A play about beginning acting students taking a course taught in a small Vermont town by a former hippie would seem to fall into the kind of self-congratulatory martyrdom that many plays about theater slip into. But not this Annie Baker-penned jewel: There was a reason Circle Mirror Transformation won the 2010 Obie award for Best New Drama, and the ensemble collected for South Coast Repertory's January production emphatically showed why. The five actors (the always-mesmerizing Linda Gehringer as the dauntless instructor; Brian Kerwin as her hapless but likable husband; Arye Gross as a lonely, recently divorced man; Marin Hinkle as an attractive refugee from the Big Apple; and Lily Holleman as an introverted teen) expertly mined the depths of their characters. They succeeded in transforming a relatively simple play about ordinary people into a masterful exploration of human connection.