Two young men are both friends and writers. On the same day, they dispatch their manuscripts from the same mailbox. When they do, their lives also take off, in ways that are at once unpredictable and understandable. Joachim Trier, who made super-8mm films before he learned to read and write, celebrates life’s options even when they are lousy. The daring risks he takes as a filmmaker propel this vivacious cinematic meditation on creativity, madness, and love into an engrossing adventure, and a shooting star of a debut feature that is wildly inventive and wise beyond the youthful exuberance of its makers.