In this simple but hectic level, you must pretty much do the same thing you did in the Ruin level. Shoot anything that moves and don't get hit. A few things to be wary of are the squadrons of small ships and the bird ships. They come at you in large numbers and it can be hard to shoot or avoid all of them (use a Hunter if you have it). Some bird ships can be found just hovering in one spot. These are extremely hard to kill, and if you get to close to its top or bottom it will rapidly change its altitude to smash into you, so just leave them alone. At the hard or maniac difficulty level you will see groups of blue triangles flying around. These are hard to kill, but not too dangerous, so just ignore them. The mini-boss isn't too hard. Just shoot at its head until it blows up, but be careful not to get hit by its tail. If its orbs start to glow, get out from in front of it and don't go back in front of it until the orbs come back.
After you hear the music change, it's not too far until the boss. This level's boss, Formalhaut, is a tad more difficult than the last few. He has a shield of red orbs that can't be destroyed, and sometimes these orbs will shoot streams of small fireballs that head in your general direction. Formalhaut will also shoot large rapidly moving energy blasts at you occasionally. When you have done significant damage to his midsection, part of him will explode and the red orbs will fly off at you in a spread pattern. This happens two or three times, then he will lose his shield and release a single red orb that will follow you around slowly. He will release more orbs and the orbs will fire on you at harder difficulty levels. Continue to blast his body, and when his body is gone hit his head until he dies.