​

function setup() {

  createCanvas(600, 600);

  noStroke();

}

​

function draw() {

  background(0);

​

  for (let x = 20; x < width; x += spaceX) {

    for (let y = 20; y < height; y += spaceY) {

      drawEllipse(x, y);

    }

  }

}

​

function drawEllipse(x, y) {

  let d = dist(mouseX, mouseY, x, y);

  if (d < 100) {

    fill(255, 0, 0, 100);

    diam = map(d, 0, 100, 50, 1);

  } else {

    fill(255, 30);

    diam = 15;

  }

  ellipse(x, y, diam);

}

​