The puzzle doesn't have to come from here
Every board on this site carries its own hint button, so a puzzle of ours can already explain itself. This bench exists for everything that isn't ours: the newspaper grid abandoned over breakfast, the magazine page with three corners done, the phone app that will sell you the answer but won't say why. Copy the position in — or paste it, if it already lives as text — and the full ladder of human techniques is held up against it, each rung lighting when it has a genuine deduction to offer.
The bench takes classic 9×9 grids only, and that is a choice rather than a gap. A classic position travels as eighty-one characters, which is why it fits in a paste box and a link. A killer puzzle is mostly its cages and a jigsaw mostly its regions — layouts that would need drawing tools, not a text field — and both of those boards already reason about their own geometry when you press their hint buttons.
Named moves, not answers
There is a real difference between a tool that fills a square and a tool that tells you why a square can be filled. Read the digit and the puzzle is over; you are a spectator to the rest of it. Read the reasoning and you keep the puzzle — plus one more piece of vocabulary for the next one that fights back. So the bench never volunteers a solution. It finds the pattern, shades the squares involved, describes the logic in a sentence, and leaves the applying to you.
Being stuck rarely means the logic has run out. It means your list of moves has.
That reframing is the whole point of the ladder display. When nothing you know works, the lit rungs show you exactly which ideas do — and their level tells you how deep the water is. A position that only answers to grid-spanning patterns is a different afternoon from one with a hidden pair sitting in plain sight, and knowing which you are facing is worth more than any single digit.
Getting a printed grid in without a typo
Type it the way you read it
Click the first square and use the keyboard: digits drop in, arrows walk the grid, and working left to right along each row matches the way your eye scans the page, which is the entry order least likely to smuggle in a mistake. Thirty seconds of typing is normal for a grid with a typical number of clues. If the puzzle exists digitally, the paste box underneath is faster still — eighty-one characters with dots or zeros for empties, the format nearly every sudoku site and book archive uses.
The checker runs while you type
Transcription errors are the quiet ruin of helper tools, because a grid with one wrong given produces confident nonsense. The bench guards this three ways. A digit that collides with its row, column or box is flagged the moment it lands. A grid whose digits are individually legal but jointly impossible — the classic symptom of a mistyped clue — is caught by the solver counting completions and finding none. And a grid with too little in it yet is reported as having several ways to finish, which matters more than it sounds: one deduction on the ladder leans on the promise of a unique solution, and the bench refuses to use it until that promise is proven.
Two ways to lean on the ladder
Ask for the gentlest step
One button surveys every rung and opens the easiest that fires — the same easiest-first order the hint buttons on our own boards use. Applied repeatedly it will walk a puzzle as far as the standard techniques reach, with each step named and shaded as it goes. Digits the ladder places are inked in indigo, so what you brought and what the bench contributed stay visibly separate, and every step lands in a running list you can undo back through.
Or hunt one technique deliberately
The other way round is better practice. Convinced there's an X-wing hiding somewhere? Search for it yourself first, then press its rung to check — the bench either shades the one it found or says plainly that none exists, which is how you learn to trust a negative. The cross-out mode helps here: it lets you remove pencil marks by hand, the way your paper margins already look, so the position on screen matches the position in your head. Cross out carelessly, though, and the bench reasons from your mistake — it trusts your eliminations exactly as far as you should trust them.
Three rungs stay dark on purpose
Our full registry holds nineteen techniques, and this page shows sixteen. The Law of Leftovers only exists where regions are irregular, diagonal interactions need an X grid's two extra houses, and the knight interaction needs squares that forbid each other without sharing a house at all — on a classic bench none of the three could ever light, so none is listed.
Measuring someone else's "fiendish"
Every publisher grades to a private ruler; one paper's diabolical is another's Tuesday. The measure button re-solves your position with the whole ladder and reports what it actually took: the hardest technique needed, how many times each rung fired, and how many deductions remain between here and the end. It is the same instrument that grades every puzzle we serve, pointed at a grid we didn't make.
Difficulty is a claim. From this bench, it becomes a measurement.
The verdict is calibrated against our own levels, so it translates directly: a puzzle that tops out at a naked triple would sit on our hard board, one demanding a swordfish belongs with evil, and a position the whole ladder stalls on has crossed into chain-and-conjecture territory. If you'd rather feel the scale than read about it, the worked example under the board loads one of our Expert grids paused at the exact move where the singles run dry — eleven rungs light at once, which says more about what "stuck" really means than any paragraph here.
A position also fits in a link — the copy button writes one — so a half-finished grid can travel to a friend, or to tomorrow. And if what you want is puzzles built honestly to a stated standard rather than a second opinion on somebody else's, the main board is where ours live.