Dobble (Spot It!) is a card game where special circular cards use symbols. Cards have one symbol in common, designed for various gameplay options. Exploring the design process mathematically reveals no simple formula for the number of symbols and cards. Empirical play and examples show how to create decks with requirements for unique cards and symbol distribution. The concept can be visualized as matrices or geometrically as linear spaces. Triangular numbers offer efficient ways to create decks with maximum symbol repetition. The “Dobble numbers” allow for a maximum number of cards per symbol quantity. This complex problem offers both mathematical and geometric interpretations, with lots of room for exploration.
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