Examples of addition, subtraction, multiplication and division with different levels of complexity

The application is aimed at students of all classes, as well as for those who want to test their skills in fast computing. The application has a setting for volume effects, a choice of operations (+, -, *, /) and the number of numbers in the expression.
A score is awarded for the correct answer, an error is calculated for the wrong answer. The more points, the higher the level, the higher the level, the less time is given for calculations. After the tour, you can see the statistics, where you will see examples in which you made mistakes.
This is my first application for Android, so do not judge strictly and use on health.