Once upon a time a young boy named Johnny learned how to play chess. He didn't have frequent opportunities to play, but he acquired a few chess books and played occasionally with friends. Once he visited his great-uncle Clark . Clark had a truly remarkable library, the likes of which Johnny had never seen. Johnny hoped to have a library like his great-uncle some day (a wish which has never come quite true). Clark had a number of books about chess, and generously gave several to Johnny. Johnny read the books and practiced the openings and endgames shown in them. Johnny never forgot Great-Uncle Clark! A few years later Johnny's family moved. Across the street lived a family with twin daughters a year younger than Johnny. The girls' father (we'll call him Mr. W) was a good chess player, and Johnny finally had a regular chess partner. Johnny couldn't beat Mr. W in those days; Mr. W was a patient chess partner and gave Johnny valuable pointers about the art of chess. At