This game starts with some noughts and some crosses. You and your opponent take turns removing two shapes, and adding a new one according to this rule: if the shapes are identical, add a nought; otherwise, add a cross. When only one shape remains, you win if it's a nought, and lose if it's a cross.
Is there a winning strategy for any of the players? How should you play?
(In reply to
re: Solution by Charlie)
Yes, you are correct. I wasn't sure how to interpret the rules myself - the last sentence of the problem statement does not make clear who "you" refers to. In any case, it remains that this game has no strategy - so that the answer to the puzzle doesn't change, strictly speaking.