Very unique and clever puzzle game! :) Making big changes to the curve seems to be a bit hard though (which is perfectly understandable for a gamejam entry): maybe allow the player to draw a coarse curve with the mouse and then let them finetune it? Timing stuff right is also pretty difficult as of now: I agree with tesselode that an option to pause would help. Or a view of both the curve and the level, playing in an endless loop. But I really dig the concept. Please turn this into a full game!
My puzzle game: https://njamster.itch.io/wonkey (playable in browser, not mobile friendly)