let swapped = false;

let idx = 1;

let rectWidth = 10;

​

function setup() {

  createCanvas(400, 400);

  let n = 0;

  for(let i = 0; i < width; i+=rectWidth){

    heights[n++] = random(height);

  }

  colorMode(HSB, height, 100, 100);

}

​

function draw() {

  background(color(0, 20, 20));

  let x = 0;

  for(let i = 0; i < heights.length; i++){

    fill(color(heights[i], 70, 80));

    rect(x, height, rectWidth, -heights[i]);

    x += rectWidth;

  }

  if (idx >= heights.length){

    idx = 1;

    if (swapped == false){

        for(let i = 0; i < heights.length; i++){

          heights[i] = random(height);

        }      

    }

    swapped = false;

  }

  if (heights[idx] < heights[idx-1]){

    let tmp = heights[idx];

    heights[idx] = heights[idx-1];

    heights[idx-1] = tmp;

    swapped = true;

  }

  idx++;

}