Figure 2. Virtual environment of perceptual crossing paradigm.

Players are virtually embodied as avatars on an invisible line that wraps around after 600 units of space. Each avatar consists of a binary contact sensor and a body object. Unbeknownst to the players a “shadow” object is attached to each avatar body at a fixed distance of 150 units. There are also two static objects, one for each player. All objects are 4 units long and can therefore only be distinguished interactively in terms of their different affordances for engagement.