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Curious Cheetah

Kakuro

Background

Kakuro is one of the two superstars of this puzzle genre, and like sudoku it was actually invented in the United States.
According to Will Shortz, the first "cross sums" puzzle appeared in 1966 in a Dell puzzle magazine. Around 1980, it was spotted by McKee Kaji, founder of Nikoli, who brought the puzzle to Japan. It came back to the US in the aftermath of the sudoku craze.

Puzzle and Goal

An unsolved puzzle consists of a rectangular grid resembling a crossword, with some black cells containing numbers.
The goal is to fill the (non-black) cells with numerals from 1 to 9.

Rules

The solved grid must satisfy the following conditions:

Variants

The most common variants are Cross Products, where the clues are the products rather than the sums, and puzzles where numerals are restricted to some range other than 1 to 9.
In the variant Sukrokuro, walls between cells either have a circle or not. The circle indicates that these cells contain consecutive numbers; consecutive numbers cannot appear in neighboring cells otherwise.

Other Names

Cross Addition; Cross Products; Cross Sums; Kasan Kurosu; Kreuzsumme; Sukrokuro; Zahlenschwede

Playable Online