Queen Grid: check the lines before counting the queens
A six-row teaching position explains diagonal conflicts, useful row boundaries and why an apparently safe placement may still need to be undone.
Worked examples use the Standard board unless a different size is stated. Hard and Expert may change the board dimensions or amount of information to track.
Give each placement three checks
A queen occupies one square but rules out several lines. Before adding another, check its row, its column and both diagonals. The diagonals are easy to overlook because they do not share a printed row or column number. Two squares share a diagonal when their row difference equals their column difference.
Conflict markers identify attacks in the arrangement you have already made. They do not label every empty square that would be useful later. An unmarked board is therefore a description of the present position, not a promise that your next rows can all be filled.
Read a small six-row example
Number rows from top to bottom and columns from left to right, starting at one. Put a queen at row 1, column 2, then consider row 2. Column 2 is blocked vertically. Columns 1 and 3 lie one step diagonally away, so those squares are blocked too.
Row 2, column 4 avoids those three restrictions. With queens at 1,2 and 2,4, row 3, column 6 is also safe: it shares neither column, and its diagonal differences do not match either earlier queen. This is a teaching position, not an automatic instruction for every board size.
Separate a row choice from its consequences
Working one row at a time makes omissions easier to spot. For each new row, list columns that survive the queens above it. If none survive, placing a conflicting queen does not create a new route. Reconsider a previous row instead of treating the conflict marker as a temporary detail.
Try changing the most recent choice first. Earlier queens are then a stable reference while you compare alternatives. This is a practical search discipline, not a restriction imposed by the controls: you may remove any existing queen by selecting its square.
Use Undo to compare complete attempts
Suppose two columns appear possible in the same row. Choose one, continue until you learn something useful, then use Undo to return through those placements. Notice which later row became impossible. A rejected branch is informative when you can explain the lines that caused the blockage.
Removing a queen also counts as an editable action, so Undo can restore a removal. Restart is broader: it clears the whole fixed board. There is no need to request a random layout, because the challenge for a selected size begins with the same empty grid.
Count only after the lines agree
The final condition combines quantity and geometry. Six queens on Standard are insufficient if any attack remains; five safe queens are also incomplete. Hard and Expert require eight and ten respectively. The game confirms completion only when the required number is present without shared rows, columns or diagonals.
Different complete arrangements can satisfy those conditions. This guide gives a way to inspect and revise a position, rather than a claim of a unique answer or a universally best placement order. Carry the same three checks into each larger board, while allowing more room for backtracking.
An original guide for this site's implementation. Found an unclear step? Let us know.