Invisible eni: using gaze and pupil size to control a game

We present an eyes-only computer game, Invisible Eni, which uses gaze, blinking and as a novelty pupil size to affect game state. Pupil size can be indirectly controlled by physical activation, strong emotional experiences and cognitive effort. Invisible Eni maps the pupil size variations to the game mechanics and allows players to control game objects by use of willpower. We present the design rationale behind the interaction in Invisible Eni and consider the design implications of using pupil measurements in the interface. We discuss limitations for pupil based interaction and provide suggestions for using pupil size as an active input modality.