being something of a research mathematician, which I hadn't done before." Eventually he wrote four papers with Erdős, giving him an Erdős number of 1, and solved one of Erdős' problems. Guy was intrigued by unsolved problems and wrote two books devoted to them. Many number theorists got their start trying to solve problems from Guy's book Unsolved problems in number theory. Guy described himself as an amateur mathematician, although his work was widely respected by professionals. In a career that spans eight decades he wrote or co-authored more than a dozen books and collaborated with some of the most important mathematicians of the twentieth century. Paul Erdős, John H. Conway, Donald Knuth, and Martin Gardner were among his collaborators, as were Elwyn Berlekamp, John L. Selfridge, Kenneth Falconer, Frank Harary, Lee Sallows, Gerhard Ringel, Béla Bollobás, C. B. Lacampagne, Bruce Sagan, and Neil Sloane. Over the course of his career Guy published more than 100 research papers in mathematics, including four with Erdős. Guy was influential in the field of recreational mathematics. He collaborated with Berlekamp and Conway on two volumes of Winning Ways, which Martin Gardner described in 1998 as "the greatest contribution to recreational mathematics in this century". Guy was considered briefly as a replacement for Gardner when the latter retired from the Mathematical Games column at Scientific American. Guy conducted extensive research on Conway's Game of Life, and in 1970, discovered the game's glider. Around 1968, Guy discovered a unistable polyhedron with 19 faces; no such construct with fewer faces was found until 2012. As of 2016 Guy still was active in conducting mathematical work. To mark his 100th birthday friends and colleagues organised a celebration of his life and a tribute song and video was released by Gathering 4 Gardner. Guy was one of the original directors of the Number Theory Foundation and played an active role in supporting their efforts to "foster a spirit of cooperation and goodwill among the family of number theorists" for more than twenty years. Chess problems From 1947 to 1951 Guy was the endings editor for British Chess Magazine. He is known for almost 200 endgame studies. Along with Hugh Blandford and John Roycroft, he is one of the inventors of the GBR code (Guy–Blandford–Roycroft code), a system of representing the position of chess pieces on a chessboard. Publications including EG use it to classify endgame types and to