We've had a number of interesting head-scratching threads going lately, so here's a good logic puzzle for you. It is one of my favorites, and it is absolutely solveable, if you approach it from the right viewpoint.
Scenario: You are in a completely dark room. No light can enter, so it is so dark you cannot see a thing. You have nothing with you - no flashlight, no matches, absolutely nothing. You are sitting at a chair in front of a table. On the table is a deck of ordinary playing cards. The deck has been pre-arranged for you so that exactly 13 cards are face-up, while the remaining cards are face-down. The deck has been shuffled at random. Your task is to arrange the deck into two separate piles, so that each pile has an equal number of face-up cards. The piles do not have to have the same number of total cards in them, only the same number of cards facing up. You cannot see them, but you are otherwise free to move and interact with them however you see fit. You cannot tear them or otherwise damage them. You cannot feel any difference between the faces of the cards - they are absolutely ordinary playing cards.
Question: How do you accomplish the task of creating two piles with an equal number of face-up cards?