Played the first three levels. The paper look is lovely, and I really like that the dotted trail from a failed run stays on screen after you hit Edit, so on "Three islands, two choices" I could see exactly where the marble overshot the bucket and redraw from there. Getting the bonus star for saving pencil is a nice extra nudge too.
Two small things from my run. A couple of my lines simply did not appear when I started drawing right next to a platform, and the only clue was "Draw outside the shaded areas", but I could not see any shading. A faint outline of the no-draw zone while you hold the mouse down would help a lot. Also on level 2 my first Straight drag did nothing, while freehand worked fine, so it may be worth checking how Straight handles a quick drag.