What intrigues about sudoku is not how to solve it. Given time, anyone can improve their pattern recognition skills and shorten the time to complete sudoku. What fascinates me is how many numbers (or hints) must be displayed in each sudoku puzzle before the number combination for that puzzle can be considered unique; how to reduce the number of hints by strategically planning their placements in the sudoku puzzle; and how to classify the difficulty of each puzzle (how on earth do they derive the estimated solution time?).

I guess what amazes me are the people who draw up the sudoku puzzles in the first place.