A queens book punishes a bad file in a way a sample board never shows. Your buyer judges puzzle forty-one, when the key places two queens touching at a corner in a book that promised they never touch, or a colour region is printed one cell short on the page so the region the buyer can see is not the region the key was solved against, or a board that finishes cleanly in two different ways because a second queen placement satisfies every row, column, and colour just as well. Queens — the coloured-region puzzle made a daily habit by LinkedIn's game, and a cousin, not a child, of the classic N-Queens problem — looks like the gentlest puzzle in the world: put one queen in each colour. It is a different contract, in five parts, each part exact. The standard puzzle prints a square grid — as many rows as columns — divided into exactly as many coloured regions as the grid has rows, one region per colour, each region a single connected shape. The solver's job is to place every queen using nothing but the rules. First, the count rule: there is exactly one queen per unit — never two, never zero — and the total number of queens equals the size of the grid. Second, the row rule: every row contains exactly one queen. Third, the column rule: every column contains exactly one queen. Fourth, the region rule: every coloured region contains exactly one queen, whatever its shape. Fifth, the no-touch rule: no two queens may touch each other, not horizontally, not vertically, not even diagonally at a corner. And tying it shut: exactly one solution, reachable by deduction alone, with no guessing. A board that breaks any part is not slightly harder. It is false as stated. A good queens book is a verified set: every row, column, and region on every page recounted against its own key, every pair of queens in the key checked for touching, and every board certified unique by an independent solve.
One warning belongs at the front, because it is the mistake this genre makes most often. Queens is not chess. In classic N-Queens, queens attack along whole diagonals, so two queens on the same long diagonal are forbidden however far apart they stand. In Queens, they are not. Two queens may share a diagonal freely as long as they are not adjacent — a queen at row two, column three and another at row five, column six sit on the same diagonal and are completely legal here, and illegal in chess. The only diagonal restriction in this puzzle is touching. A book that states the rule the chess way has made its own boards unsolvable as printed, because its keys will use the long diagonal the copy forbade. State the rule the Queens way, exactly, on the rules page and on the listing: one per row, one per column, one per colour, none touching — and nothing about attacking.
The book is the board set, not the sample grid
Buyers do not solve your listing image. They judge the book by whether each board can be finished as stated — every unit holding its one queen, no two queens touching, the key at the back agreeing with the page at the front. That sounds obvious until you look at how queens files are usually made. The common production shortcut is to place queens at random under the no-touch rule, draw coloured regions around the placement, and ship. Random placement guarantees a key exists — the generator is looking at it — but it guarantees nothing else. It does not guarantee the placement is the only one the printed regions allow; boards built backwards from a random placement routinely admit second and third completions, because a placement chosen first was never forced by the borders drawn afterwards. It does not guarantee the board can be solved without guessing; a solver who cannot see the key needs a chain of deductions the random board may never offer. And it does not guarantee the regions are honest: a region drawn carelessly can be so large and shapeless that its queen is barely constrained at all, or split in the drawing into two pieces that read as two regions of one colour.
A puzzle book is a promise about process, not just about answers. The app can afford a guess because the app restarts, and the daily game can afford a hint button. The book buyer who hits a forced guess on paper has no restart — the page is used, the pencil marks are down, and the failure reads as the book's fault, because it is. So the unit of quality is not the board that looks right. It is the board whose solve was walked, queen by queen, from its own printed page, by someone or something that was not allowed to peek at the key. If your production process cannot describe how each board was proven to have exactly one completion, the book is a stack of unverified claims with page numbers.
Sell the set for what it is: a graded run of boards, each with a stated grid size, each colour map printed on the page, each key at the back marking every queen. Say on the listing which sizes are inside, say that every board is solvable by deduction alone, and only say it if the verification below actually happened.
The contract, part by part
The count rule fixes the arithmetic of the whole board. A grid with eight rows holds exactly eight queens — no more, no fewer — and the same eight must also satisfy eight columns and eight regions at one each. The total is a solving tool, not decoration: late in a hard board, counting the queens still owed to a set of rows or regions is often the fact that closes the last deduction, and a key whose total disagrees with the grid size has broken the solver's final instrument. This is also what makes Queens a matching puzzle at heart — rows, columns, and colours are three sets of the same size, and every queen is one match claimed in all three at once.
