Calcudoku is a variation of sudoku that involves more simple arithmetic calculations, but adds extra rules to the game. How to play calcudoku? The aim, as in sudoku, is to fill in all the rows and columns using all the available numbers without repeating them, so that the coloured areas indicating a result and an arithmetic operation are fulfilled using the numbers in that area. If a region has only one block, we will directly place the number it indicates. If a region has two blocks and says +5, the possible solutions are 3 and 2 or 1 and 4. In the regions the numbers CAN be repeated, but never in the rows and columns, which is the fundamental rule of Sudoku.