function setup() {

  createCanvas(400, 300);

}

​

function preload() {

    img = loadImage('sunrise-Jonathan-Petersson-Pexels-scaled.jpg');

}

function draw() {

  background(220);

  noStroke();

  for (let x = 0; x < width; x += 10) {

    for (let y = 0; y < height; y += 10) {

      // Calculate the distance of this cell to the mouse

      let d = dist(x, y, mouseX, mouseY);

      // Use the distance to color the cell

      let c = map(d, 0, 100, 255, 0);

      fill(c);

      rect(x, y, 10, 10);

    }

  }

}