Click on a spool of string on the rack to select a color and thickness. Click on "nail heads" to fasten the string there, and move to another nail (no need to drag). Click on any spool to "cut" the string. Click on the center of the circle to change it's color. Press "R" to reset (clear ALL strings!!!) Press "U" to undo one move.
100% pen (100% string?) credit to @cherryowl for inspiration from the source project. I used to make String Art wall hangings on black velvet back in the '70s (Ya! That was a thing back then!) so I just had to do a remix. Only one shape so far. I may add more in the future.