I build the chassis from perspex and brass, turning my own spacers to hold the various boards in the right places. I used DC motors, made my own power controllers, opto-isolators, shaft encoders, IR wall distance detectors, servo steering assembly, bearings for the front wheel, ...
Everything.
Then the night before the competition I blew out my one and only EEPROM by plugging it into the programmer backwards.
Never got to compete.
But I still have Harvey[0] somewhere. I should pull him out and make a series of videos about his construction. But it was 35 years ago and the technology has changed ... I doubt anyone would be interested, especially because he never competed.
But I was proud of building the computer from scratch and having it work first time, and of being able to run down my homebuilt section of "corridor" without hitting the walls. At the time no mice had run diagonally, so I really was in the running, provided it ran.
Oh well.
[0] No, not named after the cocktail[1], but after the smallest species of mouse in the UK. It's the "Harvest Mouse", or "Micromys minutus".