mmm to clarify a bit more:
the blue dot indicates the position where black just moved. and the 4 red crosses indicate all the legal moves available to white.
[ some reversi strategy/detail: when black just moved at c5, this kind of move is called "checker-boarding". ie , black has just "checkerboarded" white. the idea is that black has just "split-up" white's seeds "all over the place" . which is not good for white. so, in return, white has to regain control of the board. the correct/recommended move for white will be to play accordign to "flatness". and according to the <theory of flatness>, when "flatness" is achieved no matter what positioning of the seeds on the board, there is a distinct partition of the black n white seeds into distinct "localised groups". and when flatness exists anywhere on the board, that part is tricky to play..coz "flatness" is a double-edged sword...

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