To defend your galaxy you have to move your spaceship with your finger and hit the enemy aliens with your projectiles. Some of the enemy aliens have more life than others and some can hit you with more damage than others. You start with 3 shields, if they are all hit you will be destroyed. You can also, if you have lost shields, get some back. Sometimes destroyed enemies lose one of their shields, if you collect it, it's yours. In the main menu, you'll be able to upgrade your spaceship so that