This paper presents a design case study of SIDES: Shared Interfaces to Develop Effective Social Skills. SIDES is a tool designed to help adolescents with Asperger’s Syndrome practice effective group work skills using a four-player cooperative computer game that runs on tabletop technology. We present the design process and evaluation of SIDES conducted over six months with a middle school social group therapy class. Our findings indicate that cooperative tabletop computer games are a motivating and supportive tool for facilitating effective group work among our target population and reveal several design lessons to inform the development of similar systems. Categories and Subject Descriptors H.5.3 [Information Interfaces and Presentation (e.g., HCI)]: Group and Organization Interfaces – computer-supported cooperative work. General Terms Design, Human Factors. Keywords Tabletop groupware, CSCW, computer games, Asperger’s Syndrome, social skills development.