'Knock Once for Yes' - Knocking as feedback in the location-based game passing on

In this paper the design, implementation and testing of the Location-Based game Passing On is explored. It is a multi-player game for mobile phones, with a focus on asymmetric and limited communication. While one player can communicate by talking, the other can answer only by knocking. This limited and asymmetric communication became one of the central gameplay resources in the game, shaping much of the experience for the players. Using observations and interviews, the knocking and the experience it created is analyzed and discussed. It is shown how this made the game emphasize social interaction, moving the focus from the phone to the environment, and how the knocking helped create a sense of presence for the player feeling them.