Sundance: Aidan Zamiri’s mockumentary portrait feels like a face sheet in motion for Charli's +1s, though the singer/star gives a commanding screen performance as, well, herself. What happens when Brat Summer — that slime-green cultural phenomenon in which Charli XCX dared us to all be much messier, much less apologetic, to send that first text and not regret it — really ends? What is astronomically lost in the supernova of when fame and art collide? And is there such a thing as metaphorical