12x12 Queens Puzzle #203
Difficulty: easy. Place 12 queens on this 12x12 board so that no two share a row, column or color region and none touch — including diagonally. This puzzle has exactly one solution, and it has been verified solvable by deduction alone: the complete 21-step reasoning is written out below.
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Step-by-step solution for puzzle #203
What follows is a complete solve of puzzle #203, worked the way a person works it rather than the way a computer does. It runs to 21 deductions — 12 queen placements and 9 elimination steps that narrow the board between them. Each step names the rule that forces it, so nothing below is a guess, and the hardest idea required is the pairing argument on rows.
Techniques this board needs: last square in a region, region shadow, pairing argument on rows, region confined to one line, last square in a column.
Show the full walkthrough (14 steps) — contains the solution
Step 1. Only row 12, column 4 is still open in rose, and since each colour must take a queen, that settles it. That clears row 12, column 4, the rest of the rose region and every square adjacent to it — diagonals included.
Step 2. Sea green is down to 3 candidates in rows 10 and 11, columns 1 and 2, and they overlap enough to cover 1 square elsewhere. Cross those out without deciding anything about sea green itself.
Step 3. The teal region has 6 squares left, spread across rows 10 and 11, columns 5–8. You do not need to know which of them takes the queen: every one of those options attacks the same 1 square, so they can be crossed out now.
Step 4. Here is the pairing argument. The sea green and teal regions have no open squares outside rows 10 and 11 — 2 colours confined to 2 rows. Between them they must take one row each, in some order, so every other colour is shut out of all of them: 9 squares come off in one stroke.
Step 5. Khaki is down to 3 candidates in rows 8 and 9, columns 11 and 12, and they overlap enough to cover 3 squares elsewhere. Cross those out without deciding anything about khaki itself.
The board after step 5 — 1 of 12 queens placed. Step 6. All of the orange region's remaining squares (4 open squares) lie in row 9. Its queen therefore has to be somewhere on that row, which means no other colour may use it: 6 squares come off.
Step 7. Khaki cannot leave row 8 — every one of its open squares (2 open squares) sits there. That row belongs to khaki, so every square on it owned by another colour is dead: 9 squares in all.
Step 8. From here the board cascades. Keep alternating the region sweep and the line sweep and 5 queens fall out in order without any new idea being needed: pale yellow has one square left, so its queen takes row 7, column 5; red has one square left, so its queen takes row 6, column 8; slate has one square left, so its queen takes row 5, column 2; mint has one square left, so its queen takes row 4, column 12; khaki has one square left, so its queen takes row 8, column 11. After each one, clear that row, that column, the rest of the colour and the ring of neighbours before looking for the next. The last of them seats the queen on row 8, column 11.
Step 9. Amber cannot leave row 2 — every one of its open squares (2 open squares) sits there. That row belongs to amber, so every square on it owned by another colour is dead: 8 squares in all.
The board after step 9 — 6 of 12 queens placed. Step 10. Column 10 now has exactly one open square, row 2, column 10, in the amber region. Columns must each hold a queen, so that placement is forced. That clears row 2, column 10, the rest of the amber region and every square adjacent to it — diagonals included.
Step 11. Scan column 9 and only row 9, column 9 remains — a orange square. Every column takes a queen, so it takes this one. Cross out the whole of row 9 and column 9, the remaining orange squares, and the ring of neighbours around row 9, column 9.
Step 12. All of the sea green region's remaining squares (2 open squares) lie in column 1. Its queen therefore has to be somewhere in that column, which means no other colour may use it: 2 squares come off.
Step 13. Indigo is down to 2 candidates in rows 1 and 3, columns 3 and 7, and they overlap enough to cover 2 squares elsewhere. Cross those out without deciding anything about indigo itself.
