The Skill Level Slider varies from levels 1 - 10. The complexity of each game card increases with higher level numbers. The > symbol allows you to enter numbers from left to right. The < symbol allows you to enter numbers from right to left. Beginning users will most likely use the < right to left direction, but as you gain skill, you may choose the > right to left direction. To check your score of right and wrong, press SCORE. To play the Subtraction game, press PLAY. To quit, press QUIT. In the PLAY screen you type your answer and press Enter. If you make a mistake you may TRY AGAIN. If you want to clear your answer press CLR. To learn the answer, press ANS.