Rullo is a simple math puzzle where you have a board full of numbers. The goal is to make the sum of numbers in each row and column be equal to the answer in the box. What you have to do is to remove some numbers from the equation by clicking on them. The board sizes range from 5×5 to 8×8. There are also 3 levels of difficulty: 1-9, 2-4, and 1-19. 1-9 means the numbers to calculate will range from 1 to 9.