let w;

let swSize = 360/numSwatch

let off = 0;

​

function setup() {

  createCanvas(400, 400);

  colorMode(HSB,360,100,100);

  w = width/36;

}

​

function draw() {

  background(220);

  noStroke();

  off++

  for(let sw = 0; sw < numSwatch; sw++){

    let x = sw* w

    let h = sw * swSize + off;

    h %=360;

    fill(h,100,100);

  rect(x,0,w,height);

​

  }

}