Spot it!, or Dobble, is a party matching game, released in 2009 by French designer Denis Blanchot, based on the prior work of Jacques Cottereau. The players aim to be the first to identify the matching symbol present between two cards, where amongst all the cards, only one symbol will ever match between any two given cards.
…yeah that’s pretty much it. It’s a quick party game that’s not very complicated. So instead, let me try to give a maths/history lesson as to how that works, noting I am not a maths person: Cotterau devised the original design of the game in 1976 on the Kirkman’s Schoolgirl Problem, and made a deck of 31 cards that featured insects instead of assorted objects like in Dobble. Blanchot would later find copies of these cards, and from there develop Dobble.
The maths of how to determine how many cards and symbols are needed can be thought of using some geometry: if we have a triangle, and we put a point at each corner of the triangle, then the points would represent the different symbols on each card, and the lines connecting the symbols would be the cards needed. In this case, we would end up with a very simplified version with 3 cards, and 2 symbols on each card. If we wanted to add more symbols onto each card, then the diagram goes from looking like a triangle, to a grid of labeled points on a hypothetical finite plane. We still want to draw a line between all those points, and we can use the equation (n²-n+1) to tell us how many cards and objects we’ll need, with n being the amount of points/objects. In the case of Dobble, there are 8 objects per card, so the equation looks like (8²-8+1), which comes out to 57 cards. In Dobble’s case, however, there are actually 55 cards, not 57, as 55 is the amount of cards standard decks of cards are printed with.
