That is beautiful.
I'm thinking of adding some accessibility settings; the ability to click rather than drag, different colors for those who want them, the ability to switch to a kemonomimi rather than a furry, metric units, the works.
...And a bra, and a better method of upgrading than just a prestige mechanic that gets a little too exponential in its growth.
...And a zoom feature. And the ability to adjust the line thickness for those with weird computers.
Again, this was just a prototype.
Here's a newer one, as a reward :D