The O?THO exhibit, situated within the LivingLab at Copernicus Science Centre (CSC) in Warsaw, Poland, introduces visitors to the Cartesian principles of representing numerical data as points in a two-dimensional space--the coordinate system. This interactive tabletop digital exhibit takes the form of a collaborative two-player game where participants manually control a virtual ball's x- and y-axis values, respectively, to navigate it through maze-like paths, with the objective of completing the course in the shortest time and with the fewest moves. An action-based embodied design, O?THO draws on: (1) the enactivist tenet that individuals' cognitive structures emerge from recurring task-effective sensorimotor patterns discovered through explorative perceptuomotor activity; and (2) cognitive-anthropological theorizations of shared ontologies as emerging through multimodal social interaction to facilitate the coordinated enactment of joint action. We overview the exhibit's theoretical underpinnings and design conjectures; detail design challenges particular to the museum context, both in terms of the institution's civic mandate and in terms of attracting and sustaining user engagement; present the exhibit itself; and speculate on the typology of research projects centered on mixed-methods multimodal data analysis based on expected 70,000 annual users.