Futoshiki

Futoshiki (不等式, futōshiki), or More or Less, is a logic puzzle game from Japan.

Inequality constraints are initially specified between some of the squares, such that one must be higher or lower than its neighbor.

Solving the puzzle requires a combination of logical techniques.

Once the table of possibilities has been determined, a crucial tactic to solve the puzzle involves "AB elimination", in which subsets are identified within a row whose range of values can be determined.

Another important technique is to work through the range of possibilities in open inequalities.