What is the no-room test in Queens?

Pick an open tile and imagine a queen on it. If that queen would rule out every remaining open tile of some other row, column or colour, then that unit would have nowhere to put its own queen, which is impossible. So the tile you picked can't hold a queen, and you can cross it out.

An example

queenalready ruled outplay herecross out nowtiles to look at

A queen on the crossed tile would rule out every open tile in row 2, leaving it with nowhere to put its own queen. So that tile can't hold a queen.

Is this guessing?

No. Guessing is placing a queen and hoping. Here you look exactly one step ahead and reach a certain conclusion: the tile is impossible. You never have to place anything you might take back.

How to spot it

• Find the row, column or colour with the fewest open tiles, usually two or three.
• Look for a tile outside it that touches or lines up with all of those open tiles at once.
• Tiles diagonal to a two-tile colour are the classic case: a queen there would touch both.

Related techniques

Use this after the counting techniques: a colour trapped in one line and pairs and triples are quicker to check.