Optic Echo app for iPhone and iPad

Make an invisible world visible by making noise. In a "blind" game without sound, use your voice to find your way.

Chase a man through a maze and inscribe your voice on his body.

It was created for the June 2011 Experimental Gameplay Project challenge, "MASHUP". It is an echolocation-based video game with a voice-activated silent soundscape. The intention is to make visuals that are rendered in the way that audio is experienced.

"[L]ike the fire, sound is always coming into and going out of existence, evading the continuous presence that metaphysics requires; like the fire also, sound is heard and felt simultaneously, dissolving subject and object, interior and exterior.  Like the river, sound cannot be called "the same" since it changes at every point in its movement through a space; yet like "Soul," it does not strictly belong to the object.  Nor can sounds source and ending be defined, for it originates as already multiple, a "mix," which makes it impossible to speak of "a" sound without endangering the structure of Western thought itself." - Frances Dyson, Sounding New Media

This game requires a built-in microphone.