Creedence Clearwater Revival was a rock band.
Zen of Sudoku is a Sudoku based computer game developed by Charlie Cleveland of Unknown Worlds Entertainment and released on June 20 , 2006 .. Unknown Worlds Entertainment. Unknown Worlds Entertainment. Sudoku. Sudoku. computer game. computer and video games. 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 .. Sudoku. Sudoku. casual games. casual games. Natural Selection 2. Natural Selection 2. Natural Selection. Natural Selection ( computer game ). Half-Life. Half-Life ( video game ). Cleveland cites casual games development as a `` last option '' for funding this sequel , having been unwilling to sacrifice control of the company to external investors .. casual games. casual games. The game features automated generation of sudoku puzzles at varying difficulty levels as well as a hint and tutorial system , which not only teaches players the basics of the game , but also teaches them further advanced strategies .. sudoku. sudoku. Currently , the game is available for purchase directly from the website at http : /  / www.zenofsudoku.com /  , and on Valve Corporation 's Steam platform .. Valve Corporation. Valve Corporation. Steam platform. Steam ( software ). A flash based web version is also in production .. flash. Adobe Flash