3 ms·

They correspond to the number of circles that this circle touches. The lines in the center of the circle show the directions.

• XaspR8d 7y ago
  At first glance, blues seem to have 2 contact points and magentas have none, but the correspondence seems to break for yellow and orange, which each have several (overlapping) numbers of neighbors that they are used with.
  • pavel_lishin 7y ago
    Ah, I see it now. A magenta circle touches no other circles. A blue circle touches one other circle. An orange circle touches two other circles. A yellow circle touches three other circles.
    • deleted 7y ago
      [deleted]
    • dhritzkiv 7y ago
      That's what I thought as well, but that theory doesn't appear to hold up. For example: http://hydra.nat.uni-magdeburg.de/packing/cci/cci14.html http://hydra.nat.uni-magdeburg.de/packing/cci/cci14.html
  • deleted 7y ago
    [deleted]