somebody other than the crude crew of the Kappa Alpha Apatow frat house.

(500) Days of Summer Four of five stars Cast: Joseph Gordon-Levitt, Zooey Deschanel. Director: Marc Webb. Running time: 1 hour, 35 minutes. Industry rating: PG-13 for sexual material and language.