# St Thomas of Canterbury, 1 February 2019

We explored the Pigpen cipher at Bletchley Juniors this week. I had written a different riddle in pigpen for each child. I asked them what a riddle was. The answers were a little unclear so I explained that it takes the same form as a joke (a question followed by an answer) but is designed to make them think hard and/or creatively to get the answer, which may involve a double meaning. I gave each child their riddle and the pigpen key, and asked them to decode the ciphertext question, think about the answer, then turn over and decode the ciphertext answer. An example was: ‘What starts with an ‘e’, ends with an ‘e’ and has one letter in it?’. Of course the answer is ‘envelope’! The child with this riddle had a Eureka moment when they understood the answer.

To introduce some variety we played a game in the second half of the session. I chose Zoo’s On Top as it involves both players (we actually played in teams) setting an animal code and trying to be the first to crack the other side’s code. It is a good game of deductive reasoning, a key skill for codebreakers. Each team chose four animal tiles and slid them into their zoo tower, in an order of their choosing, to set their code. Each team took turns asking questions with Yes or No answers, with an extra turn given when the answer was Yes. An example was ‘Is the kangaroo above the gorilla?’. Each team had four cardboard animal tiles to replicate the other team’s choice of tiles and help keep track of the information gained, which was used to deduce the animal code.

With four tiles in the code, it did not take very long for a team to win. We then increased the difficulty by using five animal tiles. This game lasted quite a bit longer and the children required a bit of guidance to help think about the possibilities of where each tile could go. We did have a winning team, but the other team would have won on their next go when it was their turn to give the solution!