Put yourself in the pants of this alien and survive as much as possible to see that you destroy your enemies with your portal of shots, which will improve when you get new items of weapon, to set a goal is enough to select once your enemy And the portal will take care of the rest, you will also have access to the defense items which will reduce the damage received.
Remember that to make a jump only touch the screen just once in any place and to make a double jump touches the screen twice.
Enjoy the game!