  Learning to code, and more broadly, learning about computer science is a
growing field of activity and research. Under the label of computational
thinking, computational concepts are increasingly used as cognitive tools in
many subject areas, beyond computer science. Using playful approaches and
gamification to motivate educational activities, and to encourage exploratory
learning is not a new idea since play has been involved in the learning of
computational concepts by children from the very start. There is a tension
however, between learning activities and opportunities that are completely open
and playful, and learning activities that are structured enough to be easily
replicable among contexts, countries and classrooms. This paper describes the
conception, refinement, design and evaluation of a set of playful computational
activities for classrooms or code clubs, that balance the benefits of
playfulness with sufficient rigor and structure to enable robust replication.
