Wer Beobachtet Besser?

A game for two that tests your powers of observation. There are two decks of cards, 40 cards per deck. The cards show a grid of 6 squares 4 of which are blank and two have either a red triangle or a red circle, or, indeed, a blue triangle or a blue circle. Each card will have a red and a blue example of the shape. Each player shuffles their deck and then gives it to his or her opponent. Interestingly, it is allowed to shuffle them with some cards the wrong way round. Not sure if this adds to the difficulty or not. At the word Go, both players start searching through the deck they have been given. The object is to find a matching pair. No two cards are identical so a pair is two cards that have the two shapes reversed, so to speak. For example, if a card had a Blue triangle in the top left corner and a red circle in the bottom right corner, the the matching card will be one thast has a red triangle in the top left corner and a blue triangle in the bottom right corner. The first player to match the 20 pairs available, wins