From the Publisher:
Each round a different player (The Judge) reads a multiple-choice trivia question. The remaining players secretly input their answers using ABC response cards. Without revealing which answer they chose, they must explain to the Judge how or why they know the correct answer...even if they're completely clueless! The Judge interrogates the other players to figure out who knows the correct answer (Brilliant) and who's only pretending to know (BS). Players earn points for convincing the Judge of their brilliance. After everyone reveals their answers, the Judge earns points for correct predictions and loses points for incorrect predictions.