Sweet is a line-following robot made from a metal candy container. The robot follows either light or dark lines. When someone presses the exhaust-pipe switch, the robot determines the type of line by comparing the edge sensors to the center sensors. Then, the robot races away! Six phototransistors are located under the front. If a high-contrast line is used, the robot handles 90-degree turns and can stop when the line ends. If the surface contrast is poor, the robot can still follow tiny differences because of an autocontrasting algorithm applied after each sensor read. For fun, Sweet's grill includes a 10-segment LED bar graph. A red pulse sweeps back and forth while driving, and indicates the line location when stopped. It took one and a half calendar months (evenings and weekends) to design and build. Reusing code and designs from a recent mini Sumo robot saved a lot of time. Also, I made my own circuit boards for the first time, which took some time to learn, but saved time in wiring. Cost: $ 5 candy can (less candy) $ 8 MC68HC08GP32 microcontroller $20 motors $ 5 tires, hubs $10 emitters and detectors $20 rechargeable batteries $10 PCB copper boards $ 5 switches $10 MOSFET H-bridge $20 buttons, capacitors, resistors, diodes, nuts, bolts, solder, paint, wires, Velcro, connectors $ 7 LCD The total is around $120. More information and pictures of Sweet can be found at http://www.robotroom.com/Sweet.html Email: david@robotroom.com