What Counts as a Corner in a Logic Puzzle?

If one clue quietly ruins more solves than any other, it’s the corner clue. “The gardener is not in a corner” sounds obvious — until you realise most solvers have the wrong definition of “corner” in their heads. Get it right and these clues become some of the most powerful on the board.

The definition

A corner is any square where a horizontal wall and a vertical wall meet. That’s it. A wall is any edge where a room ends — either the outer boundary of the grid, or the line between two different rooms.

The crucial consequence: corners are not just the four corners of the whole grid. Every room has its own corners, tucked inside the puzzle, wherever that room’s walls turn. An L-shaped room can have several.

Corner vs. corridor

Two parallel walls do not make a corner. A square with a wall on its left and right — a corridor cell — is not a corner, because both walls run the same direction. You need one horizontal wall and one vertical wall meeting at the same square. Think of it as an L, not a pair of tram tracks.

Why it matters so much

“Not in a corner” can eliminate a surprising number of squares at once — often across several rooms — which is exactly the kind of wide cut that kicks off a cascade of placements. Solvers who under-count corners leave that power on the table; solvers who over-count (assuming only grid corners) make false eliminations and end up stuck or guessing.

Once corners click, the rest of the clue vocabulary is easy. The companion guide breaks down “beside”, “alone” and the others.