​

let x, h;

​

function setup() {

  createCanvas(500, 500);

  w = width / 20;

}

​

function draw() {

  x = 0;

  while (x < 500) {

    if (mouseX >= x && mouseX < x + w) {

      fill("red");

    } else {

      fill("white");

    }

    rect(x, 0, w, height);

    x += w;

  }

}

​