Ooooo, I really like the paper aesthetic! Was one of the main reasons your game caught my attention. Couple of things:
1) Would be cool to have the level reset and not the whole game as Keays mentioned. Precision shots can be tricky so that would be a nice addition to make up for that.
2) For the paper background, I would look into seamless textures. If you take that image you have of paper and then offest the X and Y axis equal to half those dimensions, you can easily make it look like seamless notepad paper by drawing over these hard edges.
3) Wasn't able to get that far due to the full-level resets, but a feature where your ball could absorb ink, writing, or just contents that would go on the paper would be cool. Not sure how that would be developed but that was my initial thought of what the game could be about when going in.
Either way, that game has a nice charm to it. Keep it up!