Queens puzzle: rules and solving techniques

How to play

1. The board is a square grid split into colored regions, as many regions as rows. Thick walls outline each region, so you can tell them apart without relying on color.
2. Place exactly one queen in every row, every column and every colored region. An 8×8 board needs eight queens.
3. Two queens may never touch, not even diagonally. All eight cells around a queen stay empty.
4. Tap a cell once to mark ✕ (no queen), a second time to place a queen and a third time to clear it. Drag across empty cells to mark several ✕ at once.
5. Queens that share a row, column or region, or that touch, turn red straight away. With Auto ✕ on, every cell your queens rule out shows a faint ✕.
6. The board is solved when all queens are placed with no conflict. Every board has exactly one solution that you can reach by logic, without guessing.

Controls

Mouse or touch

Tap a cell to cycle it: ✕, queen, empty. Drag across empty cells to mark them ✕. Undo takes back the last change and Clear empties the board.

Keyboard

Arrow keys move between cells; Space or Enter cycles a cell. Q places a queen, X marks ✕ and Delete clears. U or Ctrl+Z undoes.

Score and progress

There are no lives and no scores. A timer runs from your first tap and pauses with Pause or when you leave the tab. Your solved count and fastest time for each size, your daily results and your streak are saved in this browser when local storage is available.

Tips

• Mark the eight cells around every queen as soon as you place it, or keep Auto ✕ on.
• A region of one cell is a free queen. A region of two adjacent cells still rules out the cells that touch both.
• Count rows and regions together: if three regions live entirely in three rows, every other region must find its queen elsewhere.
• If a queen turns red, undo rather than clear. The conflict tells you which rule broke, and the earlier marks stay useful.

Stuck on a board? The game opens your current board, queens and ✕ marks included, in the Queens Puzzle Solver, which shows the next logical step and the rule behind it.

How to solve a Queens puzzle: five techniques

You never need to guess. Each step below either places a queen for certain or rules out cells; repeat them until every row has its queen.

1. Last open cell. When a row, a column or a region has only one cell left that is not ruled out, its queen goes there. Then mark ✕ on the rest of that row, column and region, and on the eight cells around the new queen.
2. Region inside one line. When every open cell of a region lies in a single row (or column), that region’s queen will fill the line. Mark ✕ on every other cell of that row or column. The same works the other way round: a row whose open cells all sit in one region claims that region.
3. Neighbor exclusion. Look at a small region. If a queen on some cell would touch, or share a line with, every open cell of that region, the region would be left empty, so that cell is out. Two-cell regions side by side make this very common.
4. Groups of lines. When two regions fit only inside the same two rows (or columns), those two lines belong to them. No other region can use those rows, so cross off everything else in them. The same counting works for three regions in three lines.
5. Start small, then check. Begin with the smallest regions and the corners, and recount open cells after every queen. Turning on Auto ✕ keeps the ruled-out cells visible so the single remaining spot stands out.

Why every board here has exactly one answer

Each board was generated by placing N non-touching queens, growing N colored regions around them at random, and keeping the board only if an exact search finds exactly one way to place the queens. A second check makes sure the four rules above, applied in order, reach that solution from an empty board. That is why a board here never needs trial and error, and why the solver can explain every step.