The fourth book in the Big Red Ideas series. Young children enjoy Clifford's Big Red Ideas, and parents love the lessons they teach. In this story based on a Clifford TV episode, Clifford and his friends play a game of Red Light, Green Light. Clifford helps Mac see why it's important to play by the rules. Each story in this series has a lesson, or a "big idea". And who better to gently teach these lessons than Clifford!