MANILA, Philippines—What do you do when you fall in love with somebody who does not believe in true love and therefore has no desire to fall in love with you? Friendship’s OK, and a little sex on the side isn’t bad, but that’s about as far as the relationship can go. So, what do you do?

That’s the big, confounding question that confronts Tom (Joseph Gordon-Levitt), the protagonist and searcher in “(500) Days of Summer”—and it eventually pushes him into deep depression. Especially when he finds out that, without even consulting him, the frustrating love of his life, Summer, decides to fall in love with somebody else.

Whatever happened to her loud protestation against love? Why does she feel she can change the rules and leave him high and dry like this? Dunno, she just does, leaving his heart and self-respect in tatters. Until he meets another girl, takes a big (second) chance on love— and fares much better in his quest for love and happiness.

The film directed by Marc Webb pursues two thematic lines with varying degrees of effectivity. First, don’t be like Tom and settle for half a relationship —on somebody else’s terms. You’ll never be happy—unless you’re a pathetic, whining masochist.

Second, learn from your sad experience and assert yourself the next time around, or you’ll be fated to live a miserable love life of ever-diminishing returns.

To give the movie a fresher and less structured touch, its events are made to unfold in a nonlinear way. After a while, however, this storytelling conceit adds to the viewer’s confusion, because it’s inchoate and lacks focus.

Another problem is the fact that the movie is slanted way too much in Tom’s favor, and Summer’s character and agenda are much less productively developed.

Since rom-coms play to a largely female audience, this is a curious state of affairs. Granted, some female viewers may watch the film to get enlightened about how losers like Tom feel, but many more may just find him a clumsy klutz and refuse to empathize with his self-inflicted travails.

To be sure, the choice of actor Joseph Gordon-Levitt to play Tom is a great empathy booster, because he’s both vulnerable and boy-next-door accessible. He isn’t that good-looking, but he’s as sensitive as all heck and makes women want to mother him. So, when he finally gets his young-adult act together, they can be relied on to root for him all the way to the movie’s upbeat denouement.

Still, the movie’s lack of clarity and focus ends up working against it, as does its whimsically subjective approach. We’ve seen nonlinear storytelling work more effectively in movies like “When Harry Met Sally” and “Two for the Road.” Webb’s film can be viewed for its own plus points, but too many of its elements turn out to be less felicitous and choice.