The 555 astable timer circuit integrated with the 4017 decade counter circuit completes the microcontroller free light chaser.
A final note: See the black and blue wires at the bottom of the picture? These go to my 8 ohm speaker where I can also hear the frequency generated by the 555 astable circuit.
A final final note: I hope I didn't sound to contrite but my goal was to guide you through building this device with a minimum of words and the simplist pictures I could. There are thousands of web pages that will take you deeper into theory on these devices and circuits and I hope that you will also look at those.