Joanna Arnow’s fascination with the power balance in relationships continues with her acclaimed narrative short film, “Bad at Dancing,” which won the Silver Bear at this year’s Berlin International Film Festival. Eleanore Pienta beguiles as Isabel, a young woman whose various attempts at having sex with her boyfriend, Matt (Keith Poulson), are interrupted by her roommate, Joanna (Arnow herself), who routinely bursts in on the couple mid-coitus and proceeds to converse with them in an entirely disaffected manner. Viewers will initially find themselves laughing out of sheer disbelief, yet there is a wealth of provocative depth within the film’s awkward, protracted silences. Bad at Dancing is outrageous. It is cringe-inducing. It is uncomfortably sexual, yet entirely unsexy. It is fantastically implausible, yet simultaneously and disgustingly real. It is a genius work that, once viewed, you might never want to watch again, and these internal contradictions and juxtapositions within a simple film largely set in one location, herald the arrival of a fascinating new storytelling voice in writer/director/actor Joanna Arnow