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This is the Cybug I built. It has no software, only hardware. There are two CdS cells up front to sense light.
They are attached to a 556 dual timer IC which sends out pulses to the L293 H-Bridge driver. The whiskers are connected
to two transistors which reverse the motors when activated. This bug will move toward the lightest area of a room.
I was able to find some geared motors at Alltronics for about $10. The Cybug schematic is here.