Hello! Welcome in a world of pain.
The unofficial harder-than-sub-150(tm) CELESTE Classic mod is here.
This mod was designed as first to be a parody of "add spikes" mods, but I actually put a lot of time and efforts into this to make it actually interesting.
This doesn't require any rem manipulation, spike clip or that kind of crap (you can't see rem and spike clip is lazy), but includes a lot of setups that require extended knowlage of the game and pixel/frame perfect precision.
All the levels were verified by me, they are humanly doable without any spike clip. If you think than it's too easy for some reason, try beating it without spike clip like I did.
You probably won't want to beat this, but I really appreciate your interest :)
Have fun!