Avoid the sun and fly from planet to planet. When you land, you refill your oxygen tank for the next flight. If you cannot make the landing, you will be reset to the last planet you landed on when your oxygen tank is empty, provided it has not yet been devoured by the sun. But be careful, asteroids and enemy Alienbullets can be dangerous if they collide with your planet. Buy upgrades to get ahead.
Every time you land, you get money that increases exponentially with a higher score.