The aliens have attacked earth and now you have to join a special forces army and save the planet by destroying all the extraterrestrial beings. use your wasd keys to move, your q key to change your weapon, your r key to reload the weapon and your mouse to aim and shoot. in the upper left corner of the screen you can see your health bar and your shield bar, in the middle you will see how many marines are in the battle and how many were killed and also the same numbers for the aliens and in the upper right corner you will see your bullets. during the battle you will be able to get new weapons, shields or health power ups. try to kill as many aliens as possible without being hit. have an incredible time playing this game!