The main purpose of this Sudoku Trainer is to show how a Sudoku can be solved. However, the application can also act as a pure Sudoku Solver by switching off Training Mode.

New Sudoku
On startup the Sudoku Trainer shows an empty grid which subsequently can be filled either automatically or manually. To create a Sudoku automatically, press the NEW button and select the desired level. The level Difficult gives a Sudoku that can still be solved using logic only; Easy means some additional numbers are provided, and Impossible results in a Sudoku where some guesswork is needed to solve it. In Settings you can decide yourself how easy is Easy and how impossible is Impossible. To define a Sudoku manually, e.g. one copied from a magazine, just start with the empty grid and then use the keypad - number first, Sudoku cell to fill next - to enter the initial numbers.

Resolution in Training Mode
Once a Sudoku has been defined, press the Solve button repeatedly to see how the Sudoku Trainer solves the puzzle step-by-step. First the cells that can be resolved are marked in blue, next the cells that can be filled are actually given their correct number. Since it may not be possible to solve the Sudoku with logic alone, the Sudoku Trainer occasionally needs to make an educated guess of a cell\'s value. Only in this case the cell will first be marked in red instead of blue. If desired, e.g. when running the application as a Sudoku Solver, guessing can be switched off in Settings.

Training Strategy
At any time during the resolution process you can use the keypad to fill (or empty) Sudoku cells manually. This provides a great opportunity to train if first you let the Sudoku Trainer mark the cells can be resolved in blue and then you try to come up with the correct number yourself. A big help is the INV(erse) button, which switches to the view showing the possible values of each cell.
Nevertheless the number you enter may be wrong, leaving the Sudoku in an inconsistent state. You can find out about this by pressing the Check button, which tells you if the Sudoku is still solvable or not. In case it is not you can either enter a different number or use the undo button ❰ to retrace your steps; note that there is also a redo button ❱. Using Reset you can revert the Sudoku to its initial state.

Sudoku Solver
If you are not interested in the resolution process but only in its outcome, you can switch off Training Mode in Settings to run the application as a Sudoku Solver. If you also uncheck the option to Guess, the Sudoku Solver will go as far as it can using logic alone i.e. without guessing. At this point you can switch back to Training Mode to see which cell is a good candidate for guessing, or use the undo/redo buttons to browse the solution history, or try to solve or modify the Sudoku yourself manually. But of course you can also activate the Guess option again and let the Sudoku Solver present you with the final solution.