Kakuro (also known as Cross sums) is a mathematical puzzle game which can be solved using logic.
Kakuro grid has 3 types of cells. 1. Blank cells which are not used in the game.
2. Hint cells which are divided using a diagonal line. The two halves can have numbers in one or both.
Right halve contains a number which is sum of associated cells to the right (horizontally). Left halve contains a number which is sum of associated cells below it (vertically).
3. Input cells which can have a digit from 1 to 9 such that no digit is duplicated and sum of numbers in a group matches the hint associated with it.
More details can be found here