Entertainment

BITTERSWEET SYMPHONY

‘THIS is not a love story,” warns the omniscient narrator of “(500) Days of Summer,” which opens with a breakup on Day 488 of what may well turn out to be Generation Y’s answer to “When Harry Met Sally.”

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Indie stalwarts Joseph Gordon-Levitt and Zooey Deschanel have combustible chemistry as Tom, a hopeless romantic, and Summer, the alluring, flirty, commitment-phobic beauty with whom he’s lucky/unlucky enough to be smitten.

It’s the oldest bittersweet story in the book, of course, but music-video director Marc Webb approaches his feature debut with great confidence, flair and a minimum of schmaltz.

The screenplay by Scott Neustadter and Michael Weber (the credited writers of “The Pink Panther 2”) draws the audience in by cleverly skipping back and forth through the 500 days between Tom and Summer’s first and final meetings.

Tom is an architect by training who works as a greeting-card writer in Los Angeles (which has rarely, if ever, looked so great or romantic in a movie).

Our hero and Summer — the new assistant to his super-tolerant boss (Clark Gregg) — hit it off immediately, but she makes it clear she’s looking for a fun time and nothing more.

The movie is told entirely from the point of view of Tom, who takes the position more often assigned to women in romantic comedies. He wants something more than a fling with Summer, and that yearning is going to sabotage their burgeoning relationship.

When it inevitably does, Gordon-Levitt has both the dramatic and comic chops to depict man-boy Tom’s very real pain and confusion.

Though it holds out the distant possibility of reconciliation, this glossily produced, indie-inflected movie (which employs animation and a hip soundtrack) is more interested in how he tempers his romantic ideals.

There is actually a ruefully funny split-screen sequence with panels labeled “expectation” and “reality.” Other high points include a full-blown musical production number, a romantic sequence set at an Ikea store — and an elaborate homage/spoof of the French New Wave in black and white.

The filmmakers, who borrow from everyone from Woody Allen to Cameron Crowe, sometimes get carried away trying to cover every possible convention of the genre — including characters talking directly to the audience.

Some may be disappointed that — beyond a token reference to her parents’ divorce — we never really understand Summer’s reluctance to commit to a man who seems in almost every way like her soul mate.

That’s the whole guy-centric point of “(500) Days of Summer,” though. Sometimes you never, ever truly figure out why these mysterious creatures break your heart.

lou.lumenick@nypost.com