Cubelets come in three types: Sense blocks, Action blocks, and Think blocks. Sense blocks are black, Action blocks are clear, and Think blocks are different colors. Most Cubelets have five connection faces and one special face, which identifies the function of that Cubelet. Others have six connection faces and their function is indicated by their color. Modrobotics site 
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Random pulses cascade among tiny computers each programmed to interface one more device into their signaling pathways. site