About Single Line Drawings
Without doubt, the most famous single line drawings are those of Pablo Picasso, who would take complex entities and distill them down to the simplest form, using just one unbroken line. Picasso's single line work looks so simplistic and easy, and appeals to the eye, but don't be mistaken! It's (as you have probably learned playing with this single line tool), not the simplest task at all.
The best way to go about a beautiful single line creation is iteration, focusing on small areas at a time until your overall composition is neat and clean. While Picasso often used multiple lines, I've felt the focus for this paint toy would be best applied to the single line, with a small shadow to help refine your work
Some Development Notes:
All in all this is the simplest paint toy on the site to date (Jan 2022), and I suspect it will likely stay that way, although if you have a thought of what could be simpler, of course let me know! It's built more or less entirely upon open source work.
The SVG drawing tool used here is scribby, which allows for some nice SVG drawing, using some of the systems explained within this stack overflow article
The pencil style effect, is using SVG filters, which was borrowed from this fantastic onbservable HQ resource, using a noise function gave a nice pencil style effect. I tried the pen-esque ones too, which is what I had really wanted (something displaying pressures would have been nice), but after a lot of fiddling I decided the pencil looked best/
And last but not least! The star of the show, the SVG single line dog, which itself is modled off one of picasso's works is from this codepen demo, another tribute to the great master himself.