The CE2S uses an IC and 7 transistor circuit with adjustable controls for motor activation times and sound sensitivity. Uses a sensitive microphone which constantly ?sniffs? the area for sound. When it detects it the colorful LEDs at the front of the robot flash and the robot stops for a second and then changes direction.
Uses 15 LEDs total and is very colorful. You can even paint the PC board before you assemble it if you wish.