This puzzle/game is played with groups of people, in which some of the participants know the rules, and others are trying to figure them out.
All players must sit in a circle, facing each other. Then one person who is familiar with the rules starts by pointing at another and saying "cross-cross", "cross-parallel", "parallel-cross", or "parallel-parallel". After that the person who got picked must choose another one and guess which one of the four expressions above he must say. If he gets it wrong, he gets corrected, and then the next person continues. The game ends when everyone finds out what the secret is.
To play this puzzle game with your friends, at least one of you must know the secret rules and solution, which are explained below. Just keep in mind that whoever learns the rules, will lose the enjoyment of figuring them out by himself.
When you point at somebody, you say "cross-cross", if yours and the other person's legs are crossed, "cross-parallel", if yours are crossed and the other person's are parallel, etc.