Step 14. From here the board cascades. Keep alternating the region sweep and the line sweep and 4 queens fall out in order without any new idea being needed: column 3 is down to one square, putting a queen on row 1, column 3; blue has one square left, so its queen takes row 3, column 6; teal has one square left, so its queen takes row 11, column 7; sea green has one square left, so its queen takes row 10, column 1. After each one, clear that row, that column, the rest of the colour and the ring of neighbours before looking for the next. The last of them seats the queen on row 10, column 1.
The board after step 14 — 12 of 12 queens placed.
That completes the board: 12 queens seated, one in every row, one in every column and one in every colour, with no two of them touching. Notice that nothing in the sequence above required a guess — each placement followed from an elimination already on the grid, which is what “single solution, solvable by logic” actually means in practice.
About 12x12 Queens puzzle #203
12x12 puzzle #203 is rated easy. Twelve colored regions cover its 144 squares, and your job is to seat twelve queens so that every row, column and color contains exactly one — with no queen touching another, including diagonally.
Like every board on this site, #203 has been verified to have exactly one valid solution, and that solution is reachable by deduction alone. You never have to guess and then unwind; every queen can be justified by something already visible on the grid. What changes from puzzle to puzzle is where the first certainty appears and how long the chain of reasoning runs before the next one — and that is entirely a product of how these particular colors are shaped.
How the colors divide this board
From smallest to largest, the regions on puzzle #203 are: rose (1 square), khaki (5 squares), sea green (8 squares), mint (9 squares), slate (10 squares), red (10 squares), amber (11 squares), pale yellow (12 squares), teal (12 squares), orange (15 squares), indigo (19 squares), blue (32 squares). An even split would hand every color 12 squares, so the rose region is running 11 squares under that average while the blue region is the roomiest area on the grid with 32 squares.
That imbalance is the first thing to read, because every region takes exactly one queen regardless of how much space it owns. Rose has only 1 place to put its queen; blue has 32. The spread between them on this board is 31 squares, and the wider that spread runs, the more it pays to solve from the small end inward.
A region's outline can constrain it more than its size does. Here rose is the most solid, filling 100% of its 1×1 box, and red the most diffuse at 50% of its 4×5 box. Solid blocks give clean eliminations; diffuse ones spread across the board and stay open longer.
Region by region
The complete breakdown of each region on this board follows, ordered from tightest to roomiest. Skimming the spans first tells you where the board is crowded and where it has slack.
Rose occupies 1 square within rows 12–12, columns 4–4. It never leaves row 12, so its queen is locked to that row.
Khaki: 5 squares across rows 8–10, columns 10–12.
Sea green covers 8 squares, spanning 3 rows and 4 columns (rows 10–12, columns 1–4).
Mint occupies 9 squares within rows 4–7, columns 10–12.
Slate: 10 squares across rows 5–9, columns 1–3.
Red covers 10 squares, spanning 4 rows and 5 columns (rows 6–9, columns 6–10).
Amber occupies 11 squares within rows 1–4, columns 9–12.
Pale yellow: 12 squares across rows 7–10, columns 2–6.
Teal covers 12 squares, spanning 3 rows and 5 columns (rows 10–12, columns 5–9).
Orange occupies 15 squares within rows 9–12, columns 6–12.
Indigo: 19 squares across rows 1–5, columns 1–7.
Blue covers 32 squares, spanning 6 rows and 8 columns (rows 1–6, columns 3–10).
Where to start on this board
Begin where the choices are fewest. On this board that means rose, which owns just 1 square inside a 1×1 window running from row 12 to row 12 and column 4 to column 4. A queen is guaranteed somewhere in there, so every line that window crosses is under pressure from the very first move.
Because rose never leaves row 12, its queen must be in that row — and that instantly settles row 12 for everyone else. Sweep along it and X out every square that is not rose. Then look at which colors just lost ground: on a grid this size that one observation usually forces a second region within a move or two.
Nothing on this grid is pinned to one or two lines, which is why the opening takes patience. Scan the columns for one where only two or three colors appear — whichever region is forced into it claims that column outright. Chaining two of those observations is normally enough to break #203 open.
