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
