Futoshiki

Futoshiki — Japanese for "inequality" — is a Latin-square puzzle with a twist. Each row and column must contain every number from 1 to n once, just like Sudoku without boxes. Between some neighbouring squares there are < and > signs that the two numbers must obey. A few starting numbers are given, and the signs do the rest.

Each puzzle is generated and checked to make sure it has exactly one solution.

1. Select a square, then tap a number on the pad (or type it).
2. Each row and column must contain every number once.
3. Every sign must be true: the open side of the sign faces the larger number.
4. Conflicts are highlighted. Fill the grid correctly to win.

• Chains limit values. In a chain a < b < c, the square a cannot be larger than n − 2.
• The largest number never sits on the small side of a sign, and 1 never sits on the large side.
• Combine signs with the row rule. Once only two numbers are left in a row, a single sign often decides them.