Press the D12 button to "start" the robot. The robot should start driving straight. After the robot has counted 3 line markers (meaning it has reached the 3rd line after the start line), the robot should stop, turn around, and then drive back. After counting another 3 line markers (meaning the robot has returned to the start line), the robot should stop and turn around again (facing its original direction). The robot will "pause" itself automatically.