In a science fair in 2026, we prepared an activity to teach primary and secondary schoolers about full binary trees and search. The object is a sheet of paper that tries to guess a fruit you are thinking about.
It is a simple physical version of Akinator that you can print. We built a full binary tree with common fruits people in Spain are likely to think about. Each fold corresponds to a yes/no answer, so after five questions you have followed one path through the tree to one of $2^5=32$ leaves.
Many people had a lot of fun with it. The paper version is especially good because the search becomes something physical: answer, fold, keep the half that matches your answer, and repeat. You can download and print our fruit tree. Or hack it.
It is not perfect, in the same way that Akinator is not perfect. People sometimes answer the wrong thing, or interpret a question differently. For a group activity, it works better if the person says the fruit out loud first and everyone agrees on the yes/no answers as the paper is folded.
Here is a computer version of the same tree, but I recommend printing it and showing it to people.