In this talk, Dr Huw Lloyd will report on recent work that has been done on solving Japanese Pencil Puzzles with nature-inspired algorithms. Many (if not most) of these puzzles belong to a class of problems which is known to be computationally intractable. In this talk, Huw will discuss how the initial work on solving Sudoku with Ant Colony Optimization has broadened into a general study of how these puzzles may be used to study the properties of existing algorithms, or as a playground for developing new computational intelligence techniques.