Wondering how is this game?

This is a very simple game at first, that surprise his friends Olly and Beth, Deep Sea Diver Doug, Ranger and others. Your mission is very simple at first: get 4 cards, face down. To see the image on them, you have to click on each card. For each book there will be two pieces, so everything you need to do is to group 2 by 2. So far everything is easy. Heaviness follows only after this first round, because you will get increasingly more books and should retain their place, because if you find the identical pair, to remember which was the first book! Becomes increasingly difficult as the number of books increases. The game is long, so you must hurry to find as many pairs of cards before time runs out. The more books you find, the higher your score will be. Practice your memory with this great game with submarine Olly and his friends!