Change difficulty or change weapons
I generally enjoy these games, but this isn't planned out very well.
Fountains of ships should not come from behind. There's no reason I should do better with four rear facing homing missiles, than four front, on any level, ever.
Homing missiles attack things which can not be attacked, making them less than effective on some levels.
The ship itself is remarkably sluggish considering the later levels seem to require much more speed. Further, the ship is friggin huge, making dodging impossible in many later levels. It really seems as if the whole game was designed around a small fast fighter, but instead you were given somebody's bloated frigate.
I was particularly annoyed with the 3rd boss, taking up the VAST majority of the screen, firing projectiles to move the player up, then raking the top of the screen. That might not have been an issue if that was the only time the tactic was deployed, but it starts becoming frequent thereafter. Push player to one side of the screen, warp 9 enemy comes out and rams player.
Unfortunately, I did my initial voting in world 2 of 4/5. By the end of world 4, it's down to 4/10 on the review. Sounds even to me.