Use keys 1, 2, 3 and 4 to select a quadrant. Then choose an operation, using the keys +, -, * and /. You can use addition, subtraction, multiplication and division. If you choose another quadrant after that, it will perform your operation on the two quadrants. The goal of the game is to make the number 24 when you have only one quadrant left.
A quadrant can be one of four sections of the window. The 1st is top right, the 2nd is top left, the 3rd is bottom left and the 4th is bottom right.