How does the system know where to move the lightbulb to? A Microsoft Kinect figures out where your head is, and reports that position back to a Processing sketch. The sketch does a bit of math to shift the position data from the Kinect's coordinate system to the coordinate system that the Arduino uses to position the motors. Processing sends serial commands to the Arduino that communicate where in three-space the lightbulb should be.

The Arduino reads this serial command and does some further math (see below) to determine what position each spool should go to, and then moves the motors appropriately. This whole process—from reading head position at the Kinect to transmitting transformed coordinates to the Arduino to driving the motors to a new position—is done nominally ten times per second in normal operation.