I was asked to help out a group of high-school seniors, with their advanced physics project druing the winter of 2001. This was a rather busy year for them (getting all their college applications ready, etc.) and so they had left themselves very little time to do a "robotics" performance. We tried to distill things down to the simplest possible scheme: one stepper motor, controlling the bot's position on a strung cable (see right).
We decided to add a solenoid, which would magnetically carry a payload (candy bar) over the crowd, and then release it (hence the name).