Exploit the dimension of time, like PIPS:Lab's Diespace (but using modern face tracking now instead of simple LED tracking 11 years ago). Nod your head for yes,

Exploit the dimension of time, like PIPS:Lab's Diespace (but using modern face tracking now instead of simple LED tracking 11 years ago). Nod your head for yes, shake your head for no. That's a "hands free interaction", and less flamboyant and spectacular than waving your hands around, for shy and lazy people.