function setup() {
  createCanvas(720, 720);
  colorMode(HSB, 360, 100, 100, 100);
  noFill();
  strokeWeight(2);
  strokeColor = color(0, 10);
}
drawing with a changing shape by draging the mouse.

MOUSE
position x          : length
position y          : thickness and number of lines
drag                : draw

KEYS
1-3                 : stroke color
del, backspace      : erase
s                   : save png