Sudoku Classic

Sudoku with the things that make a long puzzle bearable: pencil notes for the candidates you have not committed to, a check that tells you whether what you have written so far is still consistent, a hint when a grid has beaten you, and number entry straight from the keyboard instead of a mouse trip to a palette. The nine-by-nine rule needs no explaining and the difficulty settings go from a grid you can fill by scanning to one that needs a written note in every cell.