This practice-based PhD opens an original dialectical discourse between theory and practice in the domain of themed playground design. It introduces the concept that action research involving playworkers and young people, as well as with designers of playground equipment, can lead to novel and socially empowering new forms of design specifications that can enrich children's play in numerous ways. The thesis argues against the aesthetic of many of the types of apparatus currently available in commercially themed playground equipment, on the grounds that most such equipment fails to adapt to the variability of thought and engagement as expressed in early childhood narratives of play. Underpinned by this argument, the thesis proposes and expounds a research methodology which is multi-disciplinary and based on the contribution of Developmental Psychology (from the academic fields of Education and Psychology), Playground Equipment Design (from the fields of Design, Interaction Design and Technology), and Play and Narrative theories and practices (from the fields of Literary and Narrative Studies, and Early Years Play Theory). These theories address the deconstruction and redevelopment of a holistic approach to themed playground equipment aesthetics that aims to serve two of the most essential characteristics of early childhood play: pretence and construction. The thesis' theoretical offering is the new `Ludic Aesthetic', proposed as a model of adaptive function that leads to variable narrative defined by five design criteria, described here as `design events'. These are: assemblage, motion, transformation, ludic symbolism and condensation (concepts that are discussed at length in these pages). The emergent theory of the `Ludic Aesthetic' arising from this study of design practice is closely related to the study of a new form of playground tool: the `ludic machine', defined in the thesis as a form of original themed playground equipment that deliberately affords a proposed aesthetic of play. The thesis makes an original contribution to scholarship in the area of play-based action-oriented research, with findings that underpin both educational social design methodologies for future study of children's play. It further contributes to the domain of playground equipment design by demonstrating the core design principles and outcomes achievable by applying a play-based model to this important field, both in terms of theory and of daily practice.