I think you may be misunderstanding what I was suggesting. I was not saying you needed to give each person a unique card. What I was saying was that the different cards should contain the same numbers, but in a different order from each other.
Say there are two cards available to choose from, one about Aragorn and the other about Feanor. Aragorn has the B row of: 1 3 5 2 4, whereas the Feanor card has the B row of 1 2 3 4 5. (And so on with the other rows.) So when you call out B4, then both Aragorn and Feanor players are guaranteed a prompt that day. The chance element is that it won't occupy the same space on their respective cards, which means that it won't line up in the same way - the Aragorn card may luck out, and get a Bingo off the first eight prompts, whereas for Feanor they might bump around so it takes much longer. Obviously the more cards you have (up to a point of course) the more variety you get. But it wouldn't be any harder than making a card for each prompt. The main difference is that each day you're guaranteed to have a prompt available to you.
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Say there are two cards available to choose from, one about Aragorn and the other about Feanor. Aragorn has the B row of: 1 3 5 2 4, whereas the Feanor card has the B row of 1 2 3 4 5. (And so on with the other rows.) So when you call out B4, then both Aragorn and Feanor players are guaranteed a prompt that day. The chance element is that it won't occupy the same space on their respective cards, which means that it won't line up in the same way - the Aragorn card may luck out, and get a Bingo off the first eight prompts, whereas for Feanor they might bump around so it takes much longer. Obviously the more cards you have (up to a point of course) the more variety you get. But it wouldn't be any harder than making a card for each prompt. The main difference is that each day you're guaranteed to have a prompt available to you.