1. Creative Technology Group, Department of Informatics, University of Sussex, Brighton BN1 9PH, UK
2. Industrial Design, Eindhoven University of Technology, 5612 AE Eindhoven, The Netherlands
3. Interaction Design Centre, University of Limerick, V94 T9PX Limerick, Ireland
4. Department of Computer Science, University College of London, London WC1E 6BT, UK