(a) Extreme Sudoku puzzles are usually designed for defying our logical reasonings, so we can counter with the Principle of Least Choice (PLC) by selecting the least likely one when facing the multiple choices of our next move. The harder the puzzle, the more often PLC is recommended to be used; (b) This is the first of many volumes of the condensed collection of my previous lecture series 0-5 for promoting the natural Sudoku (Sudoku with 17 givens). Accordingly, I plan to give a series of

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... res, each containing 1 puzzle with illustrative solution and 49 practice puzzles with annotated solutions. All (approximately 5000) natural Sudoku puzzles can be downloaded from Gordon Royle list; (c) The minimum of 17 givens is required for a Sudoku puzzle to not having multiple solutions. There are no extra givens that puzzle makers can maneuver to design extremely hard Sudoku. Therefore, we shall not use PLC at all for our insuing lectures; (d) The purpose of my lectures is for you not to waste time in playing Sudoku. In addition to the introduction of efficient methods, we most importantly screen out those puzzles with multiple solutions in the collection of practice sets for you; and (e) The lectures are presented in the power point format, convenient for any interested instructors to use. I sincerely hope some of you could join me for the completion of 100 lectures of the natural Sudoku, which would be a precious asset of the mankind thanks to Leonhard Euler's Latin Square.