The row and column rules are the board's frame. Each is local and absolute: a row with its queen placed is closed, and every other cell in it is empty — a fact the solver uses constantly. This is also the rule a sloppy layout breaks when a queen is nudged one cell during production and its row and column quietly change, or a key is pasted from a neighbouring board. Any edit to a queen, anywhere, changes one row, one column, and one region at once. There is no such thing as a small fix to a finished board — there is only recounting.
The region rule is what makes the puzzle itself. Regions are irregular — bent, snaking, sometimes a single row tall in one place and three deep in another — and each must hold exactly one queen regardless of shape. The region map is the puzzle's identity: change which region a single cell belongs to and you have made a different board, with a different solution or none. That is why a colour error is not a cosmetic error. A cell assigned to the wrong colour on the printed page means the buyer is solving a board that may have no solution at all, while holding a key to a board that was never printed. Regions must also each be one connected shape; a colour that appears in two separated pieces reads to the solver as one region with a queen owed, or as two regions with a queen owed each, and either reading breaks the count the page states.
The no-touch rule carries more weight than beginners think. Queens may not be adjacent in any of the eight directions, which means every queen in the key casts a shadow: the eight cells around it are all empty. This rule is the engine of the solve — placing one queen eliminates its whole neighbourhood, and a crowded corner can force placements three units away. It is also the rule keys break most quietly, because two queens touching only at a corner are easy to miss by eye in a grid of eight or ten. A single touching pair does not just break one board rule — it invalidates every deduction a solver made by trusting that the touching could not happen. And it is the only diagonal rule there is: adjacency, not attack, as the warning at the front states.
Exactly one solution ties the contract shut, and the no-guess promise rides on it. Two different placements can satisfy every row, column, and region count more often than intuition suggests, especially where a region lies almost entirely inside two rows and the queens can be swapped between them. When that happens, a buyer can solve the board "wrong" — every count satisfied, no queens touching — and still disagree with the key. That buyer did nothing wrong. The board did. Uniqueness is a property you test by solving, not a property you assume from generation.
Verification you can actually run
None of this needs trust. It needs three mechanical passes, run on the final pages, not on the generator's intentions.
First, the recount pass. Take the key — the queen placement alone — and recount the page from it: for each row, count the queens and confirm exactly one; for each column, the same; for each region, the same; then confirm the key's total equals the grid size. Then run the adjacency pass over the same key: for every pair of queens, confirm they are not neighbours horizontally, vertically, or diagonally — and confirm, just as deliberately, that no pair was rejected merely for sharing a long diagonal, because that is the chess rule, not this puzzle's. Any mismatch anywhere fails the board. This pass is pure counting and catches every layout accident, every nudged queen, every stale key left over from an earlier draft of the board.
Second, the independent solve. Solve the board from its printed page using deduction only — a unit whose remaining legal cells have narrowed to one forces that cell to be a queen; a placed queen eliminates its eight neighbours and every other cell in its row, column, and region; a set of units that together contain exactly the cells of a set of other units locks those queens inside both — and keep solving until the board is finished or no rule fires. A finished solve proves the board is guess-free along at least one honest path. A stalled solve with cells unplaced proves the opposite, no matter how the board was generated. Ideally a second solver, human or program, walks it independently; two different deduction paths reaching the same placement is the strongest practical evidence a small publisher can get.
Third, the uniqueness check. The independent solve doubles as a uniqueness test when it is run strictly: if deduction forces every queen, the placement it reaches is the only one deduction allows, and any alternative placement would have to contradict a forced step. Where a solver uses search, run it to completion and count solutions — the answer must be exactly one. Boards that fail are not repaired by adding a hint or redrawing one colour in the listing copy. They are regenerated or dropped, and the page count is whatever survives verification. A forty-board book that is forty times true beats a hundred-board book with six liars in it, every time, because the buyer meets the liars.
