This is a web-based installation of Erratic Turtle Graphics.
It's turtle graphics, except there's a small margin of error. You might ask for "Turn right 90 degrees" but you might get only "Turn right 89.91 degrees".
It uses a faint pen, so if you repeat the drawing instructions many times over, you get a nice pencilly noisy effect.
There is support for a rudimentary command language similar to Logo, for user-created designs. The commands are:
fd NUM move forward this many pixels
rt NUM rotate right this many degrees
lt NUM rotate left this many degrees
setxyr NUM NUM set the coordinates, as a percentage of the
width and height of the canvas
shiftxyr NUM NUM adjust the coordinates, as a percentage of the
width and height of the canvas
seterr NUM NUM set the error rate for rotations and
movements respectively
shifterr NUM NUM adjust the error rate for rotations and
movements respectively
Note that the canvas may be larger than the viewport that it is displayed in, and that on mobile, the viewport may not display scrollbars to indicate this. You can still scroll the canvas.