You are sitting with one opponent at an empty, round table. Taking turns, you should place one euro on the table, in such a way that it touches none of the coins that are already on the table. The first player that is not able to place a euro on the table has lost. By tossing a coin, it has been decided that you may start.
Which strategy will you follow to make sure you are guaranteed to win?

Put the first euro exactly in the middle of the table. Place each next coin "mirrored" to the coin your opponent has just placed: draw an imaginary line from the last coin of your opponent, through the center of the table, and place your coin on that line, exactly as far from the center of the table as your opponent's coin. In this way, you are sure that you can always place a euro and that your opponent is the first one that can no longer place a euro.