This robot was the third robot in the sequence. It was activated by an ultrasonic sensor triggered by the preceding group. The next robot in the sequence was activated by exposing its light sensor, so they placed a solid object above the sensor that we knocked off at the appropriate time. We created a helicopter rotor-like arm that swung when activated. To keep the system stable, we added a counterbalance to the swinging arm with the use of extra wheels. This action triggered the next motion and continue the chain of events.