The tightest lines on puzzle #203
A quick way to find the next move is to count how many different colors touch each line. On this board, rows 1, 2, 3 and 11 are the narrowest, touched by only 3 colors. Column 1 is the tightest column, with 3 colors.
The fewer colors a line touches, the sooner it surrenders its queen. A row meeting just 3 colors has to be claimed by one of them, which pushes every remaining region into the other 11 rows. Row 10, meeting 5 colors, is the opposite case — the busiest line on #203 and the last one you should expect to crack.
Working through the middle game
The middle of #203 is where careless play costs time. Every queen you place kills a row, a column and the eight surrounding squares; if you do not mark all of that immediately, you will later "discover" a move that was available several turns ago. Mark first, then look.
With twelve queens to seat and twelve regions competing over 144 squares, keep two questions in rotation. Does any region now have exactly one open square left? That queen is forced. Does any row or column now have exactly one open square left? That queen is forced too. Alternating between the region view and the row-and-column view is what keeps a solve moving, and it is the clearest difference between players who finish 12x12 boards quickly and players who stall halfway.
Resist the plausible-looking queen. On #203 every correct placement has a stated reason behind it, and any move you cannot justify is a guess wearing a disguise. Backing out of a wrong guess on a single-solution board takes far longer than finding the real deduction would have.
Why puzzle #203 is rated easy
Ratings track how generous the opening is. On #203 you get two regions pinned to a single row or column, a smallest color of 1 square, a tightest row crossed by 3 colors, and a 31-square gap between the largest and smallest regions. Those four numbers largely explain the easy label.
The scale has nothing to do with maths or luck — every puzzle here is solvable by deduction and has exactly one answer. It measures reasoning depth: how many eliminations must stack up before a placement becomes provable. That depth is what separates a easy board from the rest.
If #203 feels harder than its rating suggests, the usual culprit is incomplete marking rather than a difficult deduction. Check that every queen already on the grid has its full cross of eliminations recorded — including the diagonal neighbours, which are by far the easiest to miss. More stalled solves come from one forgotten diagonal X than from any genuinely deep chain of logic.
Techniques that work well at 12x12
At 12x12 you are managing 144 squares, and holding the whole board in your head will not work. Split it into quadrants and solve locally. Most useful deductions on a grid this large are regional — a color pinched between two placed queens, or a band of rows that two regions must share. Trust the marks on the board over your memory.
One pattern is worth learning at every size, and it is available here. When two regions can only fit inside the same two rows, they must take one row each — which locks every other region out of both. The same argument works for columns, and for any matching count: three regions sharing three rows, four sharing four. Spotting these pairings turns a slow grind into a quick cascade, and on #203 the place to look for one is around row 1.
Here is a shape check that gives nothing away: when #203 is solved, 4 queens sit on the outer edge of the grid and 8 sit inside it, and no queen lands in a corner. A work-in-progress board that clusters its queens in one quadrant while leaving others bare is usually carrying a mistake.
How to play Queens
- The board is an N×N grid divided into N colored regions.
- Place exactly one queen (♛) in each row, each column, and each colored region.
- No two queens may touch each other — not horizontally, vertically, or diagonally.
- Tap once to mark a square with an X (where a queen can't go), tap again to place a queen, and once more to clear it.
- There is always exactly one valid solution. Use logic, never guessing, to find it.
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Questions about this puzzle
How hard is 12x12 Queens puzzle #203?
Puzzle #203 is rated easy. Its smallest color region holds 1 square, its tightest row is touched by 3 colors, and two of its regions are confined to a single row or column, which gives you a forced move early.
Does 12x12 puzzle #203 have only one solution?
Yes. Every puzzle in the 12x12 collection, including #203, has been verified to have exactly one valid arrangement of twelve queens, and it can always be reached by logic alone — no guessing or backtracking needed.
Where should I place my first queen on puzzle #203?
Start with the rose region — the most constrained color on this board, with 1 square spanning rows 12–12 and columns 4–4. Narrowing the smallest region first removes the most squares elsewhere on the grid.