Run the same passes on the key pages themselves, and on the colour maps. Keys get transposed, mirrored, and pasted from the wrong board during layout more often than any other error in puzzle publishing, and region colours get redrawn one cell off when a page is reflowed. The map on the puzzle page, the map implied by the key's region counts, and the map in the production file must be the same map, cell by cell — and the region count on the page must equal the grid size, because a board with nine colours on an eight-row grid has broken the count rule before the solver places a single queen.
Difficulty is not just grid size
Listings love to sort boards by grid size and stop there, as if a 10 by 10 board were automatically harder than an 8 by 8. Size matters, but it is the bluntest of the levers, and a book graded by size alone will feel uneven to every buyer who works through it in order.
Region shape is where real difficulty lives. A compact, blocky region constrains its queen loosely; a long, thin, snaking region that crosses many rows and columns constrains it tightly, because the queen must sit somewhere along its length without touching the queens of the regions it winds between. Small regions are forcing: a region of one cell is a given queen printed as a colour, and a region of two or three cells has very few legal arrangements — the solver knows it, and an honest book uses those boards early, as teaching boards, not buried at the back as filler. The interaction is the genuine skill the expert buyer is paying to exercise — a region that lies inside exactly two rows forces those rows to take their queens from it in a fixed way, and that bookkeeping across overlapping rows, columns, and regions is the length and branching of the deduction chain, not the dimensions of the square.
The no-touch rule bends difficulty in a way size never captures. On a small grid the shadows overlap constantly, so a single placement closes much of the board and boards solve fast once the first queen falls; on a larger grid the shadows thin out, placements interact at a distance through rows and columns instead, and the solver must hold more open units in mind at once. Neither is simply "harder" — they are different pressures, and a graded book says which pressure each section leans on instead of pretending the page order is a difficulty curve because the grids grow.
Opening pressure differs from most puzzles, and listings should say so plainly. Queens prints no givens in its standard form: every board starts as a bare colour map, so difficulty is entirely in the map itself — how early the first placement is forced, and how long the solver works by elimination before it comes. A variant board that does print a starting queen is a different, gentler product, and it must be labelled as one, not mixed silently into a no-givens book. A book graded honestly says how its boards progress — by size, and by how interlocked the regions are — in an order a buyer can actually progress through. The buyer who wanted a gentle evening book and got a wall of interlocked boards does not leave a neutral review, and the expert who bought a book of loose, blocky boards leaves a worse one. Both were sold the wrong book by copy that only talked about size.
Print honesty: colours are the whole game
In Queens, the printed colour is not decoration on the puzzle. It is the puzzle. Every decision the solver makes is counting inside regions, so print quality is not cosmetic — a misread colour is a changed puzzle, and a changed puzzle is usually an unsolvable one.
Legibility starts with the borders between regions. Ordinary cell lines must be light enough to read as background; region borders must be unmistakably heavier, continuous, and checkable cell by cell against the key's map. If a border segment is faint, broken, or ambiguous at a corner where four cells meet, the solver will assign a cell to the wrong region and burn twenty minutes proving a board "broken" that was only misprinted. Proof the actual printed size, not the zoomed screen, and check every border junction on the proof. Colours support the borders; they must never be asked to replace them.
Colour itself is the trap in this genre, bigger here than in any neighbouring puzzle, because the region's name is its colour. Neighbouring regions printed in similar tints collapse into one apparent region on screen glare, on a cheap home print, and for the many solvers with colour-vision deficiency — for whom two of your carefully chosen colours may simply be the same colour. Design for those pages: adjacent regions must differ in lightness, not only in hue, so a greyscale print still separates them; borders must carry the whole map alone, with tints as decoration only; and no information may exist only in colour. If two regions cannot be told apart on a cheap greyscale print except by their border, that is correct — the border is the record. Say on the listing that the book is greyscale-safe and colourblind-safe only if you have proofed both, because in this genre that claim is a solving claim, not a design claim.
