Part 1
Protection powerup should be just above the first platform. There is a speed powerup holding stationary in the next upper alcove, and an ball powerup approaching from the middle. When you reach the next alcove located on the bottom, that's a speed powerup, which you will collect as soon as you shoot it.
The final powerup provides a wide hoop shot. Unless you have a spread shot (or something that makes the final enemy more dangerous), you will want to avoid it.
At the end of this part are three mirror images that move up and down. They have the same weapon as you do, which may make the fight extremely difficult, but their shots more slowly than yours. They also don't have any secondary weapons, such as a ball or missiles.
Even if you collected the wide hoop shot, it's not too difficult to dodge their shots. However, you will want to advance slightly to get more vertical room to dodge.
 Part 2
You are now introduced to a new hazard. From time to time, there will be beams appearing between two nodes, which kill if you get caught in them.
The first powerup is speed, followed by a weapon, a ball, protection, and a 3-way spread weapon
The guardian of this stage is a giant robot. It shoots a three-shot spread from its head, and alternates between beams and a spread from its arms. Like most other bosses in the game, you can park yourself in one place, and open fire. The best place is on the left, just below horizontal fire from the head. Here, you can hit it with missiles. If you don't have missiles, there's still enough distance between the shots to move back and forth.