Welcome

Sudoku Explainer tries to cater for everyone who's interested in Sudoku puzzles, from gromets up to Western European university professors, but the focus is on hard (ie beyond a humans ability to solve) puzzles. The Solving Techniques herein have been described as "old school". That's fine with me.

If you're having trouble reading this then right-click in this hint details area to copy the HTML to the clipboard, paste it into temp.html and open it in your browser, which will allow you to enlarge the font. The hints TreeView (upper right) also has this right-click to copy feature. If the GUI fonts are too small for you then all I can offer is Windows magnifying glass, it's in accessibility settings. Sorry I can't be more help. GUI's just s__t me.

Sudoku Explainer shows you how to solve any Sudoku puzzle step by step, explaining each solving technique as it's applied. It also allows you to get all the hints (ie solving techniques) that can be applied to a puzzle, and to apply any of them (singularly or multiply).

Sudoku Explainer solves "the worlds hardest Sudoku puzzle" according to conceptis.com in 125.610 seconds with all A*E's enabled and unhacked on my i7 (see the Solving techniques section below for my config preferences):

  8..........36......7..9.2...5...7.......457.....1...3...1....68..85...1..9....4..
  (copy-and-paste this puzzle (Edit menu ~ Paste grid) then press F9 to analyse).
  
If you just want a bit of help with a puzzle then the first step is punching it in. Either left-click on the small grey digit (the maybe) so set the cells value, or with the keyboard: navigate to cell-to-set with the arrow-keys and then press the value key (1..9).

If you stuff-up then Ctrl-Z goes back one step at a time. Spacebar, delete, backspace, or 0 (zero) all clear the selected cells value. Ctrl-Y does a redo.

When you've got your whole puzzle punched-in do NOT forget to Ctrl-S for save BEFORE you start solving it. A reload might be handy. I always forget to save. Sigh.

If you get stuck press F5 for a hint. To apply that hint and get the next one just press enter.

Anyway, that's probably enough to get you started. Have fun with it. Come back and read the advanced stuff when you get bored.

Advanced Stuff

More "advanced" users will want to remove maybes (the cells potential values). That's those small grey digits in the empty cells. To do that just right-click on the small grey digit. With the keyboard: select the cell with the arrow keys and then Ctrl-digit to remove/restore the maybe. You can't restore an illegal maybe.

You'll notice that Sudoku Explainer enforces the basic rule of Sudoku: "There will be one-and-only-one instance of each value in each region". So when you punch a 7 into a cell then all the 7's disappear from the other cells in it's box (the 3x3 thingummy), row, and col (column).

Sudoku puzzle books are all a bit soft (on an expert scale) so just seeing the maybes could get you unstuck; but if not then press F5 to find a hint. Then you can just press enter to apply that hint and get the next one, and the next, and the next... Sudoku Solvered! Too Bloody Easy!

The following "frequently used" buttons are arranged along the bottom of the form (I never use them. I do hope they still work):

Some other stuff also worth a mention:

I should also mention the LogicalSolverTester, which solves a MagicTour (.mt) file containing multiple (upto 9999) puzzles, just to see how quickly we can do it, and optionally (with Log.MODE=VERBOSE_5_MODE) what hints apply to each puzzle, which is how I find test-case puzzles.

Try the RecursiveSolverTester if what you're really after is solving Sudoku puzzles quickly. It's Knuth's (IIRC) recursive algorithm, plus the Four Quick Foxes, plus my Cell.set(AUTOSOLVE). It did top1465.d5.mt in about a second, which is tantamount to FTL, IMHO. All I did was tune it up a bit.