For instance, the sponge was used by two children as a springboard for working with two simple geometric concepts: a circle and a square. They started by each making their own impressions on the sponge; one was making a circle and the other was making a square. Spontaneously, they started putting each of their impressions on top of the other's impression.
As the boy put down the circle, the girl would place her square over it. In doing so, the circle disappeared. The boy would then put his circle over the square and the square would disappear. The children did not know they were doing math, but the concepts of a circle and a square were being consolidated for them in their play in a very unique way.
Not only were these children learning math concepts, but they were also displaying social and emotional learning. These two children had not played together before, but still they were able to create their own game that had a simple rule (take turns) and that was very playful (making the other's impression disappear).