This interactive installation comprises a dark room with white walls, 49 lights suspended from the ceiling in a 7 X 7 array, 28 modulated infra-red beams, 28 sensors and a control box incorporating 8 micro-controllers. 

When you enter the room, the sensors determine your position and the light above you slowly becomes brighter. It takes about a second to reach full brightness. When you move away, the light becomes dimmer, taking about 20 seconds to turn fully off. As you move around the room, you leave a temporary trace of your recent past in light.

The photograph shows a long exposure detail.