A very very good concept, and good art, this really feels like it could be a full game with a lot of length and different universe ! I don't know what to think with the slow movement and high jump, it "artificially" adds difficulty, but it also makes the game interesting because we're not really used to this... so not necessarily bad.
Also, first time I tried it, I was blocked at the beginning. Then saw a comment on the itch page and understood, and then I could finish the game ! so at the beginning, yeah it's not very clear I think. But once you get the base mechanic, It's very good.
Some line make the cgravity change, some not, it depend (like the one at the left of the beginning, works only to go from inverted gravity to normal gravity), and it's frustrating having to suicide yourself to find out. I think they need some visual indication, like color or something to get a sense of the "direction", because it's a very cool mechanic that it doesn't work in every direction !
I also think some blocks could be a bit clearer visually : it's not natural for that big block that on the top side you can walk on it, but on the bottom side... it's behind you ? but other blocks don't behave that way, honestly it was a bit disturbing from time to time. Also, that dark corner with the shadow, looks good, but when you have to jump from the edge, and the background is black, you see nothing and it's frustrating, maybe could be a lighter shade of dark, more grey-ish ?
I'm making lots of criticism, but bear in mind that I really loved the game, very very great concept !