While it lacks such sophistication as some of the other robots here, it has been a challenge to me. As you can see, it is grafted from an old PowerWheels vehicle. It is funny to watch it run around in the house as it more closely resembles a bull in a china closet. So far, the only sensors it has are the bump whiskers on the front. Commodore64 Computer, modified to operate on 12VDC, otherwise unmodified.
Tape Drive on board for field loading of software.
The other was all the mods to make the C64 battery-friendly. Continuing. . . I have used nothing but salvaged and junk box parts. Infrared 'following' system. Encoders on the drive wheels for distance measurement.