Build a calcareous masterpiece without noticing that you’re practicing addition with another marine polyp. Object: To use all of your corals in building a reef. You Need * Two decks of poker cards, ideally with identical backs. * Alternatively, you could use a bag of number tiles, like the ones available in the children’s section of department stores or a teachers’ supply store. Take four nines from the deck and lay them out face-up as seeds for four stacks. Taking turns, each player attempts to get rid of all of his 'corals' (cards/tiles) by placing any number of corals on top of one stack such that the sum of the corals he places equals the number that had been on the top coral at the beginning of his turn. Corals are worth their pip value, except for face cards which are worth negative points. The first one out of corals wins.