The mechanics is very simple, just take down all the alien enemy ships to win. But be careful because they are shooting back. Be hit 3 times and you are done. And not only their bullets you should be afraid off because they are suicidal too, they will crashed their ships to you to take you down.
EVADE and BLAST them!!!
Opps I forgot the important thing, how to blast their ships. Well its not that hard, just move your ship to left or right and once its started moving it will continuously fire bullets and all you have to do is guide it to enemy ships.