createCanvas(500, 500);

  slider = createSlider(0, 10, 1);

  textSize(12);

  slider.position(10, 10);

  slider.style('width', '100px');

  frameRate(3);

}

​

function draw() {

  background(0);

​

  let unitWidth = 20;

  let unitHeight = 20;

  let strokeWidth = slider.value();

  let rColor = 255-mouseX/2;

  let gColor = 255-mouseY/2;

  let bColor = 255-(mouseX+mouseY)/4;

  let lightness = 30;

  if (mouseIsPressed) {

    background(random(lightness,rColor), random(lightness,gColor), random(lightness,bColor));

    rColor = 0;

    gColor = 0;

    bColor = 0;

  }

  for (i=0; i<width; i=i+unitWidth) {

    for (k=0; k<height; k=k+unitHeight) {

      let x = round(random(3))

      stroke(random(lightness,rColor), random(lightness,gColor), random(lightness,bColor));

      strokeWeight(strokeWidth);

      if (x==0){

        line(i, k+unitHeight/2, i+unitWidth, k+unitHeight/2);

        //ellipse(unitWidth/2+i, unitHeight/2+k, unitWidth, unitHeight);

      } else if (x==1) {

        line(i+unitWidth/2, k, i+unitWidth/2, k+unitHeight);

        //rect(i, k, unitWidth, unitHeight);

      } else if (x==2) {

        line(i, k, i+unitWidth, k+unitHeight);

      } else if (x==3) {

        line(i+unitWidth, k, i, k+unitHeight);

      }

    }

  }

  fill(255);

  noStroke();

  text('stroke width', 125, 23);

}