Electricity Project - Line Tracker Mouse. A complete kit for building a robotic vehicle which can follow a black line, e.g. drawn on paper, or black tape on a floor. Three photo interrupters are employed as eyes which can distinguish black and white by projecting infra-red rays. The mouse is sound activated, incorporates a programmed IC and 2 sets of geared motors. Requires 4 x AA size batteries (not included). Full comprehensive assembly instructions included.