Use this workpad for working on Sudoku puzzles. To enter a puzzle:

Click on Input Puzzle String and enter the values for the 81 squares, left to right, top to bottom. Use periods or zeros for empty squares, e.g., ..846..5.....

Each empty square shows the numbers that can go in it. To choose one, double-click it. To hide a number you have deduced can't go in a square, single-click on it. Click on it again to reveal it.

Click on Do Singleton Squares to automatically fill in all squares with only one possible value. Click on << or >> to undo or redo a choice.

If you get stuck, I recommend Andrew Stuart's most excellent Sudoku Solver. Just click on Try Sudoku Solver to set up Andrew's solver with your current board.