Hello, thanks for your detailed feedback, I'm glad you liked it anyway :)
Your solution to that problem with having to release and pressing the button again definitely is an interesting approach I would consider next time I implement this mechanic into the game. I noticed this problem in my own playtests and the way I tried to fix it was to simply removing the possibility to accelerate downwards after hitting a spring for a very short time period (around 0.2 seconds). This way you are forgiven for "messing up" releasing the button. Think of it like the time frame that is often given after you run off a floor and you still can jump.
I think the problem in this game was that this mechanic apparently was very new to most people (even considering myself, but I quickly got the hang out of it by playtesting a lot of course ^^') and I placed a very hard jump right at the beginning. Apparently many players quickly got frustrated that way since they hadn't had any chance practicing with easier jumps and being rewarded for that. Also there could have been things supporting the player by somehow making him understand how to deal with this mechanic. (Could have explained that the player has to build up as much momentum as he could by pressing the down key at the highest point and releasing it right as he was about to fall on the spring).
That you can't trigger the fast fall after falling off the floor most likely is a bug. I don't quite remember how I coded this atm but it probably had to do with the way I coded the jump mechanic and tied it directly to the accelerate downwards mechanic so that you can only do that if you had first jumped once (even after falling off an edge). So it pretty much is just a bug I could have fixed if I noticed ^^'
Yes, I didn't tell much in the game itself, that was mostly a time problem because of the jam. It would have been written in the description on the game page though but I know that few people first read the description so yeah, my bad :)
The knockback was depending on the size of the creep hitting you and you could kinda handle how much you where being knocked back by moving against the knockback. The way I handled it was not ideal but it felt kinda intuitive since you didn't lose control over your character after being hit (which is often the case in other games).
Anyway, once again, thank you VERY MUCH for your feedback. It helped me a lot by re-thinking about everything you mentioned. I probably won't work much on this game anymore but I really this down-mechanic and it definitely made me realize other find this idea interesting too so I might consider including this feature in another game I am currently working on :)