Sum me up

In this small game you have to add up pairs of numbers, entering the result modulus 10 into the numpad on the screen. The speed of additions and the error rate are saved into a highscore table where you may put your name in case you are faster with less errors than at least one other highscore entry.
This game will help you to concentrate for a period of time in order you are already familiar with adding small numbers. If you are not, you will learn the sums of small numbers.
There are several levels with different numbers of additions to be made before a addition round is called finished.