Fill the grid so every row and column holds each number once, while obeying every less-than and greater-than sign between the cells.
Each row and each column must contain the numbers 1 to N exactly once, like a Latin square. The inequality signs printed between neighbouring cells must also be satisfied: the open end always points to the larger number. Use the given numbers and the signs to deduce the rest.
Futoshiki is Japanese and recent — developed by Tamaki Seto in 2001. Its name, 不等式, simply means "inequality", which is an unusually literal description of what the puzzle does.
The grid is a Latin square: each digit appears once in every row and column. What replaces sudoku's boxes is a set of greater-than and less-than signs printed between adjacent cells, each one a constraint that must hold in the finished grid.
That single change alters how it is solved. Sudoku is reasoning about where a digit can go; futoshiki is reasoning about order — chains of inequalities that pin down a cell not by what it is, but by how many values must sit above and below it.
Futoshiki is a logic puzzle that crosses a Latin square with inequality constraints. This is an original, free browser version with daily and practice puzzles, notes, and hints, no download or sign-up required.