The solver's own marks join the system. A queens page is worked in three states — queen, eliminated, undecided — usually a drawn crown or queen mark, a cross, and a blank. Leave cells big enough to hold a small pencil queen and a tentative cross without crowding the neighbouring borders, and print the queen symbol in the key in a form that survives greyscale and cannot be confused with the elimination mark. Proof one full board, printed, worked in pencil, erased once, and worked again. That battered page is the product. The pristine PDF preview is not.
Licensing, provenance, and the errata rule
Puzzle books get bought by more than solo evening solvers, and the licence is part of the product. State, in plain language on the listing and inside the file, what each kind of buyer may do. Solo use: one buyer, their own boards, forever — say so. Family use: a household printing copies for its own table is the use most buyers assume; either grant it or say clearly that you do not, because silence here reads as permission followed by disappointment. Classroom use: a teacher printing a board for thirty students is republication at small scale, and it is either a tier you sell, a use you grant, or a use you forbid — pick one and write it down. Club and care settings — puzzle clubs, libraries, memory-care groups, waiting rooms — live on reprinting the same board for new hands; a licence that ignores them ignores some of this genre's best buyers. Republication — another seller, a newsletter, a worksheet site printing your boards for their audience — is the one use to reserve explicitly unless you are selling it, because a board set is trivially copyable and your only practical protection is that the terms were stated before the sale.
Provenance matters in this genre now, and honest sellers say it. State whether the boards were made by hand, generated and then hand-verified, or generated and machine-verified — and what "verified" meant in your process: the three passes above, or something less. Buyers of puzzle books have learned, from a flood of unverified generated books, to ask whether anyone ever solved the boards in the file. The seller who can answer precisely — every board deduction-solved from its printed page, every key recounted, uniqueness counted, not assumed — is answering the exact question the disappointed buyers of other books taught them to ask. Do not claim a hand-made book for a generated one, and do not claim verification you did not run; both lies are found out on puzzle forty-one, in public, in a review.
The errata rule is the promise that closes the sale. Name the failures that earn every buyer a corrected file, and mean the list: a row, column, or region whose key holds zero queens or two; two queens touching in a key, in any of the eight directions; a colour map on the page that differs from the key's map by even one cell; a region printed in two pieces, or a region count that does not equal the grid size; a board that forces a guess; a board with a second placement that satisfies every rule. Any one of those is not a difficulty spike — it is a broken board, and the fix goes to every buyer, not only the one who wrote in. State where corrections are announced and how a buyer gets the corrected file without buying again. A book with a real errata rule can survive one bad board. A book whose seller argues with the buyer who found it cannot survive its reviews.
Delivery is the last, quiet part of the contract, and it is where a download store earns its fee or does not. The buyer should get the file immediately, from a link that does not expire before they have had a fair chance to use it, with a way back to their purchase when the first download is lost to a full downloads folder. This is the part FileFreight exists for: flat-rate delivery for digital sellers, with expiring links you control and license keys where a product needs them, at a price that does not grow with every sale. Whichever delivery you use, test it as a buyer: buy your own book, on a phone, on home wifi, and print the file you actually receive — not the production file — before the listing goes live.
The launch checklist
Before the listing goes live, walk the book once, in order, as its harshest buyer:
- Rules stated the Queens way — one queen per row, column, and colour; no touching, even diagonally; long diagonals explicitly allowed — on the rules page and the listing, with no chess language anywhere.
- Every board recounted from its key: exactly one queen per row, per column, and per region, and a queen total equal to the grid size.
- Every key adjacency-checked: no two queens touching in any of the eight directions.
- Every board independently deduction-solved from its printed page, with no guessing, and its solution count confirmed as exactly one.
- Every colour map three-way consistent — puzzle page, key, production file, cell by cell — with each region one connected shape and the region count equal to the grid size.
- Print proofed at real size, in greyscale and for colour-vision safety: borders carrying the map alone, adjacent regions separated by lightness, cells big enough for a pencil queen and a cross.
- Licence and provenance stated in plain language, the errata rule printed in the book, and the delivered file test-bought and printed before the first real buyer arrives.
A queens book that passes all seven is a small, exact thing: a set of boards that are true as stated, in a file a buyer can print, solve, and trust. That is the whole product. Sell that, and the reviews write the next listing for you.
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