This game is similar to "space invaders" but with fractions and decimals.
In every trial a simple fraction will appear on the lower left corner of the screen.
Decimal aliens will be descending slowly from above.
Find the alien with the decimal equivalent to the fraction given, and get your hero under it using the keyboard arrows. When you are in place, press the spacebar, to shoot a calculator and eliminate that alien.
Don't let the aliens reach the ground.
Pay attention, this is not an easy game, it starts with easy fractions, but as you progress through the levels, you get harder fractions (such as 7/9) and you need to act fast.