Guiller's Mental Calculation is an app to help children in the practice of mental calculation.

The app includes 3 levels: Addition and subtraction, Arithmetic operations (addition, subtraction, multiplication and division) and Multiplicative and fractional numbers (double, triple, quadruple, quintuple, sextuple, the half, one third, one fourth, one fifth, one sixth).

The app allows to set a limit time to give the solution of a problem (3 to 60 seconds), the quantity of numbers for operations (2 to 5) and the quantity of digits for each number (1 to 3).

If child finds problem solution before time limit, he/she gets a number of points equal to the number of seconds left.

Each problem presented to the child is saved in a list that can be reviewed and reseted in any moment.