He wanted to include a light sensor but the problem is, the Pi doesn’t have a built-in ADC to read the voltage off the light-dependent resistor that he (presumably) had in his junk box.

No one likes a flickering light source, but lighting is often dependent on the quality of ... a way to do so with an NPN phototransistor, a resistor, and a 3.5 mm audio plug.

and lamps close lampA component which produces light when ... in a parallel circuit, the total resistance of two resistors is less than the resistance of the smallest individual resistor.