Consider first building an analog version of the marble wheel. Doing so showed the importance of aligning the two cardboard circles as well as centering the spindle of the motor on both circles.

Add an action to the project triggered by the motion sensor. In this case, the motion sensor triggers a "disco room" with two oversized RGB LEDs attached to a position servo. Also, notice the green LED on top indicating the triggering of the sensor.

Also note that because of wire lengths, we added a stand to hold the hummingbird microcontroller closer to their connections.

Don't be surprised if the distance sensor does not always trigger the action. The sensors are not always accurate or responsive enough.