the controller is an arduino nano.
the coreless motors used in this project are from a small toy rc helikopter.
the bearings for the gears are just tubes from an antenna and this works very good.
the parts are printed in PLA plastic.
I used superglue to glue al the pieces together.
The transistors used are some I had lying around.
have you considered using some sort of distance sensor or dropping the tether (not for the 1KB challenge, but for the sake of hacking) with like a infrared module?