Futoshiki

How to play

Fill the grid so every row and every column holds each number exactly once. The clues are the signs between squares: each one says which of the two it sits between is the larger. There are no regions and no arithmetic, and a well-made board never needs a guess. What makes it read differently from a Sudoku is that a sign tells you about a gap rather than about a square, and gaps chain — a run of signs all pointing the same way pins its ends long before anything in the middle is known.