See the Wednesday Problem’s vague rules here.
Some games again. According to Sam, from whom I heard this riddle, it divides people into cathegories i) those who realize the answer immidiately and ii) those who think quite long about it.
The game board is a round table of diameter d>0. The two players place one after another coins of diameter s>0 on the table. The coins cannot overlap. If there is no place left on the table to place the next coin, the player whose turn it is, loses. Which one of the players has a winning strategy?