Kakuro by Nikoli is a single-player puzzle game in which players solve Kakuro puzzles, a logic-based number placement game similar to crosswords but with numbers. In this game, players are presented with a grid where they must fill in numbers that sum up to specified totals, following specific rules to ensure each number is used only once per sum. It stands out with its high-quality puzzles created by Nikoli, the original publisher of the Kakuro puzzle, offering a wide range of difficulty levels and meticulously designed challenges.