Alien attack can lower your life and even kill you if you don`t kill them first.
Types of Aliens
Attacks you when they get close to you or by shooting a laser; it doesn`t matter if you are on a planet or in space.
If killed before they get into the planet`s atmosphere, they give one Crystal. On the other hand, if they get into the atmosphere, they spawn little aliens, which also give a crystal. Additionally, some Saucers are "shiny" and have a blinking color, which drop a weapon upgrade. Be careful, though! Getting hit physically by any alien will take the upgrade away (a laser will not reduce your upgrade)
Comes in different spices, they all drop a crystal in death.
Sentinels are a little harder to kill, they move from place to place, and although they may not shoot as often as the saucer, their shots do more damage. They start appearing once you have saved two planets, and you get out of the planets atmosphere. More will appear the further you progress.
There are multiple dragon types: the first (blue) shoots fire three fireballs, the second (red) shoots more fireballs, and the third (white) shoots snowballs and chunks of ice that freeze you.
The ground worm is an alien that appears at the planet`s surface and damages your health. It is a way of making you be more active: it will only attack if you stay still for a while.