Constructional ability is a necessary part of everyday functioning for adults and children alike. In children, the need for adequate levels of constructional ability is evident during both recreational and school activities. PlayCubes is a dynamic tool that supports monitoring a variety of the perceptual-motor processes needed while children perform constructional tasks. PlayCubes is based on ActiveCube (AC), an electronic, Lego-like tangible user interface (TUI) designed to construct three-dimensional (3D) objects in both the physical and virtual realms simultaneously. In this paper we explore PlayCubes' use as a concrete, ecologically valid tool which reveals the dynamic functional processes underlying constructional ability among typically developed children. Our paper describes the PlayCubes interface including its interactive playground virtual setting, the motivation for the study, the experimental design and results to date. We conclude that, despite several technical limitations, the PlayCubes system and playground apparatus tasks appear to be sensitive to differences in children constructional abilities while presenting an engaging and enjoyable assessment tool.