Killer Sudoku Puzzle Volume 4 EBook contains total of 228 puzzles organized at 5 different difficulty levels (1-5) with all of their solutions. The instruction to play both in English and Spanish. Each individual puzzle has a single unique solution based on logical strategies and no "guessing" or "Trial & Error" are required. Please note that this is a DRM FREE EPUB format EBook and you should be able to print your puzzles or solve them on any device that allows drawing or typing text over an image (EXAMPLE: Paint Application with the *.JPEG, *.GIF, *.PNG image) and it is not an interactive game.