For the treasure hunt game, first of all we secretly decide on and write down the coordinates of the treasure. Our partner then has to guess the coordinates. We say "hot" if the guess is in the squares around the buried treasure - and we mark that with a red cube. We say "warm" if it's int he squares around those, marking this with a yellow cube. And "cold" if it's anywhere else.
We've also used created some coordinates quizzes using Hot Potatoes. Here's one of them: