Think of a rule to group some of the objects. It could be something like “all of the animals” or “all of the objects with four sides.”
Slowly add and/or remove objects from the circle to conform to the rules you set. Ask the children to talk and indicate “what’s the rule” that is dictating what you add and remove from the group.
Ian O’Byrne discusses the use of the game ‘What’s the Rule’ to develop Computational Thinking, another unplugged activity.