Who is “Her”?

In the most literal sense, I suppose she is an operating system that goes by the name Samantha, a futuristic computerized program that takes an important place in the life of ordinary guy Theodore Twombly.

But “Her” might also refer to any woman who comes into Theodore’s life, because he clearly hasn’t figured out how to understand and relate to the opposite sex. He’s the main character of “Her,” the new film by Spike Jonze, and he’s played by Joaquin Phoenix in a technically tricky performance.

The setting is the near future, and things look different — in a wonderfully visualized way. Los Angeles is a city of elevated sidewalks and soulless towers (an effect created in part by shooting in Shanghai), men wear pants without belts, and the streets are full of people more engaged by their personal devices than by the world around them.

All right, so that last part doesn’t sound so futuristic. In any case, Theodore is in the dumps about divorcing his wife (Rooney Mara), but finds himself strangely attuned to his computer’s new operating system. Samantha has the voice of Scarlett Johansson, and despite being a computer, she has the ability to learn and emotionally adapt to her new owner.

This leads to unusual situations, most definitely including sex. It also means that Phoenix’s performance is a challenging one, as he plays many scenes staring off into space rather than at another person.

There are other visible people in the film (Johansson’s performance is entirely vocal), including Amy Adams as Theodore’s married buddy.

Phoenix is very good at his task, although I couldn’t help thinking an actor with a lighter touch might’ve generated more excitement.

“Her” is inventive, and I liked looking at its fascinating world. You’d expect originality from the director of “Adaptation” and “Being John Malkovich,” and this does feel like something we haven’t quite seen before.

But the ideas behind it — of Theodore’s learning lessons about how complicated two-way relationships are, and the messy business of actually being with a live human — don’t feel new. This is a movie of breathtaking design and conventional ideas.

So far, lots of critics have disagreed. “Her” won best picture nods from the L.A. film critics, the National Board of Review, and a couple of other critics groups. As a crystal ball, “Her” will probably prove correct — the real Samanthas, and the virtual love affairs they will bring with them, are undoubtedly just a few clicks into the future.

“Her” 2 ½ stars

A lovesick guy (Joaquin Phoenix) develops an emotional relationship with his new computer operating system (voiced by Scarlett Johansson). Spike Jonze’s movie is a visual dazzler of the near-future, although its ideas about a man learning to appreciate the complicated realities of an actual woman seem pretty old-fashioned.

Rated: R for nudity, language, subject matter.

Showing: Opens Christmas Day at various area theaters.