Spot it! or Dobble (https://de.m.wikipedia.org/wiki/Dobble) is a game with 57 cards, each showing 8 symbols. For every pair of cards, there is exactly one common symbol. This is possible because of the projective plane with the cards as points and the common symbols as lines, and it is 57=8^2-8+1.

Spot it! or Dobble (https://de.wikipedia.org/wiki/Dobble) is a game with 57 cards, each showing 8 symbols. For every pair of cards, there is exactly one common symbol. This is possible because of the projective plane with the cards as points and the common symbols as lines, and it is 57=8^2-8+1.