Is this new form of rom-com solely a summer fling? Or, sums up Kimberly Gadette, might (500) Days of Summer become a perennial favorite?

By the numbers, you wouldn't think the arithmetic of (500) Days of Summer would add up. Take one debut feature film director, add in newbie screenwriters, scramble the rom-com chronology, play with split screens, animation and throw in the variable of a leading man who's made a name for himself as a child actor in a hit TV series ... and then ask the final question. Does this equation work?

Number theories be damned, in this case - you can count on it.

As in any romantic comedy, it's still "boy meets girl." And boy gets girl. Sort of. The boy is Tom (Joseph Gordon-Levitt), a twentysomething greeting card copywriter. The girl is Summer (Zooey Deschanel), the boss's new assistant. As the narrator states, she's "just another girl … except she wasn't." In a barrage of flashes both forward and back, we get a scattershot overview of their love affair. Day #30 follows Day #300, then back to #1, followed by #40, etc. Which makes for great fun: we'll see an ebullient Tom, the elevator doors closing in front of him during the earliest throes of their courtship on Day #35, followed by a deeply depressed Tom, the same elevator doors opening in front of him on Day #303.

The film skewers much of the modern rom-com stereotypes: drunken karaoke, the re-connect at an acquaintance's wedding, the new-couple-in-lust theory that because they love the same singer, they're perfect for each other. We encounter the protagonist's usual duo of wacky best friends: the affable Paul (Matthew Gray Gubler), who's had the same girlfriend for a decade, balanced against the loser McKenzie (Geoffrey Arend), who's relationship history consists of three good hours with a girl back in grade school. They handle their roles well, punching up the humor and serving as foils for Gordon-Levitt's Tom.

Much is being made of the fact that this film is fresh because it looks at love from the point of view of the lovelorn male, rather than the lovesick female. A historical inaccuracy; aside from Judd Apatow's male-centric oeuvre, multitudes of romantic comedies exist in which the boy yearns after the girl (eg, movies from Frank Capra, Ernst Lubitsch, Howard Hawks).

Instead, what makes 500 Days a standout is its examination of the frustrating "why?" of this particular relationship's end. The ex-factor, as it were. It is due to Tom's tenacious desire to understand what happened with Summer that we get to take another look at our own lost loves; the ones who slipped away much too soon, during what we thought was the best of times. Try though we might, our memories bathed in rosy hindsight, we can't figure out what went wrong – and so we replay it in our heads, long past the point of accepted standards of sanity. Were we too needy? Did we push for a commitment too early? Did we reveal that one slightly off-kilter fact about ourselves much too soon? No matter how often our friends had told us to get over it, we'd insisted on thrashing it out, long past any modicum of self-respect. Tom is us; we are Tom.

And Summer is indeed the harshest season of all.

Credit the filmmakers who nail the concept of broken love just right. (Co-writer Scott Neustadter states that his inspiration for the story comes from his being dumped twice by previous girlfriends.)

The clever concept and smarm-free humor aside, much of the film's appeal is due to the light-handed touch of Gordon-Levitt. No longer the goofy kid from 3rd Rock from the Sun, he's grown into a sensitive man with a natural funny bone who takes us with him on his emotional roller coaster ride. It's not Summer we need to love, but Tom. And with this stellar performance, he wins us over completely.

As for Summer, it's the perfectly-cast Deschanel playing the kooky girlfriend once again. Though she can expertly juggle charming and funny, while still remaining emotionally distant, we have indeed seen this performance before.

Like the clunky parentheses bogging down the title, the film contains a few imperfections: the younger sister who's the go-to romance expert stretches the bounds of believability, and Tom's anti-sentiment rant during an all-staff company meeting is a bit too pat. But these are minor cavils in an otherwise truly delightful film.

Rating on a scale of 5 overpriced greeting cards: 4

Release date: US: July 24, 2009 UK: September 4, 2009
Directed by: Marc Webb
Written by: Scott Neustadter & Michael H. Weber
Cast: Joseph Gordon-Levitt, Zooey Deschanel, Geoffrey Arend, Chloe Grace Moritz, Matthew Gray Gubler, Clark Gregg, Rachel Boston, Minka Kelly
Rating: US = PG-13; UK = 12A
Running time: 95 minutes