The game Addition Aliens Attack is designed to help improve your ability to add and subtract quickly. The first think you do when playing the game is select the difficulty you would like to play on.
Beginner has you adding only small numbers. It is primarily for kids who have just recently learned how to add and subtract. The aliens move slowly, and there is usually only one on the game screen at a time.
The Intermediate difficulty has larger numbers that are being added and subtracted. You need to be able to add and subtract two digit numbers on this difficulty. The aliens still move fairly slow, so speed is not yet critical.
On the Advanced difficulty, the numbers get larger and the aliens come more quickly. You should play advanced if you are pretty good at arithmetic, but you would like to be able to improve the speed at which you can add and subtract numbers.
Impossible is really difficult, and only should be chosen by players who are already really good at arithmetic. Play Impossible if you want to see just how good you really are.
When you start to play the game, aliens will begin to drop down from the top of the screen with Addition and Subtraction math problems above them. You must solve the math problem and type in the numbers on your keyboard. If there is more than one number (e.g. 10) just type it in like you would type it into a calculator. If you hit an incorrect number, an error will be displayed and you will get a score penalty. When the "Remaining" number in the top right of the game screen is 0, you will pass the level.
If you take too long, the aliens will drop bombs on your city. If your entire city is destroyed you will lose the game.