You ever get that feeling of deja vu? This game reminds me distinctly of my last project with the flipping mechanic :P
I love the spritework in this game! Great work on that
Double jumping to invert gravity feels "off" for lack of a better word. I'd recommend either migrating gravity flipping to a separate button, or doing it VVVVV style where the player can't jump, they can only flip gravity
If you choose to keep the jump, consider migrating it to a separate button as well. Pressing S to jump when on the ceiling also just feels wrong
I like where you're going with it, can't wait to see what it turns into!