Arcs line

float count = 0;

void setup() {

  size(600, 400, P2D); 

  colorMode(RGB, 2);

}

​

void draw() {

  // fill(0, .01);

  noStroke();

  rect(0, 0, width, height);

  if (mouseX != pmouseX || mouseY != pmouseY) {

    noFill();

    stroke(1+sin(count/30), 1+cos(count/42), 1+sin(count/25));

    float d = dist(mouseX, mouseY, pmouseX, pmouseY);

    translate((mouseX+pmouseX)/2, (mouseY+pmouseY)/2);

    rotate(atan2(mouseY-pmouseY, mouseX-pmouseX));

    arc(0, 0, d, d, (count%2 == 0) ? 0 : -PI, (count%2 == 0) ? PI : 0);

    count++;

  }

}

​