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PLORE and RETRACE. The former was in effect when the mouse was directed to continue moving straight along the maze corridor until it entered territory that it had visited previously, whereupon the RETRACE phase took over. While the mouse was in the EXPLORE phase, it continually remembered all of the paths it had traversed. When it entered the RETRACE phase, the shortest path to the nearest unvjsited territory was computed, and it was directed to it. Then the EXPLORE path took over again.
A two-level design
Cattywampus was built on two levels. The football-shaped lower level was 15.2 cm wide. It contained two small dc motors, one for each of two wheels that were on the same level; rechargeable Ni-Cd batteries (six 1.5-V Size C; three 1.5-V Size AA, and two 9-V transistor batteries) and the circuitry to switch the motors. The upper level measuring 20.3 by 25.4 cm contained the microprocessor system, interface circuits, switches, and status-indicator LEDs.
Four infrared LED/photodetector pairs (one in from, one in back, and one on each side) were mounted on the top level to detect the presence of walls. A small black-and-white cylinder was placed on each of the two motor shafts. An LED/photodetector pair, aimed at each shaft, allowed accurate determination (within a resolution of 0.64 cm) of the mouse's relative position in the maze.
A complex maze at finals
The Spectrum maze used at the finals was more complex than any that the contestants had encountered heretofore (Fig. 7). The fact that it favored right-wall-hugging micromice over left-wall huggers was arbitrary. As it turned out. all of the wall hungers at the finals were right-handed
ones.
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