One of the puzzles in The McGuffin Game called for building 17 "bases" to spread around a baseball diamond in several inset diamond patterns. Each base had some number of columns of LEDs, between one and six, which lit up in sequence. That is, the centermost LEDs would all light up, then the next set, then the next set, all the way to the outside. It's a puzzle and encodes information; how the information was encoded was the set of LEDs that actually lit up. On this base, for instance, not all the red LEDs would ever light. To make the letter F, the second and third LEDs would light; in binary, 01100 equals 6 decimal, and F is the sixth letter of the alphabet.
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