Noah Baumbach's ebullient film shows what it's like to be alive and in one's 20s and living in New York—or, briefly, Sacramento—and aware of one's potential slipping away. Greta Gerwig stars as an aspiring dancer, whose signature move might be flightiness, and whose slow drift toward true adulthood might also be away from her best friend, played by Mickey Sumner. Shot in sumptuous black-and-white, this subtly romanticized slice of life amounts to a minimal assembly of improbably resonant nonevents, almost unthinkable as a film without the specific virtue of Gerwig's daffy, guileless poise. Otherwise, Baumbach's style could be called homage-happy; it's French New Wave meets vintage Woody Allen meets Girls. What's key is how playfully at ease Baumbach seems among his many tasteful influences, including obvious muse Gerwig, his co-writer and vital spark. Inspired by her spontaneity, and scripted to cultivate it, the movie does turn up some occasional stilted line readings here and there, but periodic awkwardness also is shrewdly elemental to its charm.