I decided to limit the electronic components that I could use to only those in Dad's recycled assortments.
Dad didn't have any microcontrollers or motor controller ICs in his collection and so I attempted to create the comparator, PWM generator and H-bridge from discrete transistors and resistors. Dad also didn't have any light dependent resistors but he did have a handful of very old LEDs. These were not very bright but they could function as a light sensor when reverse biased.

One problem with Dad's recycle components is that because they were desoldered from a circuit board, the legs were very short and encrusted with solder. This made them unsuitable for use in a breadboard prototype. So I've used some new components during the prototyping with the intention to swap them for the recycled equivalents when soldering the final circuit.