Nah, screw the challenge design.

I like the gameplay, and it feels insanely good to cut off big sections of the bosses by doing such tiny gaps. But when the grand mayority of people cannot complete the 4th boss there's something wrong with how you make them deal with bullets.

Essentially, this game likes to overwhelm you. There seem to be static background hazards happening at a set time, and then you have to add the boss' own attacks to it as well.
So it isn't impossible for you to be dodging RNG bullets + homing bullets + Xulgon minions + insanely long walls + rain + boss collision at the same time on some of the final bosses, all while you're trying to do some tiny cuts with your mouse aim.
And I wouldn't complain about it that much it this was a normal shoot 'em up but with the whole monitor filling up plus your snappy movement, it doesn't feel as fun.
You have powerups, yeah, and shields and special bullets, but they only do so much.
Then Xulgon, the final boss which at the time I abandoned the game had less than 50 clears, was just too unfair.
Being forced to wait a whole minute or two before being able to attack is not good design. The bronce medal was for beating it within 20 minutes!!

I know there was an update after I played, the redux one. I don't feel like doing it because it added an even harder campaign according to my pals who played the game as well.