In nature, animals often are sensitive to the outside environment, retreating into a hole, shell, or other protective structure upon sensing sudden movements. If you were to envision this kind of behavior in robot form, you might come up with something like “The Shy Machine” from Daric Gill Studios.

When it detects motion via a PIR sensor, the shell-like robot takes a reading of the ambient sound level using an internal microphone. If things are sufficiently quiet, it opens up using a stepper motor and lead screw, revealing a rainbow of colors provided by an array of RGB LEDs inside.

Its construction and a demo video are shown below, and you can see more about how this Arduino-powered robot was built and the results on Gill’s website.