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Very nice and mathy. It would be nice if the order of the hands were shuffled. The solution to any given problem is too often directly derivable from the one before it because the hands are too similar. The term "turn" is a little confusing. I would use "hand" since that is clearer within your playing card metaphor.
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to cche: for most cases, there is only one choice for the final operator, so I make it auto selected. If there are many players don't like this, I will change the design.