Leader chooses a topic, but keeps it quiet, only saying that “You can bring a ____ through the green door.” Students are then forced to deduce the topic by asking if other things can be brought through the green door as well, e.g., “Can I bring a _____ through the green door?”
Leader can only reply yes or no. When topic is identified, topic resets. Topics can be content related, such as parts of speech, colors, geometric figures, historical figures, etc.