Play is a frequent and relevant activity during childhood, and developmental psychologists agree that it offers a unique window on development. Play, however, remains a fuzzy concept, and difficulties persist in its definition, often leading to obstacles in building and comparing experimental studies. This may be due to widespread tendencies to define play by referring to non-observable inner states, to consider playing something that occurs in the head rather than in-the-world and to overreliance on developmental stages. Enactive approaches to child (...) play have instead recently stressed the importance of play contexts, considering child play an activity in-the-world rather than a mental state, thereby de-intellectualizing play and pretense. Along these lines, in this paper the authors propose a novel approach to the definition of play types by considering the roles of organism, environment, and task constraints, within the framework of Material Engagement Theory. Focusing on the material world surrounding the child and the interactions which characterize play, we critically review the strategy of resorting to non-observable categories in the study of play, and we propose a new model (the Kaleidoscope Model) for play analysis. (shrink)