Make sure to get as many stars as possible on a "stars" level. Because there are no obstacles, you can earn a large amount of points.
Obstacles
After avoiding obstacles, return to the center. This position makes it easier to avoid the next set of obstacles. This is especially true for circles; although it may be easier to get past them from the sides, remain in the center to avoid what is coming after them. Although a head on collision with obstacles is bad, you can touch them with the sides of your ship without trouble.