Making the video, did you control the character directly or was it like a tool-assisted speedrun? And how much actually requires your own input, given how (iirc) there's some tracks that just run themselves?
(Not the author, but I've played Line Rider a lot a long time ago.) The character isn't directly controllable. They're affected by gravity, and collision with user-drawn lines. You can also draw "boost" lines that accelerate the character when touching, and "decoration" lines that don't interact with the character.