there's nothing wrong with the difficulty, the problem is how jank the controls are.
for starters, there should only be limited fixed jump heights. one short jump, one high jump, maybe a medium jump.
as it is now, there's too many different "jumps" that have no use besides getting yourself killed.
i hate it when i try to short jump onto a platform, but i didn't press the button "long enough" and i just faceplant into the wall. or i pressed it "too long" and i just barely jump past it (but it's not a long jump so i don't even get to the next platform).
there's also something about the timing of your jumps, where you either don't have enough time to jump on consecutive short jumps, or it doesn't register having landed on the ground, but sometimes the jump doesn't come out?
this is just a me problem, but i also feel like the characters runs just slightly too fast, and that also affects the time you have to perform jumps correctly
the wall-jumping mechanic introduced in the third level is really weird because there's only one fixed jump height for it (despite the many problems caused by having multiple heights on the normal jump).
this isn't especially relevant on later levels, where you can change the height of your double and triple jumps, but level 3 becomes one of the hardest levels because of this.
also not sure how it's actually supposed to behave, but it doesn't really work properly when trying to get the egg on that level, because you try to wall-jump to get out of the cave and it still sticks to the wall.
i have to mash at different intervals until it randomly decides to get me out of there, and hope i don't accidentally fall to my death when it actually starts running again.
on level 4, you need to pick the high path on the last few jumps, because your double jump doesn't come out on the last spike pit if you take the low road, at around 97% (turns out if you hit your head on a ceiling mid-jump, you lose your double jumps)
the hitboxes on the spikes are way too big.
one such example is that they can hit you from below.
this is especially relevant on level 5, since wall-jumping pushes you up a fair bit before leaving the wall, and most pillars in this level have a spike on top, forcing you to slide down a bunch first before being able to jump.
on 64%, theres a gap where you'd think you can just walk and fall to the next lower platform (like every other time), but the spike on the ceiling will hit you as you're falling if you're walking. you're forced to make a specific jump from the previous platform that crosses the gap without landing to make it through, even though it's at the same distance from the spike.
the way glide is introduced in level 7 is awful, because you're immediately thrown into a narrow spike tunnel, followed by circular saws. you have no idea how glide works, and by the time you think you have it figured out, it expires and you're either falling or flying, and you have no idea if it's due to the glide mechanics or not until you realize it's on a time limit.
also half of the "difficulty" introduced by gliding is just adding blind jumps that lead to immediate death unless you trigger glide at the right time, which isn't great imo.
the variation on level 8 is already much better, because you go straight, and you can decide when it ends. though for some reason it takes a lot more time to restart on level 8 previous levels, which is somewhat annoying.
also the egg on level 8 is impossible to get without the debug controls.
there's only one ledge you can wall-jump against to reach the left platform with the egg:
if you jump too early, you slide up and hit the bottom of the spikes (same bug as level 5).
if you jump too late, you hit the death plane at the bottom.
if you manage to jump in time, you still won't make it on the left ledge, because the first wall-jump has fixed height (which is too low), and the double jump doesn't come out. you'll end up clinging on the left wall.
from the left wall, if you hold the left arrow mid-jump you can wall jump up the left wall and make it onto the left ledge, otherwise it's impossible.
same for the level 9 egg. you can get there just fine, but once you've gotten it you can't wall-jump away from that position onless you're holding left while wall-jumping, for some reason.
EDIT: i didn't realize no one ever managed to get past level 9, but i can see why.
i happened to encounter a glitch at around 45% with the glide boxes, which somehow bounced me off the vertical wall and sent me flying upward, which allowed me to use arrow keys to scroll over the layout of the level. it's honestly evil, and i have no idea how it's even physically possible.
https://www.newgrounds.com/dump/item/22103d3f3f39f45ed15707ebe25e7bbb
it also awarded me the "level complete" medal once i reached 100, so i had to manually remove it because that's wack. best i could do legitimately was 51%