Human–Computer Interaction (HCI) is no longer restricted to interaction between
users and computers via keyboard and screen: Currently one of the most challenging
aspects of interactive systems is the integration of the physical and digital aspects of
interaction in a smooth and usable way. The design challenge of such mixed reality
(MR) systems lies in the fluid and harmonious fusion of the physical and digital
worlds. Examples of MR systems include tangible user interfaces, augmented reality,
augmented virtuality and embodied interfaces. The diversity of terms highlights
the ever growing interest in MR systems and the very dynamic and challenging
domain they define.