When our children were babies, they were obsessed with the game of Peek-a-boo. It never got old and they thrived at that game as they learned about object permanence. This giddiness that observed in a game of peek-a-boo is the reaction you can expect during this game. Playing a game of What's Missing builds memory skills while practicing sight words. I have played this game in many places... at a restaurant while we are waiting for our food to arrive, I bring out the sight word cards and practice. I've played at the airport when waiting for a flight. We sit on the floor and play what is missing. It so simple and effective!