Mommy is already the fifth feature from 25-year-old French Canadian auteur Xavier Dolan, and while his latest film still possesses an overeager youthfulness, it's also a visually tense, emotionally ecstatic and unforgettable experience. Set “in a fictional Canada” (don't worry, Celine Dion still exists), Mommy stars Dolan regular Anne Dorval as Diane “Die” Despres, a single mother in bedazzled jeans struggling to raise her blonde, tit-squeezing hellcat son. Die is devoted to her boy (an excellent Antoine Olivier-Pilon, loathsome and strangely charming), but also terrified of his violent mood swings and sexually inappropriate behavior. Dolan shoots most of Mommy in a claustrophobic, 1x1 aspect ratio, emphasizing vertical lines in the framing, and he makes gonzo use of slow motion and 1990s pop songs. But the film's ostentatiousness never overshadows the brilliantly complex lead performance by Dorval, who runs the gamut from tacky gusto to cynical calculation.