Improve Your Maths

Improve your math skills. Try to solve 10 problems in as little time as possible. Choose any one of the four basic math operations at any one of three different difficulty levels.

MENU CONTROLS:
'left' and 'right' or click to change difficulty level;
click or enter the first character of the operation to begin.

Except for the main background "blackboard" image, everything seen is a SimpleActor object. The following is the entire SimpleActor class code:

public class SimpleActor extends greenfoot.Actor {}