An array of sensors detects the color ... Color sensing (as well as detecting empty spaces) settled on IR-based sensors commonly used in line-following robots. You can watch the clock in action ...

The awesome find is an 8×8 IR array sensor on a breakout board… the hack is all in what you do with it. Already taken by “LED fever,” [Xose’s] mind immediately fixated on an 8×8 IR array ...