I like it the way it is. When it is a team game, I know the time slots when I need to plan to play, and when I can relax. IF I could set it to a countable game each time, I would feel increased pressure to play every two hours (bad for my sleep!) and the increased pressure of deciding which level of difficulty to choose. I am often surprised to find that my top score of a day when I was playing came from one of the difficult sets, not the intermediate ones that seem easier. I haven't taken the time to actually analyse it, but I suspect there is a time factor involved, meaning that the same time for getting them all correct gets a better result in the difficult game. Whatever the reason, having the extra dimension of choosing a difficulty level would make the game less enjoyable for me.
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(Editor in Humanities, Religion, Literature and For Children)
That's all, folks!