. "Zen of Sudoku is a Sudoku based computer game developed by Charlie Cleveland of Unknown Worlds Entertainment and released on June 20, 2006. Although the casual games market is not the intended direction of Unknown Worlds, or of Cleveland, Zen of Sudoku was produced in order to generate revenue towards funding Natural Selection 2, a sequel to the original Natural Selection modification for Half-Life."@en . "2006-06-20Z"^^ . .