ok so, update on hard mode.
i managed to clear hard mode, but game crashed on the third boss, so i had to do it again because it didn't save the medal.
it would have been absolute pain, if i didn't accidentally discover a bug: as long as you don't refresh the page, you can press esc on the main world to return to menu, then play game to resume without losing progress; long story short, you can clear the first two bosses on normal mode, then switch to hard mode only for the last boss. might want to get that fixed somehow.
in regards to bosses, the first boss is considerably harder, between the disleveled floor, increased speed and density of the attacks, which makes them harder to dodge.
though none of these compare to the difficulty that the white orb alone poses by simply existing. it's much faster, you have to constantly dodge it and it lingers for an insane amount of time. honestly that one change alone is what makes the first hard mode boss difficult, everything else simply locks you out of movement options while you're trying to avoid the white orb.
the second boss is probably the hardest of the 3 by a large margin. the missing floor is pretty annoying because you have to watch out your movement just to not get damaged, but the boss itself seems to have 3 different jump speeds and frequency of jumps that sporadically change between attempts, which make its movements wildly unpredictable.
however, phase 2 and 3 are simply unfair. you're already limited in your movement options by the missing floor, so you don't have many opportunities to deal damage, but then when the small window to attack shows up, you still can't do anything because you get damaged by the spawning bullets.
even if you just end up running away, you still get hit because you either jump and get hit by oncoming bullets, or don't move and get hit by the boss. and if you move and don't jump you fall and still take damage.
in the end i was forced to get the double jump upgrade and get to the 3rd phase on full health just to damage boost and get enough hits in, otherwise it's nigh impossible.
i can't really comment on the third boss, since i always cheese it by not moving from the spawn point and just timing my jumps. having double jump due to the previous boss also made it insanely easy, so there is virtually no difference between the easy and hard mode of the third boss, which makes the glitch to clear hard mode that much more appalling.
if i were to grade the difficulty of each boss (relative to each other), it would be:
1st boss (easy) - 3
2nd boss (easy) - 7
3rd boss (easy) - unranked
1st boss (hard) - 12
2nd boss (hard) - 20
3rd boss (hard) - unranked
for real, the second boss is such BS compared to the other ones.
the reason for the 3rd boss being unranked is that you can clear either one without moving, which removes the difficulty caused by spikes and the missing floor entirely. honestly i'm not sure how difficult they would be if i had to jump around while avoiding obstacles, but as they are now they're about as easy as the first boss on easy mode.
still some issues with the sporadic black screens out of nowhere, although it's not as annoying depending on whether the hard mode glitch gets fixed or not. honestly if i didn't discover that i would have never bothered trying to get the medal again, the second hard mode boss is too hard (too many lingering bullets; their slow speed makes it so different layers of bullets stack and form a wall as the boss moves towards you, so you can't really jump past it without getting damaged)