Futoshiki
Greater than, less than: the signs guide every digit.
Place one digit in each cell with no repeats in any row or column, respecting every inequality sign between neighbouring cells.
- Players
- 1 player
- Length
- 3 to 30 min
- Solo
15 days of full access, no account · No download
How to play
Goal of the game
Fill the grid of n × n cells with the digits 1 to n: each digit appears only once in every row and column. The signs between neighbouring cells must be respected: the point of the chevron always faces the smaller cell.
Controls
- Tap a cell, then a digit on the pad (or type it on the keyboard).
- Notes (N key): pencil in candidates; Auto notes fills them in for you.
- Backspace or 0: erase. Arrow keys: move. Ctrl + Z: undo.
Techniques
- Bounds: a cell smaller than its neighbour cannot exceed that neighbour’s maximum, and vice versa.
- Chains: a run of signs pointing the same way forces extreme values (the bottom of a chain of four cells is at most n − 3).
- Pairs, triples, X-Wing as in Sudoku, on rows and columns.
- At the Devilish level, you sometimes have to assume a value and see that it leads to a contradiction.
About the AI
The generator starts from a random Latin square and all possible signs, then removes signs and digits for as long as the grid stays solvable with the techniques of the chosen level. The uniqueness of the solution is checked by an exhaustive search. Hints and the Solve button use a logical solver that explains each deduction in plain language.
Difficulty levels
- EasySmall, generous grid: singles and inequality bounds.
- MediumMinimal grid, solvable with singles and inequality bounds.
- HardNeeds naked or hidden pairs.
- ExpertNeeds triples or an X-Wing.
- DiabolicalNeeds you to push a hypothesis all the way to a contradiction.
