The book is about user interfaces to applications that have been designed for social and physical interaction. The interfaces are ¿playful¿, that is, users feel challenged to engage in social and physical interaction because that will be fun. The topics that will be present in this book are interactive playgrounds, urban games using mobiles, sensor-equipped environments for playing, child-computer interaction, tangible game interfaces, interactive tabletop technology and applications, full-body interaction, exertion games, persuasion, engagement, evaluation and user experience. Readers of the book will not only get a survey of state-of-the-art research in these areas, but the chapters in this book will also provide a vision of the future where playful interfaces will be ubiquitous, that is, present and integrated in home, office, recreational, sports and urban environments, emphasizing that in the future in these environments game elements will be integrated and welcomed.

Anton Nijholt is Professor in the Human Media Interaction research group of the University of Twente. He studied mathematics and computer science at the Delft University of Technology and did his PhD research at the Vrije Universiteit in Amsterdam. Since then he held positions as post-doc and professor at universities in Canada, the Netherlands and Belgium, before he took a permanent position in 1989 as a full professor at the University of Twente, the Netherlands. His research interests changed from theoretical computer science to human-computer interaction. In Twente he initiated the Human-Media Interaction research group and supervised close to fifty PhD students. Anton Nijholt has more than two hundred scientific applications. He has been (and will be) general and program chair of the main international conferences on intelligent agents, affective computing, and entertainment computing. In addition he has introduced workshops, special sessions and special issues of journals devoted to new and advanced issues in human-computer interactions, such as smart material interfaces, brain-computer interfacing, and child-computer interaction.

Introduction.- Public Interfaces Requiring Full-Body Interaction.- Multiplayer Mobile Games.- Smart Ball Applications.- New Exertion Games.- Tabletop Interfaces for Children with Autism.- Tabletop Interfaces for Children¿s Museum Visits.- Tangible Game Interfaces.- Child-Computer Interaction.- Interactive Playgrounds for Children.- Engagement in Playful Collective Interaction.- Head Up Games.