I suspect this to be between difficult and impossible to do as CSS doesn't have any way of knowing the past; I don't think there's a way to remember moves as su

I suspect this to be between difficult and impossible to do as CSS doesn't have any way of knowing the past; I don't think there's a way to remember moves as such. All I can think of is to somehow have an #anchor for each possible configuration and to select the visible links for the next move depending on which anchor is active. This isn't really any more elegant than having a separate page for each configuration; you're not encoding any actual logic in the CSS, just the graph of possible outcomes.