Step 1: Overview
parts needed include:
an NPN transistor
a resistor (the value of which later be determined later)
batteries (between 6 to 12 volts depending on size of robot and motor requirements, I used two 3v button cells).
two motor and gearbox assemblies
a light dependent resistor (LDR)
and a suitable shell. (mine was the clear case from a toy, it measures 45mm in diameter).
a multimeter or ammeter
note: the picture does not include the transistor because at the time of taking the picture i was still in the process of designing and didnt think that the transistor was neccesary. also, only one resistor was needed.