Introduction

The name Sudoku(数独) is short for "数字は独身に限る" which is read, "Sūji wa dokushin ni kagiru", meaning "the numbers must be single", or "the numbers must occur only once". 

Sudoku puzzles can be intimidating and difficult to solve, but with a proper strategy, focusing on elimination, you can finish a Sudoku puzzle in mere minutes.

Strategies

The strategy for solving a puzzle may be regarded as comprising a combination of three processes: scanning, marking up, and analyzing. The approach to analysis may vary according to the concepts and the representations on which the puzzle is based.  A great resource for sudoku tactics is the Wipideia website, which you can view here.

Difficulty ratings

The difficulty of a puzzle is based on the relevance and the positioning of the given numbers rather than their quantity. Surprisingly, the number of givens do not reflect a puzzle's difficulty.

Many publications sort their Sudoku puzzles into three or five rating levels. An easy puzzle can be solved using only scanning; an intermediate puzzle may take markup to solve; a hard puzzle will usually take analysis.

  Recent popularity

In 1997, retired Hong Kong judge Wayne Gould, 59, a New Zealander, saw a partly completed puzzle in a Japanese bookshop. Over six years he developed a computer program to produce puzzles quickly. Knowing that British newspapers have a long history of publishing crosswords and other puzzles, he promoted Sudoku to The Times in Britain, which launched it on 12 November 2004 (calling it Su Doku).

For more information on Sudoku, instructions and tactics, please visit the extensive resources on the Wikipedia website.

Special thanks to Binny for his great work with the JavaScript powering this puzzle.