Posey: Embedding Computation in a Poseable Hub and Strut Construction Kit for Undirected Play Michael Philetus Weller 1 , Ellen Yi_Luen Do 2 , and Mark D Gross 1 [1] CoDe Lab Carnegie Mellon University Pittsburgh, PA 15213 USA {philetus,mdgross}@cmu.edu [2] ACME Lab Georgia Institute of Technology Atlanta GA 30332 USA ellendo@cc.gatech.edu ABSTRACT We describe Posey, a computationally-enhanced hub-and- strut construction kit for learning and play. Posey employs a ball and socket connection that allows users to move the parts of an assembled model. Hubs and struts are optocou- pled in the ball and socket joints using infrared LEDs and phototransistors. Wireless transmitters in the hubs send connection and geometry information to a host computer. The host computer assembles a representation of the physi- cal model as the user creates and configures it. This repre- sentation can then be used by application programs to con- trol models in particular domains. ACM Classification Keywords K.3.1: Computers and Education: Computer Uses in Edu- cation. H.1.2: Models and Principles: User/Machine Sys- tems. H.5.2: Information Interfaces and Presentation: User Interfaces, Input devices and strategies General terms: Design, Human Factors Keywords: Construction Kits, Tangible, Play INTRODUCTION Construction kits display a variety of qualities that have endeared them to several generations of children and educa- tors. Foremost among these qualities is that children enjoy playing with them, and through play they are introduced to the rewards of working out their own plans and dreams in a tangible medium that demands the resolution of issues of form and structure. Working out design problems with construction kits builds both general problem-solving skills and strengthens a child's ability to think and imagine in three dimensions. Construction kits are also used to model the properties of particular domains. For example Lincoln Logs help children understand and explore the de- sign space of log buildings; ball and spring molecule kits help students build a robust understanding of the geometry of molecules and the inter-atomic forces that govern their formation. And perhaps most importantly the open-ended nature of construction kit play introduces children to the ‘hacker ethos’ of building things as a way of having ideas. As microprocessors and wireless communication technolo- gies become cheaper, smaller, and more robust it is rapidly becoming feasible to embed computation in each individual piece of a construction kit. By enabling applications run- ning on a personal computer to monitor the topology and configuration of assemblies as they are manipulated these computationally enhanced construction kits promise to allow software developers to create novel and accessible environments for undirected play. These applications can improve on traditional construction kits in two ways: they can map additional domain-specific information to the cur- rent assembly, and they can serve as playmates by provid- ing feedback in response to manipulations of the assembly. Systems such as Topobo [13], Backpacks [12], Computa- tional Building Blocks [2], (and others discussed below) add computational power to traditional physical construc- tion kits, lending themselves to creative exploratory and ‘constructionist’ play. None of the current computationally enhanced construction kits combine assemblage from parts with the sensing capa- bilities necessary to allow an application on a personal computer to respond to manipulations of an assembly's pose. This combination of features would provide a rich style of interaction that allows three dimensional forms to be mapped to a domain to create custom input devices that allow simple intuitive control of complex models. That was our goal in building Posey. Figure 1: Posey is an instrumented hub-and-strut construction kit that is poseable and can provide input for applications in various domains. Posey is a computationally enhanced poseable hub and strut construction kit. Its hub and strut form maps to model anything that can be described in a graph structure, for example an articulated skeleton, a chemical molecule, or a kinematic linkage or building structure. Figure 1 shows a model used to create an animated three-legged animal character. Keep this space free for the ACM copyright notice.